[PD-dev] GEM: pix_video

Johannes M Zmoelnig zmoelnig at iem.at
Mon Dec 13 11:30:08 CET 2004

Georg Holzmann wrote:
> Hallo IOhannes && others!
> I just bought a webcam and it doesn't work corretly in GEM (as we talked
>   about yesterday).
> You were rigth: blue and red was exchanged, so I changed this in
> GemPixUtil.cpp (line 630 - is attached).
> You handle this two cases in the same way:
>    case GL_RGBA:
>    case GL_BGRA_EXT:
> maybe this is the problem of the mixed blue-red channel?
> (in the attached file I simple exchanged the blue and red channel - so I
> think now it's wrong for GL_BGRA_EXT !)

well, the GL_BGRA_EXT is there for a good reason: because "normally" 
(this is: most (but not all) devices i tested, revert blue and red so we 
are using BGRA instead of RGBA (which i would have expected to be the 

probably i should read the documentation or pdp's code.

> But the quality of the picture is still not that good as in pdp. There's
> a lot of noise in it - it looks like it was compressed with a
> low-quality JPEG algorithm.
> Do you know where I can improve the quality of the picture ?

maybe the problem is really hidden in the yuv2rgb conversion of the 
driver. (pushing it away from me...)
is the quality the same if you are using [colorspace YUV< (vs. 
[colorspace RGBA< ) ?

or use a higher resolution...


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