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• ffmpeg, /dev/video0, -f decklink

  20 mars 2019, par Camille Goudeseune

  I’m trying to capture video from a PCI card, the Blackmagic DeckLink Mini Recorder, via ffmpeg, on a headless host running Ubuntu 18.04.2 LTS, hopefully with a command like

  ffmpeg -f decklink -i /dev/video0 ...

  How can I make that work ? I have two obstacles.

  No /dev/video0

  ffmpeg -i /dev/video0 ... fails : /dev/video0: No such device or address.
  v4l2-ctl --list-devices fails with the same error message.

  I built /dev/video0, and it looks okay :

  mknod /dev/video0 c 81 0
  
  chown root.video /dev/video0
  
  chmod g+rw /dev/video0

  To compare this file with a working one, I ran strace cat /dev/video0 on this host, and on another host (Ubuntu 14) with a working /dev/video0. The outputs began to differ here (good, then bad) :

  fstat(1, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
  
  open("/dev/video0", O_RDONLY)           = 3  
  
  fstat(3, {st_mode=S_IFCHR|0660, st_rdev=makedev(81, 0), ...}) = 0
  
  fadvise64(3, 0, 0, POSIX_FADV_SEQUENTIAL) = 0
  
  ----
  
  
  
  fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 0), ...}) = 0
  
  openat(AT_FDCWD, "/dev/video0", O_RDONLY) = -1 ENXIO (No such device or address)

  So /dev/video0 is broken at a level lower than ffmpeg or v4l2 or even cat.

  On Ubuntu 14, man 8 MAKEDEV suggests that the error message means that "the kernel does not have the driver configured or loaded."

  This Ubuntu 18 host lacks that manpage, but it does have a few /snap/core/*/sbin/MAKEDEV, all the same, so I tried

  /snap/core/6350/sbin/MAKEDEV -n -v video

  It would have created over a hundred devices videoXX, radioXX, vtxXX, vbiXX. Those devices didn’t exist yet, so it seemed harmless to try it.

  rm /dev/video0; /snap/core/6350/sbin/MAKEDEV video

  That rebuilt /dev/video0, but "No such device" remains, from cat or ffmpeg.

  No decklink

  ffmpeg -f decklink ... fails with Unknown input format: 'decklink'.

  Neither black nor deck nor link is mentioned by ffmpeg -devices (fbdev, lavfi, oss, v4l2) and ffmpeg -formats (about 350), either for Ubuntu’s own version 3.4.4-0ubuntu0.18.04.1, or for version N-93330-g7ff89574c7 compiled from source on 2019 Mar 13 :

  git clone https://git.ffmpeg.org/ffmpeg.git ffmpeg
  
  cd ffmpeg
  
  ./configure --enable-nonfree --disable-doc --disable-w32threads --enable-pthreads

  (Although ./configure --help mentions --enable-decklink, using that yielded "ERROR : DeckLinkAPI.h not found." updatedb && locate DeckLinkAPI.h finds no file with that name, either.)

  The DeckLink PCI card is recognized by hwinfo and lspci.

  lsmod reports the loaded modules blackmagic and blackmagic_io.

  Maybe the PCI card is installed ok, but ffmpeg just can’t reach it because I can’t configure it for that.

  Edit : Rebooting didn’t fix anything.

• FFMPEG Cannot Init CUDA

  7 novembre 2016, par Alan

  I am working to install ffmpeg with hardware GPU support on a Xenserver virtual server (Ubuntu 16.04). I am following the guide from : http://developer.download.nvidia.com/compute/redist/ffmpeg/1511-patch/FFMPEG-with-NVIDIA-Acceleration-on-Ubuntu_UG_v01.pdf

  While updating the directions for the newest versions of the SDK and versions for 16.04. I have everything built and all seems fine when doing version checks :

  ffmpeg version N-82277-ge2193b5 Copyright (c) 2000-2016 the FFmpeg developers
  
    built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.2) 20160609
  
    configuration: --prefix=/root/ffmpeg_build --pkg-config-flags=--static 
  
  --extra-cflags=-I/root/ffmpeg_build/include
  
  --extra-ldflags=-L/root/ffmpeg_build/lib --bindir=/root/bin --enable-gpl --enable-libass --enable-libfdk-aac 
  
  --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx 
  
  --enable-libx264 --enable-libx265 --enable-libvidstab --enable-nonfree --enable-nvenc
  
  
  
  #nvcc --version
  
  nvcc: NVIDIA (R) Cuda compiler driver
  
  Copyright (c) 2005-2015 NVIDIA Corporation
  
  Built on Tue_Aug_11_14:27:32_CDT_2015
  
  Cuda compilation tools, release 7.5, V7.5.17

  When I try doing the test using the GPU I get this :

  #time ffmpeg -y -i 337.mp4 -vcodec h264_nvenc -b:v 5M -acodec copy OUTPUT.mp4
  
  
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '337.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf56.25.101
  
    Duration: 00:00:22.74, start: 0.000000, bitrate: 537 kb/s
  
      Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 720x480 [SAR 1:1 DAR 3:2], 434 kb/s, 29.97 fps, 29.97 tbr, 11988 tbn, 59.94 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(eng): Audio: mp3 (mp4a / 0x6134706D), 48000 Hz, stereo, s16p, 96 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler
  
  modprobe: ERROR: could not insert 'nvidia_367_uvm': No such device
  
  [h264_nvenc @ 0x3da6400] Cannot init CUDA
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (h264 (native) -> h264 (h264_nvenc))
  
    Stream #0:1 -> #0:1 (copy)
  
  Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height

  In particular I get an error [h264_nvenc @ 0x3da6400] Cannot init CUDA

  I can’t seem to find any info on this. I am not running any desktop GUI, strictly command line trying to accelerate video encoding with a Nvidia GTX 960.

• Write webcam video with avconv

  31 juillet 2012, par Jones

  Have problem to write video avi with avconv

  I try using

  avconv -v debug -f video4linux2 -i /dev/video1 frontal.avi

  but video not correct. I see this line [video4linux2 @ 0x8100b00] The v4l2 frame is 8160 bytes, but 614400 bytes are expected and I don't identify options to correct this.

  Output of debug

  avconv version 0.8.3-4:0.8.3-0ubuntu0.12.04.1, Copyright (c) 2000-2012 the Libav developers
  
    built on Jun 12 2012 16:37:58 with gcc 4.6.3
  
    configuration: --extra-version='4:0.8.3-0ubuntu0.12.04.1' --arch=i386 --prefix=/usr --libdir=/usr/lib/i386-linux-gnu --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --enable-runtime-cpudetect --enable-libfreetype --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i386-linux-gnu/i686/cmov --cpu=i686 --enable-shared --disable-static
  
    libavutil    51. 22. 1 / 51. 22. 1
  
    libavcodec   53. 35. 0 / 53. 35. 0
  
    libavformat  53. 21. 0 / 53. 21. 0
  
    libavdevice  53.  2. 0 / 53.  2. 0
  
    libavfilter   2. 15. 0 /  2. 15. 0
  
    libswscale    2.  1. 0 /  2.  1. 0
  
    libpostproc  52.  0. 0 / 52.  0. 0
  
  [video4linux2 @ 0x8100b00] [3]Capabilities: 4000001
  
  [video4linux2 @ 0x8100b00] Querying the device for the current frame size
  
  [video4linux2 @ 0x8100b00] Setting frame size to 640x480
  
  [video4linux2 @ 0x8100b00] The V4L2 driver set input_id: 0, input: Camera 1
  
  [video4linux2 @ 0x8100b00] The v4l2 frame is 8160 bytes, but 614400 bytes are expected
  
  [rawvideo @ 0x8102920] err{or,}_recognition separate: 1; 1
  
  [rawvideo @ 0x8102920] err{or,}_recognition combined: 1; 1
  
  [video4linux2 @ 0x8100b00] Estimating duration from bitrate, this may be inaccurate
  
  Input #0, video4linux2, from '/dev/video1':
  
    Duration: N/A, bitrate: 147456 kb/s
  
      Stream #0.0, 0, 1/1000000: Video: rawvideo, yuyv422, 640x480, 1/30, 147456 k
  
  File 'frontal.avi' already exists. Overwrite ? [y/N] y
  
  Incompatible pixel format 'yuyv422' for codec 'mpeg4', auto-selecting format 'yu
  
  [buffer @ 0x81020c0] w:640 h:480 pixfmt:yuyv422
  
  [avsink @ 0x81022a0] auto-inserting filter 'auto-inserted scaler 0' between the
  
  [scale @ 0x81026e0] w:640 h:480 fmt:yuyv422 -> w:640 h:480 fmt:yuv420p flags:0x4
  
  [mpeg4 @ 0x81019a0] err{or,}_recognition separate: 1; 1
  
  [mpeg4 @ 0x81019a0] err{or,}_recognition combined: 1; 1
  
  [mpeg4 @ 0x81019a0] detected 1 logical cores
  
  [mpeg4 @ 0x81019a0] Unsupported bit depth: 0
  
  [rawvideo @ 0x8102920] err{or,}_recognition separate: 1; 1
  
  [rawvideo @ 0x8102920] err{or,}_recognition combined: 1; 1
  
  Output #0, avi, to 'frontal.avi':
  
    Metadata:
  
      ISFT            : Lavf53.21.0
  
      Stream #0.0, 0, 1/30: Video: mpeg4, yuv420p, 640x480, 1/30, q=2-31, 200 kb/s