[PD] [pix_video] with v4l

IOhannes m zmoelnig zmoelnig at iem.at
Tue Sep 8 09:10:43 CEST 2009

Mathieu Bouchard wrote:
> On Mon, 7 Sep 2009, IOhannes m zmoelnig wrote:
>> Miha Tomi wrote:
>>> On Linux using Gem 0.92 from SVN I am using [pix_video] with Logitech
>>> QuickCam 4000 and v4l driver but the red and blue colours are swapped.
>>> Is there a way to instruct [pix_video] to use different colorspace (BGR
>>> instead of RGB)? If not what is the cheapest way to convert from one
>>> colorspace to the other.
>> a simple _hack_ is to use YUV-colorspace with [pix_video] and then (if 
>> you really need it) [pix_rgba] to convert to RGBA.
> Do you mean that the BGR thing is a bug in Gem or what? Because if it 

yep, i suspect so (but then there are of course also broken drivers 
and/or APIs; i thought that all these issues are kindof "fixed" (by 
explicitely ignoring them) in v4l2...which leaves Gem as the culprit).

pix_film will capture and convert (most?) YUV-spaces correctly into it's 
own UYVY, but seems to have problems with converting them into RGBA.
the fix is braindead, but i hadn't had to time to check why and when it 
is happening.

> isn't, then YUV might as well be YVU, in which case you'd still use 
> [pix_colormatrix], but possibly with different constants... what is 
> [pix_colormatrix] supposed to do on a YUV image ? are its coefficients 
> still RGB-wise in that case?

rtfs... [pix_colormatrix] currently only works on RGBA...

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