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.
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 * gst_buffer_ref() is used to increase the refcount of a buffer. This must be
66 * done when you want to keep a handle to the buffer after pushing it to the
69 * To efficiently create a smaller buffer out of an existing one, you can
70 * use gst_buffer_create_sub().
72 * If the plug-in wants to modify the buffer in-place, it should first obtain
73 * a buffer that is safe to modify by using gst_buffer_make_writable(). This
74 * function is optimized so that a copy will only be made when it is necessary.
76 * Several flags of the buffer can be set and unset with the
77 * GST_BUFFER_FLAG_SET() and GST_BUFFER_FLAG_UNSET() macros. Use
78 * GST_BUFFER_FLAG_IS_SET() to test it a certain #GstBufferFlag is set.
80 * Buffers can be efficiently merged into a larger buffer with
81 * gst_buffer_merge() and gst_buffer_span() if the gst_buffer_is_span_fast()
82 * function returns TRUE.
84 * An element should either unref the buffer or push it out on a src pad
85 * using gst_pad_push() (see #GstPad).
87 * Buffers usually are freed by unreffing them with gst_buffer_unref(). When
88 * the refcount drops to 0, the buffer memory will be freed again.
90 * Last reviewed on September 24th, 2005 (0.9.0)
92 #include "gst_private.h"
94 #include "gstbuffer.h"
97 #include "gstminiobject.h"
100 static void gst_buffer_init (GTypeInstance * instance, gpointer g_class);
101 static void gst_buffer_class_init (gpointer g_class, gpointer class_data);
102 static void gst_buffer_finalize (GstBuffer * buffer);
103 static GstBuffer *_gst_buffer_copy (GstBuffer * buffer);
107 _gst_buffer_initialize (void)
111 gst_buffer_get_type ();
113 /* the GstMiniObject types need to be class_ref'd once before it can be
114 * done from multiple threads;
115 * see http://bugzilla.gnome.org/show_bug.cgi?id=304551 */
116 ptr = g_type_class_ref (GST_TYPE_BUFFER);
117 g_type_class_unref (ptr);
121 gst_buffer_get_type (void)
123 static GType _gst_buffer_type;
125 if (G_UNLIKELY (_gst_buffer_type == 0)) {
126 static const GTypeInfo buffer_info = {
127 sizeof (GstBufferClass),
130 gst_buffer_class_init,
139 _gst_buffer_type = g_type_register_static (GST_TYPE_MINI_OBJECT,
140 "GstBuffer", &buffer_info, 0);
142 return _gst_buffer_type;
146 gst_buffer_class_init (gpointer g_class, gpointer class_data)
148 GstBufferClass *buffer_class = GST_BUFFER_CLASS (g_class);
150 buffer_class->mini_object_class.copy =
151 (GstMiniObjectCopyFunction) _gst_buffer_copy;
152 buffer_class->mini_object_class.finalize =
153 (GstMiniObjectFinalizeFunction) gst_buffer_finalize;
158 gst_buffer_finalize (GstBuffer * buffer)
160 g_return_if_fail (buffer != NULL);
162 GST_CAT_LOG (GST_CAT_BUFFER, "finalize %p", buffer);
165 if (buffer->malloc_data) {
166 g_free (buffer->malloc_data);
169 gst_caps_replace (&GST_BUFFER_CAPS (buffer), NULL);
173 _gst_buffer_copy (GstBuffer * buffer)
178 g_return_val_if_fail (buffer != NULL, NULL);
180 /* create a fresh new buffer */
181 copy = gst_buffer_new ();
183 GST_CAT_LOG (GST_CAT_BUFFER, "copy %p to %p", buffer, copy);
185 /* copy relevant flags */
186 mask = GST_BUFFER_FLAG_PREROLL | GST_BUFFER_FLAG_IN_CAPS |
187 GST_BUFFER_FLAG_DELTA_UNIT;
188 GST_MINI_OBJECT (copy)->flags |= GST_MINI_OBJECT (buffer)->flags & mask;
190 /* we simply copy everything from our parent */
191 copy->data = g_memdup (buffer->data, buffer->size);
192 /* make sure it gets freed (even if the parent is subclassed, we return a
194 copy->malloc_data = copy->data;
196 copy->size = buffer->size;
198 GST_BUFFER_TIMESTAMP (copy) = GST_BUFFER_TIMESTAMP (buffer);
199 GST_BUFFER_DURATION (copy) = GST_BUFFER_DURATION (buffer);
200 GST_BUFFER_OFFSET (copy) = GST_BUFFER_OFFSET (buffer);
201 GST_BUFFER_OFFSET_END (copy) = GST_BUFFER_OFFSET_END (buffer);
203 if (GST_BUFFER_CAPS (buffer))
204 GST_BUFFER_CAPS (copy) = gst_caps_ref (GST_BUFFER_CAPS (buffer));
206 GST_BUFFER_CAPS (copy) = NULL;
212 gst_buffer_init (GTypeInstance * instance, gpointer g_class)
216 buffer = (GstBuffer *) instance;
218 GST_CAT_LOG (GST_CAT_BUFFER, "init %p", buffer);
220 GST_BUFFER_TIMESTAMP (buffer) = GST_CLOCK_TIME_NONE;
221 GST_BUFFER_DURATION (buffer) = GST_CLOCK_TIME_NONE;
222 GST_BUFFER_OFFSET (buffer) = GST_BUFFER_OFFSET_NONE;
223 GST_BUFFER_OFFSET_END (buffer) = GST_BUFFER_OFFSET_NONE;
229 * Creates a newly allocated buffer without any data.
231 * Returns: the new #GstBuffer.
236 gst_buffer_new (void)
240 newbuf = (GstBuffer *) gst_mini_object_new (GST_TYPE_BUFFER);
242 GST_CAT_LOG (GST_CAT_BUFFER, "new %p", newbuf);
248 * gst_buffer_new_and_alloc:
249 * @size: the size of the new buffer's data.
251 * Creates a newly allocated buffer with data of the given size.
253 * Returns: the new #GstBuffer.
258 gst_buffer_new_and_alloc (guint size)
262 newbuf = gst_buffer_new ();
264 newbuf->malloc_data = g_malloc (size);
265 GST_BUFFER_DATA (newbuf) = newbuf->malloc_data;
266 GST_BUFFER_SIZE (newbuf) = size;
268 GST_CAT_LOG (GST_CAT_BUFFER, "new %p of size %d", newbuf, size);
274 * gst_buffer_get_caps:
275 * @buffer: a #GstBuffer to get the caps of.
277 * Gets the media type of the buffer. This can be NULL if there
278 * is not media type attached to this buffer or when the media
279 * type is the same as the previous received buffer.
281 * Returns: a reference to the #GstCaps, or NULL if there were no caps on this
284 /* FIXME can we make this threadsafe without a lock on the buffer?
285 * We can use compare and swap and atomic reads. */
287 gst_buffer_get_caps (GstBuffer * buffer)
291 g_return_val_if_fail (buffer != NULL, NULL);
293 ret = GST_BUFFER_CAPS (buffer);
302 * gst_buffer_set_caps:
303 * @buffer: a #GstBuffer to set the caps of.
304 * @caps: a #GstCaps to set.
306 * Sets the media type on the buffer. The caps' refcount will
307 * be increased and any previous caps on the buffer will be
310 /* FIXME can we make this threadsafe without a lock on the buffer?
311 * We can use compare and swap and atomic reads. Another idea is to
312 * not attach the caps to the buffer but use an event to signal a caps
315 gst_buffer_set_caps (GstBuffer * buffer, GstCaps * caps)
317 g_return_if_fail (buffer != NULL);
319 gst_caps_replace (&GST_BUFFER_CAPS (buffer), caps);
323 typedef struct _GstSubBuffer GstSubBuffer;
324 typedef struct _GstSubBufferClass GstSubBufferClass;
326 #define GST_TYPE_SUBBUFFER (gst_subbuffer_get_type())
328 #define GST_IS_SUBBUFFER(obj) (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GST_TYPE_SUBBUFFER))
329 #define GST_SUBBUFFER(obj) (G_TYPE_CHECK_INSTANCE_CAST ((obj), GST_TYPE_SUBBUFFER, GstSubBuffer))
338 struct _GstSubBufferClass
340 GstBufferClass buffer_class;
343 static GstBufferClass *sub_parent_class;
345 static void gst_subbuffer_init (GTypeInstance * instance, gpointer g_class);
346 static void gst_subbuffer_class_init (gpointer g_class, gpointer class_data);
347 static void gst_subbuffer_finalize (GstSubBuffer * buffer);
350 gst_subbuffer_get_type (void)
352 static GType _gst_subbuffer_type = 0;
354 if (G_UNLIKELY (_gst_subbuffer_type == 0)) {
355 static const GTypeInfo subbuffer_info = {
356 sizeof (GstSubBufferClass),
359 gst_subbuffer_class_init,
362 sizeof (GstSubBuffer),
368 _gst_subbuffer_type = g_type_register_static (GST_TYPE_BUFFER,
369 "GstSubBuffer", &subbuffer_info, 0);
371 return _gst_subbuffer_type;
375 gst_subbuffer_class_init (gpointer g_class, gpointer class_data)
377 GstBufferClass *buffer_class = GST_BUFFER_CLASS (g_class);
379 sub_parent_class = g_type_class_ref (GST_TYPE_BUFFER);
381 buffer_class->mini_object_class.finalize =
382 (GstMiniObjectFinalizeFunction) gst_subbuffer_finalize;
386 gst_subbuffer_finalize (GstSubBuffer * buffer)
388 gst_buffer_unref (buffer->parent);
390 GST_MINI_OBJECT_CLASS (sub_parent_class)->finalize (GST_MINI_OBJECT (buffer));
394 gst_subbuffer_init (GTypeInstance * instance, gpointer g_class)
396 GST_BUFFER_FLAG_SET (GST_BUFFER_CAST (instance), GST_BUFFER_FLAG_READONLY);
400 * gst_buffer_create_sub:
401 * @parent: a parent #GstBuffer to create a subbuffer from.
402 * @offset: the offset into parent #GstBuffer.
403 * @size: the size of the new #GstBuffer sub-buffer (with size > 0).
405 * Creates a sub-buffer from the parent at a given offset.
406 * This sub-buffer uses the actual memory space of the parent buffer.
407 * This function will copy the offset and timestamp field when the
408 * offset is 0, else they are set to _NONE.
409 * The duration field of the new buffer are set to GST_CLOCK_TIME_NONE.
411 * Returns: the new #GstBuffer, or NULL if there was an error.
416 gst_buffer_create_sub (GstBuffer * buffer, guint offset, guint size)
418 GstSubBuffer *subbuffer;
421 g_return_val_if_fail (buffer != NULL, NULL);
422 g_return_val_if_fail (buffer->mini_object.refcount > 0, NULL);
423 g_return_val_if_fail (size > 0, NULL);
424 g_return_val_if_fail (buffer->size >= offset + size, NULL);
426 /* find real parent */
427 if (GST_IS_SUBBUFFER (buffer)) {
428 parent = GST_SUBBUFFER (buffer)->parent;
432 gst_buffer_ref (parent);
434 /* create the new buffer */
435 subbuffer = (GstSubBuffer *) gst_mini_object_new (GST_TYPE_SUBBUFFER);
436 subbuffer->parent = parent;
438 GST_CAT_LOG (GST_CAT_BUFFER, "new subbuffer %p (parent %p)", subbuffer,
441 /* set the right values in the child */
442 GST_BUFFER_DATA (GST_BUFFER_CAST (subbuffer)) = buffer->data + offset;
443 GST_BUFFER_SIZE (GST_BUFFER_CAST (subbuffer)) = size;
445 /* we can copy the timestamp and offset if the new buffer starts at
448 GST_BUFFER_TIMESTAMP (subbuffer) = GST_BUFFER_TIMESTAMP (buffer);
449 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET (buffer);
451 GST_BUFFER_TIMESTAMP (subbuffer) = GST_CLOCK_TIME_NONE;
452 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET_NONE;
455 GST_BUFFER_DURATION (subbuffer) = GST_CLOCK_TIME_NONE;
456 GST_BUFFER_OFFSET_END (subbuffer) = GST_BUFFER_OFFSET_NONE;
458 GST_BUFFER_CAPS (subbuffer) = NULL;
460 return GST_BUFFER_CAST (subbuffer);
464 * gst_buffer_is_span_fast:
465 * @buf1: a first source #GstBuffer.
466 * @buf2: the second source #GstBuffer.
468 * Determines whether a gst_buffer_span() can be done without copying
469 * the contents, that is, whether the data areas are contiguous.
471 * Returns: TRUE if the buffers are contiguous,
472 * FALSE if a copy would be required.
477 gst_buffer_is_span_fast (GstBuffer * buf1, GstBuffer * buf2)
479 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, FALSE);
480 g_return_val_if_fail (buf1->mini_object.refcount > 0, FALSE);
481 g_return_val_if_fail (buf2->mini_object.refcount > 0, FALSE);
483 /* it's only fast if we have subbuffers of the same parent */
484 return (GST_IS_SUBBUFFER (buf1) &&
485 GST_IS_SUBBUFFER (buf2) &&
486 (GST_SUBBUFFER (buf1)->parent == GST_SUBBUFFER (buf2)->parent) &&
487 ((buf1->data + buf1->size) == buf2->data));
492 * @buf1: a first source #GstBuffer to merge.
493 * @offset: the offset in the first buffer from where the new
494 * buffer should start.
495 * @buf2: the second source #GstBuffer to merge.
496 * @len: the total length of the new buffer.
498 * Creates a new buffer that consists of part of buf1 and buf2.
499 * Logically, buf1 and buf2 are concatenated into a single larger
500 * buffer, and a new buffer is created at the given offset inside
501 * this space, with a given length.
503 * If the two source buffers are children of the same larger buffer,
504 * and are contiguous, the new buffer will be a child of the shared
505 * parent, and thus no copying is necessary. you can use
506 * gst_buffer_is_span_fast() to determine if a memcpy will be needed.
508 * Returns: the new #GstBuffer that spans the two source buffers.
513 gst_buffer_span (GstBuffer * buf1, guint32 offset, GstBuffer * buf2,
518 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, NULL);
519 g_return_val_if_fail (buf1->mini_object.refcount > 0, FALSE);
520 g_return_val_if_fail (buf2->mini_object.refcount > 0, FALSE);
521 g_return_val_if_fail (len > 0, NULL);
522 g_return_val_if_fail (len <= buf1->size + buf2->size - offset, NULL);
524 /* if the two buffers have the same parent and are adjacent */
525 if (gst_buffer_is_span_fast (buf1, buf2)) {
526 GstBuffer *parent = GST_SUBBUFFER (buf1)->parent;
528 /* we simply create a subbuffer of the common parent */
529 newbuf = gst_buffer_create_sub (parent,
530 buf1->data - parent->data + offset, len);
532 GST_CAT_DEBUG (GST_CAT_BUFFER,
533 "slow path taken while spanning buffers %p and %p", buf1, buf2);
534 /* otherwise we simply have to brute-force copy the buffers */
535 newbuf = gst_buffer_new_and_alloc (len);
537 /* copy the first buffer's data across */
538 memcpy (newbuf->data, buf1->data + offset, buf1->size - offset);
539 /* copy the second buffer's data across */
540 memcpy (newbuf->data + (buf1->size - offset), buf2->data,
541 len - (buf1->size - offset));
542 /* if the offset is 0, the new buffer has the same timestamp as buf1 */
544 GST_BUFFER_OFFSET (newbuf) = GST_BUFFER_OFFSET (buf1);
545 GST_BUFFER_TIMESTAMP (newbuf) = GST_BUFFER_TIMESTAMP (buf1);
548 /* if we completely merged the two buffers (appended), we can
549 * calculate the duration too. Also make sure we's not messing with
550 * invalid DURATIONS */
551 if (offset == 0 && buf1->size + buf2->size == len) {
552 if (GST_BUFFER_DURATION_IS_VALID (buf1) &&
553 GST_BUFFER_DURATION_IS_VALID (buf2)) {
555 GST_BUFFER_DURATION (newbuf) = GST_BUFFER_DURATION (buf1) +
556 GST_BUFFER_DURATION (buf2);
558 if (GST_BUFFER_OFFSET_END_IS_VALID (buf2)) {
560 GST_BUFFER_OFFSET_END (newbuf) = GST_BUFFER_OFFSET_END (buf2);