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);
126 static GType _gst_buffer_type = 0;
129 _gst_buffer_initialize (void)
131 /* the GstMiniObject types need to be class_ref'd once before it can be
132 * done from multiple threads;
133 * see http://bugzilla.gnome.org/show_bug.cgi?id=304551 */
134 g_type_class_ref (gst_buffer_get_type ());
139 _gst_buffer_type = g_define_type_id; \
142 G_DEFINE_TYPE_WITH_CODE (GstBuffer, gst_buffer, GST_TYPE_MINI_OBJECT, _do_init);
145 gst_buffer_class_init (GstBufferClass * klass)
147 klass->mini_object_class.copy = (GstMiniObjectCopyFunction) _gst_buffer_copy;
148 klass->mini_object_class.finalize =
149 (GstMiniObjectFinalizeFunction) gst_buffer_finalize;
153 gst_buffer_finalize (GstBuffer * buffer)
155 g_return_if_fail (buffer != NULL);
157 GST_CAT_LOG (GST_CAT_BUFFER, "finalize %p", buffer);
160 if (G_LIKELY (buffer->malloc_data))
161 buffer->free_func (buffer->malloc_data);
163 gst_caps_replace (&GST_BUFFER_CAPS (buffer), NULL);
166 gst_buffer_unref (buffer->parent);
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 #if GST_VERSION_NANO == 1
201 /* we enable this extra debugging in git versions only for now */
202 g_return_if_fail (gst_buffer_is_metadata_writable (dest));
205 GST_CAT_LOG (GST_CAT_BUFFER, "copy %p to %p", src, dest);
207 if (flags & GST_BUFFER_COPY_FLAGS) {
210 /* copy relevant flags */
211 mask = GST_BUFFER_FLAG_PREROLL | GST_BUFFER_FLAG_IN_CAPS |
212 GST_BUFFER_FLAG_DELTA_UNIT | GST_BUFFER_FLAG_DISCONT |
213 GST_BUFFER_FLAG_GAP | GST_BUFFER_FLAG_MEDIA1 |
214 GST_BUFFER_FLAG_MEDIA2 | GST_BUFFER_FLAG_MEDIA3;
215 GST_MINI_OBJECT_FLAGS (dest) |= GST_MINI_OBJECT_FLAGS (src) & mask;
218 if (flags & GST_BUFFER_COPY_TIMESTAMPS) {
219 GST_BUFFER_TIMESTAMP (dest) = GST_BUFFER_TIMESTAMP (src);
220 GST_BUFFER_DURATION (dest) = GST_BUFFER_DURATION (src);
221 GST_BUFFER_OFFSET (dest) = GST_BUFFER_OFFSET (src);
222 GST_BUFFER_OFFSET_END (dest) = GST_BUFFER_OFFSET_END (src);
225 if (flags & GST_BUFFER_COPY_CAPS) {
226 gst_caps_replace (&GST_BUFFER_CAPS (dest), GST_BUFFER_CAPS (src));
231 _gst_buffer_copy (GstBuffer * buffer)
235 g_return_val_if_fail (buffer != NULL, NULL);
237 /* create a fresh new buffer */
238 copy = gst_buffer_new ();
240 /* we simply copy everything from our parent */
241 copy->data = g_memdup (buffer->data, buffer->size);
242 /* make sure it gets freed (even if the parent is subclassed, we return a
244 copy->malloc_data = copy->data;
245 copy->size = buffer->size;
247 gst_buffer_copy_metadata (copy, buffer, GST_BUFFER_COPY_ALL);
253 gst_buffer_init (GstBuffer * buffer)
255 GST_CAT_LOG (GST_CAT_BUFFER, "init %p", buffer);
257 GST_BUFFER_TIMESTAMP (buffer) = GST_CLOCK_TIME_NONE;
258 GST_BUFFER_DURATION (buffer) = GST_CLOCK_TIME_NONE;
259 GST_BUFFER_OFFSET (buffer) = GST_BUFFER_OFFSET_NONE;
260 GST_BUFFER_OFFSET_END (buffer) = GST_BUFFER_OFFSET_NONE;
261 GST_BUFFER_FREE_FUNC (buffer) = g_free;
267 * Creates a newly allocated buffer without any data.
270 * Returns: the new #GstBuffer.
273 gst_buffer_new (void)
277 newbuf = (GstBuffer *) gst_mini_object_new (_gst_buffer_type);
279 GST_CAT_LOG (GST_CAT_BUFFER, "new %p", newbuf);
285 * gst_buffer_new_and_alloc:
286 * @size: the size of the new buffer's data.
288 * Creates a newly allocated buffer with data of the given size.
289 * The buffer memory is not cleared. If the requested amount of
290 * memory can't be allocated, the program will abort. Use
291 * gst_buffer_try_new_and_alloc() if you want to handle this case
292 * gracefully or have gotten the size to allocate from an untrusted
293 * source such as a media stream.
296 * Note that when @size == 0, the buffer data pointer will be NULL.
299 * Returns: the new #GstBuffer.
302 gst_buffer_new_and_alloc (guint size)
306 newbuf = gst_buffer_new ();
308 newbuf->malloc_data = g_malloc (size);
309 GST_BUFFER_DATA (newbuf) = newbuf->malloc_data;
310 GST_BUFFER_SIZE (newbuf) = size;
312 GST_CAT_LOG (GST_CAT_BUFFER, "new %p of size %d", newbuf, size);
318 * gst_buffer_try_new_and_alloc:
319 * @size: the size of the new buffer's data.
321 * Tries to create a newly allocated buffer with data of the given size. If
322 * the requested amount of memory can't be allocated, NULL will be returned.
323 * The buffer memory is not cleared.
325 * Note that when @size == 0, the buffer data pointer will be NULL.
329 * Returns: a new #GstBuffer, or NULL if the memory couldn't be allocated.
334 gst_buffer_try_new_and_alloc (guint size)
339 malloc_data = g_try_malloc (size);
341 if (G_UNLIKELY (malloc_data == NULL && size != 0)) {
342 GST_CAT_WARNING (GST_CAT_BUFFER, "failed to allocate %d bytes", size);
346 /* FIXME: there's no g_type_try_create_instance() in GObject yet, so this
347 * will still abort if a new GstBuffer structure can't be allocated */
348 newbuf = gst_buffer_new ();
350 GST_BUFFER_MALLOCDATA (newbuf) = malloc_data;
351 GST_BUFFER_DATA (newbuf) = malloc_data;
352 GST_BUFFER_SIZE (newbuf) = size;
354 GST_CAT_LOG (GST_CAT_BUFFER, "new %p of size %d", newbuf, size);
360 * gst_buffer_get_caps:
361 * @buffer: a #GstBuffer.
363 * Gets the media type of the buffer. This can be NULL if there
364 * is no media type attached to this buffer.
366 * Returns: a reference to the #GstCaps. unref after usage.
367 * Returns NULL if there were no caps on this buffer.
369 /* this is not made atomic because if the buffer were reffed from multiple
370 * threads, it would have a refcount > 2 and thus be immutable.
373 gst_buffer_get_caps (GstBuffer * buffer)
377 g_return_val_if_fail (buffer != NULL, NULL);
379 ret = GST_BUFFER_CAPS (buffer);
388 * gst_buffer_set_caps:
389 * @buffer: a #GstBuffer.
392 * Sets the media type on the buffer. The refcount of the caps will
393 * be increased and any previous caps on the buffer will be
396 /* this is not made atomic because if the buffer were reffed from multiple
397 * threads, it would have a refcount > 2 and thus be immutable.
400 gst_buffer_set_caps (GstBuffer * buffer, GstCaps * caps)
402 g_return_if_fail (buffer != NULL);
403 #if GST_VERSION_NANO == 1
404 /* we enable this extra debugging in git versions only for now */
405 g_return_if_fail (gst_buffer_is_metadata_writable (buffer));
408 gst_caps_replace (&GST_BUFFER_CAPS (buffer), caps);
412 * gst_buffer_is_metadata_writable:
415 * Similar to gst_buffer_is_writable, but this only ensures that the
416 * refcount of the buffer is 1, indicating that the caller is the sole
417 * owner and can change the buffer metadata, such as caps and timestamps.
419 * Returns: TRUE if the metadata is writable.
422 gst_buffer_is_metadata_writable (GstBuffer * buf)
424 return (GST_MINI_OBJECT_REFCOUNT_VALUE (GST_MINI_OBJECT_CAST (buf)) == 1);
428 * gst_buffer_make_metadata_writable:
431 * Similar to gst_buffer_make_writable, but does not ensure that the buffer
432 * data array is writable. Instead, this just ensures that the returned buffer
433 * is solely owned by the caller, by creating a subbuffer of the original
434 * buffer if necessary.
436 * After calling this function, @buf should not be referenced anymore. The
437 * result of this function has guaranteed writable metadata.
439 * Returns: A new #GstBuffer with writable metadata.
442 gst_buffer_make_metadata_writable (GstBuffer * buf)
446 if (gst_buffer_is_metadata_writable (buf)) {
449 ret = gst_buffer_create_sub (buf, 0, GST_BUFFER_SIZE (buf));
451 gst_buffer_unref (buf);
457 #define GST_IS_SUBBUFFER(obj) (GST_BUFFER_CAST(obj)->parent != NULL)
460 * gst_buffer_create_sub:
461 * @parent: a #GstBuffer.
462 * @offset: the offset into parent #GstBuffer at which the new sub-buffer
464 * @size: the size of the new #GstBuffer sub-buffer, in bytes.
466 * Creates a sub-buffer from @parent at @offset and @size.
467 * This sub-buffer uses the actual memory space of the parent buffer.
468 * This function will copy the offset and timestamp fields when the
469 * offset is 0. If not, they will be set to #GST_CLOCK_TIME_NONE and
470 * #GST_BUFFER_OFFSET_NONE.
471 * If @offset equals 0 and @size equals the total size of @buffer, the
472 * duration and offset end fields are also copied. If not they will be set
473 * to #GST_CLOCK_TIME_NONE and #GST_BUFFER_OFFSET_NONE.
476 * Returns: the new #GstBuffer.
477 * Returns NULL if the arguments were invalid.
480 gst_buffer_create_sub (GstBuffer * buffer, guint offset, guint size)
482 GstBuffer *subbuffer;
486 g_return_val_if_fail (buffer != NULL, NULL);
487 g_return_val_if_fail (buffer->mini_object.refcount > 0, NULL);
488 g_return_val_if_fail (buffer->size >= offset + size, NULL);
490 /* find real parent */
491 if (GST_IS_SUBBUFFER (buffer)) {
492 parent = buffer->parent;
496 gst_buffer_ref (parent);
498 /* create the new buffer */
499 subbuffer = gst_buffer_new ();
500 subbuffer->parent = parent;
501 GST_BUFFER_FLAG_SET (GST_BUFFER_CAST (subbuffer), GST_BUFFER_FLAG_READONLY);
503 GST_CAT_LOG (GST_CAT_BUFFER, "new subbuffer %p (parent %p)", subbuffer,
506 /* set the right values in the child */
507 GST_BUFFER_DATA (GST_BUFFER_CAST (subbuffer)) = buffer->data + offset;
508 GST_BUFFER_SIZE (GST_BUFFER_CAST (subbuffer)) = size;
510 if ((offset == 0) && (size == GST_BUFFER_SIZE (buffer))) {
511 /* copy all the flags except IN_CAPS */
512 GST_BUFFER_FLAG_SET (subbuffer, GST_BUFFER_FLAGS (buffer));
513 GST_BUFFER_FLAG_UNSET (subbuffer, GST_BUFFER_FLAG_IN_CAPS);
515 /* copy only PREROLL & GAP flags */
516 GST_BUFFER_FLAG_SET (subbuffer, (GST_BUFFER_FLAGS (buffer) &
517 (GST_BUFFER_FLAG_PREROLL | GST_BUFFER_FLAG_GAP)));
520 /* we can copy the timestamp and offset if the new buffer starts at
523 GST_BUFFER_TIMESTAMP (subbuffer) = GST_BUFFER_TIMESTAMP (buffer);
524 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET (buffer);
525 complete = (buffer->size == size);
527 GST_BUFFER_TIMESTAMP (subbuffer) = GST_CLOCK_TIME_NONE;
528 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET_NONE;
535 /* if we copied the complete buffer we can copy the duration,
536 * offset_end and caps as well */
537 GST_BUFFER_DURATION (subbuffer) = GST_BUFFER_DURATION (buffer);
538 GST_BUFFER_OFFSET_END (subbuffer) = GST_BUFFER_OFFSET_END (buffer);
539 if ((caps = GST_BUFFER_CAPS (buffer)))
541 GST_BUFFER_CAPS (subbuffer) = caps;
543 GST_BUFFER_DURATION (subbuffer) = GST_CLOCK_TIME_NONE;
544 GST_BUFFER_OFFSET_END (subbuffer) = GST_BUFFER_OFFSET_NONE;
545 GST_BUFFER_CAPS (subbuffer) = NULL;
547 return GST_BUFFER_CAST (subbuffer);
551 * gst_buffer_is_span_fast:
552 * @buf1: the first #GstBuffer.
553 * @buf2: the second #GstBuffer.
555 * Determines whether a gst_buffer_span() can be done without copying
556 * the contents, that is, whether the data areas are contiguous sub-buffers of
560 * Returns: TRUE if the buffers are contiguous,
561 * FALSE if a copy would be required.
564 gst_buffer_is_span_fast (GstBuffer * buf1, GstBuffer * buf2)
566 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, FALSE);
567 g_return_val_if_fail (buf1->mini_object.refcount > 0, FALSE);
568 g_return_val_if_fail (buf2->mini_object.refcount > 0, FALSE);
570 /* it's only fast if we have subbuffers of the same parent */
571 return (GST_IS_SUBBUFFER (buf1) &&
572 GST_IS_SUBBUFFER (buf2) && (buf1->parent == buf2->parent)
573 && ((buf1->data + buf1->size) == buf2->data));
578 * @buf1: the first source #GstBuffer to merge.
579 * @offset: the offset in the first buffer from where the new
580 * buffer should start.
581 * @buf2: the second source #GstBuffer to merge.
582 * @len: the total length of the new buffer.
584 * Creates a new buffer that consists of part of buf1 and buf2.
585 * Logically, buf1 and buf2 are concatenated into a single larger
586 * buffer, and a new buffer is created at the given offset inside
587 * this space, with a given length.
589 * If the two source buffers are children of the same larger buffer,
590 * and are contiguous, the new buffer will be a child of the shared
591 * parent, and thus no copying is necessary. you can use
592 * gst_buffer_is_span_fast() to determine if a memcpy will be needed.
595 * Returns: the new #GstBuffer that spans the two source buffers.
596 * Returns NULL if the arguments are invalid.
599 gst_buffer_span (GstBuffer * buf1, guint32 offset, GstBuffer * buf2,
604 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, NULL);
605 g_return_val_if_fail (buf1->mini_object.refcount > 0, NULL);
606 g_return_val_if_fail (buf2->mini_object.refcount > 0, NULL);
607 g_return_val_if_fail (len > 0, NULL);
608 g_return_val_if_fail (len <= buf1->size + buf2->size - offset, NULL);
610 /* if the two buffers have the same parent and are adjacent */
611 if (gst_buffer_is_span_fast (buf1, buf2)) {
612 GstBuffer *parent = buf1->parent;
614 /* we simply create a subbuffer of the common parent */
615 newbuf = gst_buffer_create_sub (parent,
616 buf1->data - parent->data + offset, len);
618 GST_CAT_DEBUG (GST_CAT_BUFFER,
619 "slow path taken while spanning buffers %p and %p", buf1, buf2);
620 /* otherwise we simply have to brute-force copy the buffers */
621 newbuf = gst_buffer_new_and_alloc (len);
623 /* copy the first buffer's data across */
624 memcpy (newbuf->data, buf1->data + offset, buf1->size - offset);
625 /* copy the second buffer's data across */
626 memcpy (newbuf->data + (buf1->size - offset), buf2->data,
627 len - (buf1->size - offset));
629 /* if the offset is 0, the new buffer has the same timestamp as buf1 */
631 GST_BUFFER_OFFSET (newbuf) = GST_BUFFER_OFFSET (buf1);
632 GST_BUFFER_TIMESTAMP (newbuf) = GST_BUFFER_TIMESTAMP (buf1);
634 /* if we completely merged the two buffers (appended), we can
635 * calculate the duration too. Also make sure we's not messing with
636 * invalid DURATIONS */
637 if (buf1->size + buf2->size == len) {
638 if (GST_BUFFER_DURATION_IS_VALID (buf1) &&
639 GST_BUFFER_DURATION_IS_VALID (buf2)) {
641 GST_BUFFER_DURATION (newbuf) = GST_BUFFER_DURATION (buf1) +
642 GST_BUFFER_DURATION (buf2);
644 if (GST_BUFFER_OFFSET_END_IS_VALID (buf2)) {
646 GST_BUFFER_OFFSET_END (newbuf) = GST_BUFFER_OFFSET_END (buf2);