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• Sending video stream from NodeJS to python in real time [closed]

  17 juin 2021, par Tristan Delort

  I'm using a NodeJS server to catch a video stream through a WebRTC PeerConnection and I need to send it to a python script.

  


  I use NodeJS mainly because it's easy to use WebRTC in it and the package 'wrtc' supports RTCVideoSink and python's aiortc doesn't.

  


  I was thinking of using a named pipe with ffmpeg to stream the video stream but 3 questions arose :

  


  


  • Should I use python instead of NodeJS and completely avoid the stream through a named pipe part ? (This means there is a way to extract individual frames from a MediaStreamTrack in python)

    


  


  • If I stick with the "NodeJS - Python" approach, how do I send the stream from one script to the other ? Named pipe ? Unix domain sockets ? And with FFMpeg ?

    


  


  • Finally, for performance purpose I think that sending a stream and not each individual frames is better and simpler but is this true ?

    


  


  


  Thanks all !

  


• How can I encode a real-time video from dynamically spaced frames ?

  7 mai 2019, par Ujuf66

  I’m trying to create a video from a series of screenshots. The screenshots are in a database and have dynamic FPS (1-3 FPS). How can I create a video file with constant FPS ?

  Before performing av_packet_rescale_ts I tried to change the st^.codec.time_base.den value on the fly between 1 and 3.

  This is the basic cycle of encoding of one picture :

  repeat
  
    fillchar(pkt, sizeof(TAVPacket), #0);
  
    av_init_packet(@pkt);
  
  
  
    (* encode the image *)
  
    ret := avcodec_encode_video2(st^.codec, @pkt, frame, got_packet);
  
    if (ret < 0) then
  
    begin
  
      writeln(format('Error encoding video frame: %s', [av_err2str(ret)]));
  
      exit;
  
    end;
  
  
  
    if (got_packet > 0) then
  
    begin
  
      (* rescale output packet timestamp values from codec to stream timebase *)
  
      av_packet_rescale_ts(@pkt, st^.codec.time_base, st^.time_base);
  
      pkt.stream_index := st^.index;
  
  
  
      log_packet(oc, @pkt);
  
      (* Write the compressed frame to the media file. *)
  
      av_interleaved_write_frame(oc, @pkt);
  
    end;
  
    inc(frame.pts);
  
  
  
  until (av_compare_ts(frame.pts, st^.codec^.time_base, 1, av_make_q(1, 1)) >= 0);

  Changing the FPS on the fly causes the video output to fail. If I don’t change the st^.codec.time_base.den value the video speeds up and slows down.

• FFmpeg with Pipe - how can I periodically grab real-time frames out of live streams in C# ?

  2 mars 2020, par BBy

  I am new to FFmpeg and C# and I want grab frames to do image processing with IP Camera.

  I have made the following C# class and I could get a single frame from IP Camera.

  class FFmpegHandler
  
      {
  
          public Process ffmpeg = new Process();
  
          public Image image;
  
  
  
          public Image init()
  
          {
  
              ffmpeg = new Process()
  
              {
  
                  StartInfo =
  
                  {
  
                      FileName = @"./ffmpeg/ffmpeg.exe",
  
                      //Arguments = "-i http://admin:@192.168.10.1/videostream.asf -an -f image2pipe -preset ultrafast -tune zerolatency -s 320x240 pipe:1", // Hangs
  
                      Arguments = "-i http://admin:@192.168.10.1/videostream.asf -vframes 1 -an -f image2pipe -preset ultrafast -tune zerolatency -s 320x240 pipe:1",
  
                      UseShellExecute = false,
  
                      RedirectStandardOutput = true,
  
                      RedirectStandardError = true,
  
                      CreateNoWindow = true,
  
                      WorkingDirectory = "./ffmpeg/"
  
                  }
  
              };
  
  
  
              ffmpeg.EnableRaisingEvents = true;
  
              ffmpeg.Start();
  
  
  
              var stream = ffmpeg.StandardOutput.BaseStream;
  
              var img = Image.FromStream(stream);
  
              //ffmpeg.WaitForExit();
  
  
  
              return img;
  
          }
  
      }   

  The problem is that I want to grab real-time (latest) images when I request.

  If I run FFmpegHandler.init(), it will take 2 seconds to give me delayed image output.

  I have tried removing argument -vframes 1, then it will hang after image = Image.FromStream(stream) ;.

  When I check the ffmpeg output directly, it looks like ffmpeg is keep building the stream

  frame=    6 fps=0.0 q=2.2 size=      25kB time=00:00:00.24 bitrate= 861.9kbits/s dup=4 drop=0 speed=0.435x    
  
  frame=   65 fps= 60 q=24.8 size=     140kB time=00:00:02.60 bitrate= 440.9kbits/s dup=4 drop=0 speed=2.41x    
  
  frame=   77 fps= 49 q=24.8 size=     161kB time=00:00:03.08 bitrate= 428.0kbits/s dup=4 drop=0 speed=1.95x    
  
  frame=   89 fps= 43 q=24.8 size=     182kB time=00:00:03.56 bitrate= 418.6kbits/s dup=4 drop=0 speed= 1.7x    
  
  frame=  102 fps= 39 q=24.8 size=     205kB time=00:00:04.08 bitrate= 410.7kbits/s dup=4 drop=0 speed=1.57x    
  
  frame=  116 fps= 37 q=24.8 size=     229kB time=00:00:04.64 bitrate= 404.2kbits/s dup=4 drop=0 speed=1.49x    
  
  frame=  128 fps= 35 q=24.8 size=     250kB time=00:00:05.12 bitrate= 399.8kbits/s dup=4 drop=0 speed=1.41x    
  
  frame=  142 fps= 34 q=24.8 size=     274kB time=00:00:05.68 bitrate= 395.7kbits/s dup=4 drop=0 speed=1.36x    
  
  frame=  156 fps= 33 q=24.8 size=     299kB time=00:00:06.24 bitrate= 392.3kbits/s dup=4 drop=0 speed=1.32x    
  
  frame=  169 fps= 32 q=24.8 size=     322kB time=00:00:06.76 bitrate= 389.7kbits/s dup=4 drop=0 speed=1.29x    
  
  frame=  182 fps= 32 q=24.8 size=     344kB time=00:00:07.28 bitrate= 387.4kbits/s dup=4 drop=0 speed=1.26x    
  
  frame=  195 fps= 31 q=24.8 size=     367kB time=00:00:07.80 bitrate= 385.5kbits/s dup=4 drop=0 speed=1.24x    
  
  frame=  208 fps= 31 q=24.8 size=     390kB time=00:00:08.32 bitrate= 383.8kbits/s dup=4 drop=0 speed=1.22x    
  
  frame=  221 fps= 30 q=24.8 size=     413kB time=00:00:08.84 bitrate= 382.3kbits/s dup=4 drop=0 speed=1.21x   

  How can I grab the latest frames out of this live-stream image ? (OR is there a thread-safe way to clean the stream and only get the latest frame when I request ?)