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Original commit message from CVS: A commit of pending (small) changes...
308 lines
5.5 KiB
Text
308 lines
5.5 KiB
Text
<!-- ##### SECTION Title ##### -->
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GstBuffer
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<!-- ##### SECTION Short_Description ##### -->
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Data-passing buffer type, supporting sub-buffers and metadata
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<!-- ##### SECTION Long_Description ##### -->
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<para>
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Buffers are the basic unit of data transfer in GST. The GstBuffer type
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provides all the state necessary to define a region of memory as part of a
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stream. Sub-buffer are also supported, allowing a smaller region of a
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buffer to become its own buffer, with mechanisms in place to ensure that
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neither memory space goes away. Metadata is supported as a list of
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pointers to arbitrary metadata.
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</para>
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<para>
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Buffers are usually created with gst_buffer_new(). After a buffer has been
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created one will typically allocate memory for it and set the size of the
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buffer data.
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<programlisting>
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GstBuffer *buffer;
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gint size, widht, height, bpp;
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size = width * height * bpp;
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buffer = gst_buffer_new ();
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GST_BUFFER_SIZE (buffer) = size;
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GST_BUFFER_DATA (buffer) = g_alloc (size);
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...
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</programlisting>
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</para>
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<para>
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GstBuffers can also be created from a GstBufferPool with
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gst_buffer_new_from_pool(). The bufferpool can be obtained from a
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peer element with gst_pad_get_bufferpool().
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</para>
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<para>
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gst_buffer_ref() is used to increase the refcount of a buffer. This must be
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done when you want to keep a handle to the buffer after pushing it to the
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next element.
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</para>
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<para>
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To efficiently create a smaller buffer out of an existing one, you can
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use gst_buffer_create_sub().
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</para>
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<para>
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Several flags of the buffer can be set and unset with the GST_BUFFER_FLAG_SET()
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and GST_BUFFER_FLAG_UNSET() macros. Use GST_BUFFER_FLAG_IS_SET() to test it
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a certain flag is set.
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</para>
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<para>
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Buffers usually are freed by unreffing them with gst_buffer_unref().
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gst_buffer_destroy() can also be used to effectively destroy the buffer
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regardless of the refcount (dangerous).
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</para>
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<!-- ##### SECTION See_Also ##### -->
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<para>
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#GstBufferPool, #GstPad
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</para>
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<!-- ##### MACRO GST_BUFFER_FLAGS ##### -->
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<para>
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Get the flags from this buffer.
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</para>
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@buf: GstBuffer to retrieve the flags from
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<!-- ##### MACRO GST_BUFFER_FLAG_IS_SET ##### -->
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<para>
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Gives the status of a given flag.
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</para>
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@buf: GstBuffer to query
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@flag: the flag to check
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<!-- ##### MACRO GST_BUFFER_FLAG_SET ##### -->
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<para>
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Set a flag in a buffer.
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</para>
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@buf: GstBuffer to query
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@flag: the flag to set
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<!-- ##### MACRO GST_BUFFER_FLAG_UNSET ##### -->
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<para>
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Clear a flag in a buffer.
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</para>
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@buf: GstBuffer to modify
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@flag: the flag to clear
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<!-- ##### MACRO GST_BUFFER_DATA ##### -->
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<para>
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Retrieves a pointer to the data element of this buffer
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</para>
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@buf: GstBuffer
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<!-- ##### MACRO GST_BUFFER_SIZE ##### -->
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<para>
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Get the size of the data in this buffer.
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</para>
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@buf: GstBuffer
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<!-- ##### MACRO GST_BUFFER_OFFSET ##### -->
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<para>
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Get the offset in the source file of this buffer.
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</para>
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@buf: GstBuffer
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<!-- ##### MACRO GST_BUFFER_MAXSIZE ##### -->
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<para>
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Gets the maximun size of this buffer.
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</para>
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@buf: GstBuffer
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<!-- ##### MACRO GST_BUFFER_TIMESTAMP ##### -->
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<para>
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Get the timestamp for this buffer.
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</para>
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@buf: GstBuffer
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<!-- ##### MACRO GST_BUFFER_BUFFERPOOL ##### -->
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<para>
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Get the bufferpool for this buffer.
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</para>
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@buf: GstBuffer
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<!-- ##### MACRO GST_BUFFER_POOL_PRIVATE ##### -->
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<para>
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Get the bufferpool private data.
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</para>
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@buf: GstBuffer
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<!-- ##### MACRO GST_BUFFER_LOCK ##### -->
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<para>
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This macro will obtain a lock on the object, making serialization
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possible.
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</para>
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@buf: GstBuffer to lock
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<!-- ##### MACRO GST_BUFFER_TRYLOCK ##### -->
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<para>
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This macro will try to obtain a lock on the object, but will return with
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FALSE if it can't get it immediately.
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</para>
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@buf: GstBuffer to try to lock
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<!-- ##### MACRO GST_BUFFER_UNLOCK ##### -->
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<para>
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This macro releases a lock on the object.
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</para>
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@buf: GstBuffer to unlock.
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<!-- ##### MACRO GST_BUFFER_PARENT ##### -->
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<para>
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Get the parent of this buffer. The parent is set on subbuffers.
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</para>
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@buf: GstBuffer to get the parent of.
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<!-- ##### MACRO GST_BUFFER_MAXAGE ##### -->
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<para>
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Get the maximun age of a buffer.
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</para>
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@buf: GstBuffer to get the maxage of.
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<!-- ##### ENUM GstBufferFlags ##### -->
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<para>
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</para>
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@GST_BUFFER_READONLY: the buffer is read only
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@GST_BUFFER_ORIGINAL: this buffer not a copy
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@GST_BUFFER_DONTFREE: do not try to free the data when this buffer is unref-ed
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@GST_BUFFER_FLUSH: this buffer is not related to previous buffers. This flag is mainly
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used when data in a stream has been skipped
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@GST_BUFFER_EOS: this buffer is the last one in the stream
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@GST_BUFFER_DISCONTINUOUS: The buffer has a discontinuity
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<!-- ##### STRUCT GstBuffer ##### -->
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<para>
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</para>
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@lock:
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@data:
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@size:
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@maxsize:
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@offset:
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@timestamp:
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@maxage:
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@parent:
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@pool:
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@pool_private:
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@free:
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<!-- ##### FUNCTION gst_buffer_new ##### -->
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<para>
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</para>
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@Returns:
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<!-- ##### FUNCTION gst_buffer_new_from_pool ##### -->
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<para>
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</para>
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@pool:
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@Returns:
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<!-- ##### FUNCTION gst_buffer_copy ##### -->
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<para>
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</para>
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@buffer:
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@Returns:
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<!-- ##### FUNCTION gst_buffer_create_sub ##### -->
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<para>
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</para>
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@parent:
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@offset:
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@size:
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@Returns:
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<!-- ##### FUNCTION gst_buffer_append ##### -->
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<para>
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</para>
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@buffer:
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@append:
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@Returns:
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<!-- ##### FUNCTION gst_buffer_ref ##### -->
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<para>
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</para>
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@buffer:
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<!-- ##### FUNCTION gst_buffer_ref_by_count ##### -->
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<para>
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</para>
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@buffer:
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@count:
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<!-- ##### FUNCTION gst_buffer_unref ##### -->
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<para>
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</para>
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@buffer:
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<!-- ##### FUNCTION gst_buffer_destroy ##### -->
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<para>
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</para>
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@buffer:
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