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

Michael Niedermayer michaelni
Fri Jul 18 16:12:05 CEST 2008

On Fri, Jul 18, 2008 at 03:52:48PM +0300, Maksym Veremeyenko wrote:
> Michael Niedermayer ???????(??):
>> On Thu, Jul 17, 2008 at 02:18:01PM +0300, Maksym Veremeyenko wrote:
> [...]
>>> if i add option
>>>     -sws_flags accurate_rnd
>> This is invalid, its
> Sorry.
>> -sws_flags +accurate_rnd
>> or
>> -sws_flags accurate_rnd+bicubic
> Tested both:

> 422->411 cyclic loop makes picture greener,

you are using an outdated version of swscale.

> 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)

> Should i recompile with --disable-mmx --disable-mmx2 --disable-ssse3 and 
> make tests agains?


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Dictatorship naturally arises out of democracy, and the most aggravated
form of tyranny and slavery out of the most extreme liberty. -- Plato
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