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

[Maksym Veremeyenko]

Michael Niedermayer ???????(??):
> On Fri, Jul 18, 2008 at 03:52:48PM +0300, Maksym Veremeyenko wrote:
[...]
> 
>> 422->411 cyclic loop makes picture greener,
> 
> you are using an outdated version of swscale.
Just tested against SVN-r14282 - i notices a lot of commits was done 
against libswscale.

> 
> 
>> 422->420 cyclic loop produce some artifacts.
> 
> yes, you have to use the nearest neighbor scaler to avoid bluring and or
> ringing artifacts whan scaling 100 times.
> (the old scaler uses nearest neighbor for chroma as well)

Test results for color bars picture:

[-sws_flags +accurate_rnd] minor artfacts
[-sws_flags accurate_rnd+neighbor] no visible artifacts
[ ] (without -sws_flags option)
     422->411 - picture become greener, 29th iteration result attached
     422->420 - picture has green artifacts in border of luma change 
values, 50th iteration result attached


-- 
________________________________________
Maksym Veremeyenko
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