[FFmpeg-devel] [PATCH] Set generic yuv420 sampling in yuv4mpeg by default

[David Conrad]

On May 8, 2009, at 9:49 AM, Michael Niedermayer wrote:

> On Thu, May 07, 2009 at 11:43:25PM -0400, David Conrad wrote:
>> Hi,
>>
>> As discovered in #x264, the dump_psnr tool in Thusnelda actually  
>> cares
>> about chroma sample positions. This should probably be more  
>> correct; I
>> don't know for sure which codecs define which positioning.
>
> many codecs leave it unspecified
> h264 & mpeg4 match mpeg2 by default in theory, in how far the actual
> data matches this of course is another question

I didn't know that; but probably the correlation with actual data  
isn't much worse than mpeg2.

> h264 allows the exact chroma positions to be stored for 420
> we could add a chroma_sample_location field to AVCodecContext maybe

I wound up doing this and adding values for a couple codecs I looked up.

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