gstaudio

gstaudio — Support library for audio elements

Synopsis

#include <gst/audio/audio.h>

enum                GstAudioFlags;
enum                GstAudioFormat;
enum                GstAudioFormatFlags;
struct              GstAudioFormatInfo;
struct              GstAudioInfo;
void                gst_audio_info_init                 (GstAudioInfo *info);
void                gst_audio_info_clear                (GstAudioInfo *info);
GstAudioInfo *      gst_audio_info_copy                 (GstAudioInfo *info);
void                gst_audio_info_free                 (GstAudioInfo *info);
gboolean            gst_audio_info_from_caps            (GstAudioInfo *info,
                                                         const GstCaps *caps);
GstCaps *           gst_audio_info_to_caps              (GstAudioInfo *info);
gboolean            gst_audio_info_convert              (GstAudioInfo *info,
                                                         GstFormat src_fmt,
                                                         gint64 src_val,
                                                         GstFormat dest_fmt,
                                                         gint64 *dest_val);
const GstAudioFormatInfo * gst_audio_format_get_info    (GstAudioFormat format);
#define             GST_AUDIO_FORMAT_INFO_DEPTH         (info)
#define             GST_AUDIO_FORMAT_INFO_ENDIANNESS    (info)
#define             GST_AUDIO_FORMAT_INFO_FLAGS         (info)
#define             GST_AUDIO_FORMAT_INFO_FORMAT        (info)
#define             GST_AUDIO_FORMAT_INFO_IS_FLOAT      (info)
#define             GST_AUDIO_FORMAT_INFO_IS_INTEGER    (info)
#define             GST_AUDIO_FORMAT_INFO_IS_BIG_ENDIAN (info)
#define             GST_AUDIO_FORMAT_INFO_IS_LITTLE_ENDIAN(info)
#define             GST_AUDIO_FORMAT_INFO_IS_SIGNED     (info)
#define             GST_AUDIO_FORMAT_INFO_NAME          (info)
#define             GST_AUDIO_FORMAT_INFO_WIDTH         (info)
#define             GST_AUDIO_INFO_BPF                  (info)
#define             GST_AUDIO_INFO_BPS                  (info)
#define             GST_AUDIO_INFO_CHANNELS             (info)
#define             GST_AUDIO_INFO_DEPTH                (i)
#define             GST_AUDIO_INFO_FLAGS                (info)
#define             GST_AUDIO_INFO_FORMAT               (i)
#define             GST_AUDIO_INFO_HAS_DEFAULT_POSITIONS(info)
#define             GST_AUDIO_INFO_NAME                 (i)
#define             GST_AUDIO_INFO_POSITION             (info,
                                                         c)
#define             GST_AUDIO_INFO_RATE                 (info)
#define             GST_AUDIO_INFO_WIDTH                (i)
enum                GstAudioFieldFlag;
#define             GST_FRAMES_TO_CLOCK_TIME            (frames,
                                                         rate)
#define             GST_CLOCK_TIME_TO_FRAMES            (clocktime,
                                                         rate)
#define             GST_AUDIO_DEF_RATE
#define             GST_AUDIO_FLOAT_PAD_TEMPLATE_CAPS
#define             GST_AUDIO_FLOAT_STANDARD_PAD_TEMPLATE_CAPS
#define             GST_AUDIO_INT_PAD_TEMPLATE_CAPS
#define             GST_AUDIO_INT_STANDARD_PAD_TEMPLATE_CAPS
int                 gst_audio_frame_byte_size           (GstPad *pad);
long                gst_audio_frame_length              (GstPad *pad,
                                                         GstBuffer *buf);
GstClockTime        gst_audio_duration_from_pad_buffer  (GstPad *pad,
                                                         GstBuffer *buf);
gboolean            gst_audio_is_buffer_framed          (GstPad *pad,
                                                         GstBuffer *buf);
void                gst_audio_structure_set_int         (GstStructure *structure,
                                                         GstAudioFieldFlag flag);
GstBuffer *         gst_audio_buffer_clip               (GstBuffer *buffer,
                                                         GstSegment *segment,
                                                         gint rate,
                                                         gint frame_size);

Description

This library contains some helper functions for audio elements.

Details

enum GstAudioFlags

typedef enum {
  GST_AUDIO_FLAG_NONE         = 0,
  GST_AUDIO_FLAG_DEFAULT_POSITIONS = (1 << 0)
} GstAudioFlags;

Extra audio flags

`GST_AUDIO_FLAG_NONE`	no valid flag
`GST_AUDIO_FLAG_DEFAULT_POSITIONS`	unpositioned audio layout, position array contains the default layout (meaning that the channel layout was not explicitly specified in the caps)

Since 0.10.36

enum GstAudioFormat

typedef enum {
  GST_AUDIO_FORMAT_UNKNOWN,
  /* 8 bit */
  GST_AUDIO_FORMAT_S8,
  GST_AUDIO_FORMAT_U8,
  /* 16 bit */
  GST_AUDIO_FORMAT_S16LE,
  GST_AUDIO_FORMAT_S16BE,
  GST_AUDIO_FORMAT_U16LE,
  GST_AUDIO_FORMAT_U16BE,
  /* 24 bit in low 3 bytes of 32 bits*/
  GST_AUDIO_FORMAT_S24_32LE,
  GST_AUDIO_FORMAT_S24_32BE,
  GST_AUDIO_FORMAT_U24_32LE,
  GST_AUDIO_FORMAT_U24_32BE,
  /* 32 bit */
  GST_AUDIO_FORMAT_S32LE,
  GST_AUDIO_FORMAT_S32BE,
  GST_AUDIO_FORMAT_U32LE,
  GST_AUDIO_FORMAT_U32BE,
  /* 24 bit in 3 bytes*/
  GST_AUDIO_FORMAT_S24LE,
  GST_AUDIO_FORMAT_S24BE,
  GST_AUDIO_FORMAT_U24LE,
  GST_AUDIO_FORMAT_U24BE,
  /* 20 bit in 3 bytes*/
  GST_AUDIO_FORMAT_S20LE,
  GST_AUDIO_FORMAT_S20BE,
  GST_AUDIO_FORMAT_U20LE,
  GST_AUDIO_FORMAT_U20BE,
  /* 18 bit in 3 bytes*/
  GST_AUDIO_FORMAT_S18LE,
  GST_AUDIO_FORMAT_S18BE,
  GST_AUDIO_FORMAT_U18LE,
  GST_AUDIO_FORMAT_U18BE,
  /* float */
  GST_AUDIO_FORMAT_F32LE,
  GST_AUDIO_FORMAT_F32BE,
  GST_AUDIO_FORMAT_F64LE,
  GST_AUDIO_FORMAT_F64BE,
  /* native endianness equivalents */
  GST_AUDIO_FORMAT_S16 = _GST_AUDIO_FORMAT_NE(S16),
  GST_AUDIO_FORMAT_U16 = _GST_AUDIO_FORMAT_NE(U16),
  GST_AUDIO_FORMAT_S24_32 = _GST_AUDIO_FORMAT_NE(S24_32),
  GST_AUDIO_FORMAT_U24_32 = _GST_AUDIO_FORMAT_NE(U24_32),
  GST_AUDIO_FORMAT_S32 = _GST_AUDIO_FORMAT_NE(S32),
  GST_AUDIO_FORMAT_U32 = _GST_AUDIO_FORMAT_NE(U32),
  GST_AUDIO_FORMAT_S24 = _GST_AUDIO_FORMAT_NE(S24),
  GST_AUDIO_FORMAT_U24 = _GST_AUDIO_FORMAT_NE(U24),
  GST_AUDIO_FORMAT_S20 = _GST_AUDIO_FORMAT_NE(S20),
  GST_AUDIO_FORMAT_U20 = _GST_AUDIO_FORMAT_NE(U20),
  GST_AUDIO_FORMAT_S18 = _GST_AUDIO_FORMAT_NE(S18),
  GST_AUDIO_FORMAT_U18 = _GST_AUDIO_FORMAT_NE(U18),
  GST_AUDIO_FORMAT_F32 = _GST_AUDIO_FORMAT_NE(F32),
  GST_AUDIO_FORMAT_F64 = _GST_AUDIO_FORMAT_NE(F64)
} GstAudioFormat;

Enum value describing the most common audio formats.

`GST_AUDIO_FORMAT_UNKNOWN`	unknown audio format
`GST_AUDIO_FORMAT_S8`	8 bits in 8 bits, signed
`GST_AUDIO_FORMAT_U8`	8 bits in 8 bits, unsigned
`GST_AUDIO_FORMAT_S16LE`	16 bits in 16 bits, signed, little endian
`GST_AUDIO_FORMAT_S16BE`	16 bits in 16 bits, signed, big endian
`GST_AUDIO_FORMAT_U16LE`	16 bits in 16 bits, unsigned, little endian
`GST_AUDIO_FORMAT_U16BE`	16 bits in 16 bits, unsigned, big endian
`GST_AUDIO_FORMAT_S24_32LE`	24 bits in 32 bits, signed, little endian
`GST_AUDIO_FORMAT_S24_32BE`	24 bits in 32 bits, signed, big endian
`GST_AUDIO_FORMAT_U24_32LE`	24 bits in 32 bits, unsigned, little endian
`GST_AUDIO_FORMAT_U24_32BE`	24 bits in 32 bits, unsigned, big endian
`GST_AUDIO_FORMAT_S32LE`	32 bits in 32 bits, signed, little endian
`GST_AUDIO_FORMAT_S32BE`	32 bits in 32 bits, signed, big endian
`GST_AUDIO_FORMAT_U32LE`	32 bits in 32 bits, unsigned, little endian
`GST_AUDIO_FORMAT_U32BE`	32 bits in 32 bits, unsigned, big endian
`GST_AUDIO_FORMAT_S24LE`	24 bits in 24 bits, signed, little endian
`GST_AUDIO_FORMAT_S24BE`	24 bits in 24 bits, signed, big endian
`GST_AUDIO_FORMAT_U24LE`	24 bits in 24 bits, unsigned, little endian
`GST_AUDIO_FORMAT_U24BE`	24 bits in 24 bits, unsigned, big endian
`GST_AUDIO_FORMAT_S20LE`	20 bits in 24 bits, signed, little endian
`GST_AUDIO_FORMAT_S20BE`	20 bits in 24 bits, signed, big endian
`GST_AUDIO_FORMAT_U20LE`	20 bits in 24 bits, unsigned, little endian
`GST_AUDIO_FORMAT_U20BE`	20 bits in 24 bits, unsigned, big endian
`GST_AUDIO_FORMAT_S18LE`	18 bits in 24 bits, signed, little endian
`GST_AUDIO_FORMAT_S18BE`	18 bits in 24 bits, signed, big endian
`GST_AUDIO_FORMAT_U18LE`	18 bits in 24 bits, unsigned, little endian
`GST_AUDIO_FORMAT_U18BE`	18 bits in 24 bits, unsigned, big endian
`GST_AUDIO_FORMAT_F32LE`	32-bit floating point samples, little endian
`GST_AUDIO_FORMAT_F32BE`	32-bit floating point samples, big endian
`GST_AUDIO_FORMAT_F64LE`	64-bit floating point samples, little endian
`GST_AUDIO_FORMAT_F64BE`	64-bit floating point samples, big endian
`GST_AUDIO_FORMAT_S16`	16 bits in 16 bits, signed, native endianness
`GST_AUDIO_FORMAT_U16`	16 bits in 16 bits, unsigned, native endianness
`GST_AUDIO_FORMAT_S24_32`	24 bits in 32 bits, signed, native endianness
`GST_AUDIO_FORMAT_U24_32`	24 bits in 32 bits, unsigned, native endianness
`GST_AUDIO_FORMAT_S32`	32 bits in 32 bits, signed, native endianness
`GST_AUDIO_FORMAT_U32`	32 bits in 32 bits, unsigned, native endianness
`GST_AUDIO_FORMAT_S24`	24 bits in 24 bits, signed, native endianness
`GST_AUDIO_FORMAT_U24`	24 bits in 24 bits, unsigned, native endianness
`GST_AUDIO_FORMAT_S20`	20 bits in 24 bits, signed, native endianness
`GST_AUDIO_FORMAT_U20`	20 bits in 24 bits, unsigned, native endianness
`GST_AUDIO_FORMAT_S18`	18 bits in 24 bits, signed, native endianness
`GST_AUDIO_FORMAT_U18`	18 bits in 24 bits, unsigned, native endianness
`GST_AUDIO_FORMAT_F32`	32-bit floating point samples, native endianness
`GST_AUDIO_FORMAT_F64`	64-bit floating point samples, native endianness

Since 0.10.36

enum GstAudioFormatFlags

typedef enum {
  GST_AUDIO_FORMAT_FLAG_INTEGER  = (1 << 0),
  GST_AUDIO_FORMAT_FLAG_FLOAT    = (1 << 1),
  GST_AUDIO_FORMAT_FLAG_SIGNED   = (1 << 2),
  GST_AUDIO_FORMAT_FLAG_COMPLEX  = (1 << 4)
} GstAudioFormatFlags;

The different audio flags that a format info can have.

`GST_AUDIO_FORMAT_FLAG_INTEGER`	integer samples
`GST_AUDIO_FORMAT_FLAG_FLOAT`	float samples
`GST_AUDIO_FORMAT_FLAG_SIGNED`	signed samples
`GST_AUDIO_FORMAT_FLAG_COMPLEX`	complex layout

Since 0.10.36

struct GstAudioFormatInfo

struct GstAudioFormatInfo {
  GstAudioFormat      format;
  const gchar *       name;
  GstAudioFormatFlags flags;
  gint                endianness;
  gint                width;
  gint                depth;
  guint8              silence[8];
};

Information for an audio format.

GstAudioFormat `format`;	GstAudioFormat
const gchar *`name`;	string representation of the format
GstAudioFormatFlags `flags`;	GstAudioFormatFlags
gint `endianness`;	the endianness
gint `width`;	amount of bits used for one sample
gint `depth`;	amount of valid bits in `width`
guint8 `silence`[8];	`width`/8 bytes with 1 silent sample

Since 0.10.36

struct GstAudioInfo

struct GstAudioInfo {
  const GstAudioFormatInfo *finfo;
  GstAudioFlags             flags;
  gint                      rate;
  gint                      channels;
  gint                      bpf;
  GstAudioChannelPosition   position[64];
};

Information describing audio properties. This information can be filled in from GstCaps with gst_audio_info_from_caps().

Use the provided macros to access the info in this structure.

const GstAudioFormatInfo *`finfo`;	the format info of the audio
GstAudioFlags `flags`;	additional audio flags
gint `rate`;	the audio sample rate
gint `channels`;	the number of channels
gint `bpf`;	the number of bytes for one frame, this is the size of one sample * `channels`
GstAudioChannelPosition `position`[64];	the position for each channel (assume all NONE for >64 channels)

Since 0.10.36

gst_audio_info_init ()

void                gst_audio_info_init                 (GstAudioInfo *info);

gst_audio_info_clear ()

void                gst_audio_info_clear                (GstAudioInfo *info);

gst_audio_info_copy ()

GstAudioInfo *      gst_audio_info_copy                 (GstAudioInfo *info);

gst_audio_info_free ()

void                gst_audio_info_free                 (GstAudioInfo *info);

gst_audio_info_from_caps ()

gboolean            gst_audio_info_from_caps            (GstAudioInfo *info,
                                                         const GstCaps *caps);

Parse caps and update info.

`info` :	a GstAudioInfo
`caps` :	a GstCaps
Returns :	TRUE if `caps` could be parsed

Since 0.10.36

gst_audio_info_to_caps ()

GstCaps *           gst_audio_info_to_caps              (GstAudioInfo *info);

Convert the values of info into a GstCaps.

`info` :	a GstAudioInfo
Returns :	the new GstCaps containing the info of `info`. [transfer full]

Since 0.10.36

gst_audio_info_convert ()

gboolean            gst_audio_info_convert              (GstAudioInfo *info,
                                                         GstFormat src_fmt,
                                                         gint64 src_val,
                                                         GstFormat dest_fmt,
                                                         gint64 *dest_val);

gst_audio_format_get_info ()

const GstAudioFormatInfo * gst_audio_format_get_info    (GstAudioFormat format);

GST_AUDIO_FORMAT_INFO_DEPTH()

#define GST_AUDIO_FORMAT_INFO_DEPTH(info)            ((info)->depth)

GST_AUDIO_FORMAT_INFO_ENDIANNESS()

#define GST_AUDIO_FORMAT_INFO_ENDIANNESS(info)       ((info)->endianness)

GST_AUDIO_FORMAT_INFO_FLAGS()

#define GST_AUDIO_FORMAT_INFO_FLAGS(info)            ((info)->flags)

GST_AUDIO_FORMAT_INFO_FORMAT()

#define GST_AUDIO_FORMAT_INFO_FORMAT(info)           ((info)->format)

GST_AUDIO_FORMAT_INFO_IS_FLOAT()

#define GST_AUDIO_FORMAT_INFO_IS_FLOAT(info)         !!((info)->flags & GST_AUDIO_FORMAT_FLAG_FLOAT)

GST_AUDIO_FORMAT_INFO_IS_INTEGER()

#define GST_AUDIO_FORMAT_INFO_IS_INTEGER(info)       !!((info)->flags & GST_AUDIO_FORMAT_FLAG_INTEGER)

GST_AUDIO_FORMAT_INFO_IS_BIG_ENDIAN()

#define GST_AUDIO_FORMAT_INFO_IS_BIG_ENDIAN(info)    ((info)->endianness == G_BIG_ENDIAN)

GST_AUDIO_FORMAT_INFO_IS_LITTLE_ENDIAN()

#define GST_AUDIO_FORMAT_INFO_IS_LITTLE_ENDIAN(info) ((info)->endianness == G_LITTLE_ENDIAN)

GST_AUDIO_FORMAT_INFO_IS_SIGNED()

#define GST_AUDIO_FORMAT_INFO_IS_SIGNED(info)        !!((info)->flags & GST_AUDIO_FORMAT_FLAG_SIGNED)

GST_AUDIO_FORMAT_INFO_NAME()

#define GST_AUDIO_FORMAT_INFO_NAME(info)             ((info)->name)

GST_AUDIO_FORMAT_INFO_WIDTH()

#define GST_AUDIO_FORMAT_INFO_WIDTH(info)            ((info)->width)

GST_AUDIO_INFO_BPF()

#define GST_AUDIO_INFO_BPF(info)             ((info)->bpf)

GST_AUDIO_INFO_BPS()

#define GST_AUDIO_INFO_BPS(info)             (GST_AUDIO_INFO_DEPTH(info) >> 3)

GST_AUDIO_INFO_CHANNELS()

#define GST_AUDIO_INFO_CHANNELS(info)        ((info)->channels)

GST_AUDIO_INFO_DEPTH()

#define GST_AUDIO_INFO_DEPTH(i)              (GST_AUDIO_FORMAT_INFO_DEPTH((i)->finfo))

GST_AUDIO_INFO_FLAGS()

#define GST_AUDIO_INFO_FLAGS(info)           ((info)->flags)

GST_AUDIO_INFO_FORMAT()

#define GST_AUDIO_INFO_FORMAT(i)             (GST_AUDIO_FORMAT_INFO_FORMAT((i)->finfo))

GST_AUDIO_INFO_HAS_DEFAULT_POSITIONS()

#define GST_AUDIO_INFO_HAS_DEFAULT_POSITIONS(info) ((info)->flags & GST_AUDIO_FLAG_DEFAULT_POSITIONS)

GST_AUDIO_INFO_NAME()

#define GST_AUDIO_INFO_NAME(i)               (GST_AUDIO_FORMAT_INFO_NAME((i)->finfo))

GST_AUDIO_INFO_POSITION()

#define GST_AUDIO_INFO_POSITION(info,c)      ((info)->position[c])

GST_AUDIO_INFO_RATE()

#define GST_AUDIO_INFO_RATE(info)            ((info)->rate)

GST_AUDIO_INFO_WIDTH()

#define GST_AUDIO_INFO_WIDTH(i)              (GST_AUDIO_FORMAT_INFO_WIDTH((i)->finfo))

enum GstAudioFieldFlag

typedef enum {
  GST_AUDIO_FIELD_RATE          = (1 << 0),
  GST_AUDIO_FIELD_CHANNELS      = (1 << 1),
  GST_AUDIO_FIELD_ENDIANNESS    = (1 << 2),
  GST_AUDIO_FIELD_WIDTH         = (1 << 3),
  GST_AUDIO_FIELD_DEPTH         = (1 << 4),
  GST_AUDIO_FIELD_SIGNED        = (1 << 5)
} GstAudioFieldFlag;

Warning

GstAudioFieldFlag is deprecated and should not be used in newly-written code. use gst_structure_set() directly

Do not use anymore.

`GST_AUDIO_FIELD_RATE`	add rate field to caps
`GST_AUDIO_FIELD_CHANNELS`	add channels field to caps
`GST_AUDIO_FIELD_ENDIANNESS`	add endianness field to caps
`GST_AUDIO_FIELD_WIDTH`	add width field to caps
`GST_AUDIO_FIELD_DEPTH`	add depth field to caps
`GST_AUDIO_FIELD_SIGNED`	add signed field to caps

GST_FRAMES_TO_CLOCK_TIME()

#define             GST_FRAMES_TO_CLOCK_TIME(frames, rate)

Calculate clocktime from sample frames and rate.

`frames` :	sample frames
`rate` :	sampling rate

GST_CLOCK_TIME_TO_FRAMES()

#define             GST_CLOCK_TIME_TO_FRAMES(clocktime, rate)

Calculate frames from clocktime and sample rate.

`clocktime` :	clock time
`rate` :	sampling rate

GST_AUDIO_DEF_RATE

#define GST_AUDIO_DEF_RATE 44100

Standard sampling rate used in consumer audio.

GST_AUDIO_FLOAT_PAD_TEMPLATE_CAPS

#define             GST_AUDIO_FLOAT_PAD_TEMPLATE_CAPS

Template caps for float audio. Can be used when defining a GstStaticPadTemplate

GST_AUDIO_FLOAT_STANDARD_PAD_TEMPLATE_CAPS

#define             GST_AUDIO_FLOAT_STANDARD_PAD_TEMPLATE_CAPS

Template caps for 32bit float mono audio in native byte-order. Can be used when defining a GstStaticPadTemplate

GST_AUDIO_INT_PAD_TEMPLATE_CAPS

#define             GST_AUDIO_INT_PAD_TEMPLATE_CAPS

Template caps for integer audio. Can be used when defining a GstStaticPadTemplate

GST_AUDIO_INT_STANDARD_PAD_TEMPLATE_CAPS

#define             GST_AUDIO_INT_STANDARD_PAD_TEMPLATE_CAPS

Template caps for 16bit integer stereo audio in native byte-order. Can be used when defining a GstStaticPadTemplate

gst_audio_frame_byte_size ()

int                 gst_audio_frame_byte_size           (GstPad *pad);

Calculate byte size of an audio frame.

`pad` :	the GstPad to get the caps from
Returns :	the byte size, or 0 if there was an error

gst_audio_frame_length ()

long                gst_audio_frame_length              (GstPad *pad,
                                                         GstBuffer *buf);

Calculate length of buffer in frames.

`pad` :	the GstPad to get the caps from
`buf` :	the GstBuffer
Returns :	0 if there's an error, or the number of frames if everything's ok

gst_audio_duration_from_pad_buffer ()

GstClockTime        gst_audio_duration_from_pad_buffer  (GstPad *pad,
                                                         GstBuffer *buf);

Calculate length in nanoseconds of audio buffer buf based on capabilities of pad.

`pad` :	the GstPad to get the caps from
`buf` :	the GstBuffer
Returns :	the length.

gst_audio_is_buffer_framed ()

gboolean            gst_audio_is_buffer_framed          (GstPad *pad,
                                                         GstBuffer *buf);

Check if the buffer size is a whole multiple of the frame size.

`pad` :	the GstPad to get the caps from
`buf` :	the GstBuffer
Returns :	`TRUE` if buffer size is multiple.

gst_audio_structure_set_int ()

void                gst_audio_structure_set_int         (GstStructure *structure,
                                                         GstAudioFieldFlag flag);

Warning

gst_audio_structure_set_int is deprecated and should not be used in newly-written code. use gst_structure_set()

Do not use anymore.

`structure` :	a GstStructure
`flag` :	a set of GstAudioFieldFlag

gst_audio_buffer_clip ()

GstBuffer *         gst_audio_buffer_clip               (GstBuffer *buffer,
                                                         GstSegment *segment,
                                                         gint rate,
                                                         gint frame_size);

Clip the buffer to the given GstSegment.

After calling this function the caller does not own a reference to buffer anymore.

`buffer` :	The buffer to clip.
`segment` :	Segment in `GST_FORMAT_TIME` or `GST_FORMAT_DEFAULT` to which the buffer should be clipped.
`rate` :	sample rate.
`frame_size` :	size of one audio frame in bytes.
Returns :	`NULL` if the buffer is completely outside the configured segment, otherwise the clipped buffer is returned. If the buffer has no timestamp, it is assumed to be inside the segment and is not clipped

Since 0.10.14

			GStreamer Base Plugins 0.10 Library Reference Manual
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