[FFmpeg-devel] delayed H.264 B frames not being flushed by the decoder
harrison.declan at gmail.com
Thu Jul 3 08:32:43 CEST 2014
On Thu, Jul 3, 2014 at 2:44 AM, Michael Niedermayer <michaelni at gmx.at>
> On Wed, Jul 02, 2014 at 11:28:12PM +0100, declan harrison wrote:
> > Hi
> > I have a problem which is causing some issues for me. Im using the
> > libav API within my application.
> > I have an input MP4 file with an H264 video stream and an AAC audio
> > stream. The input video stream is encoded at High profile.
> > I transcode these two streams at a lower bitrate and then output to an
> > container. I also output the H.264 profile to baseline (no B frames).
> > The the last 2 frame I send to the decoder are P then B frame. After
> > is EOF I call the decoder with NULL packet to flush out the remaining
> > frames. This causes the P frame (2nd last frame) to be returned and
> > as complete which I can then encode and mux out, The decoder then returns
> > the last frame (B) to be returned. However when I encode this one its
> > marked as incomplete and cant be muxed out.
> > At this point I then attempt to flush out all delayed frames in the
> > by calling encode with a null picture type to flush the frames out.
> > However the last frame is marked as incompelte and cannot be written.
> > There are 177 samples in the video track.
> > Note: Put file through H264 Visa, it indicates that the last B frame
> > is sample number 177 is decoded as frame 176 and the sample number 176 (P
> > frame 2 nd last sample) is decoded as frame 177.
> > Is there anything I need to do to get this frame to be output
> can this be reproduced with ffmpeg (the command line tool i mean)
> No, when i create a command line variant the video stream has the same
number of frames as the input stream 177 frames.
Ive uploaded a zip file of the orginal video and a command line variant of
the same (vine.cli.mp4) to Google drive. You can download it here
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