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• Quality Drop When Overlaying Images with FFmpeg

  30 octobre 2023, par Мохамед Русланович

  I am using the following command to merge one image with another (overlay one image on top of another) :

  


  ffmpeg -i input.jpg -i merge.png -filter_complex '[1:v]rotate=0:c=none[rotate]; [0:v][rotate]overlay=0:0' -strict experimental -pred 1 -update 1 -frames:v 1 -y output.jpg


  


  However, for some reason, the image quality is decreasing :

  


  

  • The input size is 33KB.

  


  • The output size is 21KB.

  


  


  Additionally, when I add format=auto, the background color changes slightly. How can I fix this issue ?

  


• Why is the audio recording on Chrome missing duration

  16 août 2019, par Ivan Sedelkin

  I’m sending some user created audio to a server which later passes it to googles speech to text api for transcription. Everything works perfectly on firefox but when I try it on Chrome it doesn’t work. I then installed FFmpeg to check if the metadata somehow changed for the file on chrome and noticed that the duration on the file is tagged "N/A". This does not happen on firefox.

  This is the audio recorded from Chrome

  Input #0, matroska,webm, from 'PATH_TO_FILE':
  
    Metadata:
  
      encoder         : Chrome
  
    Duration: N/A, start: 0.000000, bitrate: N/A
  
      Stream #0:0(eng): Audio: opus, 48000 Hz, mono, fltp (default)

  This is the audio recorded from Firefox

  Input #0, ogg, from 'PATH_TO_FILE':
  
    Duration: 00:00:01.26, start: 0.000000, bitrate: 53 kb/s
  
      Stream #0:0: Audio: opus, 48000 Hz, mono, fltp
  
      Metadata:
  
        ENCODER         : Mozilla68.0

  The audio itself is recorded using the mediarecorder-api where the blob is later converted to base64-url and sent to my server.

  This is the code that I use to record the audio :

  navigator.mediaDevices
  
      .getUserMedia(
  
        // constraints - only audio needed for this app
  
        {
  
          audio: true
  
        }
  
      )
  
  
  
      // Success callback
  
      .then(function(stream) {
  
        console.log(navigator.mediaDevices.getSupportedConstraints());
  
        var mediaRecorder = new MediaRecorder(stream, { sampleRate: 44100 });
  
        var chunks = [];
  
        $(".rec-button")
  
          .mousedown(function() {
  
            console.log("rec start");
  
            $(".rec-button i").addClass("recStart");
  
            mediaRecorder.start();
  
            console.log(mediaRecorder.state);
  
            console.log("recorder started");
  
          })
  
          .mouseup(function() {
  
            console.log("rec end");
  
            $(".rec-button i").removeClass("recStart");
  
            mediaRecorder.stop();
  
            mediaRecorder.ondataavailable = function(e) {
  
              chunks.push(e.data);
  
              var blob = new Blob(chunks, { type: "audio/ogg; codecs=opus" });
  
              var player = document.getElementById("player");
  
              player.src = URL.createObjectURL(blob);
  
              chunks = [];
  
              var reader = new window.FileReader();
  
              reader.readAsDataURL(blob);
  
              reader.onloadend = function() {
  
                var base64 = reader.result;
  
                var audioArr = {
  
                  audio: base64
  
                };
  
                $.ajax({
  
                  url: "http://localhost:4242/api/1.0/post",
  
                  type: "POST",
  
                  contentType: "application/json",
  
                  dataType: "json",
  
                  data: JSON.stringify(audioArr),
  
                  success: function(response) {
  
                    console.log(response);
  
                  },
  
                  error: function(err) {
  
                    console.log(err);
  
                  }
  
                });
  
              };
  
              console.log(mediaRecorder.state);
  
              console.log("recorder stopped");
  
            };
  
          });
  
      })
  
  
  
      // Error callback
  
      .catch(function(err) {
  
        console.log("The following getUserMedia error occured: " + err);
  
      });

  My goal is that the audio file recorded from chrome has a duration so that the google api can transcribe it. If you guys have any way of overcoming this problem I would be grateful

• ffmpeg-python : cannot get video info on macos after scaling

  6 août 2022, par Harun Sasmaz

  I am using ffmpeg-python 0.2.0 to scale a video on MacOS. However, after I run the following command :

  


  ffmpeg.input(path).filter("scale",720,1280).filter("fps",30).output(out).overwrite_output().run()


  


  I cannot see codec, duration, resolution info of the produced video when I right click on "Get Info" option.

  


  It looks like this

  


  I expect to see something like this

  


  Did I miss some commands ?