>From: Trent Piepho <[EMAIL PROTECTED]>
>Date: Wed, 26 Jan 2005 12:55:50 -0800 (PST)
>
>On Wed, 26 Jan 2005, E.Chalaron wrote:
...
>> I know that
>> find . -name \*.tga | xargs -n1 tgatoppm | ppmtoy4m | blabla
>
>Try this:
>find . -name \*.tga | xargs -n1 cat | ppmtoy4m
^^^ .ppm, of course...
...
>> An option would be to save in TGA.
>
>If you used a digital camera, didn't it produce jpeg files? You'd get the
>best quality be going from jpeg to y4m directly, without the ppm step.
>Converting from jpeg to ppm involves a colorspace conversion (YUV->RGB) as
>well as chroma re-sampling (4:2:0 -> 4:4:4). Going from ppm to y4m involves
>converting back to YUV and 4:2:0. The files would probably be a lot smaller
>too!
It's not necessarily "direct" from jpeg to y4m; JPEG-->Y4M involves
hammering the chroma as well:
o Change of gamut -- JPEG luma is [0,255], Y4M is [16,235], etc.
o Change of subsampling -- JPEG is "4:2:0 JPEG", whereas for a DVD
you need "4:2:0 MPEG-2" --- they are different.
But, with JPEG-->PPM-->Y4M, you would be doing both of those twice.
Maybe E.'s film is black&white? :)
-matt m.
ps: If it *is* black&white... try PGM images and the new "pnmtoy4m"!
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