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Re: [Spca50x-devs] gspca questions




Le jeudi 3 janvier 2008 04:17, Russell Steicke a écrit :
> Hello,
>
> I have a few questions about reading frames from a camera, and thought
> I'd put them in one job lot.  Some of them may be v4l questions, so
> feel free to point me somewhere else if that's the case.
>
> The camera is a Logitech Quickcam IM, and it's running on a GP2X,
> which is an ARM based games console.  It runs kernel 2.4.25 and I've
> installed spca5xx-LE.
>
> - Mostly after I call ioctl(fd,VIDIOCMCAPTURE,&vmmap) followed by
>   ioctl(fd,VIDIOCSYNC,&n), the VIDIOCSYNC returns after 100
>   milliseconds or so, with a valid picture in the buffer.  But quite
>   often (about 40% of the time) it returns after a couple of
>   milliseconds, and either the buffer is empty (since I've memset() it
>   to zeroes beforehand) or it has a stream in it that doesn't appear
>   to be a valid JPEG stream.
>
>   I don't know why VIDIOCSYNC should be returning so quickly.  Any
>   ideas?
>
> - When VIDIOCSYNC does return and there is a valid picture in the
>   buffer, is there anyway to determine exactly how many bytes were
>   written?  spcaview searches the buffer for 0xff 0xd9 and I've tried
>   that.  Is that the only way?
>
> - Sometimes I get half a JPEG picture.  The stream seems to stop at a
>   bright spot in the picture, or at a spot where there is lots of
>   detail.  This may be related to VIDIOCSYNC returning early, but I'm
>   not sure about that.
>
> Some of this may be related to the ARM CPU not having enough power to
> encode a JPEG for each frame.  However, it seems that spca5xx-LE does
> not to RGB24 encoding.  The CPU is a 200MHz ARM, with 32MB memory.
> Should this be able to run the full spca5xx driver?
>
>
> Thanks for you patience,
> Russell
As i write in my doc the ARM have some trouble with mmap() specially memory 
corrupion. I used read() instead
spca5x_LE only forward the mjpeg stream to userspace so that should work with 
your 200Mhz ARM
The full driver is not done for embedded,specially a 200Mhz CPU ;-) 
-- 
Michel Xhaard
http://mxhaard.free.fr

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