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 /* ((GstMiniObjectClass *) */
169 /* gst_buffer_parent_class)->finalize (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 /* nothing to copy if the buffers are the same */
197 if (G_UNLIKELY (dest == src))
200 GST_CAT_LOG (GST_CAT_BUFFER, "copy %p to %p", src, dest);
202 if (flags & GST_BUFFER_COPY_FLAGS) {
205 /* copy relevant flags */
206 mask = GST_BUFFER_FLAG_PREROLL | GST_BUFFER_FLAG_IN_CAPS |
207 GST_BUFFER_FLAG_DELTA_UNIT | GST_BUFFER_FLAG_DISCONT |
208 GST_BUFFER_FLAG_GAP | GST_BUFFER_FLAG_MEDIA1 |
209 GST_BUFFER_FLAG_MEDIA2 | GST_BUFFER_FLAG_MEDIA3;
210 GST_MINI_OBJECT_FLAGS (dest) |= GST_MINI_OBJECT_FLAGS (src) & mask;
213 if (flags & GST_BUFFER_COPY_TIMESTAMPS) {
214 GST_BUFFER_TIMESTAMP (dest) = GST_BUFFER_TIMESTAMP (src);
215 GST_BUFFER_DURATION (dest) = GST_BUFFER_DURATION (src);
216 GST_BUFFER_OFFSET (dest) = GST_BUFFER_OFFSET (src);
217 GST_BUFFER_OFFSET_END (dest) = GST_BUFFER_OFFSET_END (src);
220 if (flags & GST_BUFFER_COPY_CAPS) {
221 gst_caps_replace (&GST_BUFFER_CAPS (dest), GST_BUFFER_CAPS (src));
226 _gst_buffer_copy (GstBuffer * buffer)
230 g_return_val_if_fail (buffer != NULL, NULL);
232 /* create a fresh new buffer */
233 copy = gst_buffer_new ();
235 /* we simply copy everything from our parent */
236 copy->data = g_memdup (buffer->data, buffer->size);
237 /* make sure it gets freed (even if the parent is subclassed, we return a
239 copy->malloc_data = copy->data;
240 copy->size = buffer->size;
242 gst_buffer_copy_metadata (copy, buffer, GST_BUFFER_COPY_ALL);
248 gst_buffer_init (GstBuffer * buffer)
250 GST_CAT_LOG (GST_CAT_BUFFER, "init %p", buffer);
252 GST_BUFFER_TIMESTAMP (buffer) = GST_CLOCK_TIME_NONE;
253 GST_BUFFER_DURATION (buffer) = GST_CLOCK_TIME_NONE;
254 GST_BUFFER_OFFSET (buffer) = GST_BUFFER_OFFSET_NONE;
255 GST_BUFFER_OFFSET_END (buffer) = GST_BUFFER_OFFSET_NONE;
256 GST_BUFFER_FREE_FUNC (buffer) = g_free;
262 * Creates a newly allocated buffer without any data.
265 * Returns: the new #GstBuffer.
268 gst_buffer_new (void)
272 newbuf = (GstBuffer *) gst_mini_object_new (_gst_buffer_type);
274 GST_CAT_LOG (GST_CAT_BUFFER, "new %p", newbuf);
280 * gst_buffer_new_and_alloc:
281 * @size: the size of the new buffer's data.
283 * Creates a newly allocated buffer with data of the given size.
284 * The buffer memory is not cleared. If the requested amount of
285 * memory can't be allocated, the program will abort. Use
286 * gst_buffer_try_new_and_alloc() if you want to handle this case
287 * gracefully or have gotten the size to allocate from an untrusted
288 * source such as a media stream.
291 * Note that when @size == 0, the buffer data pointer will be NULL.
294 * Returns: the new #GstBuffer.
297 gst_buffer_new_and_alloc (guint size)
301 newbuf = gst_buffer_new ();
303 newbuf->malloc_data = g_malloc (size);
304 GST_BUFFER_DATA (newbuf) = newbuf->malloc_data;
305 GST_BUFFER_SIZE (newbuf) = size;
307 GST_CAT_LOG (GST_CAT_BUFFER, "new %p of size %d", newbuf, size);
313 * gst_buffer_try_new_and_alloc:
314 * @size: the size of the new buffer's data.
316 * Tries to create a newly allocated buffer with data of the given size. If
317 * the requested amount of memory can't be allocated, NULL will be returned.
318 * The buffer memory is not cleared.
320 * Note that when @size == 0, the buffer data pointer will be NULL.
324 * Returns: a new #GstBuffer, or NULL if the memory couldn't be allocated.
329 gst_buffer_try_new_and_alloc (guint size)
334 malloc_data = g_try_malloc (size);
336 if (G_UNLIKELY (malloc_data == NULL && size != 0)) {
337 GST_CAT_WARNING (GST_CAT_BUFFER, "failed to allocate %d bytes", size);
341 /* FIXME: there's no g_type_try_create_instance() in GObject yet, so this
342 * will still abort if a new GstBuffer structure can't be allocated */
343 newbuf = gst_buffer_new ();
345 GST_BUFFER_MALLOCDATA (newbuf) = malloc_data;
346 GST_BUFFER_DATA (newbuf) = malloc_data;
347 GST_BUFFER_SIZE (newbuf) = size;
349 GST_CAT_LOG (GST_CAT_BUFFER, "new %p of size %d", newbuf, size);
355 * gst_buffer_get_caps:
356 * @buffer: a #GstBuffer.
358 * Gets the media type of the buffer. This can be NULL if there
359 * is no media type attached to this buffer.
361 * Returns: a reference to the #GstCaps. unref after usage.
362 * Returns NULL if there were no caps on this buffer.
364 /* this is not made atomic because if the buffer were reffed from multiple
365 * threads, it would have a refcount > 2 and thus be immutable.
368 gst_buffer_get_caps (GstBuffer * buffer)
372 g_return_val_if_fail (buffer != NULL, NULL);
374 ret = GST_BUFFER_CAPS (buffer);
383 * gst_buffer_set_caps:
384 * @buffer: a #GstBuffer.
387 * Sets the media type on the buffer. The refcount of the caps will
388 * be increased and any previous caps on the buffer will be
391 /* this is not made atomic because if the buffer were reffed from multiple
392 * threads, it would have a refcount > 2 and thus be immutable.
395 gst_buffer_set_caps (GstBuffer * buffer, GstCaps * caps)
397 g_return_if_fail (buffer != NULL);
399 gst_caps_replace (&GST_BUFFER_CAPS (buffer), caps);
403 * gst_buffer_is_metadata_writable:
406 * Similar to gst_buffer_is_writable, but this only ensures that the
407 * refcount of the buffer is 1, indicating that the caller is the sole
408 * owner and can change the buffer metadata, such as caps and timestamps.
410 * Returns: TRUE if the metadata is writable.
413 gst_buffer_is_metadata_writable (GstBuffer * buf)
415 return (GST_MINI_OBJECT_REFCOUNT_VALUE (GST_MINI_OBJECT_CAST (buf)) == 1);
419 * gst_buffer_make_metadata_writable:
422 * Similar to gst_buffer_make_writable, but does not ensure that the buffer
423 * data array is writable. Instead, this just ensures that the returned buffer
424 * is solely owned by the caller, by creating a subbuffer of the original
425 * buffer if necessary.
427 * After calling this function, @buf should not be referenced anymore. The
428 * result of this function has guaranteed writable metadata.
430 * Returns: A new #GstBuffer with writable metadata.
433 gst_buffer_make_metadata_writable (GstBuffer * buf)
437 if (gst_buffer_is_metadata_writable (buf)) {
440 ret = gst_buffer_create_sub (buf, 0, GST_BUFFER_SIZE (buf));
442 gst_buffer_unref (buf);
448 typedef struct _GstSubBuffer GstSubBuffer;
449 typedef struct _GstSubBufferClass GstSubBufferClass;
451 #define GST_IS_SUBBUFFER(obj) (G_TYPE_CHECK_INSTANCE_TYPE ((obj), _gst_subbuffer_type))
452 #define GST_SUBBUFFER_CAST(obj) ((GstSubBuffer *)(obj))
461 struct _GstSubBufferClass
463 GstBufferClass buffer_class;
466 static void gst_subbuffer_finalize (GstSubBuffer * buffer);
468 #define _do_init_sub \
470 _gst_subbuffer_type = g_define_type_id; \
473 G_DEFINE_TYPE_WITH_CODE (GstSubBuffer, gst_subbuffer, GST_TYPE_BUFFER,
477 gst_subbuffer_class_init (GstSubBufferClass * klass)
479 klass->buffer_class.mini_object_class.finalize =
480 (GstMiniObjectFinalizeFunction) gst_subbuffer_finalize;
484 gst_subbuffer_finalize (GstSubBuffer * buffer)
486 gst_buffer_unref (buffer->parent);
488 ((GstMiniObjectClass *) gst_subbuffer_parent_class)->finalize
489 (GST_MINI_OBJECT_CAST (buffer));
493 gst_subbuffer_init (GstSubBuffer * instance)
495 GST_BUFFER_FLAG_SET (GST_BUFFER_CAST (instance), GST_BUFFER_FLAG_READONLY);
499 * gst_buffer_create_sub:
500 * @parent: a #GstBuffer.
501 * @offset: the offset into parent #GstBuffer at which the new sub-buffer
503 * @size: the size of the new #GstBuffer sub-buffer, in bytes.
505 * Creates a sub-buffer from @parent at @offset and @size.
506 * This sub-buffer uses the actual memory space of the parent buffer.
507 * This function will copy the offset and timestamp fields when the
508 * offset is 0. If not, they will be set to #GST_CLOCK_TIME_NONE and
509 * #GST_BUFFER_OFFSET_NONE.
510 * If @offset equals 0 and @size equals the total size of @buffer, the
511 * duration and offset end fields are also copied. If not they will be set
512 * to #GST_CLOCK_TIME_NONE and #GST_BUFFER_OFFSET_NONE.
515 * Returns: the new #GstBuffer.
516 * Returns NULL if the arguments were invalid.
519 gst_buffer_create_sub (GstBuffer * buffer, guint offset, guint size)
521 GstSubBuffer *subbuffer;
525 g_return_val_if_fail (buffer != NULL, NULL);
526 g_return_val_if_fail (buffer->mini_object.refcount > 0, NULL);
527 g_return_val_if_fail (buffer->size >= offset + size, NULL);
529 /* find real parent */
530 if (GST_IS_SUBBUFFER (buffer)) {
531 parent = GST_SUBBUFFER_CAST (buffer)->parent;
535 gst_buffer_ref (parent);
537 /* create the new buffer */
538 subbuffer = (GstSubBuffer *) gst_mini_object_new (_gst_subbuffer_type);
539 subbuffer->parent = parent;
541 GST_CAT_LOG (GST_CAT_BUFFER, "new subbuffer %p (parent %p)", subbuffer,
544 /* set the right values in the child */
545 GST_BUFFER_DATA (GST_BUFFER_CAST (subbuffer)) = buffer->data + offset;
546 GST_BUFFER_SIZE (GST_BUFFER_CAST (subbuffer)) = size;
548 if ((offset == 0) && (size == GST_BUFFER_SIZE (buffer))) {
549 /* copy all the flags except IN_CAPS */
550 GST_BUFFER_FLAG_SET (subbuffer, GST_BUFFER_FLAGS (buffer));
551 GST_BUFFER_FLAG_UNSET (subbuffer, GST_BUFFER_FLAG_IN_CAPS);
553 /* copy only PREROLL & GAP flags */
554 GST_BUFFER_FLAG_SET (subbuffer, (GST_BUFFER_FLAGS (buffer) &
555 (GST_BUFFER_FLAG_PREROLL | GST_BUFFER_FLAG_GAP)));
558 /* we can copy the timestamp and offset if the new buffer starts at
561 GST_BUFFER_TIMESTAMP (subbuffer) = GST_BUFFER_TIMESTAMP (buffer);
562 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET (buffer);
563 complete = (buffer->size == size);
565 GST_BUFFER_TIMESTAMP (subbuffer) = GST_CLOCK_TIME_NONE;
566 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET_NONE;
573 /* if we copied the complete buffer we can copy the duration,
574 * offset_end and caps as well */
575 GST_BUFFER_DURATION (subbuffer) = GST_BUFFER_DURATION (buffer);
576 GST_BUFFER_OFFSET_END (subbuffer) = GST_BUFFER_OFFSET_END (buffer);
577 if ((caps = GST_BUFFER_CAPS (buffer)))
579 GST_BUFFER_CAPS (subbuffer) = caps;
581 GST_BUFFER_DURATION (subbuffer) = GST_CLOCK_TIME_NONE;
582 GST_BUFFER_OFFSET_END (subbuffer) = GST_BUFFER_OFFSET_NONE;
583 GST_BUFFER_CAPS (subbuffer) = NULL;
585 return GST_BUFFER_CAST (subbuffer);
589 * gst_buffer_is_span_fast:
590 * @buf1: the first #GstBuffer.
591 * @buf2: the second #GstBuffer.
593 * Determines whether a gst_buffer_span() can be done without copying
594 * the contents, that is, whether the data areas are contiguous sub-buffers of
598 * Returns: TRUE if the buffers are contiguous,
599 * FALSE if a copy would be required.
602 gst_buffer_is_span_fast (GstBuffer * buf1, GstBuffer * buf2)
604 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, FALSE);
605 g_return_val_if_fail (buf1->mini_object.refcount > 0, FALSE);
606 g_return_val_if_fail (buf2->mini_object.refcount > 0, FALSE);
608 /* it's only fast if we have subbuffers of the same parent */
609 return (GST_IS_SUBBUFFER (buf1) &&
610 GST_IS_SUBBUFFER (buf2) &&
611 (GST_SUBBUFFER_CAST (buf1)->parent == GST_SUBBUFFER_CAST (buf2)->parent)
612 && ((buf1->data + buf1->size) == buf2->data));
617 * @buf1: the first source #GstBuffer to merge.
618 * @offset: the offset in the first buffer from where the new
619 * buffer should start.
620 * @buf2: the second source #GstBuffer to merge.
621 * @len: the total length of the new buffer.
623 * Creates a new buffer that consists of part of buf1 and buf2.
624 * Logically, buf1 and buf2 are concatenated into a single larger
625 * buffer, and a new buffer is created at the given offset inside
626 * this space, with a given length.
628 * If the two source buffers are children of the same larger buffer,
629 * and are contiguous, the new buffer will be a child of the shared
630 * parent, and thus no copying is necessary. you can use
631 * gst_buffer_is_span_fast() to determine if a memcpy will be needed.
634 * Returns: the new #GstBuffer that spans the two source buffers.
635 * Returns NULL if the arguments are invalid.
638 gst_buffer_span (GstBuffer * buf1, guint32 offset, GstBuffer * buf2,
643 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, NULL);
644 g_return_val_if_fail (buf1->mini_object.refcount > 0, NULL);
645 g_return_val_if_fail (buf2->mini_object.refcount > 0, NULL);
646 g_return_val_if_fail (len > 0, NULL);
647 g_return_val_if_fail (len <= buf1->size + buf2->size - offset, NULL);
649 /* if the two buffers have the same parent and are adjacent */
650 if (gst_buffer_is_span_fast (buf1, buf2)) {
651 GstBuffer *parent = GST_SUBBUFFER_CAST (buf1)->parent;
653 /* we simply create a subbuffer of the common parent */
654 newbuf = gst_buffer_create_sub (parent,
655 buf1->data - parent->data + offset, len);
657 GST_CAT_DEBUG (GST_CAT_BUFFER,
658 "slow path taken while spanning buffers %p and %p", buf1, buf2);
659 /* otherwise we simply have to brute-force copy the buffers */
660 newbuf = gst_buffer_new_and_alloc (len);
662 /* copy the first buffer's data across */
663 memcpy (newbuf->data, buf1->data + offset, buf1->size - offset);
664 /* copy the second buffer's data across */
665 memcpy (newbuf->data + (buf1->size - offset), buf2->data,
666 len - (buf1->size - offset));
668 /* if the offset is 0, the new buffer has the same timestamp as buf1 */
670 GST_BUFFER_OFFSET (newbuf) = GST_BUFFER_OFFSET (buf1);
671 GST_BUFFER_TIMESTAMP (newbuf) = GST_BUFFER_TIMESTAMP (buf1);
673 /* if we completely merged the two buffers (appended), we can
674 * calculate the duration too. Also make sure we's not messing with
675 * invalid DURATIONS */
676 if (buf1->size + buf2->size == len) {
677 if (GST_BUFFER_DURATION_IS_VALID (buf1) &&
678 GST_BUFFER_DURATION_IS_VALID (buf2)) {
680 GST_BUFFER_DURATION (newbuf) = GST_BUFFER_DURATION (buf1) +
681 GST_BUFFER_DURATION (buf2);
683 if (GST_BUFFER_OFFSET_END_IS_VALID (buf2)) {
685 GST_BUFFER_OFFSET_END (newbuf) = GST_BUFFER_OFFSET_END (buf2);