[GEM-dev] question about the SPC900 : WAS Re: pwc problem / help appreciated

[cyrille henry]

hello

are you still using liux?
could you tell me if this webcam work great?
did you have to to install a driver or is it plug and play?
what about latency?
is there anything i have to know befor buying one?

thanks
Cyrille


Roman Haefeli a écrit :
> hi all
> 
> nobody responed to that post. i am very sorry, if it was too nasty to
> ask so directly.
> 
> however, i would like to know, how difficult it would be and probably
> how much time it would require. knowing that, i could probably hire
> someone to code it for me. it is a really essential thing for my work.
> 
> roman
> 
> 
> On Mon, 2007-09-17 at 05:07 +0200, Roman Haefeli wrote:
>> 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.
>>
>> 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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