[GEM-dev] pwc problem / help appreciated

[cyrille henry]

Roman Haefeli a écrit :
> hi all
> 
> <skip_if_no_interest_in_backgroundstory>
> i have a philips webcam, the spc 900nc, which i would like to use with
> gem. since there is the new pwc driver[1], the cam can be accessed over
> v4l and thus with gem. the problem is that certain, for me very
> important, settings are pwc specific, which means the only way to set
> them is using setpwc, which also seems to work fine at first glance. but
> there is a silly little problem with some settings, e.g automatic gain
> control: i can set the gain manually with setpwc, but when i launch
> another program afterwards, that accesses the cam (e.g. Gem), the
> cam/driver forgot about these settings and gain is set to 'auto'
> again.  
> there are two ways to overcome this problem.
> 
> 1) the probably more obvious solution would be to implement all pwc
> specific features into [pix_video], so that all these settings can be
> set from within gem. besides that it seems very awkward to implement
> driver specific options in [pix_new], it is probably also a lot of work.
> 
> 2) the other approach would require only very tiny changes to
> pix_videoNEW.cpp . philips cams are usually shipped with some kind of
> non-volatile ram, where settings can be stored and restored. now we come
> to the interesting point: if [pix_video] would send a 'restore' signal
> to the pwc driver, whenever rendering is turned on (is the same as
> 'whenever [pix_video] accesses the cam, right?). this would mean, that i
> could set all required settings beforehand using 'setpwc' with the
> option to save all settings into non-volatile ram. when running gem
> afterwards, all settings would be restored and finally i would be able
> to have a constant gain, which is fundamental for some tasks (e.g
> working with [pix_background])
> 
> [1] http://saillard.org/linux/pwc/
> </skip_if_no_interest_in_backgroundstory>
> 
> -------------------------------------------------
> 
> i want to ask you guys, if you could help me add the necessary changes
> to pix_videoNEW.cpp. i have the feeling, that it is a rather simple task
> (i might be wrong), but i am unfortunately not a c nor cpp coder.
> basically it would be transfering the function, that does create the
> 'restore' signal, from setpwc.c to pix_videoNEW.cpp . 
> please do understand me right, this isn't a request about including the
> chances to Gem-cvs, but just for me, since i cannot really use the cam
> with gem yet.

why don't you start setpwc before pd to restor data?

cyrille

> 
> you'll find setpwc.c here:
> http://romanhaefeli.net/setpwc.c
> 
> and you probably need to include this in pix_videoNEW.cpp :
> http://romanhaefeli.net/pwc-ioctl.h
>  
> have a look at line 323 of setpwc.c, there you can see, what setpwc does
> to let the cam restore the settings from ram. if this little thingie
> could be transferred to gem, it would solve all my ubs-cam problems.
> 
> i really appreciate your help here
> 
> roman
> 
>  
> 
> 
> 
> 
> 
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