Hi, I'm having kind of a random webcam unavailability on a Dell XPS L502X (Sandy Bridge) with webcam: ``` $ lsusb Bus 001 Device 003: ID 0408:2fb1 Quanta Computer, Inc. Laptop_Integrated_Webcam_2HDM ``` I already checked [1] but couldn't find no hint in how to diagnose this. Sometimes webcam works fine. There's sort of a permanent static-noise with MJPG format in qv4l2 no matter which frame size I use (sometimes it even crash), and with guvcview using MJPG makes the image unstable if I activate the 'mirror' filter; rest of the time I get a lot of: ``` V4L2_CORE: Error - Couldn't decode frame V4L2_CORE: (jpeg decoder) error while decoding frame V4L2_CORE: (jpeg decoder) error while decoding frame V4L2_CORE: (jpeg decoder) Ignoring empty buffer ``` But using YUYV in guvcview, thou slower, the video seems OK (in qv4l2 it starts with a green screen and then the proper image appears). In the other hand, when the webcam doesn't responds, YUYV in qv4l2 only shows the green screen. The hardware lights indicate that webcam is being activated, but I have no image. When not working, qv4l2 only says: `Hue error: connection time expired`, I don't see any other console output. With xawtv I get: ``` $ xawtv This is xawtv-3.107, running on Linux/x86_64 (5.11.2-arch1-1) xinerama 0: 1366x768+0+0 vid-open-auto: using grabber/webcam device /dev/video0 v4l2: oops: select timeout ``` And with guvcview (YUYV) I have: ``` $ guvcview GUVCVIEW: version 2.0.6 V4L2_CORE: (UVCIOC_CTRL_MAP) Error: The file or directory does not exist ... ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side ALSA lib pcm_route.c:877:(find_matching_chmap) Found no matching channel map ... connect(2) call to /dev/shm/jack-1000/default/jack_0 failed (err=The file or directory does not exist) attempt to connect to server failed ... ALSA lib pcm_oss.c:377:(_snd_pcm_oss_open) Unknown field port ... ALSA lib pcm_usb_stream.c:486:(_snd_pcm_usb_stream_open) Invalid type for card ... V4L2_CORE: Could not grab image (select timeout): Resource temporarily unavailable ... ``` The only related message I found on `sudo dmesg` says: ``` [33511.458233] uvcvideo: Failed to query (GET_CUR) UVC control 6 on unit 2: -110 (exp. 2). ``` `sudo journalctl -ex` doesn't seems to show nothing about. System is updated. Any idea on how to pinpoint/diagnose the source of this issue? Thanks a lot in advance! [1] https://wiki.archlinux.org/index.php/Webcam_setup