[FFmpeg-devel] pixel format convertion yuv422p->yuv420p->yuv411p->yuv422p degrade picture
Tue Jul 15 18:44:10 CEST 2008
Maksym Veremeyenko wrote:
> Michael Niedermayer ???????(??):
>> On Tue, Jul 15, 2008 at 04:22:33PM +0100, M?ns Rullg?rd wrote:
>>> 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.
> I did cyclic test for:
> | |
> no visial degrades found.
The colour drift aside, I'd expect to see gradual, if slight, blurring
of the chroma planes.
>> I suspect that dithering could reduce the drift, for normal interpolation
>> based filters but running 50 converters in a row is a stupid thing to do.
> Such condition possible in:
> Uncompressed (4:2:2) -> DV25 (4:2:0) -> DVCpro25 (4:1:1) -> Uncompr
If it hurts, don't do it. That looks like it would hurt. In fact,
4:1:1 hurts as is, even without any additional degrading.
> 50 iterations was only for proving that convertions degrade picture...
> So, as conclusion, that a normal?
The conclusion is that it's probably not worthwhile doing anything about
it. It would make the code slower with no real benefit in practical use
mans at mansr.com
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