On Sun, 13 Feb 2005 [EMAIL PROTECTED] wrote:

> that a movie media made of several layers does not have the same granularity 
> (which does obably apply on classic still cameras as well). 
> The blue layer seems to be made of bigger grains than other, therefore not 
> having the same resolution.

> Having said this, is there a way to reconstruct the Blue from the chroma 
> planes to apply a different set of processing / denoising ? or am I just 
> dreaming it... :-) 

        You can reconstruct _a_ blue from the U and V planes but it won't
        be the _original_ blue.  

        By the time you have a YUV4MPEG2 stream the RGB data has been converted
        to "YUV".  It's possible to convert YUV to RGB but there is some loss
        involved in the process - and of course you'd have to convert back
        again from RGB to YUV for encoding.

        It sounds like what you want to do is process the RGB data  _before_
        going thru the pnmtoy4m (or ppmtoy4m) stage.  Can't use y4mdenoise,
        etc for that so you'd have to write your own filter - perhaps some
        of the GIMP filters would be a good starting point since the GIMP
        does a lot of its work in the RGB space.  

        The filters in mjpegtools are all oriented around "YUV" (with
        various chroma subsamplings - 4:1:1, 4:2:0, and so on) rather than
        RGB so if you want to treat each of R/G/B differently you'll probably
        want to 1) do it before conversion and  2) write/borrow/adapt some
        other code.

        Good Luck!

        Steven Schultz



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