v4l2 should not need ENUMSTD

[ubitux]

Problem: lavd/v4l2.c now requires the device to support VIDIOC_ENUMSTD.

This seems to be a regression according to  https://github.com/umlaeute/v4l2loopback/issues/38

Steps to reproduce:

• install v4l2loopback and load the module

  git clone git://github.com/umlaeute/v4l2loopback.git
  cd v4l2loopback
  make && sudo make install
  modprobe v4l2loopback
  

• push some video to the device with for instance:

  gst-launch-0.10 videotestsrc ! v4l2sink device=/dev/video0 
  

• try to play the device with FFmpeg

  % ./ffplay -v verbose -f v4l2 /dev/video0
  ffplay version N-51026-g3313b9c Copyright (c) 2003-2013 the FFmpeg developers
    built on Mar 17 2013 04:38:52 with gcc 4.7.2 (GCC)
    configuration: --enable-gpl --enable-version3 --enable-fontconfig --enable-libfreetype --enable-libmp3lame --enable-libvorbis --enable-libxvid --enable-libx264 --enable-libvpx --enable-libtheora --enable-x11grab --enable-libopenjpeg --enable-libass --enable-libmodplug --enable-libv4l2 --cc=colorgcc --samples=/home/ubitux/fate-samples --prefix=/tmp/ffinstall --disable-runtime-cpudetect --enable-libcelt --enable-libopencv --enable-frei0r --enable-libcaca --enable-libiec61883 --enable-libopencore-amrwb --enable-libopencore-amrnb --enable-libopus --enable-libpulse --enable-libspeex --enable-openal --enable-libopencv
    libavutil      52. 19.101 / 52. 19.101
    libavcodec     55.  0.100 / 55.  0.100
    libavformat    55.  0.100 / 55.  0.100
    libavdevice    55.  0.100 / 55.  0.100
    libavfilter     3. 47.102 /  3. 47.102
    libswscale      2.  2.100 /  2.  2.100
    libswresample   0. 17.102 /  0. 17.102
    libpostproc    52.  2.100 / 52.  2.100
  [video4linux2,v4l2 @ 0x7f457c000940] fd:7 capabilities:50000030/0   
  [video4linux2,v4l2 @ 0x7f457c000940] Querying the device for the current frame size
  [video4linux2,v4l2 @ 0x7f457c000940] Setting frame size to 320x240
  [video4linux2,v4l2 @ 0x7f457c000940] ioctl(VIDIOC_ENUMSTD): Invalid argument
  /dev/video0: Invalid argument
  

The device plays fine with for example mplayer, and with older ffplay (1.1.3 is working).

[cehoyos]

Which change in FFmpeg introduced the regression?

[ubitux]

514216d8a928cf80980ca8dc5daea46e9d41cad9 is the first bad commit.

[ubitux]

Note that while supporting the latest version of v4l2loopback is also important, it seems some workaround recently got pushed in it to handle that issue (see github ticket). To reproduce properly the problem, you need to checkout 5568514931b063eda0aa83976fd9a68cacc53e52 in v4l2loopback repository.

[holden]

The problem has been fixed on v4l2loopback git/master, so now ffmpeg should work again.
I will try to see if we can apply a workaround to allow ffmpeg to work with older versions of v4l2loopback.

[ubitux]

Any news from this or it should be ignored?