[FFmpeg-devel] pixel format convertion yuv422p->yuv420p->yuv411p->yuv422p degrade picture

Måns Rullgård mans
Tue Jul 15 17:22:33 CEST 2008

Maksym Veremeyenko wrote:
> Dear Developers!
> I was testing pixel format changing and found that convertions like:
> yuv422p->yuv420p->yuv411p->yuv422p
> degrade picture - it become greener.
> To prove this i did a shell script, see attached. On 50th iteration
> picture is almost compleately green.
> Is it normal behaviour for pixel format converting or it is a bug?

Apparently, rounding errors in the chroma interpolation are accumulating.
Without thinking a little harder, I don't know whether such a conversion
sequence is possible without such drift.  It will always be lossy, as I'm
sure you already realise.

M?ns Rullg?rd
mans at mansr.com

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