Hi Jiri On Thu, 5 Jan 2023 at 09:29, Jiri Slaby <jirislaby@xxxxxxxxxx> wrote: > > On 05. 01. 23, 8:23, Laurent Pinchart wrote: > > On Wed, Jan 04, 2023 at 02:12:44PM +0100, Ricardo Ribalda wrote: > >> Hi Jiri > >> > >> > >> > >> I think that /dev/video3 belongs to your notebook webcam, not to the EasyCAP. > > > > That looks correct. > > Yes, you are right -- only 2 devices (4+5) are created. I don't know why > I thought there are 3. > > >> 720x480 I believe is the NTSC resolution. > > Ah, that makes sense. Which leads me to: sometimes, the picture distorts > after I start playing the video. It's skewed and halves of the picture > switched [1]. I assume the driver expects NTSC@720x480, but the device > sends PAL@720x576, actually. Sometimes, there are also color strips. > > [1] https://hci.fi.muni.cz/~xslaby/n/skew.jpg > > > Can you try starting the > >> VHS, *before* you connect the grabber to the USB? Maybe that way the > >> device realises that it should be working in PAL not in NTSC. > > > > Good idea. The device advertises a maximum resolution of 720x480 in the > > UVC descriptors it exposes to the host, so there's nothing the driver > > can really do to obtain 720x576. > > That doesn't help. Maybe it would sound foolish (I don't know the > internals), but would it make sense to re-read UVC parameters on each > device start in open? Only as a debug aid to see if they change. UVC is weird. The parameters are part of the USB descriptor, and the only way to change those is to re-enumerate. Some HDMI receivers simulate a usb disconnect every time the resolution of the source changes... If the hdmi signal is not very good imaging the party :) > > > If plugging an active PAL source to the device before plugging it to the > > USB port doesn't help, another option for investigation is to capture > > USB traffic under Windows to check what happens there. > > OK, I can try it. I have win10 virt machine set up. So that should be > easy using usbmon. Except I don't know how to read the mon dumps. I > should start at Documentation/usb/usbmon.rst, I believe. TL/DR: modprobe usbmon sudo wireshark; select the usbmonX device where your device is attached Good luck ;) > > thanks, > -- > js > suse labs > -- Ricardo Ribalda
