Trent Piepho wrote:
>
> > I have both ways conversions: Y'CbCr <-> RGB, and both according to the newer
> > colorspace FAQ coefficients/terminology are really Y'PbPr. I havn't tested the
> > RGB -> Y'CbCr direction, but the Y'CbCr -> RGB converts bttv YUV data and the
> > colors look normal.
>
> Are you getting the data directly from the driver, or from some application
> that might be modifiying it?
Directly from the driver - this is just a simple viewing test app. (in
fact it's in my tarball on Gleicon's site):
http://planeta.terra.com.br/informatica/gleicon/video4linux
> Try capturing a colorbars test pattern in RGB mode and then YUV mode, and
> convert using the Y'PbPr formula. Then try converting using the formula in
> the bt848 datasheet. See which one looks more like the RGB output. You can
> get the bt848 to generate a colorbars pattern internally, but you need to hack
> the driver.
That's good to know - I guess it would be easy to add a private bttv
ioctl for it. I havn't done any side-by-side RGB vs YUV->RGB converted
comparisons because previously I wasn't aware of the issue of alternate
"Y'CbCr" definitions... I'm going to redo my conversions soon based on
Justin's comment about integer multiply being cheaper than a lookup
cache miss, and I'll do it then. Right now I've got more fun stuff to
do! I've written a ground-up AVI for Linux library, and am at the point
of implementing a few test CODECs :-)
Ben
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