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Re: [Spca50x-devs] questions about the internal of the driver




Le dimanche 3 février 2008 11:59, Jean-Francois Moine a écrit :
Jean François,
> When I wrote some code for the v2l version 2, I found the grabbing
> frame state is not clear. I think that an other state should be
> required meaning the frame is treated by the application.
>
> Then, I was wondering why is there a tasklet do to the conversion.
> In other drivers such as ov51x-jpeg, 
Don't really know ov51x-jpeg sorry :(
> the conversion is done by the 
> application. So, the code may be simpler:
The gspcav1 is v4l1, v4l1 know nothing about mjpeg that is why a tasklet is 
used here.
>
> - receiving iso packets, move the data to the frame buffer, state
> 	GRABBING.
> - when end of frame (start of new frame) is detected, change the
> 	state to READY (and that's all).
> - when the application asks for a new frame (read() or iotcl()
> 	VIDIOCMCAPTURE or VIDIOC_DQBUF), convert the frame to the
> 	desired palette and change the state to DONE.
> - when the application releases the frame (end of read() or ioctl()
> 	VIDIOCSYNC or VIDIOC_QBUF, free the buffer setting its state
> 	to UNUSED.
>
> Doing so should avoid the problem occuring with 2 frame buffers:
> - one buffer being grabbed,
> - this other one being converted and
> - which one being processed by the application...
Interresting.
My firs idea was to stop developping gspcav1 and start a new branch for v4l2 
support.
http://mxhaard.free.fr/spca50x/Investigation/Gspca/
http://linuxtv.org/hg/~mchehab/gspca/
 The problem is no one seem interresting to develop this branch, of course it 
is difficult as we need to be sure the > 270 webcam are ok after each small 
change ;-)
I see you change the core driver to add your chipset.I have to double check 
all webcams are working before apply, sorry for the delay
bests regards
-- 
Michel Xhaard
http://mxhaard.free.fr

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