> On 5 Sep 2016, at 23:19, Andrey Utkin <andrey_utkin@xxxxxxxxxxxx> wrote: > > On Mon, Sep 05, 2016 at 10:43:49PM +0300, Oliver Collyer wrote: >> I do not have any knowledge of uvcvideo and the associated classes apart from the studying I’ve done the past day or two, but it seems likely that error -71 and the later setting of V4L2_BUF_FLAG_ERROR are linked. Also, the fact it only happens in captures after the first one suggests something isn’t being cleared down or released properly in uvcvideo/v4l2-core at the end of the first capture. >> >> Let me know what I need to do next to further narrow it down. > > Have tried to reproduce this (with kernel 4.6.0 and fresh build of > ffmpeg) with uvcvideo-driven laptop webcam, and it doesn't happen to me. > Also -EPROTO in uvcvideo comes from low-level USB stuff, see > drivers/media/usb/uvc/uvc_status.c:127: > > case -EPROTO: /* Device is disconnected (reported by some > * host controller). */ > > So it seems like hardware misbehaves. To further clairify situation, I > have such question: do the devices work in other operation systems on > the same machine? > Yes, they work perfectly with dshow on Windows on on multiple PCs including this one. > Reviewing your original email mentioning that two different devices > reproduce same problem, which is apparently related to disconnection in > the middle of USB communication, I came to me that the connected device > may be underpowered. So, > - try plugging your devices through reliable _active_ USB hub, > - use the most reliable cables you can get, > - plug into USB 3.0 port if available - it should provide more power > than 1.0 and 2.0. I will experiment with different ports and report back. Still, I’m not sure how that suggestion fits with the fact that it always works perfectly after "modprobe -r uvcvideo && modprobe uvcvideo” and only fails again once the capture is stopped and restarted? Perhaps some kind of “quirk” can be added for these devices that does some extra clearing up/re-initializing at the start of the capture - kind of like *some* of what reloading the module does but only for the specific device. > -- > 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 -- 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
