[platform/upstream/gstreamer.git] / gst / gstutils.c

/* GStreamer
 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
 *                    2000 Wim Taymans <wtay@chello.be>
 *                    2002 Thomas Vander Stichele <thomas@apestaart.org>
 *                    2004 Wim Taymans <wim@fluendo.com>
 *                    2015 Jan Schmidt <jan@centricular.com>
 *
 * gstutils.c: Utility functions
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 */

/**
 * SECTION:gstutils
 * @short_description: Various utility functions
 *
 */

#include "gst_private.h"
#include <stdio.h>
#include <string.h>

#include "gstghostpad.h"
#include "gstutils.h"
#include "gsterror.h"
#include "gstinfo.h"
#include "gstparse.h"
#include "gstvalue.h"
#include "gst-i18n-lib.h"
#include "glib-compat-private.h"
#include <math.h>

/**
 * gst_util_dump_mem:
 * @mem: a pointer to the memory to dump
 * @size: the size of the memory block to dump
 *
 * Dumps the memory block into a hex representation. Useful for debugging.
 */
void
gst_util_dump_mem (const guchar * mem, guint size)
{
  guint i, j;
  GString *string = g_string_sized_new (50);
  GString *chars = g_string_sized_new (18);

  i = j = 0;
  while (i < size) {
    if (g_ascii_isprint (mem[i]))
      g_string_append_c (chars, mem[i]);
    else
      g_string_append_c (chars, '.');

    g_string_append_printf (string, "%02x ", mem[i]);

    j++;
    i++;

    if (j == 16 || i == size) {
      g_print ("%08x (%p): %-48.48s %-16.16s\n", i - j, mem + i - j,
          string->str, chars->str);
      g_string_set_size (string, 0);
      g_string_set_size (chars, 0);
      j = 0;
    }
  }
  g_string_free (string, TRUE);
  g_string_free (chars, TRUE);
}


/**
 * gst_util_set_value_from_string:
 * @value: (out caller-allocates): the value to set
 * @value_str: the string to get the value from
 *
 * Converts the string to the type of the value and
 * sets the value with it.
 *
 * Note that this function is dangerous as it does not return any indication
 * if the conversion worked or not.
 */
void
gst_util_set_value_from_string (GValue * value, const gchar * value_str)
{
  gboolean res;

  g_return_if_fail (value != NULL);
  g_return_if_fail (value_str != NULL);

  GST_CAT_DEBUG (GST_CAT_PARAMS, "parsing '%s' to type %s", value_str,
      g_type_name (G_VALUE_TYPE (value)));

  res = gst_value_deserialize (value, value_str);
  if (!res && G_VALUE_TYPE (value) == G_TYPE_BOOLEAN) {
    /* backwards compat, all booleans that fail to parse are false */
    g_value_set_boolean (value, FALSE);
    res = TRUE;
  }
  g_return_if_fail (res);
}

/**
 * gst_util_set_object_arg:
 * @object: the object to set the argument of
 * @name: the name of the argument to set
 * @value: the string value to set
 *
 * Converts the string value to the type of the objects argument and
 * sets the argument with it.
 *
 * Note that this function silently returns if @object has no property named
 * @name or when @value cannot be converted to the type of the property.
 */
void
gst_util_set_object_arg (GObject * object, const gchar * name,
    const gchar * value)
{
  GParamSpec *pspec;
  GType value_type;
  GValue v = { 0, };

  g_return_if_fail (G_IS_OBJECT (object));
  g_return_if_fail (name != NULL);
  g_return_if_fail (value != NULL);

  pspec = g_object_class_find_property (G_OBJECT_GET_CLASS (object), name);
  if (!pspec)
    return;

  value_type = pspec->value_type;

  GST_DEBUG ("pspec->flags is %d, pspec->value_type is %s",
      pspec->flags, g_type_name (value_type));

  if (!(pspec->flags & G_PARAM_WRITABLE))
    return;

  g_value_init (&v, value_type);

  /* special case for element <-> xml (de)serialisation */
  if (value_type == GST_TYPE_STRUCTURE && strcmp (value, "NULL") == 0) {
    g_value_set_boxed (&v, NULL);
    goto done;
  }

  if (!gst_value_deserialize (&v, value))
    return;

done:

  g_object_set_property (object, pspec->name, &v);
  g_value_unset (&v);
}

/* work around error C2520: conversion from unsigned __int64 to double
 * not implemented, use signed __int64
 *
 * These are implemented as functions because on some platforms a 64bit int to
 * double conversion is not defined/implemented.
 */

gdouble
gst_util_guint64_to_gdouble (guint64 value)
{
  if (value & G_GINT64_CONSTANT (0x8000000000000000))
    return (gdouble) ((gint64) value) + (gdouble) 18446744073709551616.;
  else
    return (gdouble) ((gint64) value);
}

guint64
gst_util_gdouble_to_guint64 (gdouble value)
{
  if (value < (gdouble) 9223372036854775808.)   /* 1 << 63 */
    return ((guint64) ((gint64) value));

  value -= (gdouble) 18446744073709551616.;
  return ((guint64) ((gint64) value));
}

#ifndef HAVE_UINT128_T
/* convenience struct for getting high and low uint32 parts of
 * a guint64 */
typedef union
{
  guint64 ll;
  struct
  {
#if G_BYTE_ORDER == G_BIG_ENDIAN
    guint32 high, low;
#else
    guint32 low, high;
#endif
  } l;
} GstUInt64;

#if defined (__x86_64__) && defined (__GNUC__)
static inline void
gst_util_uint64_mul_uint64 (GstUInt64 * c1, GstUInt64 * c0, guint64 arg1,
    guint64 arg2)
{
  __asm__ __volatile__ ("mulq %3":"=a" (c0->ll), "=d" (c1->ll)
      :"a" (arg1), "g" (arg2)
      );
}
#else /* defined (__x86_64__) */
/* multiply two 64-bit unsigned ints into a 128-bit unsigned int.  the high
 * and low 64 bits of the product are placed in c1 and c0 respectively.
 * this operation cannot overflow. */
static inline void
gst_util_uint64_mul_uint64 (GstUInt64 * c1, GstUInt64 * c0, guint64 arg1,
    guint64 arg2)
{
  GstUInt64 a1, b0;
  GstUInt64 v, n;

  /* prepare input */
  v.ll = arg1;
  n.ll = arg2;

  /* do 128 bits multiply
   *                   nh   nl
   *                *  vh   vl
   *                ----------
   * a0 =              vl * nl
   * a1 =         vl * nh
   * b0 =         vh * nl
   * b1 =  + vh * nh
   *       -------------------
   *        c1h  c1l  c0h  c0l
   *
   * "a0" is optimized away, result is stored directly in c0.  "b1" is
   * optimized away, result is stored directly in c1.
   */
  c0->ll = (guint64) v.l.low * n.l.low;
  a1.ll = (guint64) v.l.low * n.l.high;
  b0.ll = (guint64) v.l.high * n.l.low;

  /* add the high word of a0 to the low words of a1 and b0 using c1 as
   * scrach space to capture the carry.  the low word of the result becomes
   * the final high word of c0 */
  c1->ll = (guint64) c0->l.high + a1.l.low + b0.l.low;
  c0->l.high = c1->l.low;

  /* add the carry from the result above (found in the high word of c1) and
   * the high words of a1 and b0 to b1, the result is c1. */
  c1->ll = (guint64) v.l.high * n.l.high + c1->l.high + a1.l.high + b0.l.high;
}
#endif /* defined (__x86_64__) */

#if defined (__x86_64__) && defined (__GNUC__)
static inline guint64
gst_util_div128_64 (GstUInt64 c1, GstUInt64 c0, guint64 denom)
{
  guint64 res;

  __asm__ __volatile__ ("divq %3":"=a" (res)
      :"d" (c1.ll), "a" (c0.ll), "g" (denom)
      );

  return res;
}
#else
/* count leading zeros */
static inline guint
gst_util_clz (guint32 val)
{
  guint s;

  s = val | (val >> 1);
  s |= (s >> 2);
  s |= (s >> 4);
  s |= (s >> 8);
  s = ~(s | (s >> 16));
  s = s - ((s >> 1) & 0x55555555);
  s = (s & 0x33333333) + ((s >> 2) & 0x33333333);
  s = (s + (s >> 4)) & 0x0f0f0f0f;
  s += (s >> 8);
  s = (s + (s >> 16)) & 0x3f;

  return s;
}

/* based on Hacker's Delight p152 */
static inline guint64
gst_util_div128_64 (GstUInt64 c1, GstUInt64 c0, guint64 denom)
{
  GstUInt64 q1, q0, rhat;
  GstUInt64 v, cmp1, cmp2;
  guint s;

  v.ll = denom;

  /* count number of leading zeroes, we know they must be in the high
   * part of denom since denom > G_MAXUINT32. */
  s = gst_util_clz (v.l.high);

  if (s > 0) {
    /* normalize divisor and dividend */
    v.ll <<= s;
    c1.ll = (c1.ll << s) | (c0.l.high >> (32 - s));
    c0.ll <<= s;
  }

  q1.ll = c1.ll / v.l.high;
  rhat.ll = c1.ll - q1.ll * v.l.high;

  cmp1.l.high = rhat.l.low;
  cmp1.l.low = c0.l.high;
  cmp2.ll = q1.ll * v.l.low;

  while (q1.l.high || cmp2.ll > cmp1.ll) {
    q1.ll--;
    rhat.ll += v.l.high;
    if (rhat.l.high)
      break;
    cmp1.l.high = rhat.l.low;
    cmp2.ll -= v.l.low;
  }
  c1.l.high = c1.l.low;
  c1.l.low = c0.l.high;
  c1.ll -= q1.ll * v.ll;
  q0.ll = c1.ll / v.l.high;
  rhat.ll = c1.ll - q0.ll * v.l.high;

  cmp1.l.high = rhat.l.low;
  cmp1.l.low = c0.l.low;
  cmp2.ll = q0.ll * v.l.low;

  while (q0.l.high || cmp2.ll > cmp1.ll) {
    q0.ll--;
    rhat.ll += v.l.high;
    if (rhat.l.high)
      break;
    cmp1.l.high = rhat.l.low;
    cmp2.ll -= v.l.low;
  }
  q0.l.high += q1.l.low;

  return q0.ll;
}
#endif /* defined (__GNUC__) */

/* This always gives the correct result because:
 * a) val <= G_MAXUINT64-1
 * b) (c0,c1) <= G_MAXUINT64 * (G_MAXUINT64-1)
 *    or
 *    (c0,c1) == G_MAXUINT64 * G_MAXUINT64 and denom < G_MAXUINT64
 *    (note: num==denom case is handled by short path)
 * This means that (c0,c1) either has enough space for val
 * or that the overall result will overflow anyway.
 */

/* add correction with carry */
#define CORRECT(c0,c1,val)                    \
  if (val) {                                  \
    if (G_MAXUINT64 - c0.ll < val) {          \
      if (G_UNLIKELY (c1.ll == G_MAXUINT64))  \
        /* overflow */                        \
        return G_MAXUINT64;                   \
      c1.ll++;                                \
    }                                         \
    c0.ll += val;                             \
  }

static guint64
gst_util_uint64_scale_uint64_unchecked (guint64 val, guint64 num,
    guint64 denom, guint64 correct)
{
  GstUInt64 c1, c0;

  /* compute 128-bit numerator product */
  gst_util_uint64_mul_uint64 (&c1, &c0, val, num);

  /* perform rounding correction */
  CORRECT (c0, c1, correct);

  /* high word as big as or bigger than denom --> overflow */
  if (G_UNLIKELY (c1.ll >= denom))
    return G_MAXUINT64;

  /* compute quotient, fits in 64 bits */
  return gst_util_div128_64 (c1, c0, denom);
}
#else

#define GST_MAXUINT128 ((__uint128_t) -1)
static guint64
gst_util_uint64_scale_uint64_unchecked (guint64 val, guint64 num,
    guint64 denom, guint64 correct)
{
  __uint128_t tmp;

  /* Calculate val * num */
  tmp = ((__uint128_t) val) * ((__uint128_t) num);

  /* overflow checks */
  if (G_UNLIKELY (GST_MAXUINT128 - correct < tmp))
    return G_MAXUINT64;

  /* perform rounding correction */
  tmp += correct;

  /* Divide by denom */
  tmp /= denom;

  /* if larger than G_MAXUINT64 --> overflow */
  if (G_UNLIKELY (tmp > G_MAXUINT64))
    return G_MAXUINT64;

  /* compute quotient, fits in 64 bits */
  return (guint64) tmp;
}

#endif

#if !defined (__x86_64__) && !defined (HAVE_UINT128_T)
static inline void
gst_util_uint64_mul_uint32 (GstUInt64 * c1, GstUInt64 * c0, guint64 arg1,
    guint32 arg2)
{
  GstUInt64 a;

  a.ll = arg1;

  c0->ll = (guint64) a.l.low * arg2;
  c1->ll = (guint64) a.l.high * arg2 + c0->l.high;
  c0->l.high = 0;
}

/* divide a 96-bit unsigned int by a 32-bit unsigned int when we know the
 * quotient fits into 64 bits.  the high 64 bits and low 32 bits of the
 * numerator are expected in c1 and c0 respectively. */
static inline guint64
gst_util_div96_32 (guint64 c1, guint64 c0, guint32 denom)
{
  c0 += (c1 % denom) << 32;
  return ((c1 / denom) << 32) + (c0 / denom);
}

static inline guint64
gst_util_uint64_scale_uint32_unchecked (guint64 val, guint32 num,
    guint32 denom, guint32 correct)
{
  GstUInt64 c1, c0;

  /* compute 96-bit numerator product */
  gst_util_uint64_mul_uint32 (&c1, &c0, val, num);

  /* condition numerator based on rounding mode */
  CORRECT (c0, c1, correct);

  /* high 32 bits as big as or bigger than denom --> overflow */
  if (G_UNLIKELY (c1.l.high >= denom))
    return G_MAXUINT64;

  /* compute quotient, fits in 64 bits */
  return gst_util_div96_32 (c1.ll, c0.ll, denom);
}
#endif

/* the guts of the gst_util_uint64_scale() variants */
static guint64
_gst_util_uint64_scale (guint64 val, guint64 num, guint64 denom,
    guint64 correct)
{
  g_return_val_if_fail (denom != 0, G_MAXUINT64);

  if (G_UNLIKELY (num == 0))
    return 0;

  if (G_UNLIKELY (num == denom))
    return val;

  /* on 64bits we always use a full 128bits multiply/division */
#if !defined (__x86_64__) && !defined (HAVE_UINT128_T)
  /* denom is low --> try to use 96 bit muldiv */
  if (G_LIKELY (denom <= G_MAXUINT32)) {
    /* num is low --> use 96 bit muldiv */
    if (G_LIKELY (num <= G_MAXUINT32))
      return gst_util_uint64_scale_uint32_unchecked (val, (guint32) num,
          (guint32) denom, correct);

    /* num is high but val is low --> swap and use 96-bit muldiv */
    if (G_LIKELY (val <= G_MAXUINT32))
      return gst_util_uint64_scale_uint32_unchecked (num, (guint32) val,
          (guint32) denom, correct);
  }
#endif /* !defined (__x86_64__) && !defined (HAVE_UINT128_T) */

  /* val is high and num is high --> use 128-bit muldiv */
  return gst_util_uint64_scale_uint64_unchecked (val, num, denom, correct);
}

/**
 * gst_util_uint64_scale:
 * @val: the number to scale
 * @num: the numerator of the scale ratio
 * @denom: the denominator of the scale ratio
 *
 * Scale @val by the rational number @num / @denom, avoiding overflows and
 * underflows and without loss of precision.
 *
 * This function can potentially be very slow if val and num are both
 * greater than G_MAXUINT32.
 *
 * Returns: @val * @num / @denom.  In the case of an overflow, this
 * function returns G_MAXUINT64.  If the result is not exactly
 * representable as an integer it is truncated.  See also
 * gst_util_uint64_scale_round(), gst_util_uint64_scale_ceil(),
 * gst_util_uint64_scale_int(), gst_util_uint64_scale_int_round(),
 * gst_util_uint64_scale_int_ceil().
 */
guint64
gst_util_uint64_scale (guint64 val, guint64 num, guint64 denom)
{
  return _gst_util_uint64_scale (val, num, denom, 0);
}

/**
 * gst_util_uint64_scale_round:
 * @val: the number to scale
 * @num: the numerator of the scale ratio
 * @denom: the denominator of the scale ratio
 *
 * Scale @val by the rational number @num / @denom, avoiding overflows and
 * underflows and without loss of precision.
 *
 * This function can potentially be very slow if val and num are both
 * greater than G_MAXUINT32.
 *
 * Returns: @val * @num / @denom.  In the case of an overflow, this
 * function returns G_MAXUINT64.  If the result is not exactly
 * representable as an integer, it is rounded to the nearest integer
 * (half-way cases are rounded up).  See also gst_util_uint64_scale(),
 * gst_util_uint64_scale_ceil(), gst_util_uint64_scale_int(),
 * gst_util_uint64_scale_int_round(), gst_util_uint64_scale_int_ceil().
 */
guint64
gst_util_uint64_scale_round (guint64 val, guint64 num, guint64 denom)
{
  return _gst_util_uint64_scale (val, num, denom, denom >> 1);
}

/**
 * gst_util_uint64_scale_ceil:
 * @val: the number to scale
 * @num: the numerator of the scale ratio
 * @denom: the denominator of the scale ratio
 *
 * Scale @val by the rational number @num / @denom, avoiding overflows and
 * underflows and without loss of precision.
 *
 * This function can potentially be very slow if val and num are both
 * greater than G_MAXUINT32.
 *
 * Returns: @val * @num / @denom.  In the case of an overflow, this
 * function returns G_MAXUINT64.  If the result is not exactly
 * representable as an integer, it is rounded up.  See also
 * gst_util_uint64_scale(), gst_util_uint64_scale_round(),
 * gst_util_uint64_scale_int(), gst_util_uint64_scale_int_round(),
 * gst_util_uint64_scale_int_ceil().
 */
guint64
gst_util_uint64_scale_ceil (guint64 val, guint64 num, guint64 denom)
{
  return _gst_util_uint64_scale (val, num, denom, denom - 1);
}

/* the guts of the gst_util_uint64_scale_int() variants */
static guint64
_gst_util_uint64_scale_int (guint64 val, gint num, gint denom, gint correct)
{
  g_return_val_if_fail (denom > 0, G_MAXUINT64);
  g_return_val_if_fail (num >= 0, G_MAXUINT64);

  if (G_UNLIKELY (num == 0))
    return 0;

  if (G_UNLIKELY (num == denom))
    return val;

  if (val <= G_MAXUINT32) {
    /* simple case.  num and denom are not negative so casts are OK.  when
     * not truncating, the additions to the numerator cannot overflow
     * because val*num <= G_MAXUINT32 * G_MAXINT32 < G_MAXUINT64 -
     * G_MAXINT32, so there's room to add another gint32. */
    val *= (guint64) num;
    /* add rounding correction */
    val += correct;

    return val / (guint64) denom;
  }
#if !defined (__x86_64__) && !defined (HAVE_UINT128_T)
  /* num and denom are not negative so casts are OK */
  return gst_util_uint64_scale_uint32_unchecked (val, (guint32) num,
      (guint32) denom, (guint32) correct);
#else
  /* always use full 128bits scale */
  return gst_util_uint64_scale_uint64_unchecked (val, num, denom, correct);
#endif
}

/**
 * gst_util_uint64_scale_int:
 * @val: guint64 (such as a #GstClockTime) to scale.
 * @num: numerator of the scale factor.
 * @denom: denominator of the scale factor.
 *
 * Scale @val by the rational number @num / @denom, avoiding overflows and
 * underflows and without loss of precision.  @num must be non-negative and
 * @denom must be positive.
 *
 * Returns: @val * @num / @denom.  In the case of an overflow, this
 * function returns G_MAXUINT64.  If the result is not exactly
 * representable as an integer, it is truncated.  See also
 * gst_util_uint64_scale_int_round(), gst_util_uint64_scale_int_ceil(),
 * gst_util_uint64_scale(), gst_util_uint64_scale_round(),
 * gst_util_uint64_scale_ceil().
 */
guint64
gst_util_uint64_scale_int (guint64 val, gint num, gint denom)
{
  return _gst_util_uint64_scale_int (val, num, denom, 0);
}

/**
 * gst_util_uint64_scale_int_round:
 * @val: guint64 (such as a #GstClockTime) to scale.
 * @num: numerator of the scale factor.
 * @denom: denominator of the scale factor.
 *
 * Scale @val by the rational number @num / @denom, avoiding overflows and
 * underflows and without loss of precision.  @num must be non-negative and
 * @denom must be positive.
 *
 * Returns: @val * @num / @denom.  In the case of an overflow, this
 * function returns G_MAXUINT64.  If the result is not exactly
 * representable as an integer, it is rounded to the nearest integer
 * (half-way cases are rounded up).  See also gst_util_uint64_scale_int(),
 * gst_util_uint64_scale_int_ceil(), gst_util_uint64_scale(),
 * gst_util_uint64_scale_round(), gst_util_uint64_scale_ceil().
 */
guint64
gst_util_uint64_scale_int_round (guint64 val, gint num, gint denom)
{
  /* we can use a shift to divide by 2 because denom is required to be
   * positive. */
  return _gst_util_uint64_scale_int (val, num, denom, denom >> 1);
}

/**
 * gst_util_uint64_scale_int_ceil:
 * @val: guint64 (such as a #GstClockTime) to scale.
 * @num: numerator of the scale factor.
 * @denom: denominator of the scale factor.
 *
 * Scale @val by the rational number @num / @denom, avoiding overflows and
 * underflows and without loss of precision.  @num must be non-negative and
 * @denom must be positive.
 *
 * Returns: @val * @num / @denom.  In the case of an overflow, this
 * function returns G_MAXUINT64.  If the result is not exactly
 * representable as an integer, it is rounded up.  See also
 * gst_util_uint64_scale_int(), gst_util_uint64_scale_int_round(),
 * gst_util_uint64_scale(), gst_util_uint64_scale_round(),
 * gst_util_uint64_scale_ceil().
 */
guint64
gst_util_uint64_scale_int_ceil (guint64 val, gint num, gint denom)
{
  return _gst_util_uint64_scale_int (val, num, denom, denom - 1);
}

/**
 * gst_util_seqnum_next:
 *
 * Return a constantly incrementing sequence number.
 *
 * This function is used internally to GStreamer to be able to determine which
 * events and messages are "the same". For example, elements may set the seqnum
 * on a segment-done message to be the same as that of the last seek event, to
 * indicate that event and the message correspond to the same segment.
 *
 * Returns: A constantly incrementing 32-bit unsigned integer, which might
 * overflow back to 0 at some point. Use gst_util_seqnum_compare() to make sure
 * you handle wraparound correctly.
 */
guint32
gst_util_seqnum_next (void)
{
  static gint counter = 0;
  return g_atomic_int_add (&counter, 1);
}

/**
 * gst_util_seqnum_compare:
 * @s1: A sequence number.
 * @s2: Another sequence number.
 *
 * Compare two sequence numbers, handling wraparound.
 *
 * The current implementation just returns (gint32)(@s1 - @s2).
 *
 * Returns: A negative number if @s1 is before @s2, 0 if they are equal, or a
 * positive number if @s1 is after @s2.
 */
gint32
gst_util_seqnum_compare (guint32 s1, guint32 s2)
{
  return (gint32) (s1 - s2);
}

/* -----------------------------------------------------
 *
 *  The following code will be moved out of the main
 * gstreamer library someday.
 */

#include "gstpad.h"

/**
 * gst_element_create_all_pads:
 * @element: (transfer none): a #GstElement to create pads for
 *
 * Creates a pad for each pad template that is always available.
 * This function is only useful during object initialization of
 * subclasses of #GstElement.
 */
void
gst_element_create_all_pads (GstElement * element)
{
  GList *padlist;

  /* FIXME: lock element */

  padlist =
      gst_element_class_get_pad_template_list (GST_ELEMENT_CLASS
      (G_OBJECT_GET_CLASS (element)));

  while (padlist) {
    GstPadTemplate *padtempl = (GstPadTemplate *) padlist->data;

    if (padtempl->presence == GST_PAD_ALWAYS) {
      GstPad *pad;

      pad = gst_pad_new_from_template (padtempl, padtempl->name_template);

      gst_element_add_pad (element, pad);
    }
    padlist = padlist->next;
  }
}

/**
 * gst_element_get_compatible_pad_template:
 * @element: (transfer none): a #GstElement to get a compatible pad template for
 * @compattempl: (transfer none): the #GstPadTemplate to find a compatible
 *     template for
 *
 * Retrieves a pad template from @element that is compatible with @compattempl.
 * Pads from compatible templates can be linked together.
 *
 * Returns: (transfer none) (nullable): a compatible #GstPadTemplate,
 *   or %NULL if none was found. No unreferencing is necessary.
 */
GstPadTemplate *
gst_element_get_compatible_pad_template (GstElement * element,
    GstPadTemplate * compattempl)
{
  GstPadTemplate *newtempl = NULL;
  GList *padlist;
  GstElementClass *class;
  gboolean compatible;

  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (compattempl != NULL, NULL);

  class = GST_ELEMENT_GET_CLASS (element);

  padlist = gst_element_class_get_pad_template_list (class);

  GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
      "Looking for a suitable pad template in %s out of %d templates...",
      GST_ELEMENT_NAME (element), g_list_length (padlist));

  while (padlist) {
    GstPadTemplate *padtempl = (GstPadTemplate *) padlist->data;

    /* Ignore name
     * Ignore presence
     * Check direction (must be opposite)
     * Check caps
     */
    GST_CAT_LOG (GST_CAT_CAPS,
        "checking pad template %s", padtempl->name_template);
    if (padtempl->direction != compattempl->direction) {
      GST_CAT_DEBUG (GST_CAT_CAPS,
          "compatible direction: found %s pad template \"%s\"",
          padtempl->direction == GST_PAD_SRC ? "src" : "sink",
          padtempl->name_template);

      GST_CAT_DEBUG (GST_CAT_CAPS,
          "intersecting %" GST_PTR_FORMAT, GST_PAD_TEMPLATE_CAPS (compattempl));
      GST_CAT_DEBUG (GST_CAT_CAPS,
          "..and %" GST_PTR_FORMAT, GST_PAD_TEMPLATE_CAPS (padtempl));

      compatible = gst_caps_can_intersect (GST_PAD_TEMPLATE_CAPS (compattempl),
          GST_PAD_TEMPLATE_CAPS (padtempl));

      GST_CAT_DEBUG (GST_CAT_CAPS, "caps are %scompatible",
          (compatible ? "" : "not "));

      if (compatible) {
        newtempl = padtempl;
        break;
      }
    }

    padlist = g_list_next (padlist);
  }
  if (newtempl)
    GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
        "Returning new pad template %p", newtempl);
  else
    GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "No compatible pad template found");

  return newtempl;
}

/**
 * gst_element_get_pad_from_template:
 * @element: (transfer none): a #GstElement.
 * @templ: (transfer none): a #GstPadTemplate belonging to @element.
 *
 * Gets a pad from @element described by @templ. If the presence of @templ is
 * #GST_PAD_REQUEST, requests a new pad. Can return %NULL for #GST_PAD_SOMETIMES
 * templates.
 *
 * Returns: (transfer full) (nullable): the #GstPad, or %NULL if one
 *   could not be found or created.
 */
static GstPad *
gst_element_get_pad_from_template (GstElement * element, GstPadTemplate * templ)
{
  GstPad *ret = NULL;
  GstPadPresence presence;

  /* If this function is ever exported, we need check the validity of `element'
   * and `templ', and to make sure the template actually belongs to the
   * element. */

  presence = GST_PAD_TEMPLATE_PRESENCE (templ);

  switch (presence) {
    case GST_PAD_ALWAYS:
    case GST_PAD_SOMETIMES:
      ret = gst_element_get_static_pad (element, templ->name_template);
      if (!ret && presence == GST_PAD_ALWAYS)
        g_warning
            ("Element %s has an ALWAYS template %s, but no pad of the same name",
            GST_OBJECT_NAME (element), templ->name_template);
      break;

    case GST_PAD_REQUEST:
      ret = gst_element_request_pad (element, templ, NULL, NULL);
      break;
  }

  return ret;
}

/*
 * gst_element_request_compatible_pad:
 * @element: a #GstElement.
 * @templ: the #GstPadTemplate to which the new pad should be able to link.
 *
 * Requests a pad from @element. The returned pad should be unlinked and
 * compatible with @templ. Might return an existing pad, or request a new one.
 *
 * Returns: (nullable): a #GstPad, or %NULL if one could not be found
 *   or created.
 */
static GstPad *
gst_element_request_compatible_pad (GstElement * element,
    GstPadTemplate * templ)
{
  GstPadTemplate *templ_new;
  GstPad *pad = NULL;

  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (GST_IS_PAD_TEMPLATE (templ), NULL);

  /* FIXME: should really loop through the templates, testing each for
   *      compatibility and pad availability. */
  templ_new = gst_element_get_compatible_pad_template (element, templ);
  if (templ_new)
    pad = gst_element_get_pad_from_template (element, templ_new);

  /* This can happen for non-request pads. No need to unref. */
  if (pad && GST_PAD_PEER (pad))
    pad = NULL;

  return pad;
}

/*
 * Checks if the source pad and the sink pad can be linked.
 * Both @srcpad and @sinkpad must be unlinked and have a parent.
 */
static gboolean
gst_pad_check_link (GstPad * srcpad, GstPad * sinkpad)
{
  /* generic checks */
  g_return_val_if_fail (GST_IS_PAD (srcpad), FALSE);
  g_return_val_if_fail (GST_IS_PAD (sinkpad), FALSE);

  GST_CAT_INFO (GST_CAT_PADS, "trying to link %s:%s and %s:%s",
      GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (sinkpad));

  if (GST_PAD_PEER (srcpad) != NULL) {
    GST_CAT_INFO (GST_CAT_PADS, "Source pad %s:%s has a peer, failed",
        GST_DEBUG_PAD_NAME (srcpad));
    return FALSE;
  }
  if (GST_PAD_PEER (sinkpad) != NULL) {
    GST_CAT_INFO (GST_CAT_PADS, "Sink pad %s:%s has a peer, failed",
        GST_DEBUG_PAD_NAME (sinkpad));
    return FALSE;
  }
  if (!GST_PAD_IS_SRC (srcpad)) {
    GST_CAT_INFO (GST_CAT_PADS, "Src pad %s:%s is not source pad, failed",
        GST_DEBUG_PAD_NAME (srcpad));
    return FALSE;
  }
  if (!GST_PAD_IS_SINK (sinkpad)) {
    GST_CAT_INFO (GST_CAT_PADS, "Sink pad %s:%s is not sink pad, failed",
        GST_DEBUG_PAD_NAME (sinkpad));
    return FALSE;
  }
  if (GST_PAD_PARENT (srcpad) == NULL) {
    GST_CAT_INFO (GST_CAT_PADS, "Src pad %s:%s has no parent, failed",
        GST_DEBUG_PAD_NAME (srcpad));
    return FALSE;
  }
  if (GST_PAD_PARENT (sinkpad) == NULL) {
    GST_CAT_INFO (GST_CAT_PADS, "Sink pad %s:%s has no parent, failed",
        GST_DEBUG_PAD_NAME (srcpad));
    return FALSE;
  }

  return TRUE;
}

/**
 * gst_element_get_compatible_pad:
 * @element: (transfer none): a #GstElement in which the pad should be found.
 * @pad: (transfer none): the #GstPad to find a compatible one for.
 * @caps: (allow-none): the #GstCaps to use as a filter.
 *
 * Looks for an unlinked pad to which the given pad can link. It is not
 * guaranteed that linking the pads will work, though it should work in most
 * cases.
 *
 * This function will first attempt to find a compatible unlinked ALWAYS pad,
 * and if none can be found, it will request a compatible REQUEST pad by looking
 * at the templates of @element.
 *
 * Returns: (transfer full) (nullable): the #GstPad to which a link
 *   can be made, or %NULL if one cannot be found. gst_object_unref()
 *   after usage.
 */
GstPad *
gst_element_get_compatible_pad (GstElement * element, GstPad * pad,
    GstCaps * caps)
{
  GstIterator *pads;
  GstPadTemplate *templ;
  GstCaps *templcaps;
  GstPad *foundpad = NULL;
  gboolean done;
  GValue padptr = { 0, };

  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
      "finding pad in %s compatible with %s:%s",
      GST_ELEMENT_NAME (element), GST_DEBUG_PAD_NAME (pad));

  g_return_val_if_fail (GST_PAD_PEER (pad) == NULL, NULL);

  done = FALSE;

  /* try to get an existing unlinked pad */
  if (GST_PAD_IS_SRC (pad)) {
    pads = gst_element_iterate_sink_pads (element);
  } else if (GST_PAD_IS_SINK (pad)) {
    pads = gst_element_iterate_src_pads (element);
  } else {
    pads = gst_element_iterate_pads (element);
  }

  while (!done) {
    switch (gst_iterator_next (pads, &padptr)) {
      case GST_ITERATOR_OK:
      {
        GstPad *peer;
        GstPad *current;
        GstPad *srcpad;
        GstPad *sinkpad;

        current = g_value_get_object (&padptr);

        GST_CAT_LOG (GST_CAT_ELEMENT_PADS, "examining pad %s:%s",
            GST_DEBUG_PAD_NAME (current));

        if (GST_PAD_IS_SRC (current)) {
          srcpad = current;
          sinkpad = pad;
        } else {
          srcpad = pad;
          sinkpad = current;
        }
        peer = gst_pad_get_peer (current);

        if (peer == NULL && gst_pad_check_link (srcpad, sinkpad)) {
          GstCaps *temp, *intersection;
          gboolean compatible;

          /* Now check if the two pads' caps are compatible */
          temp = gst_pad_query_caps (pad, NULL);
          if (caps) {
            intersection = gst_caps_intersect (temp, caps);
            gst_caps_unref (temp);
          } else {
            intersection = temp;
          }

          temp = gst_pad_query_caps (current, NULL);
          compatible = gst_caps_can_intersect (temp, intersection);
          gst_caps_unref (temp);
          gst_caps_unref (intersection);

          if (compatible) {
            GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
                "found existing unlinked compatible pad %s:%s",
                GST_DEBUG_PAD_NAME (current));
            gst_iterator_free (pads);

            current = gst_object_ref (current);
            g_value_unset (&padptr);

            return current;
          } else {
            GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "incompatible pads");
          }
        } else {
          GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
              "already linked or cannot be linked (peer = %p)", peer);
        }
        GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "unreffing pads");

        g_value_reset (&padptr);
        if (peer)
          gst_object_unref (peer);
        break;
      }
      case GST_ITERATOR_DONE:
        done = TRUE;
        break;
      case GST_ITERATOR_RESYNC:
        gst_iterator_resync (pads);
        break;
      case GST_ITERATOR_ERROR:
        g_assert_not_reached ();
        break;
    }
  }
  g_value_unset (&padptr);
  gst_iterator_free (pads);

  GST_CAT_DEBUG_OBJECT (GST_CAT_ELEMENT_PADS, element,
      "Could not find a compatible unlinked always pad to link to %s:%s, now checking request pads",
      GST_DEBUG_PAD_NAME (pad));

  /* try to create a new one */
  /* requesting is a little crazy, we need a template. Let's create one */
  templcaps = gst_pad_query_caps (pad, NULL);
  if (caps) {
    GstCaps *inter = gst_caps_intersect (templcaps, caps);

    gst_caps_unref (templcaps);
    templcaps = inter;
  }
  templ = gst_pad_template_new ((gchar *) GST_PAD_NAME (pad),
      GST_PAD_DIRECTION (pad), GST_PAD_ALWAYS, templcaps);
  gst_caps_unref (templcaps);

  foundpad = gst_element_request_compatible_pad (element, templ);
  gst_object_unref (templ);

  if (foundpad) {
    GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
        "found existing request pad %s:%s", GST_DEBUG_PAD_NAME (foundpad));
    return foundpad;
  }

  GST_CAT_INFO_OBJECT (GST_CAT_ELEMENT_PADS, element,
      "Could not find a compatible pad to link to %s:%s",
      GST_DEBUG_PAD_NAME (pad));
  return NULL;
}

/**
 * gst_element_state_get_name:
 * @state: a #GstState to get the name of.
 *
 * Gets a string representing the given state.
 *
 * Returns: (transfer none): a string with the name of the state.
 */
const gchar *
gst_element_state_get_name (GstState state)
{
  switch (state) {
    case GST_STATE_VOID_PENDING:
      return "VOID_PENDING";
    case GST_STATE_NULL:
      return "NULL";
    case GST_STATE_READY:
      return "READY";
    case GST_STATE_PLAYING:
      return "PLAYING";
    case GST_STATE_PAUSED:
      return "PAUSED";
    default:
      /* This is a memory leak */
      return g_strdup_printf ("UNKNOWN!(%d)", state);
  }
}

/**
 * gst_element_state_change_return_get_name:
 * @state_ret: a #GstStateChangeReturn to get the name of.
 *
 * Gets a string representing the given state change result.
 *
 * Returns: (transfer none): a string with the name of the state
 *    result.
 */
const gchar *
gst_element_state_change_return_get_name (GstStateChangeReturn state_ret)
{
  switch (state_ret) {
    case GST_STATE_CHANGE_FAILURE:
      return "FAILURE";
    case GST_STATE_CHANGE_SUCCESS:
      return "SUCCESS";
    case GST_STATE_CHANGE_ASYNC:
      return "ASYNC";
    case GST_STATE_CHANGE_NO_PREROLL:
      return "NO PREROLL";
    default:
      /* This is a memory leak */
      return g_strdup_printf ("UNKNOWN!(%d)", state_ret);
  }
}


static gboolean
gst_element_factory_can_accept_all_caps_in_direction (GstElementFactory *
    factory, const GstCaps * caps, GstPadDirection direction)
{
  GList *templates;

  g_return_val_if_fail (factory != NULL, FALSE);
  g_return_val_if_fail (caps != NULL, FALSE);

  templates = factory->staticpadtemplates;

  while (templates) {
    GstStaticPadTemplate *template = (GstStaticPadTemplate *) templates->data;

    if (template->direction == direction) {
      GstCaps *templcaps = gst_static_caps_get (&template->static_caps);

      if (gst_caps_is_always_compatible (caps, templcaps)) {
        gst_caps_unref (templcaps);
        return TRUE;
      }
      gst_caps_unref (templcaps);
    }
    templates = g_list_next (templates);
  }

  return FALSE;
}

static gboolean
gst_element_factory_can_accept_any_caps_in_direction (GstElementFactory *
    factory, const GstCaps * caps, GstPadDirection direction)
{
  GList *templates;

  g_return_val_if_fail (factory != NULL, FALSE);
  g_return_val_if_fail (caps != NULL, FALSE);

  templates = factory->staticpadtemplates;

  while (templates) {
    GstStaticPadTemplate *template = (GstStaticPadTemplate *) templates->data;

    if (template->direction == direction) {
      GstCaps *templcaps = gst_static_caps_get (&template->static_caps);

      if (gst_caps_can_intersect (caps, templcaps)) {
        gst_caps_unref (templcaps);
        return TRUE;
      }
      gst_caps_unref (templcaps);
    }
    templates = g_list_next (templates);
  }

  return FALSE;
}

/**
 * gst_element_factory_can_sink_all_caps:
 * @factory: factory to query
 * @caps: the caps to check
 *
 * Checks if the factory can sink all possible capabilities.
 *
 * Returns: %TRUE if the caps are fully compatible.
 */
gboolean
gst_element_factory_can_sink_all_caps (GstElementFactory * factory,
    const GstCaps * caps)
{
  return gst_element_factory_can_accept_all_caps_in_direction (factory, caps,
      GST_PAD_SINK);
}

/**
 * gst_element_factory_can_src_all_caps:
 * @factory: factory to query
 * @caps: the caps to check
 *
 * Checks if the factory can src all possible capabilities.
 *
 * Returns: %TRUE if the caps are fully compatible.
 */
gboolean
gst_element_factory_can_src_all_caps (GstElementFactory * factory,
    const GstCaps * caps)
{
  return gst_element_factory_can_accept_all_caps_in_direction (factory, caps,
      GST_PAD_SRC);
}

/**
 * gst_element_factory_can_sink_any_caps:
 * @factory: factory to query
 * @caps: the caps to check
 *
 * Checks if the factory can sink any possible capability.
 *
 * Returns: %TRUE if the caps have a common subset.
 */
gboolean
gst_element_factory_can_sink_any_caps (GstElementFactory * factory,
    const GstCaps * caps)
{
  return gst_element_factory_can_accept_any_caps_in_direction (factory, caps,
      GST_PAD_SINK);
}

/**
 * gst_element_factory_can_src_any_caps:
 * @factory: factory to query
 * @caps: the caps to check
 *
 * Checks if the factory can src any possible capability.
 *
 * Returns: %TRUE if the caps have a common subset.
 */
gboolean
gst_element_factory_can_src_any_caps (GstElementFactory * factory,
    const GstCaps * caps)
{
  return gst_element_factory_can_accept_any_caps_in_direction (factory, caps,
      GST_PAD_SRC);
}

/* if return val is true, *direct_child is a caller-owned ref on the direct
 * child of ancestor that is part of object's ancestry */
static gboolean
object_has_ancestor (GstObject * object, GstObject * ancestor,
    GstObject ** direct_child)
{
  GstObject *child, *parent;

  if (direct_child)
    *direct_child = NULL;

  child = gst_object_ref (object);
  parent = gst_object_get_parent (object);

  while (parent) {
    if (ancestor == parent) {
      if (direct_child)
        *direct_child = child;
      else
        gst_object_unref (child);
      gst_object_unref (parent);
      return TRUE;
    }

    gst_object_unref (child);
    child = parent;
    parent = gst_object_get_parent (parent);
  }

  gst_object_unref (child);

  return FALSE;
}

/* caller owns return */
static GstObject *
find_common_root (GstObject * o1, GstObject * o2)
{
  GstObject *top = o1;
  GstObject *kid1, *kid2;
  GstObject *root = NULL;

  while (GST_OBJECT_PARENT (top))
    top = GST_OBJECT_PARENT (top);

  /* the itsy-bitsy spider... */

  if (!object_has_ancestor (o2, top, &kid2))
    return NULL;

  root = gst_object_ref (top);
  while (TRUE) {
    if (!object_has_ancestor (o1, kid2, &kid1)) {
      gst_object_unref (kid2);
      return root;
    }
    gst_object_unref (root);
    root = kid2;
    if (!object_has_ancestor (o2, kid1, &kid2)) {
      gst_object_unref (kid1);
      return root;
    }
    gst_object_unref (root);
    root = kid1;
  }
}

/* caller does not own return */
static GstPad *
ghost_up (GstElement * e, GstPad * pad)
{
  static gint ghost_pad_index = 0;
  GstPad *gpad;
  gchar *name;
  GstState current;
  GstState next;
  GstObject *parent = GST_OBJECT_PARENT (e);

  name = g_strdup_printf ("ghost%d", ghost_pad_index++);
  gpad = gst_ghost_pad_new (name, pad);
  g_free (name);

  GST_STATE_LOCK (parent);
  gst_element_get_state (GST_ELEMENT (parent), &current, &next, 0);

  if (current > GST_STATE_READY || next >= GST_STATE_PAUSED)
    gst_pad_set_active (gpad, TRUE);

  if (!gst_element_add_pad ((GstElement *) parent, gpad)) {
    g_warning ("Pad named %s already exists in element %s\n",
        GST_OBJECT_NAME (gpad), GST_OBJECT_NAME (parent));
    gst_object_unref ((GstObject *) gpad);
    GST_STATE_UNLOCK (parent);
    return NULL;
  }
  GST_STATE_UNLOCK (parent);

  return gpad;
}

static void
remove_pad (gpointer ppad, gpointer unused)
{
  GstPad *pad = ppad;

  if (!gst_element_remove_pad ((GstElement *) GST_OBJECT_PARENT (pad), pad))
    g_warning ("Couldn't remove pad %s from element %s",
        GST_OBJECT_NAME (pad), GST_OBJECT_NAME (GST_OBJECT_PARENT (pad)));
}

static gboolean
prepare_link_maybe_ghosting (GstPad ** src, GstPad ** sink,
    GSList ** pads_created)
{
  GstObject *root;
  GstObject *e1, *e2;
  GSList *pads_created_local = NULL;

  g_assert (pads_created);

  e1 = GST_OBJECT_PARENT (*src);
  e2 = GST_OBJECT_PARENT (*sink);

  if (G_UNLIKELY (e1 == NULL)) {
    GST_WARNING ("Trying to ghost a pad that doesn't have a parent: %"
        GST_PTR_FORMAT, *src);
    return FALSE;
  }
  if (G_UNLIKELY (e2 == NULL)) {
    GST_WARNING ("Trying to ghost a pad that doesn't have a parent: %"
        GST_PTR_FORMAT, *sink);
    return FALSE;
  }

  if (GST_OBJECT_PARENT (e1) == GST_OBJECT_PARENT (e2)) {
    GST_CAT_INFO (GST_CAT_PADS, "%s and %s in same bin, no need for ghost pads",
        GST_OBJECT_NAME (e1), GST_OBJECT_NAME (e2));
    return TRUE;
  }

  GST_CAT_INFO (GST_CAT_PADS, "%s and %s not in same bin, making ghost pads",
      GST_OBJECT_NAME (e1), GST_OBJECT_NAME (e2));

  /* we need to setup some ghost pads */
  root = find_common_root (e1, e2);
  if (!root) {
    if (GST_OBJECT_PARENT (e1) == NULL)
      g_warning ("Trying to link elements %s and %s that don't share a common "
          "ancestor: %s hasn't been added to a bin or pipeline, but %s is in %s",
          GST_ELEMENT_NAME (e1), GST_ELEMENT_NAME (e2),
          GST_ELEMENT_NAME (e1), GST_ELEMENT_NAME (e2),
          GST_ELEMENT_NAME (GST_OBJECT_PARENT (e2)));
    else if (GST_OBJECT_PARENT (e2) == NULL)
      g_warning ("Trying to link elements %s and %s that don't share a common "
          "ancestor: %s hasn't been added to a bin or pipeline, and %s is in %s",
          GST_ELEMENT_NAME (e1), GST_ELEMENT_NAME (e2),
          GST_ELEMENT_NAME (e2), GST_ELEMENT_NAME (e1),
          GST_ELEMENT_NAME (GST_OBJECT_PARENT (e1)));
    else
      g_warning ("Trying to link elements %s and %s that don't share a common "
          "ancestor: %s is in %s, and %s is in %s",
          GST_ELEMENT_NAME (e1), GST_ELEMENT_NAME (e2),
          GST_ELEMENT_NAME (e1), GST_ELEMENT_NAME (GST_OBJECT_PARENT (e1)),
          GST_ELEMENT_NAME (e2), GST_ELEMENT_NAME (GST_OBJECT_PARENT (e2)));
    return FALSE;
  }

  while (GST_OBJECT_PARENT (e1) != root) {
    *src = ghost_up ((GstElement *) e1, *src);
    if (!*src)
      goto cleanup_fail;
    e1 = GST_OBJECT_PARENT (*src);
    pads_created_local = g_slist_prepend (pads_created_local, *src);
  }
  while (GST_OBJECT_PARENT (e2) != root) {
    *sink = ghost_up ((GstElement *) e2, *sink);
    if (!*sink)
      goto cleanup_fail;
    e2 = GST_OBJECT_PARENT (*sink);
    pads_created_local = g_slist_prepend (pads_created_local, *sink);
  }

  gst_object_unref (root);
  *pads_created = g_slist_concat (*pads_created, pads_created_local);
  return TRUE;

cleanup_fail:
  gst_object_unref (root);
  g_slist_foreach (pads_created_local, remove_pad, NULL);
  g_slist_free (pads_created_local);
  return FALSE;
}

static gboolean
pad_link_maybe_ghosting (GstPad * src, GstPad * sink, GstPadLinkCheck flags)
{
  GSList *pads_created = NULL;
  gboolean ret;

  if (!prepare_link_maybe_ghosting (&src, &sink, &pads_created)) {
    ret = FALSE;
  } else {
    ret = (gst_pad_link_full (src, sink, flags) == GST_PAD_LINK_OK);
  }

  if (!ret) {
    g_slist_foreach (pads_created, remove_pad, NULL);
  }
  g_slist_free (pads_created);

  return ret;
}

/**
 * gst_pad_link_maybe_ghosting_full:
 * @src: a #GstPad
 * @sink: a #GstPad
 * @flags: some #GstPadLinkCheck flags
 *
 * Links @src to @sink, creating any #GstGhostPad's in between as necessary.
 *
 * This is a convenience function to save having to create and add intermediate
 * #GstGhostPad's as required for linking across #GstBin boundaries.
 *
 * If @src or @sink pads don't have parent elements or do not share a common
 * ancestor, the link will fail.
 *
 * Calling gst_pad_link_maybe_ghosting_full() with
 * @flags == %GST_PAD_LINK_CHECK_DEFAULT is the recommended way of linking
 * pads with safety checks applied.
 *
 * Returns: whether the link succeeded.
 *
 * Since: 1.10
 */
gboolean
gst_pad_link_maybe_ghosting_full (GstPad * src, GstPad * sink,
    GstPadLinkCheck flags)
{
  g_return_val_if_fail (GST_IS_PAD (src), FALSE);
  g_return_val_if_fail (GST_IS_PAD (sink), FALSE);

  return pad_link_maybe_ghosting (src, sink, flags);
}

/**
 * gst_pad_link_maybe_ghosting:
 * @src: a #GstPad
 * @sink: a #GstPad
 *
 * Links @src to @sink, creating any #GstGhostPad's in between as necessary.
 *
 * This is a convenience function to save having to create and add intermediate
 * #GstGhostPad's as required for linking across #GstBin boundaries.
 *
 * If @src or @sink pads don't have parent elements or do not share a common
 * ancestor, the link will fail.
 *
 * Returns: whether the link succeeded.
 *
 * Since: 1.10
 */
gboolean
gst_pad_link_maybe_ghosting (GstPad * src, GstPad * sink)
{
  g_return_val_if_fail (GST_IS_PAD (src), FALSE);
  g_return_val_if_fail (GST_IS_PAD (sink), FALSE);

  return gst_pad_link_maybe_ghosting_full (src, sink,
      GST_PAD_LINK_CHECK_DEFAULT);
}

static void
release_and_unref_pad (GstElement * element, GstPad * pad, gboolean requestpad)
{
  if (pad) {
    if (requestpad)
      gst_element_release_request_pad (element, pad);
    gst_object_unref (pad);
  }
}

/**
 * gst_element_link_pads_full:
 * @src: a #GstElement containing the source pad.
 * @srcpadname: (allow-none): the name of the #GstPad in source element
 *     or %NULL for any pad.
 * @dest: (transfer none): the #GstElement containing the destination pad.
 * @destpadname: (allow-none): the name of the #GstPad in destination element,
 * or %NULL for any pad.
 * @flags: the #GstPadLinkCheck to be performed when linking pads.
 *
 * Links the two named pads of the source and destination elements.
 * Side effect is that if one of the pads has no parent, it becomes a
 * child of the parent of the other element.  If they have different
 * parents, the link fails.
 *
 * Calling gst_element_link_pads_full() with @flags == %GST_PAD_LINK_CHECK_DEFAULT
 * is the same as calling gst_element_link_pads() and the recommended way of
 * linking pads with safety checks applied.
 *
 * This is a convenience function for gst_pad_link_full().
 *
 * Returns: %TRUE if the pads could be linked, %FALSE otherwise.
 */
gboolean
gst_element_link_pads_full (GstElement * src, const gchar * srcpadname,
    GstElement * dest, const gchar * destpadname, GstPadLinkCheck flags)
{
  const GList *srcpads, *destpads, *srctempls, *desttempls, *l;
  GstPad *srcpad, *destpad;
  GstPadTemplate *srctempl, *desttempl;
  GstElementClass *srcclass, *destclass;
  gboolean srcrequest, destrequest;

  /* checks */
  g_return_val_if_fail (GST_IS_ELEMENT (src), FALSE);
  g_return_val_if_fail (GST_IS_ELEMENT (dest), FALSE);

  GST_CAT_INFO (GST_CAT_ELEMENT_PADS,
      "trying to link element %s:%s to element %s:%s", GST_ELEMENT_NAME (src),
      srcpadname ? srcpadname : "(any)", GST_ELEMENT_NAME (dest),
      destpadname ? destpadname : "(any)");

  srcrequest = FALSE;
  destrequest = FALSE;

  /* get a src pad */
  if (srcpadname) {
    /* name specified, look it up */
    if (!(srcpad = gst_element_get_static_pad (src, srcpadname))) {
      if ((srcpad = gst_element_get_request_pad (src, srcpadname)))
        srcrequest = TRUE;
    }
    if (!srcpad) {
      GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "no pad %s:%s",
          GST_ELEMENT_NAME (src), srcpadname);
      return FALSE;
    } else {
      if (!(GST_PAD_DIRECTION (srcpad) == GST_PAD_SRC)) {
        GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "pad %s:%s is no src pad",
            GST_DEBUG_PAD_NAME (srcpad));
        release_and_unref_pad (src, srcpad, srcrequest);
        return FALSE;
      }
      if (GST_PAD_PEER (srcpad) != NULL) {
        GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
            "pad %s:%s is already linked to %s:%s", GST_DEBUG_PAD_NAME (srcpad),
            GST_DEBUG_PAD_NAME (GST_PAD_PEER (srcpad)));
        /* already linked request pads look like static pads, so the request pad
         * was never requested a second time above, so no need to release it */
        gst_object_unref (srcpad);
        return FALSE;
      }
    }
    srcpads = NULL;
  } else {
    /* no name given, get the first available pad */
    GST_OBJECT_LOCK (src);
    srcpads = GST_ELEMENT_PADS (src);
    srcpad = srcpads ? GST_PAD_CAST (srcpads->data) : NULL;
    if (srcpad)
      gst_object_ref (srcpad);
    GST_OBJECT_UNLOCK (src);
  }

  /* get a destination pad */
  if (destpadname) {
    /* name specified, look it up */
    if (!(destpad = gst_element_get_static_pad (dest, destpadname))) {
      if ((destpad = gst_element_get_request_pad (dest, destpadname)))
        destrequest = TRUE;
    }
    if (!destpad) {
      GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "no pad %s:%s",
          GST_ELEMENT_NAME (dest), destpadname);
      release_and_unref_pad (src, srcpad, srcrequest);
      return FALSE;
    } else {
      if (!(GST_PAD_DIRECTION (destpad) == GST_PAD_SINK)) {
        GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "pad %s:%s is no sink pad",
            GST_DEBUG_PAD_NAME (destpad));
        release_and_unref_pad (src, srcpad, srcrequest);
        release_and_unref_pad (dest, destpad, destrequest);
        return FALSE;
      }
      if (GST_PAD_PEER (destpad) != NULL) {
        GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
            "pad %s:%s is already linked to %s:%s",
            GST_DEBUG_PAD_NAME (destpad),
            GST_DEBUG_PAD_NAME (GST_PAD_PEER (destpad)));
        release_and_unref_pad (src, srcpad, srcrequest);
        /* already linked request pads look like static pads, so the request pad
         * was never requested a second time above, so no need to release it */
        gst_object_unref (destpad);
        return FALSE;
      }
    }
    destpads = NULL;
  } else {
    /* no name given, get the first available pad */
    GST_OBJECT_LOCK (dest);
    destpads = GST_ELEMENT_PADS (dest);
    destpad = destpads ? GST_PAD_CAST (destpads->data) : NULL;
    if (destpad)
      gst_object_ref (destpad);
    GST_OBJECT_UNLOCK (dest);
  }

  if (srcpadname && destpadname) {
    gboolean result;

    /* two explicitly specified pads */
    result = pad_link_maybe_ghosting (srcpad, destpad, flags);

    if (result) {
      gst_object_unref (srcpad);
      gst_object_unref (destpad);
    } else {
      release_and_unref_pad (src, srcpad, srcrequest);
      release_and_unref_pad (dest, destpad, destrequest);
    }
    return result;
  }

  if (srcpad) {
    /* loop through the allowed pads in the source, trying to find a
     * compatible destination pad */
    GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
        "looping through allowed src and dest pads");
    do {
      GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "trying src pad %s:%s",
          GST_DEBUG_PAD_NAME (srcpad));
      if ((GST_PAD_DIRECTION (srcpad) == GST_PAD_SRC) &&
          (GST_PAD_PEER (srcpad) == NULL)) {
        gboolean temprequest = FALSE;
        GstPad *temp;

        if (destpadname) {
          temp = destpad;
          gst_object_ref (temp);
        } else {
          temp = gst_element_get_compatible_pad (dest, srcpad, NULL);
          if (temp && GST_PAD_PAD_TEMPLATE (temp)
              && GST_PAD_TEMPLATE_PRESENCE (GST_PAD_PAD_TEMPLATE (temp)) ==
              GST_PAD_REQUEST) {
            temprequest = TRUE;
          }
        }

        if (temp && pad_link_maybe_ghosting (srcpad, temp, flags)) {
          GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "linked pad %s:%s to pad %s:%s",
              GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (temp));
          if (destpad)
            gst_object_unref (destpad);
          gst_object_unref (srcpad);
          gst_object_unref (temp);
          return TRUE;
        }

        if (temp) {
          if (temprequest)
            gst_element_release_request_pad (dest, temp);
          gst_object_unref (temp);
        }
      }
      /* find a better way for this mess */
      if (srcpads) {
        srcpads = g_list_next (srcpads);
        if (srcpads) {
          gst_object_unref (srcpad);
          srcpad = GST_PAD_CAST (srcpads->data);
          gst_object_ref (srcpad);
        }
      }
    } while (srcpads);
  }
  if (srcpadname) {
    GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "no link possible from %s:%s to %s",
        GST_DEBUG_PAD_NAME (srcpad), GST_ELEMENT_NAME (dest));
    /* no need to release any request pad as both src- and destpadname must be
     * set to end up here, but this case has already been taken care of above */
    if (destpad)
      gst_object_unref (destpad);
    destpad = NULL;
  }
  if (srcpad) {
    release_and_unref_pad (src, srcpad, srcrequest);
    srcpad = NULL;
  }

  if (destpad) {
    /* loop through the existing pads in the destination */
    do {
      GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "trying dest pad %s:%s",
          GST_DEBUG_PAD_NAME (destpad));
      if ((GST_PAD_DIRECTION (destpad) == GST_PAD_SINK) &&
          (GST_PAD_PEER (destpad) == NULL)) {
        GstPad *temp = gst_element_get_compatible_pad (src, destpad, NULL);
        gboolean temprequest = FALSE;

        if (temp && GST_PAD_PAD_TEMPLATE (temp)
            && GST_PAD_TEMPLATE_PRESENCE (GST_PAD_PAD_TEMPLATE (temp)) ==
            GST_PAD_REQUEST) {
          temprequest = TRUE;
        }

        if (temp && pad_link_maybe_ghosting (temp, destpad, flags)) {
          GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "linked pad %s:%s to pad %s:%s",
              GST_DEBUG_PAD_NAME (temp), GST_DEBUG_PAD_NAME (destpad));
          gst_object_unref (temp);
          gst_object_unref (destpad);
          return TRUE;
        }

        release_and_unref_pad (src, temp, temprequest);
      }
      if (destpads) {
        destpads = g_list_next (destpads);
        if (destpads) {
          gst_object_unref (destpad);
          destpad = GST_PAD_CAST (destpads->data);
          gst_object_ref (destpad);
        }
      }
    } while (destpads);
  }

  if (destpadname) {
    GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "no link possible from %s to %s:%s",
        GST_ELEMENT_NAME (src), GST_DEBUG_PAD_NAME (destpad));
    release_and_unref_pad (dest, destpad, destrequest);
    return FALSE;
  } else {
    /* no need to release any request pad as the case of unset destpatname and
     * destpad being a requst pad has already been taken care of when looking
     * though the destination pads above */
    if (destpad) {
      gst_object_unref (destpad);
    }
    destpad = NULL;
  }

  srcclass = GST_ELEMENT_GET_CLASS (src);
  destclass = GST_ELEMENT_GET_CLASS (dest);

  GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
      "we might have request pads on both sides, checking...");
  srctempls = gst_element_class_get_pad_template_list (srcclass);
  desttempls = gst_element_class_get_pad_template_list (destclass);

  if (srctempls && desttempls) {
    while (srctempls) {
      srctempl = (GstPadTemplate *) srctempls->data;
      if (srctempl->presence == GST_PAD_REQUEST) {
        for (l = desttempls; l; l = l->next) {
          desttempl = (GstPadTemplate *) l->data;
          if (desttempl->presence == GST_PAD_REQUEST &&
              desttempl->direction != srctempl->direction) {
            GstCaps *srccaps, *destcaps;

            srccaps = gst_pad_template_get_caps (srctempl);
            destcaps = gst_pad_template_get_caps (desttempl);
            if (gst_caps_is_always_compatible (srccaps, destcaps)) {
              srcpad =
                  gst_element_request_pad (src, srctempl,
                  srctempl->name_template, NULL);
              destpad =
                  gst_element_request_pad (dest, desttempl,
                  desttempl->name_template, NULL);
              if (srcpad && destpad
                  && pad_link_maybe_ghosting (srcpad, destpad, flags)) {
                GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
                    "linked pad %s:%s to pad %s:%s",
                    GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (destpad));
                gst_object_unref (srcpad);
                gst_object_unref (destpad);
                gst_caps_unref (srccaps);
                gst_caps_unref (destcaps);
                return TRUE;
              }
              /* it failed, so we release the request pads */
              if (srcpad) {
                gst_element_release_request_pad (src, srcpad);
                gst_object_unref (srcpad);
              }
              if (destpad) {
                gst_element_release_request_pad (dest, destpad);
                gst_object_unref (destpad);
              }
            }
            gst_caps_unref (srccaps);
            gst_caps_unref (destcaps);
          }
        }
      }
      srctempls = srctempls->next;
    }
  }

  GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "no link possible from %s to %s",
      GST_ELEMENT_NAME (src), GST_ELEMENT_NAME (dest));
  return FALSE;
}

/**
 * gst_element_link_pads:
 * @src: a #GstElement containing the source pad.
 * @srcpadname: (allow-none): the name of the #GstPad in source element
 *     or %NULL for any pad.
 * @dest: (transfer none): the #GstElement containing the destination pad.
 * @destpadname: (allow-none): the name of the #GstPad in destination element,
 * or %NULL for any pad.
 *
 * Links the two named pads of the source and destination elements.
 * Side effect is that if one of the pads has no parent, it becomes a
 * child of the parent of the other element.  If they have different
 * parents, the link fails.
 *
 * Returns: %TRUE if the pads could be linked, %FALSE otherwise.
 */
gboolean
gst_element_link_pads (GstElement * src, const gchar * srcpadname,
    GstElement * dest, const gchar * destpadname)
{
  return gst_element_link_pads_full (src, srcpadname, dest, destpadname,
      GST_PAD_LINK_CHECK_DEFAULT);
}

/**
 * gst_element_link_pads_filtered:
 * @src: a #GstElement containing the source pad.
 * @srcpadname: (allow-none): the name of the #GstPad in source element
 *     or %NULL for any pad.
 * @dest: (transfer none): the #GstElement containing the destination pad.
 * @destpadname: (allow-none): the name of the #GstPad in destination element
 *     or %NULL for any pad.
 * @filter: (transfer none) (allow-none): the #GstCaps to filter the link,
 *     or %NULL for no filter.
 *
 * Links the two named pads of the source and destination elements. Side effect
 * is that if one of the pads has no parent, it becomes a child of the parent of
 * the other element. If they have different parents, the link fails. If @caps
 * is not %NULL, makes sure that the caps of the link is a subset of @caps.
 *
 * Returns: %TRUE if the pads could be linked, %FALSE otherwise.
 */
gboolean
gst_element_link_pads_filtered (GstElement * src, const gchar * srcpadname,
    GstElement * dest, const gchar * destpadname, GstCaps * filter)
{
  /* checks */
  g_return_val_if_fail (GST_IS_ELEMENT (src), FALSE);
  g_return_val_if_fail (GST_IS_ELEMENT (dest), FALSE);
  g_return_val_if_fail (filter == NULL || GST_IS_CAPS (filter), FALSE);

  if (filter) {
    GstElement *capsfilter;
    GstObject *parent;
    GstState state, pending;
    gboolean lr1, lr2;

    capsfilter = gst_element_factory_make ("capsfilter", NULL);
    if (!capsfilter) {
      GST_ERROR ("Could not make a capsfilter");
      return FALSE;
    }

    parent = gst_object_get_parent (GST_OBJECT (src));
    g_return_val_if_fail (GST_IS_BIN (parent), FALSE);

    gst_element_get_state (GST_ELEMENT_CAST (parent), &state, &pending, 0);

    if (!gst_bin_add (GST_BIN (parent), capsfilter)) {
      GST_ERROR ("Could not add capsfilter");
      gst_object_unref (capsfilter);
      gst_object_unref (parent);
      return FALSE;
    }

    if (pending != GST_STATE_VOID_PENDING)
      state = pending;

    gst_element_set_state (capsfilter, state);

    gst_object_unref (parent);

    g_object_set (capsfilter, "caps", filter, NULL);

    lr1 = gst_element_link_pads (src, srcpadname, capsfilter, "sink");
    lr2 = gst_element_link_pads (capsfilter, "src", dest, destpadname);
    if (lr1 && lr2) {
      return TRUE;
    } else {
      if (!lr1) {
        GST_INFO ("Could not link pads: %s:%s - capsfilter:sink",
            GST_ELEMENT_NAME (src), srcpadname);
      } else {
        GST_INFO ("Could not link pads: capsfilter:src - %s:%s",
            GST_ELEMENT_NAME (dest), destpadname);
      }
      gst_element_set_state (capsfilter, GST_STATE_NULL);
      /* this will unlink and unref as appropriate */
      gst_bin_remove (GST_BIN (GST_OBJECT_PARENT (capsfilter)), capsfilter);
      return FALSE;
    }
  } else {
    if (gst_element_link_pads (src, srcpadname, dest, destpadname)) {
      return TRUE;
    } else {
      GST_INFO ("Could not link pads: %s:%s - %s:%s", GST_ELEMENT_NAME (src),
          srcpadname, GST_ELEMENT_NAME (dest), destpadname);
      return FALSE;
    }
  }
}

/**
 * gst_element_link:
 * @src: (transfer none): a #GstElement containing the source pad.
 * @dest: (transfer none): the #GstElement containing the destination pad.
 *
 * Links @src to @dest. The link must be from source to
 * destination; the other direction will not be tried. The function looks for
 * existing pads that aren't linked yet. It will request new pads if necessary.
 * Such pads need to be released manually when unlinking.
 * If multiple links are possible, only one is established.
 *
 * Make sure you have added your elements to a bin or pipeline with
 * gst_bin_add() before trying to link them.
 *
 * Returns: %TRUE if the elements could be linked, %FALSE otherwise.
 */
gboolean
gst_element_link (GstElement * src, GstElement * dest)
{
  return gst_element_link_pads (src, NULL, dest, NULL);
}

/**
 * gst_element_link_many:
 * @element_1: (transfer none): the first #GstElement in the link chain.
 * @element_2: (transfer none): the second #GstElement in the link chain.
 * @...: the %NULL-terminated list of elements to link in order.
 *
 * Chain together a series of elements. Uses gst_element_link().
 * Make sure you have added your elements to a bin or pipeline with
 * gst_bin_add() before trying to link them.
 *
 * Returns: %TRUE on success, %FALSE otherwise.
 */
gboolean
gst_element_link_many (GstElement * element_1, GstElement * element_2, ...)
{
  gboolean res = TRUE;
  va_list args;

  g_return_val_if_fail (GST_IS_ELEMENT (element_1), FALSE);
  g_return_val_if_fail (GST_IS_ELEMENT (element_2), FALSE);

  va_start (args, element_2);

  while (element_2) {
    if (!gst_element_link (element_1, element_2)) {
      res = FALSE;
      break;
    }

    element_1 = element_2;
    element_2 = va_arg (args, GstElement *);
  }

  va_end (args);

  return res;
}

/**
 * gst_element_link_filtered:
 * @src: a #GstElement containing the source pad.
 * @dest: (transfer none): the #GstElement containing the destination pad.
 * @filter: (transfer none) (allow-none): the #GstCaps to filter the link,
 *     or %NULL for no filter.
 *
 * Links @src to @dest using the given caps as filtercaps.
 * The link must be from source to
 * destination; the other direction will not be tried. The function looks for
 * existing pads that aren't linked yet. It will request new pads if necessary.
 * If multiple links are possible, only one is established.
 *
 * Make sure you have added your elements to a bin or pipeline with
 * gst_bin_add() before trying to link them.
 *
 * Returns: %TRUE if the pads could be linked, %FALSE otherwise.
 */
gboolean
gst_element_link_filtered (GstElement * src, GstElement * dest,
    GstCaps * filter)
{
  return gst_element_link_pads_filtered (src, NULL, dest, NULL, filter);
}

/**
 * gst_element_unlink_pads:
 * @src: a (transfer none): #GstElement containing the source pad.
 * @srcpadname: the name of the #GstPad in source element.
 * @dest: (transfer none): a #GstElement containing the destination pad.
 * @destpadname: the name of the #GstPad in destination element.
 *
 * Unlinks the two named pads of the source and destination elements.
 *
 * This is a convenience function for gst_pad_unlink().
 */
void
gst_element_unlink_pads (GstElement * src, const gchar * srcpadname,
    GstElement * dest, const gchar * destpadname)
{
  GstPad *srcpad, *destpad;
  gboolean srcrequest, destrequest;

  srcrequest = destrequest = FALSE;

  g_return_if_fail (src != NULL);
  g_return_if_fail (GST_IS_ELEMENT (src));
  g_return_if_fail (srcpadname != NULL);
  g_return_if_fail (dest != NULL);
  g_return_if_fail (GST_IS_ELEMENT (dest));
  g_return_if_fail (destpadname != NULL);

  /* obtain the pads requested */
  if (!(srcpad = gst_element_get_static_pad (src, srcpadname)))
    if ((srcpad = gst_element_get_request_pad (src, srcpadname)))
      srcrequest = TRUE;
  if (srcpad == NULL) {
    GST_WARNING_OBJECT (src, "source element has no pad \"%s\"", srcpadname);
    return;
  }
  if (!(destpad = gst_element_get_static_pad (dest, destpadname)))
    if ((destpad = gst_element_get_request_pad (dest, destpadname)))
      destrequest = TRUE;
  if (destpad == NULL) {
    GST_WARNING_OBJECT (dest, "destination element has no pad \"%s\"",
        destpadname);
    goto free_src;
  }

  /* we're satisfied they can be unlinked, let's do it */
  gst_pad_unlink (srcpad, destpad);

  if (destrequest)
    gst_element_release_request_pad (dest, destpad);
  gst_object_unref (destpad);

free_src:
  if (srcrequest)
    gst_element_release_request_pad (src, srcpad);
  gst_object_unref (srcpad);
}

/**
 * gst_element_unlink_many:
 * @element_1: (transfer none): the first #GstElement in the link chain.
 * @element_2: (transfer none): the second #GstElement in the link chain.
 * @...: the %NULL-terminated list of elements to unlink in order.
 *
 * Unlinks a series of elements. Uses gst_element_unlink().
 */
void
gst_element_unlink_many (GstElement * element_1, GstElement * element_2, ...)
{
  va_list args;

  g_return_if_fail (element_1 != NULL && element_2 != NULL);
  g_return_if_fail (GST_IS_ELEMENT (element_1) && GST_IS_ELEMENT (element_2));

  va_start (args, element_2);

  while (element_2) {
    gst_element_unlink (element_1, element_2);

    element_1 = element_2;
    element_2 = va_arg (args, GstElement *);
  }

  va_end (args);
}

/**
 * gst_element_unlink:
 * @src: (transfer none): the source #GstElement to unlink.
 * @dest: (transfer none): the sink #GstElement to unlink.
 *
 * Unlinks all source pads of the source element with all sink pads
 * of the sink element to which they are linked.
 *
 * If the link has been made using gst_element_link(), it could have created an
 * requestpad, which has to be released using gst_element_release_request_pad().
 */
void
gst_element_unlink (GstElement * src, GstElement * dest)
{
  GstIterator *pads;
  gboolean done = FALSE;
  GValue data = { 0, };

  g_return_if_fail (GST_IS_ELEMENT (src));
  g_return_if_fail (GST_IS_ELEMENT (dest));

  GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "unlinking \"%s\" and \"%s\"",
      GST_ELEMENT_NAME (src), GST_ELEMENT_NAME (dest));

  pads = gst_element_iterate_pads (src);
  while (!done) {
    switch (gst_iterator_next (pads, &data)) {
      case GST_ITERATOR_OK:
      {
        GstPad *pad = g_value_get_object (&data);

        if (GST_PAD_IS_SRC (pad)) {
          GstPad *peerpad = gst_pad_get_peer (pad);

          /* see if the pad is linked and is really a pad of dest */
          if (peerpad) {
            GstElement *peerelem;

            peerelem = gst_pad_get_parent_element (peerpad);

            if (peerelem == dest) {
              gst_pad_unlink (pad, peerpad);
            }
            if (peerelem)
              gst_object_unref (peerelem);

            gst_object_unref (peerpad);
          }
        }
        g_value_reset (&data);
        break;
      }
      case GST_ITERATOR_RESYNC:
        gst_iterator_resync (pads);
        break;
      case GST_ITERATOR_DONE:
        done = TRUE;
        break;
      default:
        g_assert_not_reached ();
        break;
    }
  }
  g_value_unset (&data);
  gst_iterator_free (pads);
}

/**
 * gst_element_query_position:
 * @element: a #GstElement to invoke the position query on.
 * @format: the #GstFormat requested
 * @cur: (out) (allow-none): a location in which to store the current
 *     position, or %NULL.
 *
 * Queries an element (usually top-level pipeline or playbin element) for the
 * stream position in nanoseconds. This will be a value between 0 and the
 * stream duration (if the stream duration is known). This query will usually
 * only work once the pipeline is prerolled (i.e. reached PAUSED or PLAYING
 * state). The application will receive an ASYNC_DONE message on the pipeline
 * bus when that is the case.
 *
 * If one repeatedly calls this function one can also create a query and reuse
 * it in gst_element_query().
 *
 * Returns: %TRUE if the query could be performed.
 */
gboolean
gst_element_query_position (GstElement * element, GstFormat format,
    gint64 * cur)
{
  GstQuery *query;
  gboolean ret;

  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
  g_return_val_if_fail (format != GST_FORMAT_UNDEFINED, FALSE);

  query = gst_query_new_position (format);
  ret = gst_element_query (element, query);

  if (ret)
    gst_query_parse_position (query, NULL, cur);

  gst_query_unref (query);

  return ret;
}

/**
 * gst_element_query_duration:
 * @element: a #GstElement to invoke the duration query on.
 * @format: the #GstFormat requested
 * @duration: (out) (allow-none): A location in which to store the total duration, or %NULL.
 *
 * Queries an element (usually top-level pipeline or playbin element) for the
 * total stream duration in nanoseconds. This query will only work once the
 * pipeline is prerolled (i.e. reached PAUSED or PLAYING state). The application
 * will receive an ASYNC_DONE message on the pipeline bus when that is the case.
 *
 * If the duration changes for some reason, you will get a DURATION_CHANGED
 * message on the pipeline bus, in which case you should re-query the duration
 * using this function.
 *
 * Returns: %TRUE if the query could be performed.
 */
gboolean
gst_element_query_duration (GstElement * element, GstFormat format,
    gint64 * duration)
{
  GstQuery *query;
  gboolean ret;

  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
  g_return_val_if_fail (format != GST_FORMAT_UNDEFINED, FALSE);

  query = gst_query_new_duration (format);
  ret = gst_element_query (element, query);

  if (ret)
    gst_query_parse_duration (query, NULL, duration);

  gst_query_unref (query);

  return ret;
}

/**
 * gst_element_query_convert:
 * @element: a #GstElement to invoke the convert query on.
 * @src_format: a #GstFormat to convert from.
 * @src_val: a value to convert.
 * @dest_format: the #GstFormat to convert to.
 * @dest_val: (out): a pointer to the result.
 *
 * Queries an element to convert @src_val in @src_format to @dest_format.
 *
 * Returns: %TRUE if the query could be performed.
 */
gboolean
gst_element_query_convert (GstElement * element, GstFormat src_format,
    gint64 src_val, GstFormat dest_format, gint64 * dest_val)
{
  GstQuery *query;
  gboolean ret;

  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
  g_return_val_if_fail (dest_format != GST_FORMAT_UNDEFINED, FALSE);
  g_return_val_if_fail (dest_val != NULL, FALSE);

  if (dest_format == src_format || src_val == -1) {
    *dest_val = src_val;
    return TRUE;
  }

  query = gst_query_new_convert (src_format, src_val, dest_format);
  ret = gst_element_query (element, query);

  if (ret)
    gst_query_parse_convert (query, NULL, NULL, NULL, dest_val);

  gst_query_unref (query);

  return ret;
}

/**
 * gst_element_seek_simple:
 * @element: a #GstElement to seek on
 * @format: a #GstFormat to execute the seek in, such as #GST_FORMAT_TIME
 * @seek_flags: seek options; playback applications will usually want to use
 *            GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_KEY_UNIT here
 * @seek_pos: position to seek to (relative to the start); if you are doing
 *            a seek in #GST_FORMAT_TIME this value is in nanoseconds -
 *            multiply with #GST_SECOND to convert seconds to nanoseconds or
 *            with #GST_MSECOND to convert milliseconds to nanoseconds.
 *
 * Simple API to perform a seek on the given element, meaning it just seeks
 * to the given position relative to the start of the stream. For more complex
 * operations like segment seeks (e.g. for looping) or changing the playback
 * rate or seeking relative to the last configured playback segment you should
 * use gst_element_seek().
 *
 * In a completely prerolled PAUSED or PLAYING pipeline, seeking is always
 * guaranteed to return %TRUE on a seekable media type or %FALSE when the media
 * type is certainly not seekable (such as a live stream).
 *
 * Some elements allow for seeking in the READY state, in this
 * case they will store the seek event and execute it when they are put to
 * PAUSED. If the element supports seek in READY, it will always return %TRUE when
 * it receives the event in the READY state.
 *
 * Returns: %TRUE if the seek operation succeeded. Flushing seeks will trigger a
 * preroll, which will emit %GST_MESSAGE_ASYNC_DONE.
 */
gboolean
gst_element_seek_simple (GstElement * element, GstFormat format,
    GstSeekFlags seek_flags, gint64 seek_pos)
{
  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
  g_return_val_if_fail (seek_pos >= 0, FALSE);

  return gst_element_seek (element, 1.0, format, seek_flags,
      GST_SEEK_TYPE_SET, seek_pos, GST_SEEK_TYPE_SET, GST_CLOCK_TIME_NONE);
}

/**
 * gst_pad_use_fixed_caps:
 * @pad: the pad to use
 *
 * A helper function you can use that sets the FIXED_CAPS flag
 * This way the default CAPS query will always return the negotiated caps
 * or in case the pad is not negotiated, the padtemplate caps.
 *
 * The negotiated caps are the caps of the last CAPS event that passed on the
 * pad. Use this function on a pad that, once it negotiated to a CAPS, cannot
 * be renegotiated to something else.
 */
void
gst_pad_use_fixed_caps (GstPad * pad)
{
  GST_OBJECT_FLAG_SET (pad, GST_PAD_FLAG_FIXED_CAPS);
}

/**
 * gst_pad_get_parent_element:
 * @pad: a pad
 *
 * Gets the parent of @pad, cast to a #GstElement. If a @pad has no parent or
 * its parent is not an element, return %NULL.
 *
 * Returns: (transfer full) (nullable): the parent of the pad. The
 * caller has a reference on the parent, so unref when you're finished
 * with it.
 *
 * MT safe.
 */
GstElement *
gst_pad_get_parent_element (GstPad * pad)
{
  GstObject *p;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  p = gst_object_get_parent (GST_OBJECT_CAST (pad));

  if (p && !GST_IS_ELEMENT (p)) {
    gst_object_unref (p);
    p = NULL;
  }
  return GST_ELEMENT_CAST (p);
}

/**
 * gst_object_default_error:
 * @source: the #GstObject that initiated the error.
 * @error: (in): the GError.
 * @debug: (in) (allow-none): an additional debug information string, or %NULL
 *
 * A default error function that uses g_printerr() to display the error message
 * and the optional debug sting..
 *
 * The default handler will simply print the error string using g_print.
 */
void
gst_object_default_error (GstObject * source, const GError * error,
    const gchar * debug)
{
  gchar *name = gst_object_get_path_string (source);

  g_printerr (_("ERROR: from element %s: %s\n"), name, error->message);
  if (debug)
    g_printerr (_("Additional debug info:\n%s\n"), debug);

  g_free (name);
}

/**
 * gst_bin_add_many:
 * @bin: a #GstBin
 * @element_1: (transfer full): the #GstElement element to add to the bin
 * @...: (transfer full): additional elements to add to the bin
 *
 * Adds a %NULL-terminated list of elements to a bin.  This function is
 * equivalent to calling gst_bin_add() for each member of the list. The return
 * value of each gst_bin_add() is ignored.
 */
void
gst_bin_add_many (GstBin * bin, GstElement * element_1, ...)
{
  va_list args;

  g_return_if_fail (GST_IS_BIN (bin));
  g_return_if_fail (GST_IS_ELEMENT (element_1));

  va_start (args, element_1);

  while (element_1) {
    gst_bin_add (bin, element_1);

    element_1 = va_arg (args, GstElement *);
  }

  va_end (args);
}

/**
 * gst_bin_remove_many:
 * @bin: a #GstBin
 * @element_1: (transfer none): the first #GstElement to remove from the bin
 * @...: (transfer none): %NULL-terminated list of elements to remove from the bin
 *
 * Remove a list of elements from a bin. This function is equivalent
 * to calling gst_bin_remove() with each member of the list.
 */
void
gst_bin_remove_many (GstBin * bin, GstElement * element_1, ...)
{
  va_list args;

  g_return_if_fail (GST_IS_BIN (bin));
  g_return_if_fail (GST_IS_ELEMENT (element_1));

  va_start (args, element_1);

  while (element_1) {
    gst_bin_remove (bin, element_1);

    element_1 = va_arg (args, GstElement *);
  }

  va_end (args);
}

typedef struct
{
  GstQuery *query;
  gboolean ret;
} QueryAcceptCapsData;

static gboolean
query_accept_caps_func (GstPad * pad, QueryAcceptCapsData * data)
{
  if (G_LIKELY (gst_pad_peer_query (pad, data->query))) {
    gboolean result;

    gst_query_parse_accept_caps_result (data->query, &result);
    data->ret &= result;
  }
  return FALSE;
}

/**
 * gst_pad_proxy_query_accept_caps:
 * @pad: a #GstPad to proxy.
 * @query: an ACCEPT_CAPS #GstQuery.
 *
 * Checks if all internally linked pads of @pad accepts the caps in @query and
 * returns the intersection of the results.
 *
 * This function is useful as a default accept caps query function for an element
 * that can handle any stream format, but requires caps that are acceptable for
 * all opposite pads.
 *
 * Returns: %TRUE if @query could be executed
 */
gboolean
gst_pad_proxy_query_accept_caps (GstPad * pad, GstQuery * query)
{
  QueryAcceptCapsData data;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (GST_IS_QUERY (query), FALSE);
  g_return_val_if_fail (GST_QUERY_TYPE (query) == GST_QUERY_ACCEPT_CAPS, FALSE);

  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad,
      "proxying accept caps query for %s:%s", GST_DEBUG_PAD_NAME (pad));

  data.query = query;
  /* value to hold the return, by default it holds TRUE */
  /* FIXME: TRUE is wrong when there are no pads */
  data.ret = TRUE;

  gst_pad_forward (pad, (GstPadForwardFunction) query_accept_caps_func, &data);
  gst_query_set_accept_caps_result (query, data.ret);

  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "proxying accept caps query: %d",
      data.ret);

  return data.ret;
}

typedef struct
{
  GstQuery *query;
  GstCaps *ret;
} QueryCapsData;

static gboolean
query_caps_func (GstPad * pad, QueryCapsData * data)
{
  gboolean empty = FALSE;

  if (G_LIKELY (gst_pad_peer_query (pad, data->query))) {
    GstCaps *peercaps, *intersection;

    gst_query_parse_caps_result (data->query, &peercaps);
    GST_DEBUG_OBJECT (pad, "intersect with result %" GST_PTR_FORMAT, peercaps);
    intersection = gst_caps_intersect (data->ret, peercaps);
    GST_DEBUG_OBJECT (pad, "intersected %" GST_PTR_FORMAT, intersection);

    gst_caps_unref (data->ret);
    data->ret = intersection;

    /* stop when empty */
    empty = gst_caps_is_empty (intersection);
  }
  return empty;
}

/**
 * gst_pad_proxy_query_caps:
 * @pad: a #GstPad to proxy.
 * @query: a CAPS #GstQuery.
 *
 * Calls gst_pad_query_caps() for all internally linked pads of @pad and returns
 * the intersection of the results.
 *
 * This function is useful as a default caps query function for an element
 * that can handle any stream format, but requires all its pads to have
 * the same caps.  Two such elements are tee and adder.
 *
 * Returns: %TRUE if @query could be executed
 */
gboolean
gst_pad_proxy_query_caps (GstPad * pad, GstQuery * query)
{
  GstCaps *filter, *templ, *result;
  QueryCapsData data;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (GST_IS_QUERY (query), FALSE);
  g_return_val_if_fail (GST_QUERY_TYPE (query) == GST_QUERY_CAPS, FALSE);

  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "proxying caps query for %s:%s",
      GST_DEBUG_PAD_NAME (pad));

  data.query = query;

  /* value to hold the return, by default it holds the filter or ANY */
  gst_query_parse_caps (query, &filter);
  data.ret = filter ? gst_caps_ref (filter) : gst_caps_new_any ();

  gst_pad_forward (pad, (GstPadForwardFunction) query_caps_func, &data);

  templ = gst_pad_get_pad_template_caps (pad);
  result = gst_caps_intersect (data.ret, templ);
  gst_caps_unref (data.ret);
  gst_caps_unref (templ);

  gst_query_set_caps_result (query, result);
  gst_caps_unref (result);

  /* FIXME: return something depending on the processing */
  return TRUE;
}

/**
 * gst_pad_query_position:
 * @pad: a #GstPad to invoke the position query on.
 * @format: the #GstFormat requested
 * @cur: (out) (allow-none): A location in which to store the current position, or %NULL.
 *
 * Queries a pad for the stream position.
 *
 * Returns: %TRUE if the query could be performed.
 */
gboolean
gst_pad_query_position (GstPad * pad, GstFormat format, gint64 * cur)
{
  GstQuery *query;
  gboolean ret;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (format != GST_FORMAT_UNDEFINED, FALSE);

  query = gst_query_new_position (format);
  if ((ret = gst_pad_query (pad, query)))
    gst_query_parse_position (query, NULL, cur);
  gst_query_unref (query);

  return ret;
}

/**
 * gst_pad_peer_query_position:
 * @pad: a #GstPad on whose peer to invoke the position query on.
 *       Must be a sink pad.
 * @format: the #GstFormat requested
 * @cur: (out) (allow-none): a location in which to store the current
 *     position, or %NULL.
 *
 * Queries the peer of a given sink pad for the stream position.
 *
 * Returns: %TRUE if the query could be performed.
 */
gboolean
gst_pad_peer_query_position (GstPad * pad, GstFormat format, gint64 * cur)
{
  GstQuery *query;
  gboolean ret = FALSE;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (format != GST_FORMAT_UNDEFINED, FALSE);

  query = gst_query_new_position (format);
  if ((ret = gst_pad_peer_query (pad, query)))
    gst_query_parse_position (query, NULL, cur);
  gst_query_unref (query);

  return ret;
}

/**
 * gst_pad_query_duration:
 * @pad: a #GstPad to invoke the duration query on.
 * @format: the #GstFormat requested
 * @duration: (out) (allow-none): a location in which to store the total
 *     duration, or %NULL.
 *
 * Queries a pad for the total stream duration.
 *
 * Returns: %TRUE if the query could be performed.
 */
gboolean
gst_pad_query_duration (GstPad * pad, GstFormat format, gint64 * duration)
{
  GstQuery *query;
  gboolean ret;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (format != GST_FORMAT_UNDEFINED, FALSE);

  query = gst_query_new_duration (format);
  if ((ret = gst_pad_query (pad, query)))
    gst_query_parse_duration (query, NULL, duration);
  gst_query_unref (query);

  return ret;
}

/**
 * gst_pad_peer_query_duration:
 * @pad: a #GstPad on whose peer pad to invoke the duration query on.
 *       Must be a sink pad.
 * @format: the #GstFormat requested
 * @duration: (out) (allow-none): a location in which to store the total
 *     duration, or %NULL.
 *
 * Queries the peer pad of a given sink pad for the total stream duration.
 *
 * Returns: %TRUE if the query could be performed.
 */
gboolean
gst_pad_peer_query_duration (GstPad * pad, GstFormat format, gint64 * duration)
{
  GstQuery *query;
  gboolean ret = FALSE;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (GST_PAD_IS_SINK (pad), FALSE);
  g_return_val_if_fail (format != GST_FORMAT_UNDEFINED, FALSE);

  query = gst_query_new_duration (format);
  if ((ret = gst_pad_peer_query (pad, query)))
    gst_query_parse_duration (query, NULL, duration);
  gst_query_unref (query);

  return ret;
}

/**
 * gst_pad_query_convert:
 * @pad: a #GstPad to invoke the convert query on.
 * @src_format: a #GstFormat to convert from.
 * @src_val: a value to convert.
 * @dest_format: the #GstFormat to convert to.
 * @dest_val: (out): a pointer to the result.
 *
 * Queries a pad to convert @src_val in @src_format to @dest_format.
 *
 * Returns: %TRUE if the query could be performed.
 */
gboolean
gst_pad_query_convert (GstPad * pad, GstFormat src_format, gint64 src_val,
    GstFormat dest_format, gint64 * dest_val)
{
  GstQuery *query;
  gboolean ret;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (dest_format != GST_FORMAT_UNDEFINED, FALSE);
  g_return_val_if_fail (dest_val != NULL, FALSE);

  if (dest_format == src_format || src_val == -1) {
    *dest_val = src_val;
    return TRUE;
  }

  query = gst_query_new_convert (src_format, src_val, dest_format);
  if ((ret = gst_pad_query (pad, query)))
    gst_query_parse_convert (query, NULL, NULL, NULL, dest_val);
  gst_query_unref (query);

  return ret;
}

/**
 * gst_pad_peer_query_convert:
 * @pad: a #GstPad, on whose peer pad to invoke the convert query on.
 *       Must be a sink pad.
 * @src_format: a #GstFormat to convert from.
 * @src_val: a value to convert.
 * @dest_format: the #GstFormat to convert to.
 * @dest_val: (out): a pointer to the result.
 *
 * Queries the peer pad of a given sink pad to convert @src_val in @src_format
 * to @dest_format.
 *
 * Returns: %TRUE if the query could be performed.
 */
gboolean
gst_pad_peer_query_convert (GstPad * pad, GstFormat src_format, gint64 src_val,
    GstFormat dest_format, gint64 * dest_val)
{
  GstQuery *query;
  gboolean ret = FALSE;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (GST_PAD_IS_SINK (pad), FALSE);
  g_return_val_if_fail (dest_format != GST_FORMAT_UNDEFINED, FALSE);
  g_return_val_if_fail (dest_val != NULL, FALSE);

  query = gst_query_new_convert (src_format, src_val, dest_format);
  if ((ret = gst_pad_peer_query (pad, query)))
    gst_query_parse_convert (query, NULL, NULL, NULL, dest_val);
  gst_query_unref (query);

  return ret;
}

/**
 * gst_pad_query_caps:
 * @pad: a  #GstPad to get the capabilities of.
 * @filter: (allow-none): suggested #GstCaps, or %NULL
 *
 * Gets the capabilities this pad can produce or consume.
 * Note that this method doesn't necessarily return the caps set by sending a
 * gst_event_new_caps() - use gst_pad_get_current_caps() for that instead.
 * gst_pad_query_caps returns all possible caps a pad can operate with, using
 * the pad's CAPS query function, If the query fails, this function will return
 * @filter, if not %NULL, otherwise ANY.
 *
 * When called on sinkpads @filter contains the caps that
 * upstream could produce in the order preferred by upstream. When
 * called on srcpads @filter contains the caps accepted by
 * downstream in the preferred order. @filter might be %NULL but
 * if it is not %NULL the returned caps will be a subset of @filter.
 *
 * Note that this function does not return writable #GstCaps, use
 * gst_caps_make_writable() before modifying the caps.
 *
 * Returns: (transfer full): the caps of the pad with incremented ref-count.
 */
GstCaps *
gst_pad_query_caps (GstPad * pad, GstCaps * filter)
{
  GstCaps *result = NULL;
  GstQuery *query;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);
  g_return_val_if_fail (filter == NULL || GST_IS_CAPS (filter), NULL);

  GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad,
      "get pad caps with filter %" GST_PTR_FORMAT, filter);

  query = gst_query_new_caps (filter);
  if (gst_pad_query (pad, query)) {
    gst_query_parse_caps_result (query, &result);
    gst_caps_ref (result);
    GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad,
        "query returned %" GST_PTR_FORMAT, result);
  } else if (filter) {
    result = gst_caps_ref (filter);
  } else {
    result = gst_caps_new_any ();
  }
  gst_query_unref (query);

  return result;
}

/**
 * gst_pad_peer_query_caps:
 * @pad: a  #GstPad to get the capabilities of.
 * @filter: (allow-none): a #GstCaps filter, or %NULL.
 *
 * Gets the capabilities of the peer connected to this pad. Similar to
 * gst_pad_query_caps().
 *
 * When called on srcpads @filter contains the caps that
 * upstream could produce in the order preferred by upstream. When
 * called on sinkpads @filter contains the caps accepted by
 * downstream in the preferred order. @filter might be %NULL but
 * if it is not %NULL the returned caps will be a subset of @filter.
 *
 * Returns: (transfer full): the caps of the peer pad with incremented
 * ref-count. When there is no peer pad, this function returns @filter or,
 * when @filter is %NULL, ANY caps.
 */
GstCaps *
gst_pad_peer_query_caps (GstPad * pad, GstCaps * filter)
{
  GstCaps *result = NULL;
  GstQuery *query;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);
  g_return_val_if_fail (filter == NULL || GST_IS_CAPS (filter), NULL);

  GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad,
      "get pad peer caps with filter %" GST_PTR_FORMAT, filter);

  query = gst_query_new_caps (filter);
  if (gst_pad_peer_query (pad, query)) {
    gst_query_parse_caps_result (query, &result);
    gst_caps_ref (result);
    GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad,
        "peer query returned %" GST_PTR_FORMAT, result);
  } else if (filter) {
    result = gst_caps_ref (filter);
  } else {
    result = gst_caps_new_any ();
  }
  gst_query_unref (query);

  return result;
}

/**
 * gst_pad_query_accept_caps:
 * @pad: a #GstPad to check
 * @caps: a #GstCaps to check on the pad
 *
 * Check if the given pad accepts the caps.
 *
 * Returns: %TRUE if the pad can accept the caps.
 */
gboolean
gst_pad_query_accept_caps (GstPad * pad, GstCaps * caps)
{
  gboolean res = TRUE;
  GstQuery *query;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (GST_IS_CAPS (caps), FALSE);

  GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad, "accept caps of %"
      GST_PTR_FORMAT, caps);

  query = gst_query_new_accept_caps (caps);
  if (gst_pad_query (pad, query)) {
    gst_query_parse_accept_caps_result (query, &res);
    GST_DEBUG_OBJECT (pad, "query returned %d", res);
  }
  gst_query_unref (query);

  return res;
}

/**
 * gst_pad_peer_query_accept_caps:
 * @pad: a  #GstPad to check the peer of
 * @caps: a #GstCaps to check on the pad
 *
 * Check if the peer of @pad accepts @caps. If @pad has no peer, this function
 * returns %TRUE.
 *
 * Returns: %TRUE if the peer of @pad can accept the caps or @pad has no peer.
 */
gboolean
gst_pad_peer_query_accept_caps (GstPad * pad, GstCaps * caps)
{
  gboolean res = TRUE;
  GstQuery *query;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (GST_IS_CAPS (caps), FALSE);

  query = gst_query_new_accept_caps (caps);
  if (gst_pad_peer_query (pad, query)) {
    gst_query_parse_accept_caps_result (query, &res);
    GST_DEBUG_OBJECT (pad, "query returned %d", res);
  }
  gst_query_unref (query);

  return res;
}

static GstPad *
element_find_unlinked_pad (GstElement * element, GstPadDirection direction)
{
  GstIterator *iter;
  GstPad *unlinked_pad = NULL;
  gboolean done;
  GValue data = { 0, };

  switch (direction) {
    case GST_PAD_SRC:
      iter = gst_element_iterate_src_pads (element);
      break;
    case GST_PAD_SINK:
      iter = gst_element_iterate_sink_pads (element);
      break;
    default:
      g_return_val_if_reached (NULL);
  }

  done = FALSE;
  while (!done) {
    switch (gst_iterator_next (iter, &data)) {
      case GST_ITERATOR_OK:{
        GstPad *peer;
        GstPad *pad = g_value_get_object (&data);

        GST_CAT_LOG (GST_CAT_ELEMENT_PADS, "examining pad %s:%s",
            GST_DEBUG_PAD_NAME (pad));

        peer = gst_pad_get_peer (pad);
        if (peer == NULL) {
          unlinked_pad = gst_object_ref (pad);
          done = TRUE;
          GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
              "found existing unlinked pad %s:%s",
              GST_DEBUG_PAD_NAME (unlinked_pad));
        } else {
          gst_object_unref (peer);
        }
        g_value_reset (&data);
        break;
      }
      case GST_ITERATOR_DONE:
        done = TRUE;
        break;
      case GST_ITERATOR_RESYNC:
        gst_iterator_resync (iter);
        break;
      case GST_ITERATOR_ERROR:
        g_return_val_if_reached (NULL);
        break;
    }
  }
  g_value_unset (&data);
  gst_iterator_free (iter);

  return unlinked_pad;
}

/**
 * gst_bin_find_unlinked_pad:
 * @bin: bin in which to look for elements with unlinked pads
 * @direction: whether to look for an unlinked source or sink pad
 *
 * Recursively looks for elements with an unlinked pad of the given
 * direction within the specified bin and returns an unlinked pad
 * if one is found, or %NULL otherwise. If a pad is found, the caller
 * owns a reference to it and should use gst_object_unref() on the
 * pad when it is not needed any longer.
 *
 * Returns: (transfer full) (nullable): unlinked pad of the given
 * direction, %NULL.
 */
GstPad *
gst_bin_find_unlinked_pad (GstBin * bin, GstPadDirection direction)
{
  GstIterator *iter;
  gboolean done;
  GstPad *pad = NULL;
  GValue data = { 0, };

  g_return_val_if_fail (GST_IS_BIN (bin), NULL);
  g_return_val_if_fail (direction != GST_PAD_UNKNOWN, NULL);

  done = FALSE;
  iter = gst_bin_iterate_recurse (bin);
  while (!done) {
    switch (gst_iterator_next (iter, &data)) {
      case GST_ITERATOR_OK:{
        GstElement *element = g_value_get_object (&data);

        pad = element_find_unlinked_pad (element, direction);
        if (pad != NULL)
          done = TRUE;
        g_value_reset (&data);
        break;
      }
      case GST_ITERATOR_DONE:
        done = TRUE;
        break;
      case GST_ITERATOR_RESYNC:
        gst_iterator_resync (iter);
        break;
      case GST_ITERATOR_ERROR:
        g_return_val_if_reached (NULL);
        break;
    }
  }
  g_value_unset (&data);
  gst_iterator_free (iter);

  return pad;
}

static void
gst_bin_sync_children_states_foreach (const GValue * value, gpointer user_data)
{
  gboolean *success = user_data;
  GstElement *element = g_value_get_object (value);

  if (gst_element_is_locked_state (element)) {
    *success = TRUE;
  } else {
    *success = *success && gst_element_sync_state_with_parent (element);

    if (GST_IS_BIN (element))
      *success = *success
          && gst_bin_sync_children_states (GST_BIN_CAST (element));
  }
}

/**
 * gst_bin_sync_children_states:
 * @bin: a #GstBin
 *
 * Synchronizes the state of every child of @bin with the state
 * of @bin. See also gst_element_sync_state_with_parent().
 *
 * Returns: %TRUE if syncing the state was successful for all children,
 *  otherwise %FALSE.
 *
 * Since: 1.6
 */
gboolean
gst_bin_sync_children_states (GstBin * bin)
{
  GstIterator *it;
  GstIteratorResult res = GST_ITERATOR_OK;
  gboolean success = TRUE;

  it = gst_bin_iterate_sorted (bin);

  do {
    if (res == GST_ITERATOR_RESYNC) {
      success = TRUE;
      gst_iterator_resync (it);
    }
    res =
        gst_iterator_foreach (it, gst_bin_sync_children_states_foreach,
        &success);
  } while (res == GST_ITERATOR_RESYNC);
  gst_iterator_free (it);

  return success;
}

/**
 * gst_parse_bin_from_description:
 * @bin_description: command line describing the bin
 * @ghost_unlinked_pads: whether to automatically create ghost pads
 *     for unlinked source or sink pads within the bin
 * @err: where to store the error message in case of an error, or %NULL
 *
 * This is a convenience wrapper around gst_parse_launch() to create a
 * #GstBin from a gst-launch-style pipeline description. See
 * gst_parse_launch() and the gst-launch man page for details about the
 * syntax. Ghost pads on the bin for unlinked source or sink pads
 * within the bin can automatically be created (but only a maximum of
 * one ghost pad for each direction will be created; if you expect
 * multiple unlinked source pads or multiple unlinked sink pads
 * and want them all ghosted, you will have to create the ghost pads
 * yourself).
 *
 * Returns: (transfer floating) (type Gst.Bin) (nullable): a
 *   newly-created bin, or %NULL if an error occurred.
 */
GstElement *
gst_parse_bin_from_description (const gchar * bin_description,
    gboolean ghost_unlinked_pads, GError ** err)
{
  return gst_parse_bin_from_description_full (bin_description,
      ghost_unlinked_pads, NULL, GST_PARSE_FLAG_NONE, err);
}

/**
 * gst_parse_bin_from_description_full:
 * @bin_description: command line describing the bin
 * @ghost_unlinked_pads: whether to automatically create ghost pads
 *     for unlinked source or sink pads within the bin
 * @context: (transfer none) (allow-none): a parse context allocated with
 *     gst_parse_context_new(), or %NULL
 * @flags: parsing options, or #GST_PARSE_FLAG_NONE
 * @err: where to store the error message in case of an error, or %NULL
 *
 * This is a convenience wrapper around gst_parse_launch() to create a
 * #GstBin from a gst-launch-style pipeline description. See
 * gst_parse_launch() and the gst-launch man page for details about the
 * syntax. Ghost pads on the bin for unlinked source or sink pads
 * within the bin can automatically be created (but only a maximum of
 * one ghost pad for each direction will be created; if you expect
 * multiple unlinked source pads or multiple unlinked sink pads
 * and want them all ghosted, you will have to create the ghost pads
 * yourself).
 *
 * Returns: (transfer floating) (type Gst.Element): a newly-created
 *   element, which is guaranteed to be a bin unless
 *   GST_FLAG_NO_SINGLE_ELEMENT_BINS was passed, or %NULL if an error
 *   occurred.
 */
GstElement *
gst_parse_bin_from_description_full (const gchar * bin_description,
    gboolean ghost_unlinked_pads, GstParseContext * context,
    GstParseFlags flags, GError ** err)
{
#ifndef GST_DISABLE_PARSE
  GstPad *pad = NULL;
  GstElement *element;
  GstBin *bin;
  gchar *desc;

  g_return_val_if_fail (bin_description != NULL, NULL);
  g_return_val_if_fail (err == NULL || *err == NULL, NULL);

  GST_DEBUG ("Making bin from description '%s'", bin_description);

  /* parse the pipeline to a bin */
  if (flags & GST_PARSE_FLAG_NO_SINGLE_ELEMENT_BINS) {
    element = gst_parse_launch_full (bin_description, context, flags, err);
  } else {
    desc = g_strdup_printf ("bin.( %s )", bin_description);
    element = gst_parse_launch_full (desc, context, flags, err);
    g_free (desc);
  }

  if (element == NULL || (err && *err != NULL)) {
    if (element)
      gst_object_unref (element);
    return NULL;
  }

  if (GST_IS_BIN (element)) {
    bin = GST_BIN (element);
  } else {
    return element;
  }

  /* find pads and ghost them if necessary */
  if (ghost_unlinked_pads) {
    if ((pad = gst_bin_find_unlinked_pad (bin, GST_PAD_SRC))) {
      gst_element_add_pad (GST_ELEMENT (bin), gst_ghost_pad_new ("src", pad));
      gst_object_unref (pad);
    }
    if ((pad = gst_bin_find_unlinked_pad (bin, GST_PAD_SINK))) {
      gst_element_add_pad (GST_ELEMENT (bin), gst_ghost_pad_new ("sink", pad));
      gst_object_unref (pad);
    }
  }

  return GST_ELEMENT (bin);
#else
  gchar *msg;

  GST_WARNING ("Disabled API called");

  msg = gst_error_get_message (GST_CORE_ERROR, GST_CORE_ERROR_DISABLED);
  g_set_error (err, GST_CORE_ERROR, GST_CORE_ERROR_DISABLED, "%s", msg);
  g_free (msg);

  return NULL;
#endif
}

/**
 * gst_util_get_timestamp:
 *
 * Get a timestamp as GstClockTime to be used for interval measurements.
 * The timestamp should not be interpreted in any other way.
 *
 * Returns: the timestamp
 */
GstClockTime
gst_util_get_timestamp (void)
{
#if defined (HAVE_POSIX_TIMERS) && defined(HAVE_MONOTONIC_CLOCK) &&\
    defined (HAVE_CLOCK_GETTIME)
  struct timespec now;

  clock_gettime (CLOCK_MONOTONIC, &now);
  return GST_TIMESPEC_TO_TIME (now);
#else
  GTimeVal now;

  g_get_current_time (&now);
  return GST_TIMEVAL_TO_TIME (now);
#endif
}

/**
 * gst_util_array_binary_search:
 * @array: the sorted input array
 * @num_elements: number of elements in the array
 * @element_size: size of every element in bytes
 * @search_func: (scope call): function to compare two elements, @search_data will always be passed as second argument
 * @mode: search mode that should be used
 * @search_data: element that should be found
 * @user_data: (closure): data to pass to @search_func
 *
 * Searches inside @array for @search_data by using the comparison function
 * @search_func. @array must be sorted ascending.
 *
 * As @search_data is always passed as second argument to @search_func it's
 * not required that @search_data has the same type as the array elements.
 *
 * The complexity of this search function is O(log (num_elements)).
 *
 * Returns: (transfer none) (nullable): The address of the found
 * element or %NULL if nothing was found
 */
gpointer
gst_util_array_binary_search (gpointer array, guint num_elements,
    gsize element_size, GCompareDataFunc search_func, GstSearchMode mode,
    gconstpointer search_data, gpointer user_data)
{
  glong left = 0, right = num_elements - 1, m;
  gint ret;
  guint8 *data = (guint8 *) array;

  g_return_val_if_fail (array != NULL, NULL);
  g_return_val_if_fail (element_size > 0, NULL);
  g_return_val_if_fail (search_func != NULL, NULL);

  /* 0. No elements => return NULL */
  if (num_elements == 0)
    return NULL;

  /* 1. If search_data is before the 0th element return the 0th element */
  ret = search_func (data, search_data, user_data);
  if ((ret >= 0 && mode == GST_SEARCH_MODE_AFTER) || ret == 0)
    return data;
  else if (ret > 0)
    return NULL;

  /* 2. If search_data is after the last element return the last element */
  ret =
      search_func (data + (num_elements - 1) * element_size, search_data,
      user_data);
  if ((ret <= 0 && mode == GST_SEARCH_MODE_BEFORE) || ret == 0)
    return data + (num_elements - 1) * element_size;
  else if (ret < 0)
    return NULL;

  /* 3. else binary search */
  while (TRUE) {
    m = left + (right - left) / 2;

    ret = search_func (data + m * element_size, search_data, user_data);

    if (ret == 0) {
      return data + m * element_size;
    } else if (ret < 0) {
      left = m + 1;
    } else {
      right = m - 1;
    }

    /* No exact match found */
    if (right < left) {
      if (mode == GST_SEARCH_MODE_EXACT) {
        return NULL;
      } else if (mode == GST_SEARCH_MODE_AFTER) {
        if (ret < 0)
          return (m < num_elements) ? data + (m + 1) * element_size : NULL;
        else
          return data + m * element_size;
      } else {
        if (ret < 0)
          return data + m * element_size;
        else
          return (m > 0) ? data + (m - 1) * element_size : NULL;
      }
    }
  }
}

/* Finds the greatest common divisor.
 * Returns 1 if none other found.
 * This is Euclid's algorithm. */

/**
 * gst_util_greatest_common_divisor:
 * @a: First value as #gint
 * @b: Second value as #gint
 *
 * Calculates the greatest common divisor of @a
 * and @b.
 *
 * Returns: Greatest common divisor of @a and @b
 */
gint
gst_util_greatest_common_divisor (gint a, gint b)
{
  while (b != 0) {
    int temp = a;

    a = b;
    b = temp % b;
  }

  return ABS (a);
}

/**
 * gst_util_greatest_common_divisor_int64:
 * @a: First value as #gint64
 * @b: Second value as #gint64
 *
 * Calculates the greatest common divisor of @a
 * and @b.
 *
 * Returns: Greatest common divisor of @a and @b
 */
gint64
gst_util_greatest_common_divisor_int64 (gint64 a, gint64 b)
{
  while (b != 0) {
    gint64 temp = a;

    a = b;
    b = temp % b;
  }

  return ABS (a);
}


/**
 * gst_util_fraction_to_double:
 * @src_n: Fraction numerator as #gint
 * @src_d: Fraction denominator #gint
 * @dest: (out): pointer to a #gdouble for the result
 *
 * Transforms a fraction to a #gdouble.
 */
void
gst_util_fraction_to_double (gint src_n, gint src_d, gdouble * dest)
{
  g_return_if_fail (dest != NULL);
  g_return_if_fail (src_d != 0);

  *dest = ((gdouble) src_n) / ((gdouble) src_d);
}

#define MAX_TERMS       30
#define MIN_DIVISOR     1.0e-10
#define MAX_ERROR       1.0e-20

/* use continued fractions to transform a double into a fraction,
 * see http://mathforum.org/dr.math/faq/faq.fractions.html#decfrac.
 * This algorithm takes care of overflows.
 */

/**
 * gst_util_double_to_fraction:
 * @src: #gdouble to transform
 * @dest_n: (out): pointer to a #gint to hold the result numerator
 * @dest_d: (out): pointer to a #gint to hold the result denominator
 *
 * Transforms a #gdouble to a fraction and simplifies
 * the result.
 */
void
gst_util_double_to_fraction (gdouble src, gint * dest_n, gint * dest_d)
{

  gdouble V, F;                 /* double being converted */
  gint N, D;                    /* will contain the result */
  gint A;                       /* current term in continued fraction */
  gint64 N1, D1;                /* numerator, denominator of last approx */
  gint64 N2, D2;                /* numerator, denominator of previous approx */
  gint i;
  gint gcd;
  gboolean negative = FALSE;

  g_return_if_fail (dest_n != NULL);
  g_return_if_fail (dest_d != NULL);

  /* initialize fraction being converted */
  F = src;
  if (F < 0.0) {
    F = -F;
    negative = TRUE;
  }

  V = F;
  /* initialize fractions with 1/0, 0/1 */
  N1 = 1;
  D1 = 0;
  N2 = 0;
  D2 = 1;
  N = 1;
  D = 1;

  for (i = 0; i < MAX_TERMS; i++) {
    /* get next term */
    A = (gint) F;               /* no floor() needed, F is always >= 0 */
    /* get new divisor */
    F = F - A;

    /* calculate new fraction in temp */
    N2 = N1 * A + N2;
    D2 = D1 * A + D2;

    /* guard against overflow */
    if (N2 > G_MAXINT || D2 > G_MAXINT) {
      break;
    }

    N = N2;
    D = D2;

    /* save last two fractions */
    N2 = N1;
    D2 = D1;
    N1 = N;
    D1 = D;

    /* quit if dividing by zero or close enough to target */
    if (F < MIN_DIVISOR || fabs (V - ((gdouble) N) / D) < MAX_ERROR) {
      break;
    }

    /* Take reciprocal */
    F = 1 / F;
  }
  /* fix for overflow */
  if (D == 0) {
    N = G_MAXINT;
    D = 1;
  }
  /* fix for negative */
  if (negative)
    N = -N;

  /* simplify */
  gcd = gst_util_greatest_common_divisor (N, D);
  if (gcd) {
    N /= gcd;
    D /= gcd;
  }

  /* set results */
  *dest_n = N;
  *dest_d = D;
}

/**
 * gst_util_fraction_multiply:
 * @a_n: Numerator of first value
 * @a_d: Denominator of first value
 * @b_n: Numerator of second value
 * @b_d: Denominator of second value
 * @res_n: (out): Pointer to #gint to hold the result numerator
 * @res_d: (out): Pointer to #gint to hold the result denominator
 *
 * Multiplies the fractions @a_n/@a_d and @b_n/@b_d and stores
 * the result in @res_n and @res_d.
 *
 * Returns: %FALSE on overflow, %TRUE otherwise.
 */
gboolean
gst_util_fraction_multiply (gint a_n, gint a_d, gint b_n, gint b_d,
    gint * res_n, gint * res_d)
{
  gint gcd;

  g_return_val_if_fail (res_n != NULL, FALSE);
  g_return_val_if_fail (res_d != NULL, FALSE);
  g_return_val_if_fail (a_d != 0, FALSE);
  g_return_val_if_fail (b_d != 0, FALSE);

  /* early out if either is 0, as its gcd would be 0 */
  if (a_n == 0 || b_n == 0) {
    *res_n = 0;
    *res_d = 1;
    return TRUE;
  }

  gcd = gst_util_greatest_common_divisor (a_n, a_d);
  a_n /= gcd;
  a_d /= gcd;

  gcd = gst_util_greatest_common_divisor (b_n, b_d);
  b_n /= gcd;
  b_d /= gcd;

  gcd = gst_util_greatest_common_divisor (a_n, b_d);
  a_n /= gcd;
  b_d /= gcd;

  gcd = gst_util_greatest_common_divisor (a_d, b_n);
  a_d /= gcd;
  b_n /= gcd;

  /* This would result in overflow */
  if (a_n != 0 && G_MAXINT / ABS (a_n) < ABS (b_n))
    return FALSE;
  if (G_MAXINT / ABS (a_d) < ABS (b_d))
    return FALSE;

  *res_n = a_n * b_n;
  *res_d = a_d * b_d;

  gcd = gst_util_greatest_common_divisor (*res_n, *res_d);
  *res_n /= gcd;
  *res_d /= gcd;

  return TRUE;
}

/**
 * gst_util_fraction_add:
 * @a_n: Numerator of first value
 * @a_d: Denominator of first value
 * @b_n: Numerator of second value
 * @b_d: Denominator of second value
 * @res_n: (out): Pointer to #gint to hold the result numerator
 * @res_d: (out): Pointer to #gint to hold the result denominator
 *
 * Adds the fractions @a_n/@a_d and @b_n/@b_d and stores
 * the result in @res_n and @res_d.
 *
 * Returns: %FALSE on overflow, %TRUE otherwise.
 */
gboolean
gst_util_fraction_add (gint a_n, gint a_d, gint b_n, gint b_d, gint * res_n,
    gint * res_d)
{
  gint gcd;

  g_return_val_if_fail (res_n != NULL, FALSE);
  g_return_val_if_fail (res_d != NULL, FALSE);
  g_return_val_if_fail (a_d != 0, FALSE);
  g_return_val_if_fail (b_d != 0, FALSE);

  gcd = gst_util_greatest_common_divisor (a_n, a_d);
  a_n /= gcd;
  a_d /= gcd;

  gcd = gst_util_greatest_common_divisor (b_n, b_d);
  b_n /= gcd;
  b_d /= gcd;

  if (a_n == 0) {
    *res_n = b_n;
    *res_d = b_d;
    return TRUE;
  }
  if (b_n == 0) {
    *res_n = a_n;
    *res_d = a_d;
    return TRUE;
  }

  /* This would result in overflow */
  if (G_MAXINT / ABS (a_n) < ABS (b_n))
    return FALSE;
  if (G_MAXINT / ABS (a_d) < ABS (b_d))
    return FALSE;

  *res_n = (a_n * b_d) + (a_d * b_n);
  *res_d = a_d * b_d;

  gcd = gst_util_greatest_common_divisor (*res_n, *res_d);
  if (gcd) {
    *res_n /= gcd;
    *res_d /= gcd;
  } else {
    /* res_n == 0 */
    *res_d = 1;
  }

  return TRUE;
}

/**
 * gst_util_fraction_compare:
 * @a_n: Numerator of first value
 * @a_d: Denominator of first value
 * @b_n: Numerator of second value
 * @b_d: Denominator of second value
 *
 * Compares the fractions @a_n/@a_d and @b_n/@b_d and returns
 * -1 if a < b, 0 if a = b and 1 if a > b.
 *
 * Returns: -1 if a < b; 0 if a = b; 1 if a > b.
 */
gint
gst_util_fraction_compare (gint a_n, gint a_d, gint b_n, gint b_d)
{
  gint64 new_num_1;
  gint64 new_num_2;
  gint gcd;

  g_return_val_if_fail (a_d != 0 && b_d != 0, 0);

  /* Simplify */
  gcd = gst_util_greatest_common_divisor (a_n, a_d);
  a_n /= gcd;
  a_d /= gcd;

  gcd = gst_util_greatest_common_divisor (b_n, b_d);
  b_n /= gcd;
  b_d /= gcd;

  /* fractions are reduced when set, so we can quickly see if they're equal */
  if (a_n == b_n && a_d == b_d)
    return 0;

  /* extend to 64 bits */
  new_num_1 = ((gint64) a_n) * b_d;
  new_num_2 = ((gint64) b_n) * a_d;
  if (new_num_1 < new_num_2)
    return -1;
  if (new_num_1 > new_num_2)
    return 1;

  /* Should not happen because a_d and b_d are not 0 */
  g_return_val_if_reached (0);
}

static gchar *
gst_pad_create_stream_id_internal (GstPad * pad, GstElement * parent,
    const gchar * stream_id)
{
  GstEvent *upstream_event;
  gchar *upstream_stream_id = NULL, *new_stream_id;
  GstPad *sinkpad;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);
  g_return_val_if_fail (GST_PAD_IS_SRC (pad), NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (parent), NULL);

  g_return_val_if_fail (parent->numsinkpads <= 1, NULL);

  /* If the element has multiple source pads it must
   * provide a stream-id for every source pad, otherwise
   * all source pads will have the same and are not
   * distinguishable */
  g_return_val_if_fail (parent->numsrcpads <= 1 || stream_id, NULL);

  /* First try to get the upstream stream-start stream-id from the sinkpad.
   * This will only work for non-source elements */
  sinkpad = gst_element_get_static_pad (parent, "sink");
  if (sinkpad) {
    upstream_event =
        gst_pad_get_sticky_event (sinkpad, GST_EVENT_STREAM_START, 0);
    if (upstream_event) {
      const gchar *tmp;

      gst_event_parse_stream_start (upstream_event, &tmp);
      if (tmp)
        upstream_stream_id = g_strdup (tmp);
      gst_event_unref (upstream_event);
    }
    gst_object_unref (sinkpad);
  }

  /* The only case where we don't have an upstream start-start event
   * here is for source elements */
  if (!upstream_stream_id) {
    GstQuery *query;
    gchar *uri = NULL;

    /* Try to generate one from the URI query and
     * if it fails take a random number instead */
    query = gst_query_new_uri ();
    if (gst_element_query (parent, query)) {
      gst_query_parse_uri (query, &uri);
    }

    if (uri) {
      GChecksum *cs;

      /* And then generate an SHA256 sum of the URI */
      cs = g_checksum_new (G_CHECKSUM_SHA256);
      g_checksum_update (cs, (const guchar *) uri, strlen (uri));
      g_free (uri);
      upstream_stream_id = g_strdup (g_checksum_get_string (cs));
      g_checksum_free (cs);
    } else {
      /* Just get some random number if the URI query fails */
      GST_FIXME_OBJECT (pad, "Creating random stream-id, consider "
          "implementing a deterministic way of creating a stream-id");
      upstream_stream_id =
          g_strdup_printf ("%08x%08x%08x%08x", g_random_int (), g_random_int (),
          g_random_int (), g_random_int ());
    }

    gst_query_unref (query);
  }

  if (stream_id) {
    new_stream_id = g_strconcat (upstream_stream_id, "/", stream_id, NULL);
  } else {
    new_stream_id = g_strdup (upstream_stream_id);
  }

  g_free (upstream_stream_id);

  return new_stream_id;
}

/**
 * gst_pad_create_stream_id_printf_valist:
 * @pad: A source #GstPad
 * @parent: Parent #GstElement of @pad
 * @stream_id: (allow-none): The stream-id
 * @var_args: parameters for the @stream_id format string
 *
 * Creates a stream-id for the source #GstPad @pad by combining the
 * upstream information with the optional @stream_id of the stream
 * of @pad. @pad must have a parent #GstElement and which must have zero
 * or one sinkpad. @stream_id can only be %NULL if the parent element
 * of @pad has only a single source pad.
 *
 * This function generates an unique stream-id by getting the upstream
 * stream-start event stream ID and appending @stream_id to it. If the
 * element has no sinkpad it will generate an upstream stream-id by
 * doing an URI query on the element and in the worst case just uses
 * a random number. Source elements that don't implement the URI
 * handler interface should ideally generate a unique, deterministic
 * stream-id manually instead.
 *
 * Returns: A stream-id for @pad. g_free() after usage.
 */
gchar *
gst_pad_create_stream_id_printf_valist (GstPad * pad, GstElement * parent,
    const gchar * stream_id, va_list var_args)
{
  gchar *expanded = NULL, *new_stream_id;

  if (stream_id)
    expanded = g_strdup_vprintf (stream_id, var_args);

  new_stream_id = gst_pad_create_stream_id_internal (pad, parent, expanded);

  g_free (expanded);

  return new_stream_id;
}

/**
 * gst_pad_create_stream_id_printf:
 * @pad: A source #GstPad
 * @parent: Parent #GstElement of @pad
 * @stream_id: (allow-none): The stream-id
 * @...: parameters for the @stream_id format string
 *
 * Creates a stream-id for the source #GstPad @pad by combining the
 * upstream information with the optional @stream_id of the stream
 * of @pad. @pad must have a parent #GstElement and which must have zero
 * or one sinkpad. @stream_id can only be %NULL if the parent element
 * of @pad has only a single source pad.
 *
 * This function generates an unique stream-id by getting the upstream
 * stream-start event stream ID and appending @stream_id to it. If the
 * element has no sinkpad it will generate an upstream stream-id by
 * doing an URI query on the element and in the worst case just uses
 * a random number. Source elements that don't implement the URI
 * handler interface should ideally generate a unique, deterministic
 * stream-id manually instead.
 *
 * Returns: A stream-id for @pad. g_free() after usage.
 */
gchar *
gst_pad_create_stream_id_printf (GstPad * pad, GstElement * parent,
    const gchar * stream_id, ...)
{
  va_list var_args;
  gchar *new_stream_id;

  va_start (var_args, stream_id);
  new_stream_id =
      gst_pad_create_stream_id_printf_valist (pad, parent, stream_id, var_args);
  va_end (var_args);

  return new_stream_id;
}

/**
 * gst_pad_create_stream_id:
 * @pad: A source #GstPad
 * @parent: Parent #GstElement of @pad
 * @stream_id: (allow-none): The stream-id
 *
 * Creates a stream-id for the source #GstPad @pad by combining the
 * upstream information with the optional @stream_id of the stream
 * of @pad. @pad must have a parent #GstElement and which must have zero
 * or one sinkpad. @stream_id can only be %NULL if the parent element
 * of @pad has only a single source pad.
 *
 * This function generates an unique stream-id by getting the upstream
 * stream-start event stream ID and appending @stream_id to it. If the
 * element has no sinkpad it will generate an upstream stream-id by
 * doing an URI query on the element and in the worst case just uses
 * a random number. Source elements that don't implement the URI
 * handler interface should ideally generate a unique, deterministic
 * stream-id manually instead.
 *
 * Since stream IDs are sorted alphabetically, any numbers in the
 * stream ID should be printed with a fixed number of characters,
 * preceded by 0's, such as by using the format \%03u instead of \%u.
 *
 * Returns: A stream-id for @pad. g_free() after usage.
 */
gchar *
gst_pad_create_stream_id (GstPad * pad, GstElement * parent,
    const gchar * stream_id)
{
  return gst_pad_create_stream_id_internal (pad, parent, stream_id);
}

/**
 * gst_pad_get_stream_id:
 * @pad: A source #GstPad
 *
 * Returns the current stream-id for the @pad, or %NULL if none has been
 * set yet, i.e. the pad has not received a stream-start event yet.
 *
 * This is a convenience wrapper around gst_pad_get_sticky_event() and
 * gst_event_parse_stream_start().
 *
 * The returned stream-id string should be treated as an opaque string, its
 * contents should not be interpreted.
 *
 * Returns: (nullable): a newly-allocated copy of the stream-id for
 *     @pad, or %NULL.  g_free() the returned string when no longer
 *     needed.
 *
 * Since: 1.2
 */
gchar *
gst_pad_get_stream_id (GstPad * pad)
{
  const gchar *stream_id = NULL;
  GstEvent *event;
  gchar *ret = NULL;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  event = gst_pad_get_sticky_event (pad, GST_EVENT_STREAM_START, 0);
  if (event != NULL) {
    gst_event_parse_stream_start (event, &stream_id);
    ret = g_strdup (stream_id);
    gst_event_unref (event);
    GST_LOG_OBJECT (pad, "pad has stream-id '%s'", ret);
  } else {
    GST_DEBUG_OBJECT (pad, "pad has not received a stream-start event yet");
  }

  return ret;
}

/**
 * gst_pad_get_stream:
 * @pad: A source #GstPad
 *
 * Returns the current #GstStream for the @pad, or %NULL if none has been
 * set yet, i.e. the pad has not received a stream-start event yet.
 *
 * This is a convenience wrapper around gst_pad_get_sticky_event() and
 * gst_event_parse_stream().
 *
 * Returns: (nullable) (transfer full): the current #GstStream for @pad, or %NULL.
 *     unref the returned stream when no longer needed.
 *
 * Since: 1.10
 */
GstStream *
gst_pad_get_stream (GstPad * pad)
{
  GstStream *stream = NULL;
  GstEvent *event;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  event = gst_pad_get_sticky_event (pad, GST_EVENT_STREAM_START, 0);
  if (event != NULL) {
    gst_event_parse_stream (event, &stream);
    gst_event_unref (event);
    GST_LOG_OBJECT (pad, "pad has stream object %p", stream);
  } else {
    GST_DEBUG_OBJECT (pad, "pad has not received a stream-start event yet");
  }

  return stream;
}

/**
 * gst_util_group_id_next:
 *
 * Return a constantly incrementing group id.
 *
 * This function is used to generate a new group-id for the
 * stream-start event.
 *
 * Returns: A constantly incrementing unsigned integer, which might
 * overflow back to 0 at some point.
 */
guint
gst_util_group_id_next (void)
{
  static gint counter = 0;
  return g_atomic_int_add (&counter, 1);
}

/* Compute log2 of the passed 64-bit number by finding the highest set bit */
static guint
gst_log2 (GstClockTime in)
{
  const guint64 b[] =
      { 0x2, 0xC, 0xF0, 0xFF00, 0xFFFF0000, 0xFFFFFFFF00000000LL };
  const guint64 S[] = { 1, 2, 4, 8, 16, 32 };
  int i;

  guint count = 0;
  for (i = 5; i >= 0; i--) {
    if (in & b[i]) {
      in >>= S[i];
      count |= S[i];
    }
  }

  return count;
}

/**
 * gst_calculate_linear_regression:
 * @xy: Pairs of (x,y) values
 * @temp: Temporary scratch space used by the function
 * @n: number of (x,y) pairs
 * @m_num: (out): numerator of calculated slope
 * @m_denom: (out): denominator of calculated slope
 * @b: (out): Offset at Y-axis
 * @xbase: (out): Offset at X-axis
 * @r_squared: (out): R-squared
 *
 * Calculates the linear regression of the values @xy and places the
 * result in @m_num, @m_denom, @b and @xbase, representing the function
 *   y(x) = m_num/m_denom * (x - xbase) + b
 * that has the least-square distance from all points @x and @y.
 *
 * @r_squared will contain the remaining error.
 *
 * If @temp is not %NULL, it will be used as temporary space for the function,
 * in which case the function works without any allocation at all. If @temp is
 * %NULL, an allocation will take place. @temp should have at least the same
 * amount of memory allocated as @xy, i.e. 2*n*sizeof(GstClockTime).
 *
 * <note>This function assumes (x,y) values with reasonable large differences
 * between them. It will not calculate the exact results if the differences
 * between neighbouring values are too small due to not being able to
 * represent sub-integer values during the calculations.</note>
 *
 * Returns: %TRUE if the linear regression was successfully calculated
 *
 * Since: 1.12
 */
/* http://mathworld.wolfram.com/LeastSquaresFitting.html
 * with SLAVE_LOCK
 */
gboolean
gst_calculate_linear_regression (const GstClockTime * xy,
    GstClockTime * temp, guint n,
    GstClockTime * m_num, GstClockTime * m_denom,
    GstClockTime * b, GstClockTime * xbase, gdouble * r_squared)
{
  const GstClockTime *x, *y;
  GstClockTime *newx, *newy;
  GstClockTime xmin, ymin, xbar, ybar, xbar4, ybar4;
  GstClockTime xmax, ymax;
  GstClockTimeDiff sxx, sxy, syy;
  gint i, j;
  gint pshift = 0;
  gint max_bits;

  g_return_val_if_fail (xy != NULL, FALSE);
  g_return_val_if_fail (m_num != NULL, FALSE);
  g_return_val_if_fail (m_denom != NULL, FALSE);
  g_return_val_if_fail (b != NULL, FALSE);
  g_return_val_if_fail (xbase != NULL, FALSE);
  g_return_val_if_fail (r_squared != NULL, FALSE);

  x = xy;
  y = xy + 1;

  xbar = ybar = sxx = syy = sxy = 0;

  xmin = ymin = G_MAXUINT64;
  xmax = ymax = 0;
  for (i = j = 0; i < n; i++, j += 2) {
    xmin = MIN (xmin, x[j]);
    ymin = MIN (ymin, y[j]);

    xmax = MAX (xmax, x[j]);
    ymax = MAX (ymax, y[j]);
  }

  if (temp == NULL) {
    /* Allocate up to 1kb on the stack, otherwise heap */
    newx = n > 64 ? g_new (GstClockTime, 2 * n) : g_newa (GstClockTime, 2 * n);
    newy = newx + 1;
  } else {
    newx = temp;
    newy = temp + 1;
  }

  /* strip off unnecessary bits of precision */
  for (i = j = 0; i < n; i++, j += 2) {
    newx[j] = x[j] - xmin;
    newy[j] = y[j] - ymin;
  }

#ifdef DEBUGGING_ENABLED
  GST_CAT_DEBUG (GST_CAT_CLOCK, "reduced numbers:");
  for (i = j = 0; i < n; i++, j += 2)
    GST_CAT_DEBUG (GST_CAT_CLOCK,
        "  %" G_GUINT64_FORMAT "  %" G_GUINT64_FORMAT, newx[j], newy[j]);
#endif

  /* have to do this precisely otherwise the results are pretty much useless.
   * should guarantee that none of these accumulators can overflow */

  /* quantities on the order of 1e10 to 1e13 -> 30-35 bits;
   * window size a max of 2^10, so
   this addition could end up around 2^45 or so -- ample headroom */
  for (i = j = 0; i < n; i++, j += 2) {
    /* Just in case assumptions about headroom prove false, let's check */
    if ((newx[j] > 0 && G_MAXUINT64 - xbar <= newx[j]) ||
        (newy[j] > 0 && G_MAXUINT64 - ybar <= newy[j])) {
      GST_CAT_WARNING (GST_CAT_CLOCK,
          "Regression overflowed in clock slaving! xbar %"
          G_GUINT64_FORMAT " newx[j] %" G_GUINT64_FORMAT " ybar %"
          G_GUINT64_FORMAT " newy[j] %" G_GUINT64_FORMAT, xbar, newx[j], ybar,
          newy[j]);
      return FALSE;
    }

    xbar += newx[j];
    ybar += newy[j];
  }
  xbar /= n;
  ybar /= n;

  /* multiplying directly would give quantities on the order of 1e20-1e26 ->
   * 60 bits to 70 bits times the window size that's 80 which is too much.
   * Instead we (1) subtract off the xbar*ybar in the loop instead of after,
   * to avoid accumulation; (2) shift off some estimated number of bits from
   * each multiplicand to limit the expected ceiling. For strange
   * distributions of input values, things can still overflow, in which
   * case we drop precision and retry - at most a few times, in practice rarely
   */

  /* Guess how many bits we might need for the usual distribution of input,
   * with a fallback loop that drops precision if things go pear-shaped */
  max_bits = gst_log2 (MAX (xmax - xmin, ymax - ymin)) * 7 / 8 + gst_log2 (n);
  if (max_bits > 64)
    pshift = max_bits - 64;

  i = 0;
  do {
#ifdef DEBUGGING_ENABLED
    GST_CAT_DEBUG (GST_CAT_CLOCK,
        "Restarting regression with precision shift %u", pshift);
#endif

    xbar4 = xbar >> pshift;
    ybar4 = ybar >> pshift;
    sxx = syy = sxy = 0;
    for (i = j = 0; i < n; i++, j += 2) {
      GstClockTime newx4, newy4;
      GstClockTimeDiff tmp;

      newx4 = newx[j] >> pshift;
      newy4 = newy[j] >> pshift;

      tmp = (newx4 + xbar4) * (newx4 - xbar4);
      if (G_UNLIKELY (tmp > 0 && sxx > 0 && (G_MAXINT64 - sxx <= tmp))) {
        do {
          /* Drop some precision and restart */
          pshift++;
          sxx /= 4;
          tmp /= 4;
        } while (G_MAXINT64 - sxx <= tmp);
        break;
      } else if (G_UNLIKELY (tmp < 0 && sxx < 0 && (G_MAXINT64 - sxx >= tmp))) {
        do {
          /* Drop some precision and restart */
          pshift++;
          sxx /= 4;
          tmp /= 4;
        } while (G_MININT64 - sxx >= tmp);
        break;
      }
      sxx += tmp;

      tmp = newy4 * newy4 - ybar4 * ybar4;
      if (G_UNLIKELY (tmp > 0 && syy > 0 && (G_MAXINT64 - syy <= tmp))) {
        do {
          pshift++;
          syy /= 4;
          tmp /= 4;
        } while (G_MAXINT64 - syy <= tmp);
        break;
      } else if (G_UNLIKELY (tmp < 0 && syy < 0 && (G_MAXINT64 - syy >= tmp))) {
        do {
          pshift++;
          syy /= 4;
          tmp /= 4;
        } while (G_MININT64 - syy >= tmp);
        break;
      }
      syy += tmp;

      tmp = newx4 * newy4 - xbar4 * ybar4;
      if (G_UNLIKELY (tmp > 0 && sxy > 0 && (G_MAXINT64 - sxy <= tmp))) {
        do {
          pshift++;
          sxy /= 4;
          tmp /= 4;
        } while (G_MAXINT64 - sxy <= tmp);
        break;
      } else if (G_UNLIKELY (tmp < 0 && sxy < 0 && (G_MININT64 - sxy >= tmp))) {
        do {
          pshift++;
          sxy /= 4;
          tmp /= 4;
        } while (G_MININT64 - sxy >= tmp);
        break;
      }
      sxy += tmp;
    }
  } while (i < n);

  if (G_UNLIKELY (sxx == 0))
    goto invalid;

  *m_num = sxy;
  *m_denom = sxx;
  *b = (ymin + ybar) - gst_util_uint64_scale_round (xbar, *m_num, *m_denom);
  /* Report base starting from the most recent observation */
  *xbase = xmax;
  *b += gst_util_uint64_scale_round (xmax - xmin, *m_num, *m_denom);

  *r_squared = ((double) sxy * (double) sxy) / ((double) sxx * (double) syy);

#ifdef DEBUGGING_ENABLED
  GST_CAT_DEBUG (GST_CAT_CLOCK, "  m      = %g", ((double) *m_num) / *m_denom);
  GST_CAT_DEBUG (GST_CAT_CLOCK, "  b      = %" G_GUINT64_FORMAT, *b);
  GST_CAT_DEBUG (GST_CAT_CLOCK, "  xbase  = %" G_GUINT64_FORMAT, *xbase);
  GST_CAT_DEBUG (GST_CAT_CLOCK, "  r2     = %g", *r_squared);
#endif

  if (temp == NULL && n > 64)
    g_free (newx);

  return TRUE;

invalid:
  {
    GST_CAT_DEBUG (GST_CAT_CLOCK, "sxx == 0, regression failed");
    if (temp == NULL && n > 64)
      g_free (newx);
    return FALSE;
  }
}