gstreamer/gst/gstbufferlist.c

915 lines
24 KiB
C

/* GStreamer
* Copyright (C) 2009 Axis Communications <dev-gstreamer at axis dot com>
* @author Jonas Holmberg <jonas dot holmberg at axis dot com>
*
* gstbufferlist.c: Buffer list
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
/**
* SECTION:gstbufferlist
* @short_description: Grouped scatter data buffer type for data-passing
* @see_also: #GstPad, #GstMiniObject
*
* Buffer lists are units of grouped scatter/gather data transfer in
* GStreamer.
*
* Buffer lists are created with gst_buffer_list_new() and filled with data
* using a #GstBufferListIterator. The iterator has no current buffer; its
* cursor position lies between buffers, immediately before the buffer that
* would be returned by gst_buffer_list_iterator_next(). After iterating to the
* end of a group the iterator must be advanced to the next group by a call to
* gst_buffer_list_iterator_next_group() before any further calls to
* gst_buffer_list_iterator_next() can return buffers again. The cursor position
* of a newly created iterator lies before the first group; a call to
* gst_buffer_list_iterator_next_group() is necessary before calls to
* gst_buffer_list_iterator_next() can return buffers.
*
* <informalfigure>
* <programlisting>
* +--- group0 ----------------------+--- group1 ------------+
* | buffer0 buffer1 buffer2 | buffer3 buffer4 |
* ^ ^ ^ ^ ^ ^ ^ ^
* Iterator positions between buffers
* </programlisting>
* </informalfigure>
*
* The gst_buffer_list_iterator_remove(), gst_buffer_list_iterator_steal(),
* gst_buffer_list_iterator_take() and gst_buffer_list_iterator_do() functions
* are not defined in terms of the cursor position; they operate on the last
* element returned from gst_buffer_list_iterator_next().
*
* The basic use pattern of creating a buffer list with an iterator is as
* follows:
*
* <example>
* <title>Creating a buffer list</title>
* <programlisting>
* GstBufferList *list;
* GstBufferListIterator *it;
*
* list = gst_buffer_list_new ();
* it = gst_buffer_list_iterate (list);
* gst_buffer_list_iterator_add_group (it);
* gst_buffer_list_iterator_add (it, header1);
* gst_buffer_list_iterator_add (it, data1);
* gst_buffer_list_iterator_add_group (it);
* gst_buffer_list_iterator_add (it, header2);
* gst_buffer_list_iterator_add (it, data2);
* gst_buffer_list_iterator_add_group (it);
* gst_buffer_list_iterator_add (it, header3);
* gst_buffer_list_iterator_add (it, data3);
* ...
* gst_buffer_list_iterator_free (it);
* </programlisting>
* </example>
*
* The basic use pattern of iterating over a buffer list is as follows:
*
* <example>
* <title>Iterating a buffer list</title>
* <programlisting>
* GstBufferListIterator *it;
*
* it = gst_buffer_list_iterate (list);
* while (gst_buffer_list_iterator_next_group (it)) {
* while ((buffer = gst_buffer_list_iterator_next (it)) != NULL) {
* do_something_with_buffer (buffer);
* }
* }
* gst_buffer_list_iterator_free (it);
* </programlisting>
* </example>
*
* The basic use pattern of modifying a buffer in a list is as follows:
*
* <example>
* <title>Modifying the data of the first buffer in a list</title>
* <programlisting>
* GstBufferListIterator *it;
*
* list = gst_buffer_list_make_writable (list);
* it = gst_buffer_list_iterate (list);
* if (gst_buffer_list_iterator_next_group (it)) {
* GstBuffer *buf
*
* buf = gst_buffer_list_iterator_next (it);
* if (buf != NULL) {
* buf = gst_buffer_list_iterator_do (it,
* (GstBufferListDoFunction) gst_mini_object_make_writable, NULL);
* modify_data (GST_BUFFER_DATA (buf));
* }
* }
* gst_buffer_list_iterator_free (it);
* </programlisting>
* </example>
*
* Since: 0.10.24
*/
#include "gst_private.h"
#include "gstbuffer.h"
#include "gstbufferlist.h"
#define GST_CAT_DEFAULT GST_CAT_BUFFER_LIST
#define GROUP_START NULL
static gconstpointer STOLEN = "";
/**
* GstBufferList:
*
* Opaque list of grouped buffers.
*
* Since: 0.10.24
*/
struct _GstBufferList
{
GstMiniObject mini_object;
GQueue *buffers;
};
struct _GstBufferListClass
{
GstMiniObjectClass mini_object_class;
};
/**
* GstBufferListIterator:
*
* Opaque iterator for a #GstBufferList.
*
* Since: 0.10.24
*/
struct _GstBufferListIterator
{
GstBufferList *list;
GList *next;
GList *last_returned;
};
static GType _gst_buffer_list_type = 0;
G_DEFINE_TYPE (GstBufferList, gst_buffer_list, GST_TYPE_MINI_OBJECT);
void
_gst_buffer_list_initialize (void)
{
GType type = gst_buffer_list_get_type ();
g_type_class_ref (type);
_gst_buffer_list_type = type;
}
static void
gst_buffer_list_init (GstBufferList * list)
{
list->buffers = g_queue_new ();
GST_LOG ("init %p", list);
}
static void
gst_buffer_list_finalize (GstBufferList * list)
{
GList *tmp;
g_return_if_fail (list != NULL);
GST_LOG ("finalize %p", list);
tmp = list->buffers->head;
while (tmp) {
if (tmp->data != GROUP_START && tmp->data != STOLEN) {
gst_buffer_unref (GST_BUFFER_CAST (tmp->data));
}
tmp = tmp->next;
}
g_queue_free (list->buffers);
/* Not chaining up because GstMiniObject::finalize() does nothing
GST_MINI_OBJECT_CLASS (gst_buffer_list_parent_class)->finalize
(GST_MINI_OBJECT_CAST (list));*/
}
static GstBufferList *
_gst_buffer_list_copy (GstBufferList * list)
{
GstBufferList *list_copy;
GQueue *buffers_copy;
GList *tmp;
g_return_val_if_fail (list != NULL, NULL);
/* shallow copy of list and pointers */
buffers_copy = g_queue_copy (list->buffers);
/* ref all buffers in the list */
tmp = list->buffers->head;
while (tmp) {
if (tmp->data != GROUP_START && tmp->data != STOLEN) {
tmp->data = gst_buffer_ref (GST_BUFFER_CAST (tmp->data));
}
tmp = g_list_next (tmp);
}
list_copy = gst_buffer_list_new ();
g_queue_free (list_copy->buffers);
list_copy->buffers = buffers_copy;
return list_copy;
}
static void
gst_buffer_list_class_init (GstBufferListClass * list_class)
{
list_class->mini_object_class.copy =
(GstMiniObjectCopyFunction) _gst_buffer_list_copy;
list_class->mini_object_class.finalize =
(GstMiniObjectFinalizeFunction) gst_buffer_list_finalize;
}
/**
* gst_buffer_list_new:
*
* Creates a new, empty #GstBufferList. The caller is responsible for unreffing
* the returned #GstBufferList.
*
* Free-function: gst_buffer_list_unref
*
* Returns: (transfer full): the new #GstBufferList. gst_buffer_list_unref()
* after usage.
*
* Since: 0.10.24
*/
GstBufferList *
gst_buffer_list_new (void)
{
GstBufferList *list;
list = (GstBufferList *) gst_mini_object_new (_gst_buffer_list_type);
GST_LOG ("new %p", list);
return list;
}
/**
* gst_buffer_list_n_groups:
* @list: a #GstBufferList
*
* Returns the number of groups in @list.
*
* Returns: the number of groups in the buffer list
*
* Since: 0.10.24
*/
guint
gst_buffer_list_n_groups (GstBufferList * list)
{
GList *tmp;
guint n;
g_return_val_if_fail (list != NULL, 0);
tmp = list->buffers->head;
n = 0;
while (tmp) {
if (tmp->data == GROUP_START) {
n++;
}
tmp = g_list_next (tmp);
}
return n;
}
/**
* gst_buffer_list_foreach:
* @list: a #GstBufferList
* @func: (scope call): a #GstBufferListFunc to call
* @user_data: (closure): user data passed to @func
*
* Call @func with @data for each buffer in @list.
*
* @func can modify the passed buffer pointer or its contents. The return value
* of @func define if this function returns or if the remaining buffers in a
* group should be skipped.
*
* Since: 0.10.24
*/
void
gst_buffer_list_foreach (GstBufferList * list, GstBufferListFunc func,
gpointer user_data)
{
GList *tmp, *next;
guint group, idx;
GstBufferListItem res;
g_return_if_fail (list != NULL);
g_return_if_fail (func != NULL);
next = list->buffers->head;
group = idx = 0;
while (next) {
GstBuffer *buffer;
tmp = next;
next = g_list_next (tmp);
buffer = tmp->data;
if (buffer == GROUP_START) {
group++;
idx = 0;
continue;
} else if (buffer == STOLEN)
continue;
else
idx++;
/* need to decrement the indices */
res = func (&buffer, group - 1, idx - 1, user_data);
if (G_UNLIKELY (buffer != tmp->data)) {
/* the function changed the buffer */
if (buffer == NULL) {
/* we were asked to remove the item */
g_queue_delete_link (list->buffers, tmp);
idx--;
} else {
/* change the buffer */
tmp->data = buffer;
}
}
switch (res) {
case GST_BUFFER_LIST_CONTINUE:
break;
case GST_BUFFER_LIST_SKIP_GROUP:
while (next && next->data != GROUP_START)
next = g_list_next (next);
break;
case GST_BUFFER_LIST_END:
return;
}
}
}
/**
* gst_buffer_list_get:
* @list: a #GstBufferList
* @group: the group
* @idx: the index in @group
*
* Get the buffer at @idx in @group.
*
* Note that this function is not efficient for iterating over the entire list.
* Use an iterator or gst_buffer_list_foreach() instead.
*
* Returns: (transfer none): the buffer at @idx in @group or NULL when there
* is no buffer. The buffer remains valid as long as @list is valid.
*
* Since: 0.10.24
*/
GstBuffer *
gst_buffer_list_get (GstBufferList * list, guint group, guint idx)
{
GList *tmp;
guint cgroup, cidx;
g_return_val_if_fail (list != NULL, NULL);
tmp = list->buffers->head;
cgroup = 0;
while (tmp) {
if (tmp->data == GROUP_START) {
if (cgroup == group) {
/* we found the group */
tmp = g_list_next (tmp);
cidx = 0;
while (tmp && tmp->data != GROUP_START) {
if (tmp->data != STOLEN) {
if (cidx == idx)
return GST_BUFFER_CAST (tmp->data);
else
cidx++;
}
tmp = g_list_next (tmp);
}
break;
} else {
cgroup++;
if (cgroup > group)
break;
}
}
tmp = g_list_next (tmp);
}
return NULL;
}
static GstBufferListIterator *
gst_buffer_list_iterator_copy (const GstBufferListIterator * it)
{
GstBufferListIterator *ret;
ret = g_slice_new (GstBufferListIterator);
ret->list = it->list;
ret->next = it->next;
ret->last_returned = it->last_returned;
return ret;
}
GType
gst_buffer_list_iterator_get_type (void)
{
static GType type = 0;
if (G_UNLIKELY (type == 0)) {
type = g_boxed_type_register_static ("GstBufferListIterator",
(GBoxedCopyFunc) gst_buffer_list_iterator_copy,
(GBoxedFreeFunc) gst_buffer_list_iterator_free);
}
return type;
}
/**
* gst_buffer_list_iterate:
* @list: a #GstBufferList
*
* Iterate the buffers in @list. The owner of the iterator must also be the
* owner of a reference to @list while the returned iterator is in use.
*
* Free-function: gst_buffer_list_iterator_free
*
* Returns: (transfer full): a new #GstBufferListIterator of the buffers in
* @list. gst_buffer_list_iterator_free() after usage
*
* Since: 0.10.24
*/
GstBufferListIterator *
gst_buffer_list_iterate (GstBufferList * list)
{
GstBufferListIterator *it;
g_return_val_if_fail (list != NULL, NULL);
it = g_slice_new (GstBufferListIterator);
it->list = list;
it->next = list->buffers->head;
it->last_returned = NULL;
return it;
}
/**
* gst_buffer_list_iterator_free:
* @it: (transfer full): the #GstBufferListIterator to free
*
* Free the iterator.
*
* Since: 0.10.24
*/
void
gst_buffer_list_iterator_free (GstBufferListIterator * it)
{
g_return_if_fail (it != NULL);
g_slice_free (GstBufferListIterator, it);
}
/**
* gst_buffer_list_iterator_n_buffers:
* @it: a #GstBufferListIterator
*
* Returns the number of buffers left to iterate in the current group. I.e. the
* number of calls that can be made to gst_buffer_list_iterator_next() before
* it returns NULL.
*
* This function will not move the implicit cursor or in any other way affect
* the state of the iterator @it.
*
* Returns: the number of buffers left to iterate in the current group
*
* Since: 0.10.24
*/
guint
gst_buffer_list_iterator_n_buffers (const GstBufferListIterator * it)
{
GList *tmp;
guint n;
g_return_val_if_fail (it != NULL, 0);
tmp = it->next;
n = 0;
while (tmp && tmp->data != GROUP_START) {
if (tmp->data != STOLEN) {
n++;
}
tmp = g_list_next (tmp);
}
return n;
}
/**
* gst_buffer_list_iterator_add:
* @it: a #GstBufferListIterator
* @buffer: (transfer full): a #GstBuffer
*
* Inserts @buffer into the #GstBufferList iterated with @it. The buffer is
* inserted into the current group, immediately before the buffer that would be
* returned by gst_buffer_list_iterator_next(). The buffer is inserted before
* the implicit cursor, a subsequent call to gst_buffer_list_iterator_next()
* will return the buffer after the inserted buffer, if any.
*
* This function takes ownership of @buffer.
*
* Since: 0.10.24
*/
void
gst_buffer_list_iterator_add (GstBufferListIterator * it, GstBuffer * buffer)
{
g_return_if_fail (it != NULL);
g_return_if_fail (buffer != NULL);
/* adding before the first group start is not allowed */
g_return_if_fail (it->next != it->list->buffers->head);
/* cheap insert into the GQueue */
if (it->next != NULL) {
g_queue_insert_before (it->list->buffers, it->next, buffer);
} else {
g_queue_push_tail (it->list->buffers, buffer);
}
}
/**
* gst_buffer_list_iterator_add_list:
* @it: a #GstBufferListIterator
* @list: (transfer full) (element-type Gst.Buffer): a #GList of buffers
*
* Inserts @list of buffers into the #GstBufferList iterated with @it. The list is
* inserted into the current group, immediately before the buffer that would be
* returned by gst_buffer_list_iterator_next(). The list is inserted before
* the implicit cursor, a subsequent call to gst_buffer_list_iterator_next()
* will return the buffer after the last buffer of the inserted list, if any.
*
* This function takes ownership of @list and all its buffers.
*
* Since: 0.10.31
*/
void
gst_buffer_list_iterator_add_list (GstBufferListIterator * it, GList * list)
{
GList *last;
guint len;
g_return_if_fail (it != NULL);
g_return_if_fail (it->next != it->list->buffers->head);
if (list == NULL)
return;
last = list;
len = 1;
while (last->next) {
last = last->next;
len++;
}
if (it->next) {
last->next = it->next;
list->prev = it->next->prev;
it->next->prev = last;
if (list->prev)
list->prev->next = list;
} else {
it->list->buffers->tail->next = list;
list->prev = it->list->buffers->tail;
it->list->buffers->tail = last;
}
it->list->buffers->length += len;
}
/**
* gst_buffer_list_iterator_add_group:
* @it: a #GstBufferListIterator
*
* Inserts a new, empty group into the #GstBufferList iterated with @it. The
* group is inserted immediately before the group that would be returned by
* gst_buffer_list_iterator_next_group(). A subsequent call to
* gst_buffer_list_iterator_next_group() will advance the iterator to the group
* after the inserted group, if any.
*
* Since: 0.10.24
*/
void
gst_buffer_list_iterator_add_group (GstBufferListIterator * it)
{
g_return_if_fail (it != NULL);
/* advance iterator to next group start */
while (it->next != NULL && it->next->data != GROUP_START) {
it->next = g_list_next (it->next);
}
/* cheap insert of a group start into the GQueue */
if (it->next != NULL) {
g_queue_insert_before (it->list->buffers, it->next, GROUP_START);
} else {
g_queue_push_tail (it->list->buffers, GROUP_START);
}
}
/**
* gst_buffer_list_iterator_next:
* @it: a #GstBufferListIterator
*
* Returns the next buffer in the list iterated with @it. If the iterator is at
* the end of a group, NULL will be returned. This function may be called
* repeatedly to iterate through the current group.
*
* The caller will not get a new ref to the returned #GstBuffer and must not
* unref it.
*
* Returns: (transfer none): the next buffer in the current group of the
* buffer list, or NULL
*
* Since: 0.10.24
*/
GstBuffer *
gst_buffer_list_iterator_next (GstBufferListIterator * it)
{
GstBuffer *buffer;
g_return_val_if_fail (it != NULL, NULL);
while (it->next != NULL && it->next->data != GROUP_START &&
it->next->data == STOLEN) {
it->next = g_list_next (it->next);
}
if (it->next == NULL || it->next->data == GROUP_START) {
goto no_buffer;
}
buffer = GST_BUFFER_CAST (it->next->data);
it->last_returned = it->next;
it->next = g_list_next (it->next);
return buffer;
no_buffer:
{
it->last_returned = NULL;
return NULL;
}
}
/**
* gst_buffer_list_iterator_next_group:
* @it: a #GstBufferListIterator
*
* Advance the iterator @it to the first buffer in the next group. If the
* iterator is at the last group, FALSE will be returned. This function may be
* called repeatedly to iterate through the groups in a buffer list.
*
* Returns: TRUE if the iterator could be advanced to the next group, FALSE if
* the iterator was already at the last group
*
* Since: 0.10.24
*/
gboolean
gst_buffer_list_iterator_next_group (GstBufferListIterator * it)
{
g_return_val_if_fail (it != NULL, FALSE);
/* advance iterator to next group start */
while (it->next != NULL && it->next->data != GROUP_START) {
it->next = g_list_next (it->next);
}
if (it->next) {
/* move one step beyond the group start */
it->next = g_list_next (it->next);
}
it->last_returned = NULL;
return (it->next != NULL);
}
/**
* gst_buffer_list_iterator_remove:
* @it: a #GstBufferListIterator
*
* Removes the last buffer returned by gst_buffer_list_iterator_next() from
* the #GstBufferList iterated with @it. gst_buffer_list_iterator_next() must
* have been called on @it before this function is called. This function can
* only be called once per call to gst_buffer_list_iterator_next().
*
* The removed buffer is unreffed.
*
* Since: 0.10.24
*/
void
gst_buffer_list_iterator_remove (GstBufferListIterator * it)
{
g_return_if_fail (it != NULL);
g_return_if_fail (it->last_returned != NULL);
g_assert (it->last_returned->data != GROUP_START);
if (it->last_returned->data != STOLEN) {
gst_buffer_unref (it->last_returned->data);
}
g_queue_delete_link (it->list->buffers, it->last_returned);
it->last_returned = NULL;
}
/**
* gst_buffer_list_iterator_take:
* @it: a #GstBufferListIterator
* @buffer: (transfer full): a #GstBuffer
*
* Replaces the last buffer returned by gst_buffer_list_iterator_next() with
* @buffer in the #GstBufferList iterated with @it and takes ownership of
* @buffer. gst_buffer_list_iterator_next() must have been called on @it before
* this function is called. gst_buffer_list_iterator_remove() must not have been
* called since the last call to gst_buffer_list_iterator_next().
*
* This function unrefs the replaced buffer if it has not been stolen with
* gst_buffer_list_iterator_steal() and takes ownership of @buffer (i.e. the
* refcount of @buffer is not increased).
*
* FIXME 0.11: this conditional taking-ownership is not good for bindings
*
* Since: 0.10.24
*/
void
gst_buffer_list_iterator_take (GstBufferListIterator * it, GstBuffer * buffer)
{
g_return_if_fail (it != NULL);
g_return_if_fail (it->last_returned != NULL);
g_return_if_fail (buffer != NULL);
g_assert (it->last_returned->data != GROUP_START);
if (it->last_returned->data != STOLEN) {
gst_buffer_unref (it->last_returned->data);
}
it->last_returned->data = buffer;
}
/**
* gst_buffer_list_iterator_steal:
* @it: a #GstBufferListIterator
*
* Returns the last buffer returned by gst_buffer_list_iterator_next() without
* modifying the refcount of the buffer.
*
* Returns: (transfer none): the last buffer returned by
* gst_buffer_list_iterator_next()
*
* Since: 0.10.24
*/
GstBuffer *
gst_buffer_list_iterator_steal (GstBufferListIterator * it)
{
GstBuffer *buffer;
g_return_val_if_fail (it != NULL, NULL);
g_return_val_if_fail (it->last_returned != NULL, NULL);
g_return_val_if_fail (it->last_returned->data != STOLEN, NULL);
g_assert (it->last_returned->data != GROUP_START);
buffer = it->last_returned->data;
it->last_returned->data = (gpointer) STOLEN;
return buffer;
}
/**
* gst_buffer_list_iterator_do:
* @it: a #GstBufferListIterator
* @do_func: (scope call): the function to be called
* @user_data: (closure): the gpointer to optional user data.
*
* Calls the given function for the last buffer returned by
* gst_buffer_list_iterator_next(). gst_buffer_list_iterator_next() must have
* been called on @it before this function is called.
* gst_buffer_list_iterator_remove() and gst_buffer_list_iterator_steal() must
* not have been called since the last call to gst_buffer_list_iterator_next().
*
* See #GstBufferListDoFunction for more details.
*
* Returns: (transfer none): the return value from @do_func
*
* Since: 0.10.24
*/
GstBuffer *
gst_buffer_list_iterator_do (GstBufferListIterator * it,
GstBufferListDoFunction do_func, gpointer user_data)
{
GstBuffer *buffer;
g_return_val_if_fail (it != NULL, NULL);
g_return_val_if_fail (it->last_returned != NULL, NULL);
g_return_val_if_fail (it->last_returned->data != STOLEN, NULL);
g_return_val_if_fail (do_func != NULL, NULL);
g_return_val_if_fail (gst_buffer_list_is_writable (it->list), NULL);
g_assert (it->last_returned->data != GROUP_START);
buffer = gst_buffer_list_iterator_steal (it);
buffer = do_func (buffer, user_data);
if (buffer == NULL) {
gst_buffer_list_iterator_remove (it);
} else {
gst_buffer_list_iterator_take (it, buffer);
}
return buffer;
}
/**
* gst_buffer_list_iterator_merge_group:
* @it: a #GstBufferListIterator
*
* Merge a buffer list group into a normal #GstBuffer by copying its metadata
* and memcpying its data into consecutive memory. All buffers in the current
* group after the implicit cursor will be merged into one new buffer. The
* metadata of the new buffer will be a copy of the metadata of the buffer that
* would be returned by gst_buffer_list_iterator_next(). If there is no buffer
* in the current group after the implicit cursor, NULL will be returned.
*
* This function will not move the implicit cursor or in any other way affect
* the state of the iterator @it or the list.
*
* Returns: (transfer full): a new #GstBuffer, gst_buffer_unref() after usage,
* or NULL
*
* Since: 0.10.24
*/
GstBuffer *
gst_buffer_list_iterator_merge_group (const GstBufferListIterator * it)
{
GList *tmp;
guint size;
GstBuffer *buf;
guint8 *ptr;
g_return_val_if_fail (it != NULL, NULL);
/* calculate size of merged buffer */
size = 0;
tmp = it->next;
while (tmp && tmp->data != GROUP_START) {
if (tmp->data != STOLEN) {
size += GST_BUFFER_SIZE (tmp->data);
}
tmp = g_list_next (tmp);
}
if (size == 0) {
return NULL;
}
/* allocate a new buffer */
buf = gst_buffer_new_and_alloc (size);
/* copy metadata from the next buffer after the implicit cursor */
gst_buffer_copy_metadata (buf, GST_BUFFER_CAST (it->next->data),
GST_BUFFER_COPY_ALL);
/* copy data of all buffers before the next group start into the new buffer */
ptr = GST_BUFFER_DATA (buf);
tmp = it->next;
do {
if (tmp->data != STOLEN) {
memcpy (ptr, GST_BUFFER_DATA (tmp->data), GST_BUFFER_SIZE (tmp->data));
ptr += GST_BUFFER_SIZE (tmp->data);
}
tmp = g_list_next (tmp);
} while (tmp && tmp->data != GROUP_START);
return buf;
}