On Tue, Nov 09, 2010 at 09:43:29AM +0100, Michael PARKER wrote:
> I'm attempting to capture a single frame from the /dev/video0 output of
> my HVR-4000 card's analogue tuner as a JPEG.
> 
> Whilst several resources exist for capturing the output of a card with
> h/w MPEG compression, I'm unable to determine the format of the
> /dev/video0 data for a frame grabber such as the HVR-4000.

According to the sourcecode the cx88 chip can do 8 bit grayscale,
15/16/24/32 bit RGB/BGR, and two variants of 4:2:2 YCbCr.
 
> Can anyone suggest a means by which I can capture a single frame from a
> frame grabber card? Can I just use "dd if=/dev/video0 of=image.jpg bs=64K"
> or similar or do I have to access the card via the V4L2 drivers?

Yes, dd should work but you need to use a blocksize that can hold a
complete frame and count=1 if you want a single frame. JPEG, as
mentioned above, is not possible with this board.

The resolution and data format can be selected with V4L2 ioctls.

  Daniel
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