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_finalize (GstBuffer * buffer);
124 static GstBuffer *_gst_buffer_copy (GstBuffer * buffer);
125 static GType gst_subbuffer_get_type (void);
127 static GType _gst_subbuffer_type = 0;
128 static GType _gst_buffer_type = 0;
131 _gst_buffer_initialize (void)
133 /* the GstMiniObject types need to be class_ref'd once before it can be
134 * done from multiple threads;
135 * see http://bugzilla.gnome.org/show_bug.cgi?id=304551 */
136 g_type_class_ref (gst_buffer_get_type ());
137 g_type_class_ref (gst_subbuffer_get_type ());
142 _gst_buffer_type = g_define_type_id; \
145 G_DEFINE_TYPE_WITH_CODE (GstBuffer, gst_buffer, GST_TYPE_MINI_OBJECT, _do_init);
148 gst_buffer_class_init (GstBufferClass * klass)
150 klass->mini_object_class.copy = (GstMiniObjectCopyFunction) _gst_buffer_copy;
151 klass->mini_object_class.finalize =
152 (GstMiniObjectFinalizeFunction) gst_buffer_finalize;
156 gst_buffer_finalize (GstBuffer * buffer)
158 g_return_if_fail (buffer != NULL);
160 GST_CAT_LOG (GST_CAT_BUFFER, "finalize %p", buffer);
163 if (G_LIKELY (buffer->malloc_data))
164 buffer->free_func (buffer->malloc_data);
166 gst_caps_replace (&GST_BUFFER_CAPS (buffer), NULL);
168 GST_MINI_OBJECT_CLASS (gst_buffer_parent_class)->finalize
169 (GST_MINI_OBJECT_CAST (buffer));
173 * gst_buffer_copy_metadata:
174 * @dest: a destination #GstBuffer
175 * @src: a source #GstBuffer
176 * @flags: flags indicating what metadata fields should be copied.
178 * Copies the metadata from @src into @dest. The data, size and mallocdata
179 * fields are not copied.
181 * @flags indicate which fields will be copied. Use #GST_BUFFER_COPY_ALL to copy
182 * all the metadata fields.
184 * This function is typically called from a custom buffer copy function after
185 * creating @dest and setting the data, size, mallocdata.
190 gst_buffer_copy_metadata (GstBuffer * dest, const GstBuffer * src,
191 GstBufferCopyFlags flags)
193 g_return_if_fail (dest != NULL);
194 g_return_if_fail (src != NULL);
196 GST_CAT_LOG (GST_CAT_BUFFER, "copy %p to %p", src, dest);
198 if (flags & GST_BUFFER_COPY_FLAGS) {
201 /* copy relevant flags */
202 mask = GST_BUFFER_FLAG_PREROLL | GST_BUFFER_FLAG_IN_CAPS |
203 GST_BUFFER_FLAG_DELTA_UNIT | GST_BUFFER_FLAG_DISCONT |
205 GST_MINI_OBJECT_FLAGS (dest) |= GST_MINI_OBJECT_FLAGS (src) & mask;
208 if (flags & GST_BUFFER_COPY_TIMESTAMPS) {
209 GST_BUFFER_TIMESTAMP (dest) = GST_BUFFER_TIMESTAMP (src);
210 GST_BUFFER_DURATION (dest) = GST_BUFFER_DURATION (src);
211 GST_BUFFER_OFFSET (dest) = GST_BUFFER_OFFSET (src);
212 GST_BUFFER_OFFSET_END (dest) = GST_BUFFER_OFFSET_END (src);
215 if (flags & GST_BUFFER_COPY_CAPS) {
216 if (GST_BUFFER_CAPS (src))
217 GST_BUFFER_CAPS (dest) = gst_caps_ref (GST_BUFFER_CAPS (src));
219 GST_BUFFER_CAPS (dest) = NULL;
224 _gst_buffer_copy (GstBuffer * buffer)
228 g_return_val_if_fail (buffer != NULL, NULL);
230 /* create a fresh new buffer */
231 copy = gst_buffer_new ();
233 /* we simply copy everything from our parent */
234 copy->data = g_memdup (buffer->data, buffer->size);
235 /* make sure it gets freed (even if the parent is subclassed, we return a
237 copy->malloc_data = copy->data;
238 copy->size = buffer->size;
240 gst_buffer_copy_metadata (copy, buffer, GST_BUFFER_COPY_ALL);
246 gst_buffer_init (GstBuffer * buffer)
248 GST_CAT_LOG (GST_CAT_BUFFER, "init %p", buffer);
250 GST_BUFFER_TIMESTAMP (buffer) = GST_CLOCK_TIME_NONE;
251 GST_BUFFER_DURATION (buffer) = GST_CLOCK_TIME_NONE;
252 GST_BUFFER_OFFSET (buffer) = GST_BUFFER_OFFSET_NONE;
253 GST_BUFFER_OFFSET_END (buffer) = GST_BUFFER_OFFSET_NONE;
254 GST_BUFFER_FREE_FUNC (buffer) = g_free;
260 * Creates a newly allocated buffer without any data.
263 * Returns: the new #GstBuffer.
266 gst_buffer_new (void)
270 newbuf = (GstBuffer *) gst_mini_object_new (_gst_buffer_type);
272 GST_CAT_LOG (GST_CAT_BUFFER, "new %p", newbuf);
278 * gst_buffer_new_and_alloc:
279 * @size: the size of the new buffer's data.
281 * Creates a newly allocated buffer with data of the given size.
282 * The buffer memory is not cleared. If the requested amount of
283 * memory can't be allocated, the program will abort. Use
284 * gst_buffer_try_new_and_alloc() if you want to handle this case
285 * gracefully or have gotten the size to allocate from an untrusted
286 * source such as a media stream.
289 * Note that when @size == 0, the buffer data pointer will be NULL.
292 * Returns: the new #GstBuffer.
295 gst_buffer_new_and_alloc (guint size)
299 newbuf = gst_buffer_new ();
301 newbuf->malloc_data = g_malloc (size);
302 GST_BUFFER_DATA (newbuf) = newbuf->malloc_data;
303 GST_BUFFER_SIZE (newbuf) = size;
305 GST_CAT_LOG (GST_CAT_BUFFER, "new %p of size %d", newbuf, size);
311 * gst_buffer_try_new_and_alloc:
312 * @size: the size of the new buffer's data.
314 * Tries to create a newly allocated buffer with data of the given size. If
315 * the requested amount of memory can't be allocated, NULL will be returned.
316 * The buffer memory is not cleared.
318 * Note that when @size == 0, the buffer data pointer will be NULL.
322 * Returns: a new #GstBuffer, or NULL if the memory couldn't be allocated.
327 gst_buffer_try_new_and_alloc (guint size)
332 malloc_data = g_try_malloc (size);
334 if (G_UNLIKELY (malloc_data == NULL && size != 0)) {
335 GST_CAT_WARNING (GST_CAT_BUFFER, "failed to allocate %d bytes", size);
339 /* FIXME: there's no g_type_try_create_instance() in GObject yet, so this
340 * will still abort if a new GstBuffer structure can't be allocated */
341 newbuf = gst_buffer_new ();
343 GST_BUFFER_MALLOCDATA (newbuf) = malloc_data;
344 GST_BUFFER_DATA (newbuf) = malloc_data;
345 GST_BUFFER_SIZE (newbuf) = size;
347 GST_CAT_LOG (GST_CAT_BUFFER, "new %p of size %d", newbuf, size);
353 * gst_buffer_get_caps:
354 * @buffer: a #GstBuffer.
356 * Gets the media type of the buffer. This can be NULL if there
357 * is no media type attached to this buffer.
359 * Returns: a reference to the #GstCaps. unref after usage.
360 * Returns NULL if there were no caps on this buffer.
362 /* this is not made atomic because if the buffer were reffed from multiple
363 * threads, it would have a refcount > 2 and thus be immutable.
366 gst_buffer_get_caps (GstBuffer * buffer)
370 g_return_val_if_fail (buffer != NULL, NULL);
372 ret = GST_BUFFER_CAPS (buffer);
381 * gst_buffer_set_caps:
382 * @buffer: a #GstBuffer.
385 * Sets the media type on the buffer. The refcount of the caps will
386 * be increased and any previous caps on the buffer will be
389 /* this is not made atomic because if the buffer were reffed from multiple
390 * threads, it would have a refcount > 2 and thus be immutable.
393 gst_buffer_set_caps (GstBuffer * buffer, GstCaps * caps)
395 g_return_if_fail (buffer != NULL);
397 gst_caps_replace (&GST_BUFFER_CAPS (buffer), caps);
401 * gst_buffer_is_metadata_writable:
404 * Similar to gst_buffer_is_writable, but this only ensures that the
405 * refcount of the buffer is 1, indicating that the caller is the sole
406 * owner and can change the buffer metadata, such as caps and timestamps.
408 * Returns: TRUE if the metadata is writable.
411 gst_buffer_is_metadata_writable (GstBuffer * buf)
413 return (GST_MINI_OBJECT_REFCOUNT_VALUE (GST_MINI_OBJECT_CAST (buf)) == 1);
417 * gst_buffer_make_metadata_writable:
420 * Similar to gst_buffer_make_writable, but does not ensure that the buffer
421 * data array is writable. Instead, this just ensures that the returned buffer
422 * is solely owned by the caller, by creating a subbuffer of the original
423 * buffer if necessary.
425 * After calling this function, @buf should not be referenced anymore. The
426 * result of this function has guaranteed writable metadata.
428 * Returns: A new #GstBuffer with writable metadata.
431 gst_buffer_make_metadata_writable (GstBuffer * buf)
435 if (gst_buffer_is_metadata_writable (buf)) {
438 ret = gst_buffer_create_sub (buf, 0, GST_BUFFER_SIZE (buf));
440 gst_buffer_unref (buf);
446 typedef struct _GstSubBuffer GstSubBuffer;
447 typedef struct _GstSubBufferClass GstSubBufferClass;
449 #define GST_IS_SUBBUFFER(obj) (G_TYPE_CHECK_INSTANCE_TYPE ((obj), _gst_subbuffer_type))
450 #define GST_SUBBUFFER_CAST(obj) ((GstSubBuffer *)(obj))
459 struct _GstSubBufferClass
461 GstBufferClass buffer_class;
464 static void gst_subbuffer_finalize (GstSubBuffer * buffer);
466 #define _do_init_sub \
468 _gst_subbuffer_type = g_define_type_id; \
471 G_DEFINE_TYPE_WITH_CODE (GstSubBuffer, gst_subbuffer, GST_TYPE_BUFFER,
475 gst_subbuffer_class_init (GstSubBufferClass * klass)
477 klass->buffer_class.mini_object_class.finalize =
478 (GstMiniObjectFinalizeFunction) gst_subbuffer_finalize;
482 gst_subbuffer_finalize (GstSubBuffer * buffer)
484 gst_buffer_unref (buffer->parent);
486 GST_MINI_OBJECT_CLASS (gst_subbuffer_parent_class)->finalize
487 (GST_MINI_OBJECT_CAST (buffer));
491 gst_subbuffer_init (GstSubBuffer * instance)
493 GST_BUFFER_FLAG_SET (GST_BUFFER_CAST (instance), GST_BUFFER_FLAG_READONLY);
497 * gst_buffer_create_sub:
498 * @parent: a #GstBuffer.
499 * @offset: the offset into parent #GstBuffer at which the new sub-buffer
501 * @size: the size of the new #GstBuffer sub-buffer, in bytes.
503 * Creates a sub-buffer from @parent at @offset and @size.
504 * This sub-buffer uses the actual memory space of the parent buffer.
505 * This function will copy the offset and timestamp fields when the
506 * offset is 0. If not, they will be set to #GST_CLOCK_TIME_NONE and
507 * #GST_BUFFER_OFFSET_NONE.
508 * If @offset equals 0 and @size equals the total size of @buffer, the
509 * duration and offset end fields are also copied. If not they will be set
510 * to #GST_CLOCK_TIME_NONE and #GST_BUFFER_OFFSET_NONE.
513 * Returns: the new #GstBuffer.
514 * Returns NULL if the arguments were invalid.
517 gst_buffer_create_sub (GstBuffer * buffer, guint offset, guint size)
519 GstSubBuffer *subbuffer;
523 g_return_val_if_fail (buffer != NULL, NULL);
524 g_return_val_if_fail (buffer->mini_object.refcount > 0, NULL);
525 g_return_val_if_fail (buffer->size >= offset + size, NULL);
527 /* find real parent */
528 if (GST_IS_SUBBUFFER (buffer)) {
529 parent = GST_SUBBUFFER_CAST (buffer)->parent;
533 gst_buffer_ref (parent);
535 /* create the new buffer */
536 subbuffer = (GstSubBuffer *) gst_mini_object_new (_gst_subbuffer_type);
537 subbuffer->parent = parent;
539 GST_CAT_LOG (GST_CAT_BUFFER, "new subbuffer %p (parent %p)", subbuffer,
542 /* set the right values in the child */
543 GST_BUFFER_DATA (GST_BUFFER_CAST (subbuffer)) = buffer->data + offset;
544 GST_BUFFER_SIZE (GST_BUFFER_CAST (subbuffer)) = size;
546 if ((offset == 0) && (size == GST_BUFFER_SIZE (buffer))) {
547 /* copy all the flags except IN_CAPS */
548 GST_BUFFER_FLAG_SET (subbuffer, GST_BUFFER_FLAGS (buffer));
549 GST_BUFFER_FLAG_UNSET (subbuffer, GST_BUFFER_FLAG_IN_CAPS);
551 /* copy only PREROLL & GAP flags */
552 GST_BUFFER_FLAG_SET (subbuffer, (GST_BUFFER_FLAGS (buffer) &
553 (GST_BUFFER_FLAG_PREROLL | GST_BUFFER_FLAG_GAP)));
556 /* we can copy the timestamp and offset if the new buffer starts at
559 GST_BUFFER_TIMESTAMP (subbuffer) = GST_BUFFER_TIMESTAMP (buffer);
560 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET (buffer);
561 complete = (buffer->size == size);
563 GST_BUFFER_TIMESTAMP (subbuffer) = GST_CLOCK_TIME_NONE;
564 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET_NONE;
571 /* if we copied the complete buffer we can copy the duration,
572 * offset_end and caps as well */
573 GST_BUFFER_DURATION (subbuffer) = GST_BUFFER_DURATION (buffer);
574 GST_BUFFER_OFFSET_END (subbuffer) = GST_BUFFER_OFFSET_END (buffer);
575 if ((caps = GST_BUFFER_CAPS (buffer)))
577 GST_BUFFER_CAPS (subbuffer) = caps;
579 GST_BUFFER_DURATION (subbuffer) = GST_CLOCK_TIME_NONE;
580 GST_BUFFER_OFFSET_END (subbuffer) = GST_BUFFER_OFFSET_NONE;
581 GST_BUFFER_CAPS (subbuffer) = NULL;
583 return GST_BUFFER_CAST (subbuffer);
587 * gst_buffer_is_span_fast:
588 * @buf1: the first #GstBuffer.
589 * @buf2: the second #GstBuffer.
591 * Determines whether a gst_buffer_span() can be done without copying
592 * the contents, that is, whether the data areas are contiguous sub-buffers of
596 * Returns: TRUE if the buffers are contiguous,
597 * FALSE if a copy would be required.
600 gst_buffer_is_span_fast (GstBuffer * buf1, GstBuffer * buf2)
602 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, FALSE);
603 g_return_val_if_fail (buf1->mini_object.refcount > 0, FALSE);
604 g_return_val_if_fail (buf2->mini_object.refcount > 0, FALSE);
606 /* it's only fast if we have subbuffers of the same parent */
607 return (GST_IS_SUBBUFFER (buf1) &&
608 GST_IS_SUBBUFFER (buf2) &&
609 (GST_SUBBUFFER_CAST (buf1)->parent == GST_SUBBUFFER_CAST (buf2)->parent)
610 && ((buf1->data + buf1->size) == buf2->data));
615 * @buf1: the first source #GstBuffer to merge.
616 * @offset: the offset in the first buffer from where the new
617 * buffer should start.
618 * @buf2: the second source #GstBuffer to merge.
619 * @len: the total length of the new buffer.
621 * Creates a new buffer that consists of part of buf1 and buf2.
622 * Logically, buf1 and buf2 are concatenated into a single larger
623 * buffer, and a new buffer is created at the given offset inside
624 * this space, with a given length.
626 * If the two source buffers are children of the same larger buffer,
627 * and are contiguous, the new buffer will be a child of the shared
628 * parent, and thus no copying is necessary. you can use
629 * gst_buffer_is_span_fast() to determine if a memcpy will be needed.
632 * Returns: the new #GstBuffer that spans the two source buffers.
633 * Returns NULL if the arguments are invalid.
636 gst_buffer_span (GstBuffer * buf1, guint32 offset, GstBuffer * buf2,
641 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, NULL);
642 g_return_val_if_fail (buf1->mini_object.refcount > 0, NULL);
643 g_return_val_if_fail (buf2->mini_object.refcount > 0, NULL);
644 g_return_val_if_fail (len > 0, NULL);
645 g_return_val_if_fail (len <= buf1->size + buf2->size - offset, NULL);
647 /* if the two buffers have the same parent and are adjacent */
648 if (gst_buffer_is_span_fast (buf1, buf2)) {
649 GstBuffer *parent = GST_SUBBUFFER_CAST (buf1)->parent;
651 /* we simply create a subbuffer of the common parent */
652 newbuf = gst_buffer_create_sub (parent,
653 buf1->data - parent->data + offset, len);
655 GST_CAT_DEBUG (GST_CAT_BUFFER,
656 "slow path taken while spanning buffers %p and %p", buf1, buf2);
657 /* otherwise we simply have to brute-force copy the buffers */
658 newbuf = gst_buffer_new_and_alloc (len);
660 /* copy the first buffer's data across */
661 memcpy (newbuf->data, buf1->data + offset, buf1->size - offset);
662 /* copy the second buffer's data across */
663 memcpy (newbuf->data + (buf1->size - offset), buf2->data,
664 len - (buf1->size - offset));
666 /* if the offset is 0, the new buffer has the same timestamp as buf1 */
668 GST_BUFFER_OFFSET (newbuf) = GST_BUFFER_OFFSET (buf1);
669 GST_BUFFER_TIMESTAMP (newbuf) = GST_BUFFER_TIMESTAMP (buf1);
671 /* if we completely merged the two buffers (appended), we can
672 * calculate the duration too. Also make sure we's not messing with
673 * invalid DURATIONS */
674 if (buf1->size + buf2->size == len) {
675 if (GST_BUFFER_DURATION_IS_VALID (buf1) &&
676 GST_BUFFER_DURATION_IS_VALID (buf2)) {
678 GST_BUFFER_DURATION (newbuf) = GST_BUFFER_DURATION (buf1) +
679 GST_BUFFER_DURATION (buf2);
681 if (GST_BUFFER_OFFSET_END_IS_VALID (buf2)) {
683 GST_BUFFER_OFFSET_END (newbuf) = GST_BUFFER_OFFSET_END (buf2);