[PD] [pix_video] incorrect colors

IOhannes zmölnig zmoelnig at iem.at
Sun Mar 6 17:26:42 CET 2011

On 03/06/2011 04:05 PM, tim vets wrote:
> Dear list,
> When reading with [pix_video] from a camera via Webcamstudio (vloopback) at
> /dev/video1 the colors are incorrect.
> It looks like red and blue are inverted or swapped somehow, orange becomes
> blue and vice versa.
> Reading directly from the camera (driver 0 (v4l2), /dev/video2) the colors
> are correct.
> The same loopback device /dev/video1, v4lsrc is read by a Proce55ing sketch
> with correct colors.

it's a known bug which i believe is fixed in current SVN.

until the next release you could either try matju's suggestion, or try
sending a "colorspace yuv" to [pix_video].

if this works, chances are high that you have a lower processing
overhead than using [pix_colormatrix].

> I tried inserting [pix_yuv], [pix_rgba], but without success.

because the color is already wrong. [pix_yuv] and [pix_rgba] are
designed to give you (nearly) the same result, only in a different

the trick above (requesting "yuv" from [pix_video]) works (well, if it
does), because the image acquisition code for RGB32 is a broken while
the YUV acquisition code is not.
(using [pix_yuv] after [pix_video] is already too late)

unfortunately, my suggestion might as well _not_ work in your specific
case, since loopback devices  will often only ofter their format in one
single colorspace.


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