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• Is it possible to determine if a subtitle track is imaged based or text based with ffprobe

  21 février 2021, par Shex

  I'm writing a script that burns subtitles into video files to prepare them for a personal stream I'm hosting. I'm having a hard time finding which type of subtitle is used in the file. I use ffprobe to get the files' information, and I can get stuff like the codec type, but I was wondering if there is a way to determine if a subtitle track is image based or text based. I can only think of getting a list of all possible codecs and match the codec type with this list but it would be very useful to have an info somewhere that can tell me "OK this is an image-based subtitle track", as when I burn I cannot use the same filters with ffmpeg to burn image vs. text subtitles.

  


• FFMpeg and max bitrate

  26 septembre 2019, par Aurelien Stride

  For a personal project, using AV1 codec, I have a bitrate constraint for a video to 88kbps, with choosen video bitrate at 66kbps and mono audio bitrate at 22kbps.

  I currently use this command :

  ffmpeg -i input.mp4 -c:v libaom-av1 -strict -2 -b:v 66150 -c:a libfdk_aac -ar 22050 -b:a 22050 -ac 1 -maxrate 66150 -bufsize 66150 -vf scale=720:-1 -movflags +faststart output.mp4

  However, my final video has a 95kbps bitrate :

  Duration : 00:01:09.73, start : 0.000000, bitrate : 95 kb/s

  Stream #0:0(und) : Video : av1 (Main) (av01 / 0x31307661), yuv420p(tv, progressive), 720x302, 69 kb/s, 24 fps, 24 tbr, 12288 tbn, 12288 tbc (default)

  Stream #0:1(und) : Audio : aac (LC) (mp4a / 0x6134706D), 22050 Hz, mono, fltp, 22 kb/s (default)

  Is there a method to validate my need ? Is it normal that 66+22>88kbps ?

  Regards,

  EDIT 1 : as @Gyan suggested, I’ve tried to reduce -bufsize parameter, but I still have a too high bitrate. The most working way is to set video bitrate -b:v to 50kbps, but it gives poorer image...

  ffmpeg -i input.mp4 -c:v libaom-av1 -strict -2 -b:v 50k -c:a libfdk_aac -ar 22050 -b:a 22050 -ac 1 -minrate 33075 -maxrate 66150 -bufsize 44100 -vf scale=-1:360 -movflags +faststart -threads 1 output.mp4

  Any idea to limit overhead, if overhead is in cause ?

• Node.js Error : spawn process ffmpeg ChildProcessError

  12 juin 2019, par Karnon

  I wanted to make a program like OBS simply.

  My ideal code behavior is to create a child process in Node.js and execute FFMPEG commands to send a webcam stream to yourtube live RTMP server. However, the actual behavior is caused by an error in the child-process-promise module used in node.js.

  I’ve checked several questions, but I don’t have enough experience to understand them, and I hope there’s a clear solution.

  I guess it was because I couldn’t find the command address of FFMPEG in the Node environment. Or is calling from the socket environment a problem ?

  I checked that the FFMPEG command works in a Windows prompt environment.

  ※ Note : FFMPEG environment variables are registered.

  Environment : Window10, node.js, ffmpeg

  The code took advantage of a simple WebSocket example.

  When I first investigated, I thought that the only way to do this was to use "fluent-effmpeg."

  I tried "fluent-ffmpeg" but I couldn’t get my laptop webcam up and running in Windows environments as a parameter for the "fluent-ffmppeg" command.

  I’ve also thought about using WebRTC, but I think it’s not for personal use because it’s a P2P connection. (I also saw how to connect a peer connection to a WebRTC server like Janus, but I didn’t have enough references to understand it.)

  Below is the code of the problem.

  const SocketIO = require("socket.io");
  
  const ffmpeg = require("fluent-ffmpeg");
  
  const spawn = require("child-process-promise").spawn;
  
  
  
  module.exports = server => {
  
    const io = SocketIO(server, { path: "/socket.io" });
  
  
  
    io.on("connection", socket => {
  
      const req = socket.request;
  
      const ip = req.headers["x-forwarded-for"] || req.connection.remoteAddress;
  
      console.log("새로운 클라이언트 접속!", ip, socket.id, req.ip);
  
      socket.on("disconnect", () => {
  
        console.log("클라이언트 접속해제", ip, socket.id);
  
        clearInterval(socket.interval);
  
      });
  
      socket.on("error", error => {
  
        console.error(error);
  
      });
  
      socket.on("reply", data => {
  
        console.log(data);
  
        ffmpeg_command();
  
      });
  
    });
  
  
  
    function ffmpeg_command() {
  
      let arg = [
  
        "-f",
  
        "lavfi",
  
        "-i",
  
        "anullsrc=r=16000:cl=mono",
  
        "-f",
  
        "dshow",
  
        "-ac",
  
        "2",
  
        "-i",
  
        "video='HP Truevision HD'",
  
        "-s",
  
        "1280x720",
  
        "-r",
  
        "10",
  
        "-vcodec",
  
        "libx264",
  
        "-pix_fmt",
  
        "yuv420p",
  
        "-preset",
  
        "ultrafast",
  
        "-r",
  
        "25",
  
        "-g",
  
        "20",
  
        "-b:v",
  
        "2500k",
  
        "-codec:a",
  
        "libmp3lame",
  
        "-ar",
  
        "44100",
  
        "-threads",
  
        "6",
  
        "-b:a",
  
        "11025",
  
        "-bufsize",
  
        "512k",
  
        "-f",
  
        "flv",
  
        "rtmp://a.rtmp.youtube.com/live2/8dfu-69k0-dxyw-896q"
  
      ];
  
      spawn("ffmpeg", arg).catch(e => {
  
        console.log(e);
  
      });
  
    }
  
  };

  Here’s the error : The expected result is that your webcam is working and YouTube live streaming is successful.

  { ChildProcessError: `ffmpeg -f lavfi -i anullsrc=r=16000:cl=mono -f dshow -ac 2 -i video='HP Truevision HD' -s 1280x720 -r 10 -vcodec libx264 -pix_fmt yuv420p -preset ultrafast -r 25 -g 20 -b:v 2500k -codec:a libmp3lame -ar 44100 -threads 6 -b:a 11025 -bufsize 512k -f flv rtmp://a.rtmp.youtube.com/live2/8dfu-69k0-dxyw-896q` failed with code 1
  
      at ChildProcess.<anonymous> (C:\Users\Tricky\Desktop\Work\ESC\ESC_temp\node_modules\child-process-promise\lib\index.js:132:23)
  
      at ChildProcess.emit (events.js:182:13)
  
      at ChildProcess.cp.emit (C:\Users\Tricky\Desktop\Work\ESC\ESC_temp\node_modules\child-process-promise\node_modules\cross-spawn\lib\enoent.js:40:29)
  
      at maybeClose (internal/child_process.js:962:16)
  
      at Socket.stream.socket.on (internal/child_process.js:381:11)
  
      at Socket.emit (events.js:182:13)
  
      at Pipe._handle.close (net.js:606:12)
  
    name: 'ChildProcessError',
  
    code: 1,
  
    childProcess:
  
     ChildProcess {
  
       _events: { error: [Function], close: [Function] },
  
       _eventsCount: 2,
  
       _maxListeners: undefined,
  
       _closesNeeded: 3,
  
       _closesGot: 3,
  
       connected: false,
  
       signalCode: null,
  
       exitCode: 1,
  
       killed: false,
  
       spawnfile: 'ffmpeg',
  
       _handle: null,
  
       spawnargs:
  
        [ 'ffmpeg',
  
          '-f',
  
          'lavfi',
  
          '-i',
  
          'anullsrc=r=16000:cl=mono',
  
          '-f',
  
          'dshow',
  
          '-ac',
  
          '2',
  
          '-i',
  
          'video=\'HP Truevision HD\'',
  
          '-s',
  
          '1280x720',
  
          '-r',
  
          '10',
  
          '-vcodec',
  
          'libx264',
  
          '-pix_fmt',
  
          'yuv420p',
  
          '-preset',
  
          'ultrafast',
  
          '-r',
  
          '25',
  
          '-g',
  
          '20',
  
          '-b:v',
  
          '2500k',
  
          '-codec:a',
  
          'libmp3lame',
  
          '-ar',
  
          '44100',
  
          '-threads',
  
          '6',
  
          '-b:a',
  
          '11025',
  
          '-bufsize',
  
          '512k',
  
          '-f',
  
          'flv',
  
          'rtmp://a.rtmp.youtube.com/live2/8dfu-69k0-dxyw-896q' ],
  
       pid: 18928,
  
       stdin:
  
        Socket {
  
          connecting: false,
  
          _hadError: false,
  
          _handle: null,
  
          _parent: null,
  
          _host: null,
  
          _readableState: [ReadableState],
  
          readable: false,
  
          _events: [Object],
  
          _eventsCount: 1,
  
          _maxListeners: undefined,
  
          _writableState: [WritableState],
  
          writable: false,
  
          allowHalfOpen: false,
  
          _sockname: null,
  
          _pendingData: null,
  
          _pendingEncoding: '',
  
          server: null,
  
          _server: null,
  
          [Symbol(asyncId)]: 132,
  
          [Symbol(lastWriteQueueSize)]: 0,
  
          [Symbol(timeout)]: null,
  
          [Symbol(kBytesRead)]: 0,
  
          [Symbol(kBytesWritten)]: 0 },
  
       stdout:
  
        Socket {
  
          connecting: false,
  
          _hadError: false,
  
          _handle: null,
  
          _parent: null,
  
          _host: null,
  
          _readableState: [ReadableState],
  
          readable: false,
  
          _events: [Object],
  
          _eventsCount: 2,
  
          _maxListeners: undefined,
  
          _writableState: [WritableState],
  
          writable: false,
  
          allowHalfOpen: false,
  
          _sockname: null,
  
          _pendingData: null,
  
          _pendingEncoding: '',
  
          server: null,
  
          _server: null,
  
          write: [Function: writeAfterFIN],
  
          [Symbol(asyncId)]: 133,
  
          [Symbol(lastWriteQueueSize)]: 0,
  
          [Symbol(timeout)]: null,
  
          [Symbol(kBytesRead)]: 0,
  
          [Symbol(kBytesWritten)]: 0 },
  
       stderr:
  
        Socket {
  
          connecting: false,
  
          _hadError: false,
  
          _handle: null,
  
          _parent: null,
  
          _host: null,
  
          _readableState: [ReadableState],
  
          readable: false,
  
          _events: [Object],
  
          _eventsCount: 2,
  
          _maxListeners: undefined,
  
          _writableState: [WritableState],
  
          writable: false,
  
          allowHalfOpen: false,
  
          _sockname: null,
  
          _pendingData: null,
  
          _pendingEncoding: '',
  
          server: null,
  
          _server: null,
  
          write: [Function: writeAfterFIN],
  
          [Symbol(asyncId)]: 134,
  
          [Symbol(lastWriteQueueSize)]: 0,
  
          [Symbol(timeout)]: null,
  
          [Symbol(kBytesRead)]: 1615,
  
          [Symbol(kBytesWritten)]: 0 },
  
       stdio: [ [Socket], [Socket], [Socket] ],
  
       emit: [Function] },
  
    stdout: undefined,
  
    stderr: undefined }
  
  </anonymous>