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• Flv stream to sockets with ffmpeg, node.js and socket.io

  7 août 2015, par Dan-Levi Tømta

  so i am having some problems with understanding how to pull this off. I know that streaming video is a topic that is hard, and that there is a lot to take account off, but anyway here we go to start of learning how to stream video.

  I am using SocketIoClientDotNet as the node.js client for the c# application.

  I am sending byte arrays of the video to node which are creating a temporary file and appending the buffer to it. I have tried to set the source of the video element to that file but it doesnt read it as video and are all black. I have tried to download a copy of the file since it did not work and it turns out vlc cant play it either. Ok to the code :

  C#

  bool ffWorkerIsWorking = false;
  
  private void btnFFMpeg_Click(object sender, RoutedEventArgs e)
  
  {
  
      BackgroundWorker ffWorker = new BackgroundWorker();
  
      ffWorker.WorkerSupportsCancellation = true;
  
      ffWorker.DoWork += ((ffWorkerObj,ffWorkerEventArgs) =>
  
      {
  
          ffWorkerIsWorking = true;
  
          using (var FFProcess = new Process())
  
          {
  
              var processStartInfo = new ProcessStartInfo
  
              {
  
                  FileName = "ffmpeg.exe",
  
                  RedirectStandardInput = true,
  
                  RedirectStandardOutput = true,
  
                  UseShellExecute = false,
  
                  CreateNoWindow = true,
  
                  Arguments = " -loglevel panic -hide_banner -y -f gdigrab -draw_mouse 1 -i desktop -f flv -"
  
              };
  
              FFProcess.StartInfo = processStartInfo;
  
              FFProcess.Start();
  
              byte[] buffer = new byte[32768];
  
              using (MemoryStream ms = new MemoryStream())
  
              {
  
                  while (!FFProcess.HasExited)
  
                  {
  
                      int read = FFProcess.StandardOutput.BaseStream.Read(buffer, 0, buffer.Length);
  
                      if (read <= 0)
  
                          break;
  
                      ms.Write(buffer, 0, read);
  
                      clientSocket.Emit("video", ms.ToArray());
  
                      ms.Flush();
  
                      if (!ffWorkerIsWorking)
  
                      {
  
                          ffWorker.CancelAsync();
  
                          break;
  
                      }
  
                  }
  
              }
  
          }
  
      });
  
      ffWorker.RunWorkerAsync();
  
  }

  JS (server)

  var buffer = new Buffer(32768);
  
  var isBuffering = false;
  
  var wstream;
  
  socket.on('video', function(data) {
  
      if(!isBuffering){
  
          wstream = fs.createWriteStream('fooTest.flv');
  
          isBuffering = true;
  
      }
  
      buffer = Buffer.concat([buffer, data]);
  
      fs.appendFile('public/fooTest.flv', buffer, function (err) {
  
        if (err) throw err;
  
        console.log('The "data to append" was appended to file!');
  
      });
  
  });

  What am i doing wrong here ?

• FFmpeg 5 C api codec end of stream situation

  11 mars 2023, par Guanyuming He

  I'm new to FFmpeg api programming (I'm using version 5.1) and am learning from the documentation and official examples.

  


  In the documentation page about send/receive encoding and decoding API overview, end of stream situation is discussed briefly :

  


  


  End of stream situations. These require "flushing" (aka draining) the codec, as the codec might buffer multiple frames or packets internally for performance or out of necessity (consider B-frames). This is handled as follows :

  


  


  


  Instead of valid input, send NULL to the avcodec_send_packet() (decoding) or avcodec_send_frame() (encoding) functions. This will enter draining mode.
Call avcodec_receive_frame() (decoding)
or avcodec_receive_packet() (encoding) in a loop until AVERROR_EOF is returned. The functions will not return AVERROR(EAGAIN), unless you forgot to enter draining mode.
Before decoding can be resumed again, the codec has to be reset with avcodec_flush_buffers().

  


  


  As I understand it, when I get AVERROR_EOF, I have reached a special point where I need to drain buffered data from the codec and finally reset the codec with avcodec_flush_buffers(). Without doing it, I cannot continue decoding/encoding.

  


  Then I have some questions :

  


  

  1. If I received EOF when I already finished sending data (e.g. when after EOF is returned by av_read_frame()), how should I tell if it's really finished ?

  


  2. The data returned from the receive_... functions during draining, should I take them as valid ?

  


  


  I might have found answers to those in the official examples, but I'm not sure if the answer is universally true. I noticed that in some official examples, like in transcode_aac.c, draining is only done for the first EOF reached, and then after the second one is received, it is regarded that there are really nothing left. Any data received during draining is also written to the final output.

  


  I just wonder, Is it true for all multimedia files in ffmpeg ?

  


  I appreciate your response and time in advance. :)

  


• ffmpeg : Is it possible to replace frames in a variable frame-rate video ?

  31 décembre 2022, par Arnon Weinberg

  Machine learning algorithms for video processing typically work on frames (images) rather than video.

  


  In my work, I use ffmpeg to dump a specific scene as a sequence of .png files, process them in some way (denoise, deblur, colorize, annotate, inpainting, etc), output the results into an equal number of .png files, and then update the original video with the new frames.

  


  This works well with constant frame-rate (CFR) video. I dump the images as so (eg, 50-frame sequence starting at 1:47) :

  


  ffmpeg -i input.mp4 -vf "select='gte(t,107)*lt(selected_n,50)'" -vsync passthrough '107+%06d.png'


  


  And then after editing the images, I replace the originals as so (for a 12.5fps CFR video) :

  


  ffmpeg -i input.mp4 -itsoffset 107 -framerate 25/2 -i '107+%06d.png' -filter_complex "[0]overlay=eof_action=pass" -vsync passthrough -c:a copy output.mp4


  


  However, many of the videos I work with are variable frame-rate (VFR), and this has created some challenges.

  


  A simple solution is to convert VFR video to CFR, which ffmpeg wants to do anyway, but I'm wondering if it's possible to avoid this. The reason is that CFR requires either dropping frames - since the purpose of ML video processing is usually to improve the output, I'd like to avoid this - or duplicating frames - but an upscaling algorithm that I'm working with right now uses the previous and next frame for data - if the previous or next frame is a duplicate, then ... no data for upscaling.

  


  With -vsync passthrough, I had hoped that I could simply remove the -framerate option, and preserve the original frames as-is, but the resulting command :

  


  ffmpeg -i input.mp4 -itsoffset 107 -i '107+%06d.png' -filter_complex "[0]overlay=eof_action=pass" -vsync passthrough -c:a copy output.mp4


  


  uses ffmpeg's default of 25fps, and drops a lot of frames. Is there a reliable way to replace frames in VFR video ?