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 type
29 * provides all the state necessary to define a region of memory as part of a
30 * 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_alloc (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 * If an element knows what pad you will push the buffer out on, it should use
57 * gst_pad_alloc_buffer() instead to create a buffer. This allows downstream
58 * elements to provide special buffers to write in, like hardware buffers.
60 * A buffer has a pointer to a #GstCaps describing the media type of the data
61 * in the buffer. Attach caps to the buffer with gst_buffer_set_caps(); this
62 * is typically done before pushing out a buffer using gst_pad_push() so that
63 * the downstream element knows the type of the buffer.
65 * A buffer will usually have a timestamp, and a duration, but neither of these
66 * are guaranteed (they may be set to GST_CLOCK_TIME_NONE). Whenever a
67 * meaningful value can be given for these, they should be set. The timestamp
68 * and duration are measured in nanoseconds (they are #GstClockTime values).
70 * A buffer can also have one or both of a start and an end offset. These are
71 * media-type specific. For video buffers, the start offset will generally be
72 * the frame number. For audio buffers, it will be the number of samples
73 * produced so far. For compressed data, it could be the byte offset in a
74 * source or destination file. Likewise, the end offset will be the offset of
75 * the end of the buffer. These can only be meaningfully interpreted if you
76 * know the media type of the buffer (the #GstCaps set on it). Either or both
77 * can be set to GST_BUFFER_OFFSET_NONE.
79 * gst_buffer_ref() is used to increase the refcount of a buffer. This must be
80 * done when you want to keep a handle to the buffer after pushing it to the
83 * To efficiently create a smaller buffer out of an existing one, you can
84 * use gst_buffer_create_sub().
86 * If the plug-in wants to modify the buffer in-place, it should first obtain
87 * a buffer that is safe to modify by using gst_buffer_make_writable(). This
88 * function is optimized so that a copy will only be made when it is necessary.
90 * Several flags of the buffer can be set and unset with the
91 * GST_BUFFER_FLAG_SET() and GST_BUFFER_FLAG_UNSET() macros. Use
92 * GST_BUFFER_FLAG_IS_SET() to test if a certain #GstBufferFlag is set.
94 * Buffers can be efficiently merged into a larger buffer with
95 * gst_buffer_merge() and gst_buffer_span() if the gst_buffer_is_span_fast()
96 * function returns TRUE.
98 * An element should either unref the buffer or push it out on a src pad
99 * using gst_pad_push() (see #GstPad).
101 * Buffers are usually freed by unreffing them with gst_buffer_unref(). When
102 * the refcount drops to 0, any data pointed to by GST_BUFFER_MALLOCDATA() will
105 * Last reviewed on October 28th, 2005 (0.9.4)
107 #include "gst_private.h"
109 #include "gstbuffer.h"
111 #include "gstutils.h"
112 #include "gstminiobject.h"
115 static void gst_buffer_init (GTypeInstance * instance, gpointer g_class);
116 static void gst_buffer_class_init (gpointer g_class, gpointer class_data);
117 static void gst_buffer_finalize (GstBuffer * buffer);
118 static GstBuffer *_gst_buffer_copy (GstBuffer * buffer);
122 _gst_buffer_initialize (void)
126 gst_buffer_get_type ();
128 /* the GstMiniObject types need to be class_ref'd once before it can be
129 * done from multiple threads;
130 * see http://bugzilla.gnome.org/show_bug.cgi?id=304551 */
131 ptr = g_type_class_ref (GST_TYPE_BUFFER);
132 g_type_class_unref (ptr);
136 gst_buffer_get_type (void)
138 static GType _gst_buffer_type;
140 if (G_UNLIKELY (_gst_buffer_type == 0)) {
141 static const GTypeInfo buffer_info = {
142 sizeof (GstBufferClass),
145 gst_buffer_class_init,
154 _gst_buffer_type = g_type_register_static (GST_TYPE_MINI_OBJECT,
155 "GstBuffer", &buffer_info, 0);
157 return _gst_buffer_type;
161 gst_buffer_class_init (gpointer g_class, gpointer class_data)
163 GstBufferClass *buffer_class = GST_BUFFER_CLASS (g_class);
165 buffer_class->mini_object_class.copy =
166 (GstMiniObjectCopyFunction) _gst_buffer_copy;
167 buffer_class->mini_object_class.finalize =
168 (GstMiniObjectFinalizeFunction) gst_buffer_finalize;
173 gst_buffer_finalize (GstBuffer * buffer)
175 g_return_if_fail (buffer != NULL);
177 GST_CAT_LOG (GST_CAT_BUFFER, "finalize %p", buffer);
180 if (buffer->malloc_data) {
181 g_free (buffer->malloc_data);
184 gst_caps_replace (&GST_BUFFER_CAPS (buffer), NULL);
188 _gst_buffer_copy (GstBuffer * buffer)
193 g_return_val_if_fail (buffer != NULL, NULL);
195 /* create a fresh new buffer */
196 copy = gst_buffer_new ();
198 GST_CAT_LOG (GST_CAT_BUFFER, "copy %p to %p", buffer, copy);
200 /* copy relevant flags */
201 mask = GST_BUFFER_FLAG_PREROLL | GST_BUFFER_FLAG_IN_CAPS |
202 GST_BUFFER_FLAG_DELTA_UNIT;
203 GST_MINI_OBJECT (copy)->flags |= GST_MINI_OBJECT (buffer)->flags & mask;
205 /* we simply copy everything from our parent */
206 copy->data = g_memdup (buffer->data, buffer->size);
207 /* make sure it gets freed (even if the parent is subclassed, we return a
209 copy->malloc_data = copy->data;
211 copy->size = buffer->size;
213 GST_BUFFER_TIMESTAMP (copy) = GST_BUFFER_TIMESTAMP (buffer);
214 GST_BUFFER_DURATION (copy) = GST_BUFFER_DURATION (buffer);
215 GST_BUFFER_OFFSET (copy) = GST_BUFFER_OFFSET (buffer);
216 GST_BUFFER_OFFSET_END (copy) = GST_BUFFER_OFFSET_END (buffer);
218 if (GST_BUFFER_CAPS (buffer))
219 GST_BUFFER_CAPS (copy) = gst_caps_ref (GST_BUFFER_CAPS (buffer));
221 GST_BUFFER_CAPS (copy) = NULL;
227 gst_buffer_init (GTypeInstance * instance, gpointer g_class)
231 buffer = (GstBuffer *) instance;
233 GST_CAT_LOG (GST_CAT_BUFFER, "init %p", buffer);
235 GST_BUFFER_TIMESTAMP (buffer) = GST_CLOCK_TIME_NONE;
236 GST_BUFFER_DURATION (buffer) = GST_CLOCK_TIME_NONE;
237 GST_BUFFER_OFFSET (buffer) = GST_BUFFER_OFFSET_NONE;
238 GST_BUFFER_OFFSET_END (buffer) = GST_BUFFER_OFFSET_NONE;
244 * Creates a newly allocated buffer without any data.
247 * Returns: the new #GstBuffer.
250 gst_buffer_new (void)
254 newbuf = (GstBuffer *) gst_mini_object_new (GST_TYPE_BUFFER);
256 GST_CAT_LOG (GST_CAT_BUFFER, "new %p", newbuf);
262 * gst_buffer_new_and_alloc:
263 * @size: the size of the new buffer's data.
265 * Creates a newly allocated buffer with data of the given size.
268 * Returns: the new #GstBuffer.
271 gst_buffer_new_and_alloc (guint size)
275 newbuf = gst_buffer_new ();
277 newbuf->malloc_data = g_malloc (size);
278 GST_BUFFER_DATA (newbuf) = newbuf->malloc_data;
279 GST_BUFFER_SIZE (newbuf) = size;
281 GST_CAT_LOG (GST_CAT_BUFFER, "new %p of size %d", newbuf, size);
287 * gst_buffer_get_caps:
288 * @buffer: a #GstBuffer.
290 * Gets the media type of the buffer. This can be NULL if there
291 * is no media type attached to this buffer.
293 * Returns: a reference to the #GstCaps.
294 * Returns NULL if there were no caps on this buffer.
296 /* FIXME can we make this threadsafe without a lock on the buffer?
297 * We can use compare and swap and atomic reads. */
299 gst_buffer_get_caps (GstBuffer * buffer)
303 g_return_val_if_fail (buffer != NULL, NULL);
305 ret = GST_BUFFER_CAPS (buffer);
314 * gst_buffer_set_caps:
315 * @buffer: a #GstBuffer.
318 * Sets the media type on the buffer. The refcount of the caps will
319 * be increased and any previous caps on the buffer will be
322 /* FIXME can we make this threadsafe without a lock on the buffer?
323 * We can use compare and swap and atomic reads. Another idea is to
324 * not attach the caps to the buffer but use an event to signal a caps
327 gst_buffer_set_caps (GstBuffer * buffer, GstCaps * caps)
329 g_return_if_fail (buffer != NULL);
331 gst_caps_replace (&GST_BUFFER_CAPS (buffer), caps);
334 typedef struct _GstSubBuffer GstSubBuffer;
335 typedef struct _GstSubBufferClass GstSubBufferClass;
337 #define GST_TYPE_SUBBUFFER (gst_subbuffer_get_type())
339 #define GST_IS_SUBBUFFER(obj) (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GST_TYPE_SUBBUFFER))
340 #define GST_SUBBUFFER(obj) (G_TYPE_CHECK_INSTANCE_CAST ((obj), GST_TYPE_SUBBUFFER, GstSubBuffer))
349 struct _GstSubBufferClass
351 GstBufferClass buffer_class;
354 static GstBufferClass *sub_parent_class;
356 static void gst_subbuffer_init (GTypeInstance * instance, gpointer g_class);
357 static void gst_subbuffer_class_init (gpointer g_class, gpointer class_data);
358 static void gst_subbuffer_finalize (GstSubBuffer * buffer);
361 gst_subbuffer_get_type (void)
363 static GType _gst_subbuffer_type = 0;
365 if (G_UNLIKELY (_gst_subbuffer_type == 0)) {
366 static const GTypeInfo subbuffer_info = {
367 sizeof (GstSubBufferClass),
370 gst_subbuffer_class_init,
373 sizeof (GstSubBuffer),
379 _gst_subbuffer_type = g_type_register_static (GST_TYPE_BUFFER,
380 "GstSubBuffer", &subbuffer_info, 0);
382 return _gst_subbuffer_type;
386 gst_subbuffer_class_init (gpointer g_class, gpointer class_data)
388 GstBufferClass *buffer_class = GST_BUFFER_CLASS (g_class);
390 sub_parent_class = g_type_class_ref (GST_TYPE_BUFFER);
392 buffer_class->mini_object_class.finalize =
393 (GstMiniObjectFinalizeFunction) gst_subbuffer_finalize;
397 gst_subbuffer_finalize (GstSubBuffer * buffer)
399 gst_buffer_unref (buffer->parent);
401 GST_MINI_OBJECT_CLASS (sub_parent_class)->finalize (GST_MINI_OBJECT (buffer));
405 gst_subbuffer_init (GTypeInstance * instance, gpointer g_class)
407 GST_BUFFER_FLAG_SET (GST_BUFFER_CAST (instance), GST_BUFFER_FLAG_READONLY);
411 * gst_buffer_create_sub:
412 * @parent: a #GstBuffer.
413 * @offset: the offset into parent #GstBuffer at which the new sub-buffer
415 * @size: the size of the new #GstBuffer sub-buffer, in bytes (with size > 0).
417 * Creates a sub-buffer from the parent at a given offset.
418 * This sub-buffer uses the actual memory space of the parent buffer.
419 * This function will copy the offset and timestamp fields when the
420 * offset is 0, else they are set to GST_CLOCK_TIME_NONE/GST_BUFFER_OFFSET_NONE.
421 * The duration field of the new buffer is set to GST_CLOCK_TIME_NONE.
424 * Returns: the new #GstBuffer.
425 * Returns NULL if the arguments were invalid.
428 gst_buffer_create_sub (GstBuffer * buffer, guint offset, guint size)
430 GstSubBuffer *subbuffer;
433 g_return_val_if_fail (buffer != NULL, NULL);
434 g_return_val_if_fail (buffer->mini_object.refcount > 0, NULL);
435 g_return_val_if_fail (size > 0, NULL);
436 g_return_val_if_fail (buffer->size >= offset + size, NULL);
438 /* find real parent */
439 if (GST_IS_SUBBUFFER (buffer)) {
440 parent = GST_SUBBUFFER (buffer)->parent;
444 gst_buffer_ref (parent);
446 /* create the new buffer */
447 subbuffer = (GstSubBuffer *) gst_mini_object_new (GST_TYPE_SUBBUFFER);
448 subbuffer->parent = parent;
450 GST_CAT_LOG (GST_CAT_BUFFER, "new subbuffer %p (parent %p)", subbuffer,
453 /* set the right values in the child */
454 GST_BUFFER_DATA (GST_BUFFER_CAST (subbuffer)) = buffer->data + offset;
455 GST_BUFFER_SIZE (GST_BUFFER_CAST (subbuffer)) = size;
457 /* we can copy the timestamp and offset if the new buffer starts at
460 GST_BUFFER_TIMESTAMP (subbuffer) = GST_BUFFER_TIMESTAMP (buffer);
461 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET (buffer);
463 GST_BUFFER_TIMESTAMP (subbuffer) = GST_CLOCK_TIME_NONE;
464 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET_NONE;
467 GST_BUFFER_DURATION (subbuffer) = GST_CLOCK_TIME_NONE;
468 GST_BUFFER_OFFSET_END (subbuffer) = GST_BUFFER_OFFSET_NONE;
470 GST_BUFFER_CAPS (subbuffer) = NULL;
472 return GST_BUFFER_CAST (subbuffer);
476 * gst_buffer_is_span_fast:
477 * @buf1: the first #GstBuffer.
478 * @buf2: the second #GstBuffer.
480 * Determines whether a gst_buffer_span() can be done without copying
481 * the contents, that is, whether the data areas are contiguous sub-buffers of
485 * Returns: TRUE if the buffers are contiguous,
486 * FALSE if a copy would be required.
489 gst_buffer_is_span_fast (GstBuffer * buf1, GstBuffer * buf2)
491 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, FALSE);
492 g_return_val_if_fail (buf1->mini_object.refcount > 0, FALSE);
493 g_return_val_if_fail (buf2->mini_object.refcount > 0, FALSE);
495 /* it's only fast if we have subbuffers of the same parent */
496 return (GST_IS_SUBBUFFER (buf1) &&
497 GST_IS_SUBBUFFER (buf2) &&
498 (GST_SUBBUFFER (buf1)->parent == GST_SUBBUFFER (buf2)->parent) &&
499 ((buf1->data + buf1->size) == buf2->data));
504 * @buf1: the first source #GstBuffer to merge.
505 * @offset: the offset in the first buffer from where the new
506 * buffer should start.
507 * @buf2: the second source #GstBuffer to merge.
508 * @len: the total length of the new buffer.
510 * Creates a new buffer that consists of part of buf1 and buf2.
511 * Logically, buf1 and buf2 are concatenated into a single larger
512 * buffer, and a new buffer is created at the given offset inside
513 * this space, with a given length.
515 * If the two source buffers are children of the same larger buffer,
516 * and are contiguous, the new buffer will be a child of the shared
517 * parent, and thus no copying is necessary. you can use
518 * gst_buffer_is_span_fast() to determine if a memcpy will be needed.
521 * Returns: the new #GstBuffer that spans the two source buffers.
522 * Returns NULL if the arguments are invalid.
525 gst_buffer_span (GstBuffer * buf1, guint32 offset, GstBuffer * buf2,
530 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, NULL);
531 g_return_val_if_fail (buf1->mini_object.refcount > 0, NULL);
532 g_return_val_if_fail (buf2->mini_object.refcount > 0, NULL);
533 g_return_val_if_fail (len > 0, NULL);
534 g_return_val_if_fail (len <= buf1->size + buf2->size - offset, NULL);
536 /* if the two buffers have the same parent and are adjacent */
537 if (gst_buffer_is_span_fast (buf1, buf2)) {
538 GstBuffer *parent = GST_SUBBUFFER (buf1)->parent;
540 /* we simply create a subbuffer of the common parent */
541 newbuf = gst_buffer_create_sub (parent,
542 buf1->data - parent->data + offset, len);
544 GST_CAT_DEBUG (GST_CAT_BUFFER,
545 "slow path taken while spanning buffers %p and %p", buf1, buf2);
546 /* otherwise we simply have to brute-force copy the buffers */
547 newbuf = gst_buffer_new_and_alloc (len);
549 /* copy the first buffer's data across */
550 memcpy (newbuf->data, buf1->data + offset, buf1->size - offset);
551 /* copy the second buffer's data across */
552 memcpy (newbuf->data + (buf1->size - offset), buf2->data,
553 len - (buf1->size - offset));
554 /* if the offset is 0, the new buffer has the same timestamp as buf1 */
556 GST_BUFFER_OFFSET (newbuf) = GST_BUFFER_OFFSET (buf1);
557 GST_BUFFER_TIMESTAMP (newbuf) = GST_BUFFER_TIMESTAMP (buf1);
560 /* if we completely merged the two buffers (appended), we can
561 * calculate the duration too. Also make sure we's not messing with
562 * invalid DURATIONS */
563 if (offset == 0 && buf1->size + buf2->size == len) {
564 if (GST_BUFFER_DURATION_IS_VALID (buf1) &&
565 GST_BUFFER_DURATION_IS_VALID (buf2)) {
567 GST_BUFFER_DURATION (newbuf) = GST_BUFFER_DURATION (buf1) +
568 GST_BUFFER_DURATION (buf2);
570 if (GST_BUFFER_OFFSET_END_IS_VALID (buf2)) {
572 GST_BUFFER_OFFSET_END (newbuf) = GST_BUFFER_OFFSET_END (buf2);