Hello,
On 16-May-00 Dmitri wrote:
> This is a very nice idea; however all cameras produce their own variants
> of known formats; some are even compressed. The driver -must- do something
> with this totally device-specific data stream. No client would be able (or
> want) to understand device-dependent formats. V4L does not seem to have a
> good place to insert such conversion code into. V4L2 does. In the mean
> time all drivers produce RGB24 (or GRAY) output - not because they love it
> but because they must.
I would recommend BGR format, since this is what all grabber cards and most
(all?) webcam drivers do so far.
> All (or most of) camera drivers are based on CPiA code. It did YUV -> RGB
> conversion in USB interrupt thread. This is very bad performance-wise. I
> experimented recently with moving this transformation into read() or
> ioctl() calls to release USB "interrupt" faster - and it helped a lot;
*nod* I do the same in the Philips webcam driver. Not because of
performance, but I wanted to keep it out of the kernel thread and now the
time spent in conversion/decompression is registered on the user process,
not the kernel :)
- Nemosoft
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