[FFmpeg-devel] ffvhuff bug when using median prediction + adaptive tables

[Loren Merritt]

On Sat, 4 Aug 2007, infernix wrote:

> When encoding certain streams to ffvhuff .avi files with median prediction + 
> adaptive tables enabled, there are errors when playing back the finished 
> encode.
>
> I've tried to figure out how to enable median prediction + adaptive tables 
> with ffmpeg svn (today) but cannot for the life of me figure out what the 
> commandline is, so I can only show how to reproduce with mencoder using 
> libavcodec (also todays svn, of course):
>
> mencoder -oac pcm -nosound -o huffyuv_table_sample.avi -ovc lavc -lavcopts 
> vcodec=ffvhuff:vstrict=-1:pred=2:context=1 huffyuv_table_sample.264
>
> Everything is fine if i enable only adaptive tables, or only median 
> prediction, but it seems this bug is triggered when enabling both.

fixed.
Not directly related to median prediction, but may have been exacerbated 
because median prediction reduces the average size of residual 
coefficients, thus any remaining large coefficients got a longer 
codeword.

--Loren Merritt