Em Wed, 15 Mar 2017 19:04:21 +0100 Pavel Machek <pavel@xxxxxx> escreveu: > Hi! > > > > Well, I believe first question is: what applications would we want to > > > run on complex devices? Will sending control from video to subdevs > > > actually help? > > > > I would say: camorama, xawtv3, zbar, google talk, skype. If it runs > > with those, it will likely run with any other application. > > I'll take a look when I'm at better internet access. Ok. > > > mplayer is useful for testing... but that one already works (after you > > > setup the pipeline, and configure exposure/gain). > > > > > > But thats useful for testing, not really for production. Image will be > > > out of focus and with wrong white balance. > > > > > > What I would really like is an application to get still photos. For > > > taking pictures with manual settings we need > > > > > > a) units for controls: user wants to focus on 1m, and take picture > > > with ISO200, 1/125 sec. We should also tell him that lens is f/5.6 and > > > focal length is 20mm with 5mm chip. > > > > > > But... autofocus/autogain would really be good to have. Thus we need: > > > > > > b) for each frame, we need exposure settings and focus position at > > > time frame was taken. Otherwise autofocus/autogain will be too > > > slow. At least focus position is going to be tricky -- either kernel > > > would have to compute focus position for us (not trivial) or we'd need > > > enough information to compute it in userspace. > > > > > > There are more problems: hardware-accelerated preview is not trivial > > > to set up (and I'm unsure if it can be done in generic way). Still > > > photos application needs to switch resolutions between preview and > > > photo capture. Probably hardware-accelerated histograms are needed for > > > white balance, auto gain and auto focus, .... > > > > > > It seems like there's a _lot_ of stuff to be done before we have > > > useful support for complex cameras... > > > > Taking still pictures using a hardware-accelerated preview is > > a sophisticated use case. I don't know any userspace application > > that does that. Ok, several allow taking snapshots, by simply > > storing the image of the current frame. > > Well, there are applications that take still pictures. Android has > one. Maemo has another. Then there's fcam-dev. Its open source; with > modified kernel it is fully usable. I have version that runs on recent > nearly-mainline on N900. Hmm... it seems that FCam is specific for N900: http://fcam.garage.maemo.org/ If so, then we have here just the opposite problem, if want it to be used as a generic application, as very likely it requires OMAP3-specific graph/subdevs. > So yes, I'd like solution for problems a) and b). > > > > (And I'm not sure... when application such as skype is running, is > > > there some way to run autogain/autofocus/autowhitebalance? Is that > > > something we want to support?) > > > > Autofocus no. Autogain/Autowhite can be done via libv4l, provided that > > it can access the device's controls via /dev/video devnode. Other > > applications may be using some other similar algorithms. > > > > Ok, they don't use histograms provided by the SoC. So, they do it in > > software, with is slower. Still, it works fine when the light > > conditions don't change too fast. > > I guess it is going to work well enough with higher CPU > usage. Yes. > Question is if camera without autofocus is usable. I'd say "not > really".qv4l2 That actually depends on the sensor and how focus is adjusted. I'm testing right now this camera module for RPi: https://www.raspberrypi.org/products/camera-module-v2/ I might be wrong, but this sensor doesn't seem to have auto-focus. Instead, it seems to use a wide-angle lens. So, except when the object is too close, the focus look OK. > > > I believe other question is: will not having same control on main > > > video device and subdevs be confusing? Does it actually help userspace > > > in any way? Yes, we can make controls accessible to old application, > > > but does it make them more useful? > > > > Yes. As I said, libv4l (and some apps) have logic inside to adjust > > the image via bright, contrast and white balance controls, using the > > video devnode. They don't talk subdev API. So, if those controls > > aren't exported, they won't be able to provide a good quality image. > > Next question is if the libv4l will do the right thing if we just put > all controls to one node. For example on N900 you have exposure/gain > and brightness. But the brightness is applied at preview phase, so it > is "basically useless". You really need to adjust the image using the > exposure/gain. I've no idea, but I suspect it shouldn't be hard to teach libv4l to prefer use an exposure/gain instead of brightness when available. > > > > > In addition, I suspect end-users of these complex devices don't really care > > > > > about a plugin: they want full control and won't typically use generic > > > > > applications. If they would need support for that, we'd have seen much more > > > > > interest. The main reason for having a plugin is to simplify testing and > > > > > if this is going to be used on cheap hobbyist devkits. > > > > > > > > What are the needs for a cheap hobbyist devkit owner? Do we currently > > > > satisfy those needs? I'd say that having a functional driver when > > > > compiled without the subdev API, that implements the ioctl's/controls > > > > > > Having different interface based on config options... is just > > > weird. What about poor people (like me) trying to develop complex > > > applications? > > > > Well, that could be done using other mechanisms, like a modprobe > > parameter or by switching the behaviour if a subdev interface is > > opened. I don't see much trouble on allowing accessing a control via > > both interfaces. > > If we really want to go that way (is not modifying library to access > the right files quite easy?), I believe non-confusing option would be > to have '/dev/video0 -- omap3 camera for legacy applications' which > would include all the controls. Yeah, keeping /dev/video0 reserved for generic applications is something that could work. Not sure how easy would be to implement it. > > > > You can get Nokia N900 on aliexpress. If not, they are still available > > > between people :-) > > > > I have one. Unfortunately, I never had a chance to use it, as the display > > stopped working one week after I get it. > > Well, I guess the easiest option is to just get another one :-). :-) Well, I guess very few units of N900 was sold in Brazil. Importing one is too expensive, due to taxes. > But otoh -- N900 is quite usable without the screen. 0xffff tool can > be used to boot the kernel, then you can use nfsroot and usb > networking. It also has serial port (over strange > connector). Connected over ssh over usb network is actually how I do > most of the v4l work. If you pass me the pointers, I can try it when I have some time. Anyway, I got myself an ISEE IGEPv2, with the expansion board: https://www.isee.biz/products/igep-processor-boards/igepv2-dm3730 https://www.isee.biz/products/igep-expansion-boards/igepv2-expansion The expansion board comes with a tvp5150 analog TV demod. So, with this device, I can simply connect it to a composite input signal. I have some sources here that I can use to test it. Thanks, Mauro
