YUV coder - unexpected behavior

2005/12/30 v 12:57, Adam Nohejl:

> Hello,
>
> My applications reads in JPEGs, processes them and then
use the  
> resulting images as frames for an MPEG video. Therefore
getting a  
> YCbCr blob seemed like a good idea:
>
>     MagickSetImageFormat(wand, "YUV");
>     MagickGetImageBlob(...);
>
> According to coders/yuv.c, the resulting blob should be
"CCIR 601  
> 4:1:1 or 4:2:2". In my case it was too small for
4:2:2, so I  
> figured out it must be 4:1:1, but it finally turned out
to be 4:2:0  
> - contrary to what yuv.c says. I also found out that
the blob isn't  
> CCIR 601 (luminance values not in full 0...255 range),
as it has a  
> full-scale 8bit luminance like in JPEG.
>
> YCbCr 4:2:0 with full-scale luminance works well for
me, but I  
> don't like to depend on behavior that doesn't
correspond to the  
> documentation (yuv.c comments).
>
> As I'm still quite new to all this image-processing
stuff  
> (colorspaces, subsampling etc.), could anyone check
whether I'm  
> wrong or not? Or should I get the raw YCbCr data in a
different way?
>
> Thanks for any suggestions,

As there's been no reply so far I'll assume it's a bug and
post it to  
the bugs list.

-- 
Adam Nohejl
Loki Software
mailto:adamlokisw.com
http://lokisw.com

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