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• FFmpeg change output to specific pixel format ?

  22 mars 2021, par R.martinez

  I am working on an openCV project, I have a stable running variant that is taking input from an HDMI capture card and using FFmpeg to output to a v4L2 loopback device (/dev/video0) my openCV project takes its input from /dev/video0.

  



  The issue comes when I try to use an rtsp feed, the following command works to send the feed to my loopback device :

  



  ffmpeg -rtsp_transport tcp -i rtsp://@192.168.1.27:552//stream1 -acodec rawvideo -vcodec rawvideo -f v4l2 /dev/video0


  



  And I am able to view that feed with VLC (on /dev/video0) no problem, however when I feed it to my openCV app, I get the following error :

  



  VIDEOIO ERROR: V4L2: Pixel format of incoming image is unsupported by OpenCV


  



  When I run v4l2-ctl -d /dev/video0 --all on both working and non working variants this is what I get :

  



  Working output

  



  Format Video Output:
Width/Height      : 1920/1080
Pixel Format      : 'UYVY'
Field             : None
Bytes per Line    : 3840
Size Image        : 4147200
Colorspace        : sRGB
Transfer Function : Default
YCbCr Encoding    : Default
Quantization      : Default
Flags             : 


  



  Nonfunctional output

  



  Format Video Output:
Width/Height      : 1280/720
Pixel Format      : 'YU12'
Field             : None
Bytes per Line    : 1280
Size Image        : 1382400
Colorspace        : sRGB
Transfer Function : Default
YCbCr Encoding    : Default
Quantization      : Default
Flags             : 


  



  So I am concluding that the pixel format 'YU12' is not compatible with openCV while format 'UYVY' is. If it's possible, how do I set the output of FFmpeg to be in pixel format UYVY when the input is YU12 ?

  


• FFMediaElement : How to stream from CamLink 4K ?

  15 janvier 2021, par Pedro

  I would like to use Unosquare's FFME library (v4.2.330) to show a live stream from a Cam Link 4K hdmi grabber.Using the following code, however, the media element remains black, even though the media has successfully been opened and no exceptions are raised.

  


      


    private void OnLoaded(object sender, RoutedEventArgs e)
    {
        this.media.Open(new Uri("device://dshow/?video=Cam Link 4K"));
    }

    private void media_MediaInitializing(object sender, Unosquare.FFME.Common.MediaInitializingEventArgs e)
    {
        e.Configuration.PrivateOptions["framerate"] = "50";
        e.Configuration.PrivateOptions["video_size"] = "1920x1080";
        e.Configuration.PrivateOptions["vcodec"] = "rawvideo"; //also tried mjpeg
        e.Configuration.PrivateOptions["pixel_format"] = "yuyv422"; //also tried yuv420p
    }
    
    private void media_MediaFailed(object sender, Unosquare.FFME.Common.MediaFailedEventArgs e)
    {
        log.Error(e.ErrorException);
    }


  


  Using VLC player everything works fine, so I suppose it has something to do with parameters set during MediaInitializing. In order to get the correct parameters I ran ffmpeg -f dshow -i video="Cam Link 4K" which outputs

  


  Input #0, dshow, from 'video=Cam Link 4K':
  Duration: N/A, bitrate: N/A
    Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 1920x1080, 50 fps, 50 tbr, 10000k tbn, 10000k tbc


  


  By running ffmpeg -f dshow -pix_fmt yuv420p -i video="Cam Link 4K" -framerate 50 -vcodec mjpeg test.mkv I am able to record everthing into the file.

  


  During startup I am setting Unosquare.FFME.Library.FFmpegDirectory = @"C:\ffmpeg";, where I put the prebuilt binaries and shared libraries for ffmpeg 4.2.1 (win64). Also I made sure my project is targeting x64. Since MediaElement works with regular mp4 files, I am not sure which parameters/settings I am missing.

  


• What ffmpeg settings to ensure 0 duplicate frames and 0 dropped frames when capturing to mpeg-2 program stream using ffmpeg/avfoundation on Mac ?

  16 février 2017, par aerodavo

  I’m trying to capture to a DVD compliant mpeg-2 file (ffmpeg : -target ntsc-dvd) from the HDMI output of a camcorder into a Magewell HDMI to USB 3.0 box into my Late 2012 15" non-retina MacBook Pro (quad core 2.3, 16gb ram, ssd), using ffmpeg/avfoundation.

  I’ve tried everything I can think of, or find online. I’m still getting duplicate and dropped frames, which either leads to audio/video sync issues, or audio dropouts, especially for longer recordings. I need this to be stable for recordings of up to 2.5 hours. This is the Terminal output for a 1.5 hour recording :

  Lapaki:~ Lapaki$ /Users/Lapaki/Desktop/ffmpeg -f avfoundation -video_size 960x540 -pixel_format uyvy422 -framerate ntsc -i "XI:XI" -vf crop=iw-240:ih:120:0 -target ntsc-dvd -aspect 4:3 -q:v 3 -ab 256k /Users/Lapaki/Desktop/FF\ Test/`date +%F`\ `date +%H_%M_%S`.mpg
  
  ffmpeg version 3.2.3-tessus Copyright (c) 2000-2017 the FFmpeg developers
  
    built with Apple LLVM version 8.0.0 (clang-800.0.42.1)
  
    configuration: --cc=/usr/bin/clang --prefix=/opt/ffmpeg --extra-version=tessus --enable-avisynth --enable-fontconfig --enable-gpl --enable-libass --enable-libbluray --enable-libfreetype --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopus --enable-libschroedinger --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzmq --enable-version3 --disable-ffplay --disable-indev=qtkit --disable-indev=x11grab_xcb
  
    libavutil      55. 34.101 / 55. 34.101
  
    libavcodec     57. 64.101 / 57. 64.101
  
    libavformat    57. 56.101 / 57. 56.101
  
    libavdevice    57.  1.100 / 57.  1.100
  
    libavfilter     6. 65.100 /  6. 65.100
  
    libswscale      4.  2.100 /  4.  2.100
  
    libswresample   2.  3.100 /  2.  3.100
  
    libpostproc    54.  1.100 / 54.  1.100
  
  Input #0, avfoundation, from 'XI:XI':
  
    Duration: N/A, start: 610606.984208, bitrate: N/A
  
      Stream #0:0: Video: rawvideo (UYVY / 0x59565955), uyvy422, 960x540, 29.97 fps, 29.97 tbr, 1000k tbn, 1000k tbc
  
      Stream #0:1: Audio: pcm_f32le, 48000 Hz, stereo, flt, 3072 kb/s
  
  Output #0, dvd, to '/Users/Lapaki/Desktop/FF Test/2017-02-15 17_46_28.mpg':
  
    Metadata:
  
      encoder         : Lavf57.56.101
  
      Stream #0:0: Video: mpeg2video (Main), yuv420p, 720x480 [SAR 8:9 DAR 4:3], q=2-31, 6000 kb/s, 29.97 fps, 90k tbn, 29.97 tbc
  
      Metadata:
  
        encoder         : Lavc57.64.101 mpeg2video
  
      Side data:
  
        cpb: bitrate max/min/avg: 9000000/0/6000000 buffer size: 1835008 vbv_delay: -1
  
      Stream #0:1: Audio: ac3, 48000 Hz, stereo, fltp, 256 kb/s
  
      Metadata:
  
        encoder         : Lavc57.64.101 ac3
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (rawvideo (native) -> mpeg2video (native))
  
    Stream #0:1 -> #0:1 (pcm_f32le (native) -> ac3 (native))
  
  Press [q] to stop, [?] for help
  
  [swscaler @ 0x7fd315892800] Warning: data is not aligned! This can lead to a speedloss
  
  frame=   20 fps=0.0 q=3.0 size=     298kB time=00:00:00.65 bitrate=3721.4kbits/sframe=   35 fps= 35 q=3.0 size=     498kB time=00:00:01.13 bitrate=3591.2kbits/sframe=   50 fps= 33 q=3.0 size=     708kB time=00:00:01.64 bitrate=3519.4kbits/sframe=   65 fps= 32 q=3.0 size=     920kB time=00:00:02.16  
  
  ...
  
   bitrate=2721.7kbits/frame=162094 fps= 30 q=3.0 size= 1796936kB time=01:30:08.47 bitrate=2721.7kbits/frame=162109 fps= 30 q=3.0 size= 1797142kB time=01:30:08.98 bitrate=2721.8kbits/frame=162110 fps= 30 q=3.0 Lsize= 1797202kB time=01:30:09.01 bitrate=2721.9kbits/s dup=221 drop=0 speed=   1x    
  
  video:1579050kB audio:168069kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 2.866632%

  I deleted the middle part (denoted by the "..."), which is just a lot more of the same accumulating information. By the end there are 221 duplicate frames, and for this one I didn’t get any dropped frames, but that happens every other time as well it seems.

  With this code, the audio seems to stay in pretty good sync, but I get little dropouts every 30 seconds to a minute or so. On this recording, there are dropouts at :

  00:00:43, 00:01:19, 00:01:47, 00:02:17, 00:03:18, ...

  I stopped listening there ; they happen at the end too, so I assume similarly spaced dropouts are happening throughout the file.

  Is there some secret ffmpeg code to ensure there are no dropped or duplicate frames when capturing from a live source to dvd compliant mpeg-2 files ?

  When I convert from pretty much any type of file to mpeg-2 files using -target ntsc-dvd, the speed is something like 10x on this machine, so it seems like it would have no problem keeping up with a live source, right ?

  I’ve also tried constant bit rate using -b:v 5000k -minrate 5000k -maxrate 5000k -bufsize 2500k, which also doesn’t prevent dropped/duplicate frames.

  I’ve tried separating out the audio and video inputs, which doesn’t solve it.

  I’ve tried using -vsync 0 on the video input, which does seem to solve the issue, because the output doesn’t report dups/drops, but the audio/video drift out of sync more and more, so that hasn’t worked either.

  Thanks so much for any help. I’ve been testing and testing and searching and searching for weeks...