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;
46 * size = width * height * bpp;
48 * buffer = gst_buffer_new ();
49 * GST_BUFFER_SIZE (buffer) = size;
50 * GST_BUFFER_MALLOCDATA (buffer) = g_alloc (size);
51 * GST_BUFFER_DATA (buffer) = GST_BUFFER_MALLOCDATA (buffer);
56 * Alternatively, use gst_buffer_new_and_alloc()
57 * to create a buffer with preallocated data of a given size.
59 * If an element knows what pad you will push the buffer out on, it should use
60 * gst_pad_alloc_buffer() instead to create a buffer. This allows downstream
61 * elements to provide special buffers to write in, like hardware buffers.
63 * A buffer has a pointer to a #GstCaps describing the media type of the data
64 * in the buffer. Attach caps to the buffer with gst_buffer_set_caps(); this
65 * is typically done before pushing out a buffer using gst_pad_push() so that
66 * the downstream element knows the type of the buffer.
68 * gst_buffer_ref() is used to increase the refcount of a buffer. This must be
69 * done when you want to keep a handle to the buffer after pushing it to the
72 * To efficiently create a smaller buffer out of an existing one, you can
73 * use gst_buffer_create_sub().
75 * If the plug-in wants to modify the buffer in-place, it should first obtain
76 * a buffer that is safe to modify by using gst_buffer_make_writable(). This
77 * function is optimized so that a copy will only be made when it is necessary.
79 * Several flags of the buffer can be set and unset with the
80 * GST_BUFFER_FLAG_SET() and GST_BUFFER_FLAG_UNSET() macros. Use
81 * GST_BUFFER_FLAG_IS_SET() to test it a certain #GstBufferFlag is set.
83 * Buffers can be efficiently merged into a larger buffer with
84 * gst_buffer_merge() and gst_buffer_span() if the gst_buffer_is_span_fast()
85 * function returns TRUE.
87 * An element should either unref the buffer or push it out on a src pad
88 * using gst_pad_push() (see #GstPad).
90 * Buffers usually are freed by unreffing them with gst_buffer_unref(). When
91 * the refcount drops to 0, the buffer memory will be freed again.
93 * Last reviewed on September 24th, 2005 (0.9.0)
95 #include "gst_private.h"
97 #include "gstbuffer.h"
100 #include "gstminiobject.h"
103 static void gst_buffer_init (GTypeInstance * instance, gpointer g_class);
104 static void gst_buffer_class_init (gpointer g_class, gpointer class_data);
105 static void gst_buffer_finalize (GstBuffer * buffer);
106 static GstBuffer *_gst_buffer_copy (GstBuffer * buffer);
110 _gst_buffer_initialize (void)
114 gst_buffer_get_type ();
116 /* the GstMiniObject types need to be class_ref'd once before it can be
117 * done from multiple threads;
118 * see http://bugzilla.gnome.org/show_bug.cgi?id=304551 */
119 ptr = g_type_class_ref (GST_TYPE_BUFFER);
120 g_type_class_unref (ptr);
124 gst_buffer_get_type (void)
126 static GType _gst_buffer_type;
128 if (G_UNLIKELY (_gst_buffer_type == 0)) {
129 static const GTypeInfo buffer_info = {
130 sizeof (GstBufferClass),
133 gst_buffer_class_init,
142 _gst_buffer_type = g_type_register_static (GST_TYPE_MINI_OBJECT,
143 "GstBuffer", &buffer_info, 0);
145 return _gst_buffer_type;
149 gst_buffer_class_init (gpointer g_class, gpointer class_data)
151 GstBufferClass *buffer_class = GST_BUFFER_CLASS (g_class);
153 buffer_class->mini_object_class.copy =
154 (GstMiniObjectCopyFunction) _gst_buffer_copy;
155 buffer_class->mini_object_class.finalize =
156 (GstMiniObjectFinalizeFunction) gst_buffer_finalize;
161 gst_buffer_finalize (GstBuffer * buffer)
163 g_return_if_fail (buffer != NULL);
165 GST_CAT_LOG (GST_CAT_BUFFER, "finalize %p", buffer);
168 if (buffer->malloc_data) {
169 g_free (buffer->malloc_data);
172 gst_caps_replace (&GST_BUFFER_CAPS (buffer), NULL);
176 _gst_buffer_copy (GstBuffer * buffer)
181 g_return_val_if_fail (buffer != NULL, NULL);
183 /* create a fresh new buffer */
184 copy = gst_buffer_new ();
186 GST_CAT_LOG (GST_CAT_BUFFER, "copy %p to %p", buffer, copy);
188 /* copy relevant flags */
189 mask = GST_BUFFER_FLAG_PREROLL | GST_BUFFER_FLAG_IN_CAPS |
190 GST_BUFFER_FLAG_DELTA_UNIT;
191 GST_MINI_OBJECT (copy)->flags |= GST_MINI_OBJECT (buffer)->flags & mask;
193 /* we simply copy everything from our parent */
194 copy->data = g_memdup (buffer->data, buffer->size);
195 /* make sure it gets freed (even if the parent is subclassed, we return a
197 copy->malloc_data = copy->data;
199 copy->size = buffer->size;
201 GST_BUFFER_TIMESTAMP (copy) = GST_BUFFER_TIMESTAMP (buffer);
202 GST_BUFFER_DURATION (copy) = GST_BUFFER_DURATION (buffer);
203 GST_BUFFER_OFFSET (copy) = GST_BUFFER_OFFSET (buffer);
204 GST_BUFFER_OFFSET_END (copy) = GST_BUFFER_OFFSET_END (buffer);
206 if (GST_BUFFER_CAPS (buffer))
207 GST_BUFFER_CAPS (copy) = gst_caps_ref (GST_BUFFER_CAPS (buffer));
209 GST_BUFFER_CAPS (copy) = NULL;
215 gst_buffer_init (GTypeInstance * instance, gpointer g_class)
219 buffer = (GstBuffer *) instance;
221 GST_CAT_LOG (GST_CAT_BUFFER, "init %p", buffer);
223 GST_BUFFER_TIMESTAMP (buffer) = GST_CLOCK_TIME_NONE;
224 GST_BUFFER_DURATION (buffer) = GST_CLOCK_TIME_NONE;
225 GST_BUFFER_OFFSET (buffer) = GST_BUFFER_OFFSET_NONE;
226 GST_BUFFER_OFFSET_END (buffer) = GST_BUFFER_OFFSET_NONE;
232 * Creates a newly allocated buffer without any data.
234 * Returns: the new #GstBuffer.
239 gst_buffer_new (void)
243 newbuf = (GstBuffer *) gst_mini_object_new (GST_TYPE_BUFFER);
245 GST_CAT_LOG (GST_CAT_BUFFER, "new %p", newbuf);
251 * gst_buffer_new_and_alloc:
252 * @size: the size of the new buffer's data.
254 * Creates a newly allocated buffer with data of the given size.
256 * Returns: the new #GstBuffer.
261 gst_buffer_new_and_alloc (guint size)
265 newbuf = gst_buffer_new ();
267 newbuf->malloc_data = g_malloc (size);
268 GST_BUFFER_DATA (newbuf) = newbuf->malloc_data;
269 GST_BUFFER_SIZE (newbuf) = size;
271 GST_CAT_LOG (GST_CAT_BUFFER, "new %p of size %d", newbuf, size);
277 * gst_buffer_get_caps:
278 * @buffer: a #GstBuffer to get the caps of.
280 * Gets the media type of the buffer. This can be NULL if there
281 * is not media type attached to this buffer or when the media
282 * type is the same as the previous received buffer.
284 * Returns: a reference to the #GstCaps, or NULL if there were no caps on this
287 /* FIXME can we make this threadsafe without a lock on the buffer?
288 * We can use compare and swap and atomic reads. */
290 gst_buffer_get_caps (GstBuffer * buffer)
294 g_return_val_if_fail (buffer != NULL, NULL);
296 ret = GST_BUFFER_CAPS (buffer);
305 * gst_buffer_set_caps:
306 * @buffer: a #GstBuffer to set the caps of.
307 * @caps: a #GstCaps to set.
309 * Sets the media type on the buffer. The caps' refcount will
310 * be increased and any previous caps on the buffer will be
313 /* FIXME can we make this threadsafe without a lock on the buffer?
314 * We can use compare and swap and atomic reads. Another idea is to
315 * not attach the caps to the buffer but use an event to signal a caps
318 gst_buffer_set_caps (GstBuffer * buffer, GstCaps * caps)
320 g_return_if_fail (buffer != NULL);
322 gst_caps_replace (&GST_BUFFER_CAPS (buffer), caps);
326 typedef struct _GstSubBuffer GstSubBuffer;
327 typedef struct _GstSubBufferClass GstSubBufferClass;
329 #define GST_TYPE_SUBBUFFER (gst_subbuffer_get_type())
331 #define GST_IS_SUBBUFFER(obj) (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GST_TYPE_SUBBUFFER))
332 #define GST_SUBBUFFER(obj) (G_TYPE_CHECK_INSTANCE_CAST ((obj), GST_TYPE_SUBBUFFER, GstSubBuffer))
341 struct _GstSubBufferClass
343 GstBufferClass buffer_class;
346 static GstBufferClass *sub_parent_class;
348 static void gst_subbuffer_init (GTypeInstance * instance, gpointer g_class);
349 static void gst_subbuffer_class_init (gpointer g_class, gpointer class_data);
350 static void gst_subbuffer_finalize (GstSubBuffer * buffer);
353 gst_subbuffer_get_type (void)
355 static GType _gst_subbuffer_type = 0;
357 if (G_UNLIKELY (_gst_subbuffer_type == 0)) {
358 static const GTypeInfo subbuffer_info = {
359 sizeof (GstSubBufferClass),
362 gst_subbuffer_class_init,
365 sizeof (GstSubBuffer),
371 _gst_subbuffer_type = g_type_register_static (GST_TYPE_BUFFER,
372 "GstSubBuffer", &subbuffer_info, 0);
374 return _gst_subbuffer_type;
378 gst_subbuffer_class_init (gpointer g_class, gpointer class_data)
380 GstBufferClass *buffer_class = GST_BUFFER_CLASS (g_class);
382 sub_parent_class = g_type_class_ref (GST_TYPE_BUFFER);
384 buffer_class->mini_object_class.finalize =
385 (GstMiniObjectFinalizeFunction) gst_subbuffer_finalize;
389 gst_subbuffer_finalize (GstSubBuffer * buffer)
391 gst_buffer_unref (buffer->parent);
393 GST_MINI_OBJECT_CLASS (sub_parent_class)->finalize (GST_MINI_OBJECT (buffer));
397 gst_subbuffer_init (GTypeInstance * instance, gpointer g_class)
399 GST_BUFFER_FLAG_SET (GST_BUFFER_CAST (instance), GST_BUFFER_FLAG_READONLY);
403 * gst_buffer_create_sub:
404 * @parent: a parent #GstBuffer to create a subbuffer from.
405 * @offset: the offset into parent #GstBuffer.
406 * @size: the size of the new #GstBuffer sub-buffer (with size > 0).
408 * Creates a sub-buffer from the parent at a given offset.
409 * This sub-buffer uses the actual memory space of the parent buffer.
410 * This function will copy the offset and timestamp field when the
411 * offset is 0, else they are set to _NONE.
412 * The duration field of the new buffer are set to GST_CLOCK_TIME_NONE.
414 * Returns: the new #GstBuffer, or NULL if there was an error.
419 gst_buffer_create_sub (GstBuffer * buffer, guint offset, guint size)
421 GstSubBuffer *subbuffer;
424 g_return_val_if_fail (buffer != NULL, NULL);
425 g_return_val_if_fail (buffer->mini_object.refcount > 0, NULL);
426 g_return_val_if_fail (size > 0, NULL);
427 g_return_val_if_fail (buffer->size >= offset + size, NULL);
429 /* find real parent */
430 if (GST_IS_SUBBUFFER (buffer)) {
431 parent = GST_SUBBUFFER (buffer)->parent;
435 gst_buffer_ref (parent);
437 /* create the new buffer */
438 subbuffer = (GstSubBuffer *) gst_mini_object_new (GST_TYPE_SUBBUFFER);
439 subbuffer->parent = parent;
441 GST_CAT_LOG (GST_CAT_BUFFER, "new subbuffer %p (parent %p)", subbuffer,
444 /* set the right values in the child */
445 GST_BUFFER_DATA (GST_BUFFER_CAST (subbuffer)) = buffer->data + offset;
446 GST_BUFFER_SIZE (GST_BUFFER_CAST (subbuffer)) = size;
448 /* we can copy the timestamp and offset if the new buffer starts at
451 GST_BUFFER_TIMESTAMP (subbuffer) = GST_BUFFER_TIMESTAMP (buffer);
452 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET (buffer);
454 GST_BUFFER_TIMESTAMP (subbuffer) = GST_CLOCK_TIME_NONE;
455 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET_NONE;
458 GST_BUFFER_DURATION (subbuffer) = GST_CLOCK_TIME_NONE;
459 GST_BUFFER_OFFSET_END (subbuffer) = GST_BUFFER_OFFSET_NONE;
461 GST_BUFFER_CAPS (subbuffer) = NULL;
463 return GST_BUFFER_CAST (subbuffer);
467 * gst_buffer_is_span_fast:
468 * @buf1: a first source #GstBuffer.
469 * @buf2: the second source #GstBuffer.
471 * Determines whether a gst_buffer_span() can be done without copying
472 * the contents, that is, whether the data areas are contiguous.
474 * Returns: TRUE if the buffers are contiguous,
475 * FALSE if a copy would be required.
480 gst_buffer_is_span_fast (GstBuffer * buf1, GstBuffer * buf2)
482 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, FALSE);
483 g_return_val_if_fail (buf1->mini_object.refcount > 0, FALSE);
484 g_return_val_if_fail (buf2->mini_object.refcount > 0, FALSE);
486 /* it's only fast if we have subbuffers of the same parent */
487 return (GST_IS_SUBBUFFER (buf1) &&
488 GST_IS_SUBBUFFER (buf2) &&
489 (GST_SUBBUFFER (buf1)->parent == GST_SUBBUFFER (buf2)->parent) &&
490 ((buf1->data + buf1->size) == buf2->data));
495 * @buf1: a first source #GstBuffer to merge.
496 * @offset: the offset in the first buffer from where the new
497 * buffer should start.
498 * @buf2: the second source #GstBuffer to merge.
499 * @len: the total length of the new buffer.
501 * Creates a new buffer that consists of part of buf1 and buf2.
502 * Logically, buf1 and buf2 are concatenated into a single larger
503 * buffer, and a new buffer is created at the given offset inside
504 * this space, with a given length.
506 * If the two source buffers are children of the same larger buffer,
507 * and are contiguous, the new buffer will be a child of the shared
508 * parent, and thus no copying is necessary. you can use
509 * gst_buffer_is_span_fast() to determine if a memcpy will be needed.
511 * Returns: the new #GstBuffer that spans the two source buffers.
516 gst_buffer_span (GstBuffer * buf1, guint32 offset, GstBuffer * buf2,
521 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, NULL);
522 g_return_val_if_fail (buf1->mini_object.refcount > 0, FALSE);
523 g_return_val_if_fail (buf2->mini_object.refcount > 0, FALSE);
524 g_return_val_if_fail (len > 0, NULL);
525 g_return_val_if_fail (len <= buf1->size + buf2->size - offset, NULL);
527 /* if the two buffers have the same parent and are adjacent */
528 if (gst_buffer_is_span_fast (buf1, buf2)) {
529 GstBuffer *parent = GST_SUBBUFFER (buf1)->parent;
531 /* we simply create a subbuffer of the common parent */
532 newbuf = gst_buffer_create_sub (parent,
533 buf1->data - parent->data + offset, len);
535 GST_CAT_DEBUG (GST_CAT_BUFFER,
536 "slow path taken while spanning buffers %p and %p", buf1, buf2);
537 /* otherwise we simply have to brute-force copy the buffers */
538 newbuf = gst_buffer_new_and_alloc (len);
540 /* copy the first buffer's data across */
541 memcpy (newbuf->data, buf1->data + offset, buf1->size - offset);
542 /* copy the second buffer's data across */
543 memcpy (newbuf->data + (buf1->size - offset), buf2->data,
544 len - (buf1->size - offset));
545 /* if the offset is 0, the new buffer has the same timestamp as buf1 */
547 GST_BUFFER_OFFSET (newbuf) = GST_BUFFER_OFFSET (buf1);
548 GST_BUFFER_TIMESTAMP (newbuf) = GST_BUFFER_TIMESTAMP (buf1);
551 /* if we completely merged the two buffers (appended), we can
552 * calculate the duration too. Also make sure we's not messing with
553 * invalid DURATIONS */
554 if (offset == 0 && buf1->size + buf2->size == len) {
555 if (GST_BUFFER_DURATION_IS_VALID (buf1) &&
556 GST_BUFFER_DURATION_IS_VALID (buf2)) {
558 GST_BUFFER_DURATION (newbuf) = GST_BUFFER_DURATION (buf1) +
559 GST_BUFFER_DURATION (buf2);
561 if (GST_BUFFER_OFFSET_END_IS_VALID (buf2)) {
563 GST_BUFFER_OFFSET_END (newbuf) = GST_BUFFER_OFFSET_END (buf2);