2 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
3 * 2000 Wim Taymans <wtay@chello.be>
5 * gstbuffer.c: Buffer operations
7 * This library is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Library General Public
9 * License as published by the Free Software Foundation; either
10 * version 2 of the License, or (at your option) any later version.
12 * This library is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Library General Public License for more details.
17 * You should have received a copy of the GNU Library General Public
18 * License along with this library; if not, write to the
19 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
20 * Boston, MA 02111-1307, USA.
25 * @short_description: Data-passing buffer type, supporting sub-buffers.
26 * @see_also: #GstPad, #GstMiniObject
28 * Buffers are the basic unit of data transfer in GStreamer. The #GstBuffer
29 * type provides all the state necessary to define a region of memory as part
30 * of a stream. Sub-buffers are also supported, allowing a smaller region of a
31 * buffer to become its own buffer, with mechanisms in place to ensure that
32 * neither memory space goes away prematurely.
34 * Buffers are usually created with gst_buffer_new(). After a buffer has been
35 * created one will typically allocate memory for it and set the size of the
36 * buffer data. The following example creates a buffer that can hold a given
37 * video frame with a given width, height and bits per plane.
39 * <title>Creating a buffer for a video frame</title>
42 * gint size, width, height, bpp;
44 * size = width * height * bpp;
45 * buffer = gst_buffer_new ();
46 * GST_BUFFER_SIZE (buffer) = size;
47 * GST_BUFFER_MALLOCDATA (buffer) = g_malloc (size);
48 * GST_BUFFER_DATA (buffer) = GST_BUFFER_MALLOCDATA (buffer);
53 * Alternatively, use gst_buffer_new_and_alloc()
54 * to create a buffer with preallocated data of a given size.
56 * The data pointed to by the buffer can be retrieved with the GST_BUFFER_DATA()
57 * macro. The size of the data can be found with GST_BUFFER_SIZE(). For buffers
58 * of size 0, the data pointer is undefined (usually NULL) and should never be used.
60 * If an element knows what pad you will push the buffer out on, it should use
61 * gst_pad_alloc_buffer() instead to create a buffer. This allows downstream
62 * elements to provide special buffers to write in, like hardware buffers.
64 * A buffer has a pointer to a #GstCaps describing the media type of the data
65 * in the buffer. Attach caps to the buffer with gst_buffer_set_caps(); this
66 * is typically done before pushing out a buffer using gst_pad_push() so that
67 * the downstream element knows the type of the buffer.
69 * A buffer will usually have a timestamp, and a duration, but neither of these
70 * are guaranteed (they may be set to #GST_CLOCK_TIME_NONE). Whenever a
71 * meaningful value can be given for these, they should be set. The timestamp
72 * and duration are measured in nanoseconds (they are #GstClockTime values).
74 * A buffer can also have one or both of a start and an end offset. These are
75 * media-type specific. For video buffers, the start offset will generally be
76 * the frame number. For audio buffers, it will be the number of samples
77 * produced so far. For compressed data, it could be the byte offset in a
78 * source or destination file. Likewise, the end offset will be the offset of
79 * the end of the buffer. These can only be meaningfully interpreted if you
80 * know the media type of the buffer (the #GstCaps set on it). Either or both
81 * can be set to #GST_BUFFER_OFFSET_NONE.
83 * gst_buffer_ref() is used to increase the refcount of a buffer. This must be
84 * done when you want to keep a handle to the buffer after pushing it to the
87 * To efficiently create a smaller buffer out of an existing one, you can
88 * use gst_buffer_create_sub().
90 * If a plug-in wants to modify the buffer data in-place, it should first obtain
91 * a buffer that is safe to modify by using gst_buffer_make_writable(). This
92 * function is optimized so that a copy will only be made when it is necessary.
94 * A plugin that only wishes to modify the metadata of a buffer, such as the
95 * offset, timestamp or caps, should use gst_buffer_make_metadata_writable(),
96 * which will create a subbuffer of the original buffer to ensure the caller
97 * has sole ownership, and not copy the buffer data.
99 * Several flags of the buffer can be set and unset with the
100 * GST_BUFFER_FLAG_SET() and GST_BUFFER_FLAG_UNSET() macros. Use
101 * GST_BUFFER_FLAG_IS_SET() to test if a certain #GstBufferFlag is set.
103 * Buffers can be efficiently merged into a larger buffer with
104 * gst_buffer_merge() and gst_buffer_span() if the gst_buffer_is_span_fast()
105 * function returns TRUE.
107 * An element should either unref the buffer or push it out on a src pad
108 * using gst_pad_push() (see #GstPad).
110 * Buffers are usually freed by unreffing them with gst_buffer_unref(). When
111 * the refcount drops to 0, any data pointed to by GST_BUFFER_MALLOCDATA() will
114 * Last reviewed on August 11th, 2006 (0.10.10)
116 #include "gst_private.h"
118 #include "gstbuffer.h"
120 #include "gstutils.h"
121 #include "gstminiobject.h"
123 static void gst_buffer_init (GTypeInstance * instance, gpointer g_class);
124 static void gst_buffer_class_init (gpointer g_class, gpointer class_data);
125 static void gst_buffer_finalize (GstBuffer * buffer);
126 static GstBuffer *_gst_buffer_copy (GstBuffer * buffer);
127 static GType gst_subbuffer_get_type (void);
129 static GType _gst_subbuffer_type = 0;
130 static GType _gst_buffer_type = 0;
133 _gst_buffer_initialize (void)
137 gst_buffer_get_type ();
138 gst_subbuffer_get_type ();
140 /* the GstMiniObject types need to be class_ref'd once before it can be
141 * done from multiple threads;
142 * see http://bugzilla.gnome.org/show_bug.cgi?id=304551 */
143 ptr = g_type_class_ref (GST_TYPE_BUFFER);
144 g_type_class_unref (ptr);
148 gst_buffer_get_type (void)
150 if (G_UNLIKELY (_gst_buffer_type == 0)) {
151 static const GTypeInfo buffer_info = {
152 sizeof (GstBufferClass),
155 gst_buffer_class_init,
164 _gst_buffer_type = g_type_register_static (GST_TYPE_MINI_OBJECT,
165 "GstBuffer", &buffer_info, 0);
167 return _gst_buffer_type;
171 gst_buffer_class_init (gpointer g_class, gpointer class_data)
173 GstBufferClass *buffer_class = GST_BUFFER_CLASS (g_class);
175 buffer_class->mini_object_class.copy =
176 (GstMiniObjectCopyFunction) _gst_buffer_copy;
177 buffer_class->mini_object_class.finalize =
178 (GstMiniObjectFinalizeFunction) gst_buffer_finalize;
183 gst_buffer_finalize (GstBuffer * buffer)
185 g_return_if_fail (buffer != NULL);
187 GST_CAT_LOG (GST_CAT_BUFFER, "finalize %p", buffer);
190 g_free (buffer->malloc_data);
192 gst_caps_replace (&GST_BUFFER_CAPS (buffer), NULL);
196 _gst_buffer_copy (GstBuffer * buffer)
201 g_return_val_if_fail (buffer != NULL, NULL);
203 /* create a fresh new buffer */
204 copy = gst_buffer_new ();
206 GST_CAT_LOG (GST_CAT_BUFFER, "copy %p to %p", buffer, copy);
208 /* copy relevant flags */
209 mask = GST_BUFFER_FLAG_PREROLL | GST_BUFFER_FLAG_IN_CAPS |
210 GST_BUFFER_FLAG_DELTA_UNIT | GST_BUFFER_FLAG_DISCONT |
212 GST_MINI_OBJECT_FLAGS (copy) |= GST_MINI_OBJECT_FLAGS (buffer) & mask;
214 /* we simply copy everything from our parent */
215 copy->data = g_memdup (buffer->data, buffer->size);
216 /* make sure it gets freed (even if the parent is subclassed, we return a
218 copy->malloc_data = copy->data;
220 copy->size = buffer->size;
222 GST_BUFFER_TIMESTAMP (copy) = GST_BUFFER_TIMESTAMP (buffer);
223 GST_BUFFER_DURATION (copy) = GST_BUFFER_DURATION (buffer);
224 GST_BUFFER_OFFSET (copy) = GST_BUFFER_OFFSET (buffer);
225 GST_BUFFER_OFFSET_END (copy) = GST_BUFFER_OFFSET_END (buffer);
227 if (GST_BUFFER_CAPS (buffer))
228 GST_BUFFER_CAPS (copy) = gst_caps_ref (GST_BUFFER_CAPS (buffer));
230 GST_BUFFER_CAPS (copy) = NULL;
236 gst_buffer_init (GTypeInstance * instance, gpointer g_class)
240 buffer = (GstBuffer *) instance;
242 GST_CAT_LOG (GST_CAT_BUFFER, "init %p", buffer);
244 GST_BUFFER_TIMESTAMP (buffer) = GST_CLOCK_TIME_NONE;
245 GST_BUFFER_DURATION (buffer) = GST_CLOCK_TIME_NONE;
246 GST_BUFFER_OFFSET (buffer) = GST_BUFFER_OFFSET_NONE;
247 GST_BUFFER_OFFSET_END (buffer) = GST_BUFFER_OFFSET_NONE;
253 * Creates a newly allocated buffer without any data.
256 * Returns: the new #GstBuffer.
259 gst_buffer_new (void)
263 newbuf = (GstBuffer *) gst_mini_object_new (_gst_buffer_type);
265 GST_CAT_LOG (GST_CAT_BUFFER, "new %p", newbuf);
271 * gst_buffer_new_and_alloc:
272 * @size: the size of the new buffer's data.
274 * Creates a newly allocated buffer with data of the given size.
275 * The buffer memory is not cleared.
277 * Note that when @size == 0, the buffer data pointer will be NULL.
280 * Returns: the new #GstBuffer.
283 gst_buffer_new_and_alloc (guint size)
287 newbuf = gst_buffer_new ();
289 newbuf->malloc_data = g_malloc (size);
290 GST_BUFFER_DATA (newbuf) = newbuf->malloc_data;
291 GST_BUFFER_SIZE (newbuf) = size;
293 GST_CAT_LOG (GST_CAT_BUFFER, "new %p of size %d", newbuf, size);
299 * gst_buffer_get_caps:
300 * @buffer: a #GstBuffer.
302 * Gets the media type of the buffer. This can be NULL if there
303 * is no media type attached to this buffer.
305 * Returns: a reference to the #GstCaps. unref after usage.
306 * Returns NULL if there were no caps on this buffer.
308 /* FIXME can we make this threadsafe without a lock on the buffer?
309 * We can use compare and swap and atomic reads. */
311 gst_buffer_get_caps (GstBuffer * buffer)
315 g_return_val_if_fail (buffer != NULL, NULL);
317 ret = GST_BUFFER_CAPS (buffer);
326 * gst_buffer_set_caps:
327 * @buffer: a #GstBuffer.
330 * Sets the media type on the buffer. The refcount of the caps will
331 * be increased and any previous caps on the buffer will be
334 /* FIXME can we make this threadsafe without a lock on the buffer?
335 * We can use compare and swap and atomic reads. Another idea is to
336 * not attach the caps to the buffer but use an event to signal a caps
339 gst_buffer_set_caps (GstBuffer * buffer, GstCaps * caps)
341 g_return_if_fail (buffer != NULL);
343 gst_caps_replace (&GST_BUFFER_CAPS (buffer), caps);
347 * gst_buffer_is_metadata_writable:
350 * Similar to gst_buffer_is_writable, but this only ensures that the
351 * refcount of the buffer is 1, indicating that the caller is the sole
352 * owner and can change the buffer metadata, such as caps and timestamps.
354 * Returns: TRUE if the metadata is writable.
357 gst_buffer_is_metadata_writable (GstBuffer * buf)
359 return (GST_MINI_OBJECT_REFCOUNT_VALUE (GST_MINI_OBJECT_CAST (buf)) == 1);
363 * gst_buffer_make_metadata_writable:
366 * Similar to gst_buffer_make_writable, but does not ensure that the buffer
367 * data array is writable. Instead, this just ensures that the returned buffer
368 * is solely owned by the caller, by creating a subbuffer of the original
369 * buffer if necessary.
371 * After calling this function, @buf should not be referenced anymore. The
372 * result of this function has guaranteed writable metadata.
374 * Returns: A new #GstBuffer with writable metadata.
377 gst_buffer_make_metadata_writable (GstBuffer * buf)
381 if (gst_buffer_is_metadata_writable (buf)) {
384 ret = gst_buffer_create_sub (buf, 0, GST_BUFFER_SIZE (buf));
386 /* copy all the flags except IN_CAPS */
387 GST_BUFFER_FLAGS (ret) = GST_BUFFER_FLAGS (buf);
388 GST_BUFFER_FLAG_UNSET (ret, GST_BUFFER_FLAG_IN_CAPS);
389 /* data should always be set to READONLY */
390 GST_BUFFER_FLAG_SET (ret, GST_BUFFER_FLAG_READONLY);
392 gst_buffer_unref (buf);
398 typedef struct _GstSubBuffer GstSubBuffer;
399 typedef struct _GstSubBufferClass GstSubBufferClass;
401 #define GST_IS_SUBBUFFER(obj) (G_TYPE_CHECK_INSTANCE_TYPE ((obj), _gst_subbuffer_type))
402 #define GST_SUBBUFFER_CAST(obj) ((GstSubBuffer *)(obj))
411 struct _GstSubBufferClass
413 GstBufferClass buffer_class;
416 static GstBufferClass *sub_parent_class;
418 static void gst_subbuffer_init (GTypeInstance * instance, gpointer g_class);
419 static void gst_subbuffer_class_init (gpointer g_class, gpointer class_data);
420 static void gst_subbuffer_finalize (GstSubBuffer * buffer);
423 gst_subbuffer_get_type (void)
425 if (G_UNLIKELY (_gst_subbuffer_type == 0)) {
426 static const GTypeInfo subbuffer_info = {
427 sizeof (GstSubBufferClass),
430 gst_subbuffer_class_init,
433 sizeof (GstSubBuffer),
439 _gst_subbuffer_type = g_type_register_static (GST_TYPE_BUFFER,
440 "GstSubBuffer", &subbuffer_info, 0);
442 return _gst_subbuffer_type;
446 gst_subbuffer_class_init (gpointer g_class, gpointer class_data)
448 GstBufferClass *buffer_class = GST_BUFFER_CLASS (g_class);
450 sub_parent_class = g_type_class_peek_parent (g_class);
452 buffer_class->mini_object_class.finalize =
453 (GstMiniObjectFinalizeFunction) gst_subbuffer_finalize;
457 gst_subbuffer_finalize (GstSubBuffer * buffer)
459 gst_buffer_unref (buffer->parent);
461 GST_MINI_OBJECT_CLASS (sub_parent_class)->
462 finalize (GST_MINI_OBJECT_CAST (buffer));
466 gst_subbuffer_init (GTypeInstance * instance, gpointer g_class)
468 GST_BUFFER_FLAG_SET (GST_BUFFER_CAST (instance), GST_BUFFER_FLAG_READONLY);
472 * gst_buffer_create_sub:
473 * @parent: a #GstBuffer.
474 * @offset: the offset into parent #GstBuffer at which the new sub-buffer
476 * @size: the size of the new #GstBuffer sub-buffer, in bytes.
478 * Creates a sub-buffer from @parent at @offset and @size.
479 * This sub-buffer uses the actual memory space of the parent buffer.
480 * This function will copy the offset and timestamp fields when the
481 * offset is 0. If not, they will be set to #GST_CLOCK_TIME_NONE and
482 * #GST_BUFFER_OFFSET_NONE.
483 * If @offset equals 0 and @size equals the total size of @buffer, the
484 * duration and offset end fields are also copied. If not they will be set
485 * to #GST_CLOCK_TIME_NONE and #GST_BUFFER_OFFSET_NONE.
488 * Returns: the new #GstBuffer.
489 * Returns NULL if the arguments were invalid.
492 gst_buffer_create_sub (GstBuffer * buffer, guint offset, guint size)
494 GstSubBuffer *subbuffer;
498 g_return_val_if_fail (buffer != NULL, NULL);
499 g_return_val_if_fail (buffer->mini_object.refcount > 0, NULL);
500 g_return_val_if_fail (buffer->size >= offset + size, NULL);
502 /* find real parent */
503 if (GST_IS_SUBBUFFER (buffer)) {
504 parent = GST_SUBBUFFER_CAST (buffer)->parent;
508 gst_buffer_ref (parent);
510 /* create the new buffer */
511 subbuffer = (GstSubBuffer *) gst_mini_object_new (_gst_subbuffer_type);
512 subbuffer->parent = parent;
514 GST_CAT_LOG (GST_CAT_BUFFER, "new subbuffer %p (parent %p)", subbuffer,
517 /* set the right values in the child */
518 GST_BUFFER_DATA (GST_BUFFER_CAST (subbuffer)) = buffer->data + offset;
519 GST_BUFFER_SIZE (GST_BUFFER_CAST (subbuffer)) = size;
521 /* we can copy the timestamp and offset if the new buffer starts at
524 GST_BUFFER_TIMESTAMP (subbuffer) = GST_BUFFER_TIMESTAMP (buffer);
525 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET (buffer);
526 complete = (buffer->size == size);
528 GST_BUFFER_TIMESTAMP (subbuffer) = GST_CLOCK_TIME_NONE;
529 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET_NONE;
536 /* if we copied the complete buffer we can copy the duration,
537 * offset_end and caps as well */
538 GST_BUFFER_DURATION (subbuffer) = GST_BUFFER_DURATION (buffer);
539 GST_BUFFER_OFFSET_END (subbuffer) = GST_BUFFER_OFFSET_END (buffer);
540 if ((caps = GST_BUFFER_CAPS (buffer)))
542 GST_BUFFER_CAPS (subbuffer) = caps;
544 GST_BUFFER_DURATION (subbuffer) = GST_CLOCK_TIME_NONE;
545 GST_BUFFER_OFFSET_END (subbuffer) = GST_BUFFER_OFFSET_NONE;
546 GST_BUFFER_CAPS (subbuffer) = NULL;
548 return GST_BUFFER_CAST (subbuffer);
552 * gst_buffer_is_span_fast:
553 * @buf1: the first #GstBuffer.
554 * @buf2: the second #GstBuffer.
556 * Determines whether a gst_buffer_span() can be done without copying
557 * the contents, that is, whether the data areas are contiguous sub-buffers of
561 * Returns: TRUE if the buffers are contiguous,
562 * FALSE if a copy would be required.
565 gst_buffer_is_span_fast (GstBuffer * buf1, GstBuffer * buf2)
567 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, FALSE);
568 g_return_val_if_fail (buf1->mini_object.refcount > 0, FALSE);
569 g_return_val_if_fail (buf2->mini_object.refcount > 0, FALSE);
571 /* it's only fast if we have subbuffers of the same parent */
572 return (GST_IS_SUBBUFFER (buf1) &&
573 GST_IS_SUBBUFFER (buf2) &&
574 (GST_SUBBUFFER_CAST (buf1)->parent == GST_SUBBUFFER_CAST (buf2)->parent)
575 && ((buf1->data + buf1->size) == buf2->data));
580 * @buf1: the first source #GstBuffer to merge.
581 * @offset: the offset in the first buffer from where the new
582 * buffer should start.
583 * @buf2: the second source #GstBuffer to merge.
584 * @len: the total length of the new buffer.
586 * Creates a new buffer that consists of part of buf1 and buf2.
587 * Logically, buf1 and buf2 are concatenated into a single larger
588 * buffer, and a new buffer is created at the given offset inside
589 * this space, with a given length.
591 * If the two source buffers are children of the same larger buffer,
592 * and are contiguous, the new buffer will be a child of the shared
593 * parent, and thus no copying is necessary. you can use
594 * gst_buffer_is_span_fast() to determine if a memcpy will be needed.
597 * Returns: the new #GstBuffer that spans the two source buffers.
598 * Returns NULL if the arguments are invalid.
601 gst_buffer_span (GstBuffer * buf1, guint32 offset, GstBuffer * buf2,
606 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, NULL);
607 g_return_val_if_fail (buf1->mini_object.refcount > 0, NULL);
608 g_return_val_if_fail (buf2->mini_object.refcount > 0, NULL);
609 g_return_val_if_fail (len > 0, NULL);
610 g_return_val_if_fail (len <= buf1->size + buf2->size - offset, NULL);
612 /* if the two buffers have the same parent and are adjacent */
613 if (gst_buffer_is_span_fast (buf1, buf2)) {
614 GstBuffer *parent = GST_SUBBUFFER_CAST (buf1)->parent;
616 /* we simply create a subbuffer of the common parent */
617 newbuf = gst_buffer_create_sub (parent,
618 buf1->data - parent->data + offset, len);
620 GST_CAT_DEBUG (GST_CAT_BUFFER,
621 "slow path taken while spanning buffers %p and %p", buf1, buf2);
622 /* otherwise we simply have to brute-force copy the buffers */
623 newbuf = gst_buffer_new_and_alloc (len);
625 /* copy the first buffer's data across */
626 memcpy (newbuf->data, buf1->data + offset, buf1->size - offset);
627 /* copy the second buffer's data across */
628 memcpy (newbuf->data + (buf1->size - offset), buf2->data,
629 len - (buf1->size - offset));
631 /* if the offset is 0, the new buffer has the same timestamp as buf1 */
633 GST_BUFFER_OFFSET (newbuf) = GST_BUFFER_OFFSET (buf1);
634 GST_BUFFER_TIMESTAMP (newbuf) = GST_BUFFER_TIMESTAMP (buf1);
636 /* if we completely merged the two buffers (appended), we can
637 * calculate the duration too. Also make sure we's not messing with
638 * invalid DURATIONS */
639 if (buf1->size + buf2->size == len) {
640 if (GST_BUFFER_DURATION_IS_VALID (buf1) &&
641 GST_BUFFER_DURATION_IS_VALID (buf2)) {
643 GST_BUFFER_DURATION (newbuf) = GST_BUFFER_DURATION (buf1) +
644 GST_BUFFER_DURATION (buf2);
646 if (GST_BUFFER_OFFSET_END_IS_VALID (buf2)) {
648 GST_BUFFER_OFFSET_END (newbuf) = GST_BUFFER_OFFSET_END (buf2);