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• How to pipe rawvideo to v4l2loopback using ffmpeg ?

  3 août 2020, par sepehr78

  I am trying to process a video by OpenCV in Python and then send each frame to a virtual camera (i.e., v4l2loopback). I have seen questions asked where OpenCV output is piped to ffmpeg and saved into a file, and other questions where a video file is piped to v4l2 using ffmpeg, but no question where these two are combined. I can do either of the above two things on their own, but not combined.

  



  My Python code uses a subprocess to pipe each frame to ffmpeg. The ffmpeg command for piping the output of OpenCV to an .mp4 file is

  



  ffmpeg -y -f rawvideo -vcodec rawvideo -s 1280x720 -pix_fmt bgr24 -i - -vcodec libx264 -crf 0 -preset fast output.mp4


  



  This works and I have tested it.

  



  The ffmpeg command to pipe a video file to the v4l2 virtual camera is

  



  ffmpeg -re -i input.mp4 -map 0:v -f v4l2 /dev/video0


  



  This also works and I have tested it.

  



  I tried combining the above two commands and came up with

  



  ffmpeg -y -f rawvideo -vcodec rawvideo -s 1280x720 -pix_fmt bgr24 -i - -vcodec libx264 -crf 0 -preset fast -map 0:v -f v4l2 /dev/video0


  



  but I get the following error

  



  


  [NULL @ 0x55a12fcc60] Unable to find a suitable output format for ''
 : Invalid argument

  


  



  I would be glad if anyone could help me figure this out.

  



  Thanks.

  


• How to add BGM when pipe opencv images to ffmpeg - python

  23 mars 2020, par karobben

  Basically, I know how to stream by Pipe opencv to ffmpeg using python.
  But my problem is I can’t add an audio file (BGM) for it. Does anyone know how to make it with python ?

  my python code is :

  import cv2 as cv
  
  import subprocess as sp
  
  
  
  # ffmpeg command
  
  
  
  command = ['ffmpeg',
  
          #'-re', '-stream_loop', '-1', 
  
          #'-i', '/home/pi/scrpt/Blive/StarBucks_BGN.mp3',
  
          '-y',
  
          '-f', 'rawvideo',
  
          '-vcodec','rawvideo',
  
          '-pix_fmt', 'bgr24',
  
          '-s', "{}x{}".format(width, height),
  
          '-r', str(fps),
  
          '-i', '-',
  
          '-c:v', 'libx264',
  
          '-pix_fmt', 'yuv420p',
  
          '-preset', 'ultrafast',
  
          '-f', 'flv',
  
          rtmpUrl]

  I know that I can achieve this by :

  sudo raspivid -o - -t 0 -w 1280 -h 720 -fps 24 -b 1000000 | 
  
                  ffmpeg  -re -stream_loop -1 -i  "/home/pi/scrpt/Blive/StarBucks_BGN.mp3" \
  
          -f h264 -i - -vcodec copy -r 30 -acodec aac -b:a 100k -preset ultrafast \
  
          -tune zerolatency -f flv "rtmp://"

  So, I tried to add -re -stream_loop -1 -i  "/home/pi/scrpt/Blive/StarBucks_BGN.mp3" into the python pipe, but it crashed with :

  [libx264 @ 0x1952aa0] using cpu capabilities: ARMv6 NEON
  
  [libx264 @ 0x1952aa0] profile Constrained Baseline, level 3.1
  
  [libx264 @ 0x1952aa0] 264 - core 148 r2748 97eaef2 - H.264/MPEG-4 AVC codec - Copyleft 2003-2016 - http://www.videolan.org/x264.html - options: cabac=0 ref=1 deblock=0:0:0 analyse=0:0 me=dia subme=0 psy=1 psy_rd=1.00:0.00 mixed_ref=0 me_range=16 chroma_me=1 trellis=0 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=0 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=0 keyint=250 keyint_min=25 scenecut=0 intra_refresh=0 rc=crf mbtree=0 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=0
  
  [flv @ 0x1951d00] FLV does not support sample rate 48000, choose from (44100, 22050, 11025)
  
  [flv @ 0x1951d00] Audio codec mp3 not compatible with flv
  
  Could not write header for output file #0 (incorrect codec parameters ?): Function not implementedStream mapping:
  
    Stream #1:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
  
    Stream #0:0 -> #0:1 (mp3 (native) -> mp3 (libmp3lame))
  
      Last message repeated 1 times
  
  Traceback (most recent call last):
  
    File "With_BG.py", line 57, in <module>
  
      p.stdin.write(BG.tostring())
  
  BrokenPipeError: [Errno 32] Broken pipe
  
  </module>

• C# Pipe images to FFmpeg as they are rendered

  22 mars 2020, par LiftPizzas

  I’ve looked all over and everything I’ve found is how to use already-generated images. I think the below code taken from this (Create video from a growing image sequence using FFMPEG) is really close to what I need, but I need to be able to send one image at a time as each one is rendered, which might take several seconds to minutes, and will be taking place in a different function instead of inline like this one does.

  static void Main()
  
  {
  
      //Async main method
  
      AsyncMain().GetAwaiter().GetResult();
  
  }
  
  
  
  static async Task AsyncMain()
  
  {
  
      Console.WriteLine("Press any key to quit prematurely.");
  
      var maintask = RunFFMPEG();
  
      var readtask = Task.Run(() => Console.Read());
  
      await Task.WhenAny(maintask, readtask);
  
  }
  
  
  
  static async Task RunFFMPEG()
  
  {
  
      await Task.Run(() =>
  
      {
  
          const int fps = 30;
  
          const string outfile = "out.mp4";
  
          const string args = "-y -framerate {0} -f image2pipe -i - -r {0} -c:v libx264 -movflags +faststart -pix_fmt yuv420p -crf 19 -preset veryslow {1}";
  
          const string dir = @"C:\testrender\";
  
          const string pattern = "{0}.png";
  
          const string path = dir + pattern;
  
          const int startNum = 0;
  
          const int endNum = 100;
  
  
  
          var pinf = new ProcessStartInfo("ffmpeg", string.Format(args, fps, outfile));
  
          pinf.UseShellExecute = false;
  
          pinf.RedirectStandardInput = true;
  
          pinf.WorkingDirectory = dir;
  
  
  
          Console.WriteLine("Starting ffmpeg...");
  
          var proc = Process.Start(pinf);
  
          using (var stream = new BinaryWriter(proc.StandardInput.BaseStream))
  
          {
  
              for (var i = startNum; i < endNum; i++)
  
              {
  
                  //"D4" turns 5 to 0005 - change depending on pattern of input files
  
                  var file = string.Format(path, i.ToString("D4"));
  
                  System.Threading.SpinWait.SpinUntil(() => File.Exists(file) && CanReadFile(file));
  
                  Console.WriteLine("Found file: " + file);
  
                  stream.Write(File.ReadAllBytes(file));
  
          // I don't have input files, I will have bitmaps at the end of an OpenGL render function.
  
              }
  
          }
  
          proc.WaitForExit();
  
          Console.WriteLine("Closed ffmpeg.");
  
      });
  
  
  
  
  
  
  
      bool CanReadFile(string file)
  
      {
  
          //Needs to be able to read file
  
          FileStream fs = null;
  
          try
  
          {
  
              fs = File.OpenRead(file);
  
              return true;
  
          }
  
          catch (IOException)
  
          {
  
              return false;
  
          }
  
          finally
  
          {
  
              if (fs != null)
  
                  fs.Close();
  
          }
  
      }
  
  }