[Libav-user] Locating the 'actual decoded picture buffer' (DPB) in H264 decoder.

백두인 barrelo89 at gmail.com
Mon Jul 13 13:59:29 EEST 2020

Hello all,

First of all, all of you are doing well and safe in this disturbed time.

I am running some experiments to see how making changes on an IDR frame
would take effect on the subsequent P and B frames in H264 code.

For the experiment, I am looking into the example code,
'doc/example/decode_video.c' and trying to access the decoded picture
buffer to modify some pixel values in the first decoded frame in the
buffer, which would affect the subsequent frames (P & B).

So far, I've accessed and tested 'DPB', 'ref_list', 'short_ref',
'long_ref', and 'default_ref_list', data fields in H264Context (
http://ffmpeg.org/doxygen/2.4/structH264Context.html) by making some
changes in their pixel values, but unfortunately expected changes on the
subsequent frames didn't occur.

As far as I understand the syntax of H264, specifically on the decoding
process in H264 codec, the decoding of P and B frames would happen by
referencing the frames in the decoded picture buffer. Could anyone give me
some guidance on where to look into this?

I've been struggling with this for months and It would be a tremendous help
if anyone can give me some tips.


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