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   sober: #wikipedia
   <br> !help
   ***: hverkuil_ has left
   Whoopie: Hi, I'm running ubuntu 18.04 in a virtualbox VM. The kernel is 4.15, and uvcvideo is 1.1.1. The virtualbox webcam is recognized properly and works with guvcview.
   <br> but cheese doesn't detect it.
   <br> in another VM with ubuntu 16.04 and kernel 4.4, cheese detects it properly.
   <br> any ideas what goes wrong in kernel 4.15?
   <br> I see the following two lines in dmesg which are shown with kernel 4.15, but not 4.4:
   <br> [ 7167.580476] uvcvideo 1-1:1.0: Entity type for entity Processing 2 was not initialized!
   <br> [ 7167.580480] uvcvideo 1-1:1.0: Entity type for entity Camera 1 was not initialized!
   pinchartl: the entity type messages can be ignored
   <br> (and we really should fix them)
   <br> does cheese provide any extra information ?
   sarnex: does anyone know about IOCTL changes to the v4l subsystem in 4.16? now when using v4l with v4l2loopback in 4.16, i get the following error in ffmpeg: ioctl(VIDIOC_G_FMT): Invalid argument
   <br> works fine in 4.15
   Whoopie: <u>pinchartl</u>: not much, http://paste.debian.net/1019309/
   pinchartl: <u>Whoopie</u>: 'cheese_camera_device_get_name: assertion 'CHEESE_IS_CAMERA_DEVICE (device)' failed' doesn't seem nice
   <br> but we need to know more
   <br> one option would be to trace system calls made by cheese to find out what goes wrong
   <br> the strace tool is your friend
   <br> it can get quite verbose though
   Whoopie: <u>pinchartl</u>: looking into it. uvcvideo module crashed, need to reboot
   pinchartl: crashed ? :-S that's really really bad
   <br> it shouldn't happen
   <br> if you can get me a stack trace I could have a look at it
   Whoopie: <u>pinchartl</u>: this is "modprobe -r uvcvideo; modprobe uvcvideo" -&gt; http://paste.debian.net/1019312/
   <br> <u>pinchartl</u>: any idea what I should look for in the strace output?
   pinchartl: <u>Whoopie</u>: possibly a V4L2 ioctl that fails
   Whoopie: <u>pinchartl</u>: nothing suspicious.
   <br> installing ubuntu 17.10 in a VM now to check if it's there, too.
   <br> how can I get more debug output for gnome apps like cheese?
   pinchartl: that's a good question. I'm not familiar with gnome I'm afraid
   <br> could you show me the strace log ?
   Whoopie: <u>pinchartl</u>: it's to big for pastebin. can I send it by mail?
   pinchartl: sure
   Whoopie: to which address?
   <br> <u>pinchartl</u>: ^
   pinchartl: <u>Whoopie</u>: ok, so cheese uses gstreamer
   <br> and it creates a few threads
   <br> (or possibly even processes)
   <br> that are not included in the strace log
   <br> as it's based on gstreamer, what happens if you set GST_DEBUG="*:2" ?
   <br> GST_DEBUG="*:2" cheese
   <br> do you get more verbose output ?
   Whoopie: no
   pinchartl: I'm afraid I don't know then
   <br> you'll need help from someone more familiar with cheese and/or gstreamer
   Whoopie: ok, many thanks anyway.
   ndufresne: Whoopie, which version of Gst, also GST_DEBUG="2,v4l2*:7" cheese is more likely to be helpful
   <br> (somehow my impression is that the delta is the version of gst, rather then kernel)