Thanks for the reply, I'll look out for those possible correction commands... But the adjustment when I cover the lens already happens in the Linux driver, so I guess it's just something internal, right? I went back to the original driver to see if I could make the camera usable again, and I succeeded by turning off the automatic white balance, and changing the values of the balance by hand. There are three values for R G and B that can be set from 0 to 127. Can gspca support something like that? v4lctl doesn't offer anything like that out of the box, and I couldn't find possible functions in the code. Does that array in the setwhitebalance function (t613.c) set these values that the win driver offers the user to set? thanks, ++nicolau On Tue, Jan 26, 2010 at 12:18:01PM -0600, Theodore Kilgore wrote: > > > On Tue, 26 Jan 2010, Nicolau Werneck wrote: > >> Hello. I have this very cheap webcam that I sent a patch to support on >> gspca the other day. The specific driver is the t613. >> >> I changed the lens of this camera, and now my images are all too >> bright, what I believe is due to the much larger aperture of this new >> lens. So I would like to try setting up a smaller exposure time on the >> camera (I would like to do that for other reasons too). >> >> The problem is there's no "exposure" option to be set when I call >> programs such as v4lctl. Does that mean there is definitely no way for >> me to control the exposure time? The hardware itself was not designed >> to allow me do that? Or is there still a chance I can create some C >> program that might do it, for example? >> >> It looks like the camera has some kind of automatic exposure control. If >> I cover the lens, and then uncover it quickly, the image is all white >> at first, and then it gradually becomes darker. Should that give me >> some hope of being able to control the exposure, or is it common for >> cheaper cameras to have just an automatic exposure control that cannot >> be overrun? > > Nicolau, > > Having had some experience with cheap cameras, I would say that they come > with all kinds of variations. Thus, this particular camera (with which I > am _not_ experienced) could either have a built-in automatic exposure > control, or it could require monitoring from software with periodic > correction of various settings. It just depends. > > Thus, one thing to do is to look carefully at some usbsnoop logs and try > to see if there are occasional correction sequences in between big hunks > of data. If there are, then the next thing is to figure out what those > correction sequences are doing. Then build those correction sequences > into the driver. An example of this kind of thing going on can be seen > in lots of the camera drivers in gspca, but not in all of them. > > Second thing, try to look for sensor setup commands which give initial > settings. If there are such, then one or more of them might control > exposure settings. > > Third, if there are no occurences of either of the previous items at all, > then either the camera does not self-adjust and can not be adjusted (i. > e. really, really cheap), or the adjustment mechanism is completely > built-in. In that case, I would say that you are probably up a tree about > getting the exposure reset. > > Hope this helps you. > > Theodore Kilgore -- Nicolau Werneck <nwerneck@xxxxxxxxx> 1AAB 4050 1999 BDFF 4862 http://www.lti.pcs.usp.br/~nwerneck 4A33 D2B5 648B 4789 0327 Linux user #460716 -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
