Bug#357626: [Pkg-spca5xx-devel] Bug#357626: kernel bug (oops) using vgrabbj on spca5xx

michel Xhaard mxhaard at free.fr
Sat Mar 18 23:24:25 UTC 2006

Le Samedi 18 Mars 2006 23:10, Florian Lohoff a écrit :
> On Sat, Mar 18, 2006 at 09:41:31PM +0100, michel Xhaard wrote:
> > Flo,
> > Are you sure a webcam with isochronous pipe can just get a single image ?
> The camera used to work a little while ago with vgrabbj like a charm -
> It did on a Dual Xeon 2.4Ghz
With your Dual Xeon 2.4Ghz you can play with 4 Vimicro webcams in real 
times :)
> > I only support stable vanilla kernel, so wait for 2.6.16
> > official. Your PII is
> As i said - i also tried 2.6.15 with no success - same oops ...
> > to low to decode jpeg in real times with a Vimicro/zstar chipset. A video
> > stream in VGA at 30 fp/s need a strong CPU, a PIII 500Mhz is a minimum :)
> > regards
> Nevertheless it should rather send empty images or nothing than die. An
> Oops or "BUG" is _always_ the kernels fault ...
Hmm, spca5xx is design for running on a strong enought machine, your PII is to 
slow and cannot decode the jpeg stream in times.  A usb isochronous webcam is 
a streaming video device and never provide a single picture but a stream of 
pictures send with small packet on the usb bus. The iso handler collect the 
packet and when a frame is empty schedule a tasklet to decode the jpeg. What 
happen here is the handler collect the frame faster than the decoder.
I have set another driver for the vimicro chips design for small hardware 
(spca5xx-LE ) this one never decode the stream but instead forward the frame 
on userspace. I use it with a small TCP/IP server that way the video is 
forward to TCP and can be used by others TCP client. I use it with a Etrax 
Soc 100Mhz and can carry VGA stream in real times. Maybe have a look
Michel Xhaard

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