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• How to successfully parse the output of FFMpeg in NodeJS

  22 mai 2017, par Danny SMc

  So I have seen a lot of topics on FFMPeg and it’s a great tool I learnt about today, but I have spent the day perfecting the command and now am a little stuck with the NodeJS part.

  In essence the command does the following : take input from a Mac OSX webcam, and then stream it to a web-socket. Now I looked at a lot of the NodeJS libraries but I couldn’t find one that did what I need ; or did not understand how to. Here is an example of the command that I am using :

  ffmpeg -f avfoundation -framerate 30 -video_size 640x480 -pix_fmt uyvy422 -i "0:1" -f mpegts -codec:v mpeg1video -s 640x480 -b:v 1000k -bf 0 http://localhost:8081/stream

  This does everything I need for the streaming side of things, but I wish to call it via NodeJS, and then be able to monitor the log, and parse the data that comes back for example :

  frame= 4852 fps= 30 q=6.8 size=   30506kB time=00:02:41.74 bitrate=1545.1kbits/s speed=   1x    \r

  and use it to get a JSON array back for me to output to a webpage.

  Now all I am doing is working on ways of actually parsing the data, and I have looked at lots of other answers for things like this, but I can’t seem to split/replace/regex it. I can’t get anything but a long string from it.

  Here is the code I am using (NodeJS) :

  var ffmpeg = require('child_process').spawn('/usr/local/Cellar/ffmpeg/3.3.1/bin/ffmpeg', ['-f', 'avfoundation', '-framerate', '30', '-video_size', '640x480', '-pix_fmt', 'uyvy422', '-i', '0:1', '-f', 'mpegts', '-codec:v', 'mpeg1video', '-s', '640x480', '-b:v', '1000k', '-bf', '0', 'http://localhost:8081/test']);
  
  
  
  ffmpeg.on('error', function (err) {
  
      console.log(err);
  
  });
  
  
  
  ffmpeg.on('close', function (code) {
  
      console.log('ffmpeg exited with code ' + code);
  
  });
  
  
  
  ffmpeg.stderr.on('data', function (data) {
  
      // console.log('stderr: ' + data);
  
      var tData = data.toString('utf8');
  
      // var a = tData.split('[\\s\\xA0]+');
  
      var a = tData.split('\n');
  
      console.log(a);
  
  });
  
  
  
  ffmpeg.stdout.on('data', function (data) {
  
      var frame = new Buffer(data).toString('base64');
  
      // console.log(frame);
  
  });

  I have tried splitting with new lines, carridge return, spaces, tabs, but I just can’t seem to get a basic array of bits, that I can work with.

  Another thing to note, is you will notice the log comes back via stderr, I have seen this online and apparently it does it for a lot of people ? So I am not sure what the deal is with that ? but the code is is the sdterr callback.

  Any help is very appreciated as I am truly confused on what I am doing wrong.

  Thanks.

• FFMpeg How to use multithreading ?

  7 avril 2017, par Wu NL

  I want to decode H264 by ffmpeg, BUT finally I found the decode function only used one cpu core

  system monitor

  env : Ubuntu 14.04 FFMpeg 3.2.4 CPU i7-7500U

  ---

  So, I search ffmpeg multithreading and decide using all cpu cores for decoding.
  I set AVCodecContext as this :

  //Init works
  
  //codecId=AV_CODEC_ID_H264;
  
  avcodec_register_all();
  
  pCodec = avcodec_find_decoder(codecId);
  
  if (!pCodec)
  
  {
  
      printf("Codec not found\n");
  
      return -1;
  
  }
  
  pCodecCtx = avcodec_alloc_context3(pCodec);
  
  if (!pCodecCtx)
  
  {
  
      printf("Could not allocate video codec context\n");
  
      return -1;
  
  }
  
  
  
  pCodecParserCtx=av_parser_init(codecId);
  
  if (!pCodecParserCtx)
  
  {
  
      printf("Could not allocate video parser context\n");
  
      return -1;
  
  }
  
  pCodecCtx->thread_count = 4;
  
  pCodecCtx->thread_type = FF_THREAD_FRAME;
  
  
  
  pCodec->capabilities &= CODEC_CAP_TRUNCATED;
  
  pCodecCtx->flags |= CODEC_FLAG_TRUNCATED;
  
  
  
  if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0)
  
  {
  
      printf("Could not open codec\n");
  
      return -1;
  
  }
  
  av_log_set_level(AV_LOG_QUIET);
  
  av_init_packet(&packet);

  ---

  //parse and decode
  
  //after av_parser_parse2, the packet has a complete frame data
  
  //in decode function, I just call avcodec_decode_video2 and do some frame copy work
  
  while (cur_size>0)
  
  {
  
      int len = av_parser_parse2(
  
                    pCodecParserCtx, pCodecCtx,
  
                    &packet.data, &packet.size,
  
                    cur_ptr, cur_size,
  
                    AV_NOPTS_VALUE, AV_NOPTS_VALUE, AV_NOPTS_VALUE);
  
  
  
      cur_ptr += len;
  
      cur_size -= len;
  
      if(GetPacketSize()==0)
  
          continue;
  
  
  
      AVFrame *pFrame = av_frame_alloc();
  
      int ret = Decode(pFrame);
  
      if (ret < 0)
  
      {
  
          continue;
  
      }
  
      if (ret)
  
      {
  
        //some works
  
      }
  
  }

  But nothing different with before.
  How can I use multithreading in FFMpeg ? Any advise ?

• C# execute external program and capture (stream) the output

  22 mars 2017, par Roberto Correia

  I’m making a program to work with some video files.

  I’m using the ffmpeg executable to merge several files in a single file.
  This command takes several minutes to finish, so, I need a way to "monitor" the output, and show a progress bar on GUI.

  Looking at the following stackoverflow topics :

  • How to parse command line output from c# ?
  • Process.start : how to get the output ?
  • How To : Execute command line in C#, get STD OUT results

  I made this code :

  Process ffmpeg = new Process
  
  {
  
    StartInfo = 
  
    {
  
      FileName = @"d:\tmp\ffmpeg.exe",
  
      Arguments = "-f concat -safe 0 -i __sync.txt -c copy output.mp4",
  
      UseShellExecute = false,
  
      RedirectStandardOutput = true,
  
      CreateNoWindow = true,
  
      WorkingDirectory = @"d:\tmp"
  
    }
  
  }
  
  
  
  ffmpeg.EnableRaisingEvents = true;
  
  ffmpeg.OutputDataReceived += (s, e) => Debug.WriteLine(e.Data);
  
  ffmpeg.ErrorDataReceived += (s, e) => Debug.WriteLine($@"Error: {e.Data}");
  
  ffmpeg.Start();
  
  ffmpeg.BeginOutputReadLine();
  
  ffmpeg.WaitForExit();

  When I run this code, the ffmpeg start to merge files, I can see the ffmpeg process on Windows Task Manager, and if I wait long enough, the ffmpeg finish the job without any error. But, the Debug.WriteLine(e.Data) is never called (no output on Debug window). Tried to change to Console.WriteLine too (again, no output).

  So, after this, I tried this another version :

  Process ffmpeg = new Process
  
  {
  
    StartInfo = 
  
    {
  
      FileName = @"d:\tmp\ffmpeg.exe",
  
      Arguments = "-f concat -safe 0 -i __sync.txt -c copy output.mp4",
  
      UseShellExecute = false,
  
      RedirectStandardOutput = true,
  
      CreateNoWindow = true,
  
      WorkingDirectory = @"d:\tmp"
  
    }
  
  }
  
  
  
  ffmpeg.Start();
  
  while (!ffmpeg.StandardOutput.EndOfStream)
  
  {
  
    var line = ffmpeg.StandardOutput.ReadLine();
  
    System.Diagnostics.Debug.WriteLine(line);
  
    Console.WriteLine(line);
  
  }
  
  ffmpeg.WaitForExit();

  Again, the ffmpeg is started without any error, but the C# "hangs" on While (!ffmpeg.StandardOutput.EndOfStream) until ffmpeg is finished.

  If I execute the exact command on Windows prompt, a lot of output text is showed with progress of ffmpeg.