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video: Document buffer ownership of the GstVideoCodecFrame more explicit

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And also the implications of calling the finish() functions.
This commit is contained in:
Sebastian Dröge 2012-07-05 14:29:42 +02:00
parent 7803ae97e9
commit 9002471c93
3 changed files with 23 additions and 8 deletions
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20
gst-libs/gst/video/gstvideodecoder.c
View file

@ -2159,6 +2159,10 @@ gst_video_decoder_drop_frame (GstVideoDecoder * dec, GstVideoCodecFrame * frame)
* If no output data is provided, @frame is considered skipped.
* In any case, the frame is considered finished and released.
*
* After calling this function the output buffer of the frame is to be
* considered read-only. This function will also change the metadata
* of the buffer.
*
* Returns: a #GstFlowReturn resulting from sending data downstream
*
* Since: 0.10.36
@ -2189,12 +2193,7 @@ gst_video_decoder_finish_frame (GstVideoDecoder * decoder,
goto done;
}
/* A reference always needs to be owned by the frame on the buffer.
* For that reason, we use a complete sub-buffer (zero-cost) to push
* downstream.
* The original buffer will be free-ed only when downstream AND the
* current implementation are done with the frame. */
output_buffer = gst_buffer_copy (frame->output_buffer);
output_buffer = frame->output_buffer;
GST_BUFFER_FLAG_UNSET (output_buffer, GST_BUFFER_FLAG_DELTA_UNIT);
@ -2211,6 +2210,12 @@ gst_video_decoder_finish_frame (GstVideoDecoder * decoder,
priv->discont = FALSE;
}
/* Get an additional ref to the buffer, which is going to be pushed
* downstream, the original ref is owned by the frame
*
* FIXME: clip_and_push_buf() changes buffer metadata but the buffer
* might have a refcount > 1 */
output_buffer = gst_buffer_ref (output_buffer);
if (decoder->output_segment.rate < 0.0) {
GST_LOG_OBJECT (decoder, "queued frame");
priv->output_queued = g_list_prepend (priv->output_queued, output_buffer);
@ -2827,6 +2832,9 @@ gst_video_decoder_alloc_output_buffer (GstVideoDecoder * decoder)
* current #GstVideoCodecState. Subclass should already have configured video
* state and set src pad caps.
*
* The buffer allocated here is owned by the frame and you should only
* keep references to the frame, not the buffer.
*
* Returns: %GST_FLOW_OK if an output buffer could be allocated
*
* Since: 0.10.36

4
gst-libs/gst/video/gstvideoencoder.c
View file

@ -1328,6 +1328,10 @@ gst_video_encoder_set_src_caps (GstVideoEncoder * encoder)
* It is subsequently pushed downstream or provided to @pre_push.
* In any case, the frame is considered finished and released.
*
* After calling this function the output buffer of the frame is to be
* considered read-only. This function will also change the metadata
* of the buffer.
*
* Returns: a #GstFlowReturn resulting from sending data downstream
*
* Since: 0.10.36

7
gst-libs/gst/video/gstvideoutils.h
View file

@ -201,10 +201,13 @@ typedef enum
* Typical usage in decoders is to set this on the opaque value provided
* to the library and get back the frame using gst_video_decoder_get_frame()
* @distance_from_sync: Distance in frames from the last synchronization point.
* @input_buffer: the input #GstBuffer that created this frame.
* @input_buffer: the input #GstBuffer that created this frame. The buffer is owned
* by the frame and references to the frame instead of the buffer should
* @output_buffer: the output #GstBuffer. Implementations should set this either
* directly, or by using the @gst_video_decoder_alloc_output_frame() or
* @gst_video_decoder_alloc_output_buffer() methods.
* @gst_video_decoder_alloc_output_buffer() methods. The buffer is owned
* by the frame and references to the frame instead of the buffer should
* be kept.
* @deadline: Running time when the frame will be used.
* @events: Events that will be pushed downstream before this frame is pushed.
*