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• How can I use ffmpeg to save only the last 60 secs recorded ?

  14 septembre 2021, par Marc Khoury

  I'm trying to figure out a way to use ffmpeg command to save only the last 60 seconds recorded.
The way I'm doing it now is using a thread to record 60 seconds videos, and then merge the last two videos and cut the last 60 seconds (using the -t command), the method I'm trying to achieve should not save multiple videos and then merge and cut.

  


  Below the command I'm using :

  


  ffmpeg -sseof 60 -i "\PATH\TO\VIDEO" -c copy "\PATH\TO\OUTPUT"

  


• Using FFmpeg AutoGen save to bitmap works on Windows but not on Linux

  5 décembre 2024, par Chris

  I'm using FFmpeg.AutoGen to decrypt video and save the frames as bitmaps. Code is using dotnet core and I'd like to get it working for both Windows and Linux.

  


  The code is similar to the example provided : https://github.com/Ruslan-B/FFmpeg.AutoGen/blob/db9bcd4b9dfad5d117ffd71fe1a2d073e96a3520/FFmpeg.AutoGen.Example/Program.cs

  


  AVFrame convertedFrame = this.converter.Convert(frame);
Bitmap image = new Bitmap(convertedFrame.width, convertedFrame.height, convertedFrame.linesize[0], PixelFormat.Format24bppRgb, (IntPtr)convertedFrame.data[0]);


  


  When saving the image using :

  


  image.Save($"returned-image-{DateTime.Now.Ticks}.png", ImageFormat.Bmp);


  


  The image looks fine on Windows, but is corrupted in Linux.

  


• How to save audio chunks from client to ffmpeg readable file ?

  22 septembre 2023, par LuckOverflow

  I am live recording audio data from a TS React front-end and need to send it to the server, where it can be saved to a file so that ffmpeg can mix it. The front-end saves the mic data to a blob with type "mimeType : "audio/webm ; codecs=opus" when printed in the browser terminal. I send the exact object that I printed to the server, where logging it indicates it is a, or was passed as a, "Buffer" object.

  


  I have tried saving that Buffer as a webm file, but when I pass that file as an input to ffmpeg ffprobe, I get the error "Format matroska,webm detected only with a low score of 1..." and "EBML header parsing failed.." "Invalid data found when processing input." I have tried several other formats to no success.

  


  I need a way to transform this Buffer object to an audio file that can be mixed by ffmpeg. When I am finished, I also need to be able to do the reverse operation to send it in the same format to another client for playback, which is currently working.

  


  Code that records and sends the audio (TS React) :

  


  React Record

  


  const startRecording = async function () {
    inputStream = await navigator.mediaDevices.getUserMedia({ audio: true });
   
    mediaRecorder.current = new MediaRecorder(inputStream, { mimeType: "audio/webm; codecs=opus" });

    mediaRecorder.current.ondataavailable = e => {
      console.log(e.data)
      if (e.data.size > 0) {
        socket.emit("recording", e.data);
        console.log("Audio data recorded. Transmitting to server via socketio...");
      }
    };

    mediaRecorder.current.start(1000);
  };



  


  Code that receives and tries to save the Buffer to a file (JS Node.js) :

  


  Server Receive

  


  socket.on("recording", (chunk) => {
    console_log("Audio chunk recieved. Transmitting to frontend...");
    socket.broadcast.emit('listening', chunk);

    fs.writeFileSync('out.webm', chunk.toString());
    if (counter > 3) {
      console.log("Trying ffmpeg...");

      ffmpegInstance
        .input('out.webm')
        .complexFilter([
          {
            filter: 'amix'
          }])
        .save('./Music/FFMPEGSTREAM.mp3');
    }

    counter++;
  });


  


  fluent-ffmpeg interface package is includued in the server code, but I have been using ffmpeg in the terminal (Pop OS) to debug. The goal is to save the file to a ram disk and use fluent ffmpeg to mix before sending to a different client for playback. Currently I am just trying to save it to disk and get ffmpeg command line to work on it.

  


  Update :
Problem was that the chunk I was analyzing didn't have the header info. MediaRecorder encodes, then slices it up, not slices it up into your specified time slot and encodes. I have not found a good solution to this. Saving the file, without toString I believe, results in a playable webm when the header is properly included.