[FFmpeg-devel] 'ffmpeg' decoder init behaviour

Philip Langdale philipl at overt.org
Wed Jan 11 18:18:46 CET 2012

Hi all,

Regarding: http://ffmpeg.org/trac/ffmpeg/ticket/857

This is a regression in the CrystalHD decoder. When you use the
ffmpeg command line tool, it will init the decoder to probe the
file and then re-init it when doing actual decoding. This is fine
most of the time, but the CrystalHD decoder needs to use a bitstream
filter to ensure that H.264 content is in Annex B format. This becomes
a problem because the filter rewrites avctx->extradata and the decoder
has to test avctx->extradata to decide if the filter is necessary or

The end result is that the probe pass works correctly, but then the
decode pass fails because the content is misdetected. In the older 
CrystalHD code, I did the extra data detection by hand and had a work
around that would restore the avctx values after detection. But now
I use the filter all the way through - and it requires the avctx
values to be converted and stay converted. Is there anything sane I
can do to make this work?



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