Thank you for your assistance. As for the wiki, I was thinking of this one http://openfacts.berlios.de/index-en.phtml?title=Linux+UVC . I'll ask them if I should put in the info for the cameras I have on there, but I'm not really sure if it belongs. If I get something started somewhere I'll post back to this mailing list with a link, but I'm not really in a position to host it myself right now so we'll see who I can find to do that for us.
On Mon, Jul 13, 2009 at 6:12 PM, Laurent Pinchart < [email protected]> wrote: > Hi Daniel, > > On Monday 13 July 2009 12:34:04 Daniel Crews wrote: > > Background: > > I have been trying to find a good value low cost webcam for computer > vision > > on linux. My basic plan is to set the exposure high enough to max the > > framerate, and use gain to make the markers I'm tracking visible. The > > ugliness resulting from this shouldn't matter. Unfortunately, there seems > > to be no list of what webcams allow you to set the exposure manually, and > > the grab bag of various models I have now all seem to not let you do > that. > > I'm looking at trying the Philips SPC 900NC which is said to work with > the > > PWC controller, but seems discontinuedish and more expensive than I'd > like > > to pay... I'm willing to pay for the quality if I need it(and the product > > has it!), but I'm making a system where I'll want to add as many cameras > as > > possible, so cheap is good (that's why I'm not going for firewire > cameras, > > as much as I would like to). > > > > Specific questions: > > 1.)Is there anything wrong with using "# v4lctl -c /dev/videoX list" to > > check for manual exposure settings? Or could this command miss a camera > > that can do it with just the stock UVC driver? (It'd be helpful to see an > > example of what a camera that can do that would look like as well, eg. > what > > to look for.) > > It might in theory miss cameras that can do manual exposure, but in > practice I > don't think it would. UVC allows for vendor-specific extensions through so- > called extension units. While a camera could implement manual exposure > through > an extension unit, it would make little sense as the UVC standard describes > how to handle manual exposure through the Camera Terminal. > > You can also use lsusb to list controls supported by a camera. Here's a > snippet of the output with a camera that supports manual exposure: > > VideoControl Interface Descriptor: > bLength 18 > bDescriptorType 36 > bDescriptorSubtype 2 (INPUT_TERMINAL) > bTerminalID 1 > wTerminalType 0x0201 Camera Sensor > bAssocTerminal 0 > iTerminal 0 > wObjectiveFocalLengthMin 0 > wObjectiveFocalLengthMax 0 > wOcularFocalLength 0 > bControlSize 3 > bmControls 0x0000000a > Auto-Exposure Mode > Exposure Time (Absolute) > > Lokk for an Input Terminal with wTerminalType set to 0x0201 (Camera > Sensor), > and check the bmControls field. It's a bit field that lists the supported > controls. lsusb decodes it for you and will print the meaning of each set > bit. > > > 2.) Is there a list with what cameras do manual exposure? (And what frame > > rates they can actually reach...) > > None that I'm aware of. > > > 3.) If not, should we try to extend the current UVC linux cam list with > > this kind of extra data? Or at least bring this scattered data together > in > > a single, if separate, repository? (Perhaps on the wiki...) > > I've been thinking of adding lsusb output's for all cameras listed on the > website. It would also be nice to have a wiki-like page for each camera > where > users could put comments. I unfortunately don't have time to work on that > right now. > > > 4.) In the meantime, does anyone have any suggestions? Particularly so if > > you know of a camera that does infra-red out of box or is easy to mod > with > > the exposed film trick, as I'd prefer to make the markers subtle to the > > human eye. > > 5.) Some of these questions pertain to this mailing list, let me know if > > some of them don't and where I should take them elsewhere....? > > Best regards, > > Laurent Pinchart > > -- Fin
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