Re: xawtv and v4lctl with usbvision kernel driver

[Devin Heitmueller <dheitmueller@kernellabs.com>]

On Mon, Nov 16, 2009 at 10:01 AM, Sietse Achterop <s.achterop@rug.nl> wrote:
>    Dear all,
>
> Context:
>  debian/lenny with usb frame grabber:
>     Zoran Co. Personal Media Division (Nogatech) Hauppauge WinTV Pro (PAL/SECAM)
>  This uses the usbvision driver.
>
> The problem is that while xawtv works OK with color, v4lctl ONLY shows the frames
> in black-and-white.
>
> I understood that the usbvision driver needs some attention, e.g. a command like
> "v4lctl setinput 2" is not working, it will keep using setting 0.
> Because I need 2 (S-video) I patched the driver to always use 2 by setting
> channel=2 in "usbvision_muxsel" to permanently select that channel.
> With that usbvision module loaded I am getting pictures, but in BLACK_AND_WHITE,
> as mentioned.
>
> When starting "xawtv", it works fine!
>
> With a simple opencv application I do an
>        CvCapture* capture = cvCaptureFromCAM( cnum );
>                 ...
>        cam = (CvCaptureCAM_V4L*)capture;
>                 ...
>        ioctl(cam->deviceHandle,VIDIOC_G_FMT,&format))
>                 ...
> and find that the format is YV12, but the picture is black-and-white.
> But YV12 is a color format.
>
> The question is, how to get proper color pictures when using v4lctl or other
> simple applications with this driver.
>
>  Thanks in advance,
>    Sietse Achterop

I don't know about that board in particular, but on some boards the
composite and s-video are actually wired together (sharing the luma
line), so if you have the device configured in "composite" mode but
have the s-video plugged in, then you will get a black/white image
(since it expects to see both luma/chroma on the one pin that provides
luma).

I had this issue on the HVR-950q.

Devin

-- 
Devin J. Heitmueller - Kernel Labs
http://www.kernellabs.com