1 Reply Latest reply on Aug 30, 2017 10:58 AM by user_438021184

    AN75779: Failed to query (GET_DEF) UVC control

    user_438021184

      I'm trying to get a system based upon AN75779 to work. I'm running under Linux (kernel 4.12.5).

       

      When I run

       

      v4l2grab -m -q 100 -d /dev/video0 -o /tmp/grab.jpg

       

       

      When I run v4l2grab I get the following output

      Image width set to 1280 by device /dev/video0.

      Image height set to 720 by device /dev/video0.

      and then it just hangs.

       

       

      On my FX3 console I observe that streaming is activated when I start v4l2grab

       

      UVC: Completed 0 frames and 0 buffers

      UVC: Completed 0 frames and 0 buffers

      UVC: Completed 0 frames and 0 buffers

      UVC: Completed 21 frames and 3 buffers

      UVC: Completed 42 frames and 19 buffers

      UVC: Completed 63 frames and 35 buffers

      UVC: Completed 84 frames and 51 buffers

      UVC: Completed 106 frames and 9 buffers

       

       

      However, in the Linux host kernel log I observe:

       

      [ 7446.534814] uvcvideo: Found UVC 1.00 device FX3 (04b4:00f9)

      [ 7446.536477] uvcvideo 2-6:1.0: Entity type for entity Extension 3 was not initialized!

      [ 7446.536482] uvcvideo 2-6:1.0: Entity type for entity Processing 2 was not initialized!

      [ 7446.536485] uvcvideo 2-6:1.0: Entity type for entity Camera 1 was not initialized!

      [ 7446.536654] input: FX3 as /devices/pci0000:00/0000:00:14.0/usb2/2-6/2-6:1.0/input/input13

      [ 8488.136849] uvcvideo: Failed to query (GET_DEF) UVC control 2 on unit 2: 1 (exp. 2).

       

       

      What is the error "Failed to query (GET_DEF) UVC control" caused by?

       

       

      v4l2grab works fine if plug in a plain USB web camera.

        • 1. Re: AN75779: Failed to query (GET_DEF) UVC control
          user_438021184

          The v4l2grab hang was due to a format error. Running mplayer revealed that there were only half of the expected pixels being output:

           

          Frame too small! (921600<1843200) Wrong format?

          After adjusting the YCbCr format mplayer now runs without the above, and v4l2grab will complete with the grabbed image.

          The "Failed to query" kernel message is still there, but it does not seem to be fatal.