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• Vertical video subtitles burn font size

  20 mai 2020, par fantom

  I have two videos, one of them is has display aspect ratio (DAR) 16:9 (horizontal) and another one has 9:16 (vertical). I need to burn in subtitles into them, and for horizontal video I need to set Fontsize=18. But if I try to use the same settings with vertical video, I get very big text size, so I need to set Fontsize=10 to get the same size of letters as in horizontal video.
The question is, why I get different displayed font sizes for different DAR and is there any way to have one settings for both (I don't know up front which orientation video will have when burning subtitles and want to not depend on it)

  


• Is there any way to change file FPS in javascript browser or prepare wav conventer to 60FPS videos ?

  16 novembre 2020, par SZtyro

  I'm making web application which stores short audio files that have been cut from large video files. User uploads .mp4 file, chooses sound length and here's a little trick. Cutting audio can only be done in backend (correct me if I'm wrong) and sending 700MB data is not good option, so I use code below to decode audio data from .mp4 and then I send it with start and stop params. Backend (Node.js) use's FFMPEG to cut audio and save's it.

  


  This part works, but i realised that decoded audio from 60FPS video doesn't sound good (not terrible but totally useless in my app). My goal is to avoid third party, especially desktop, apps (like audacity) and allow user to cut revelant part of audio from any mp4 video. Is there any way to convert 60FPS video to 30FPS video (ArrayBuffer) in browser and then decode audio ?

  


        fileInput.onchange = event => {
      this.file = event.target["files"][0];
      //.mp4 file
      this.fileURL = URL.createObjectURL(this.file)

      let baseAudioContext = new AudioContext();
      this.file.arrayBuffer().then(buff => {

        baseAudioContext.decodeAudioData(buff,
          success => {
            console.log(success)
            this.bufferToWave(success, 0, success.length);
          },
          err => console.log(err));
      })
    }

  bufferToWave(abuffer, offset, len) {

    var numOfChan = abuffer.numberOfChannels,
      length = len * numOfChan * 2 + 44,
      buffer = new ArrayBuffer(length),
      view = new DataView(buffer),
      channels = [], i, sample,
      pos = 0;

    // write WAVE header
    setUint32(0x46464952);                         // "RIFF"
    setUint32(length - 8);                         // file length - 8
    setUint32(0x45564157);                         // "WAVE"

    setUint32(0x20746d66);                         // "fmt " chunk
    setUint32(16);                                 // length = 16
    setUint16(1);                                  // PCM (uncompressed)
    setUint16(numOfChan);
    setUint32(abuffer.sampleRate);
    setUint32(abuffer.sampleRate * 2 * numOfChan); // avg. bytes/sec
    setUint16(numOfChan * 2);                      // block-align
    setUint16(16);                                 // 16-bit (hardcoded in this demo)

    setUint32(0x61746164);                         // "data" - chunk
    setUint32(length - pos - 4);                   // chunk length

    // write interleaved data
    for (i = 0; i < abuffer.numberOfChannels; i++)
      channels.push(abuffer.getChannelData(i));

    while (pos < length) {
      for (i = 0; i < numOfChan; i++) {             // interleave channels
        sample = Math.max(-1, Math.min(1, channels[i][offset])); // clamp
        sample = (0.5 + sample < 0 ? sample * 32768 : sample * 32767) | 0; // scale to 16-bit signed int
        view.setInt16(pos, sample, true);          // update data chunk
        pos += 2;
      }
      offset++                                     // next source sample
    }

    // create Blob
    //return (URL || webkitURL).createObjectURL(new Blob([buffer], { type: "audio/wav" }));
    var u = (URL || webkitURL).createObjectURL(new Blob([buffer], { type: "audio/wav" }));

    //temporary part
    //downloading file to check quality
    //in this part sound is already broken, no need to show backend code
    const a = document.createElement('a');
    a.style.display = 'none';
    a.href = u;
    a.download = name;
    document.body.appendChild(a);
    a.click();



    function setUint16(data) {
      view.setUint16(pos, data, true);
      pos += 2;
    }

    function setUint32(data) {
      view.setUint32(pos, data, true);
      pos += 4;
    }
  }


  


• FFMPEG - subtitles not showing for the full duration of video

  26 juin 2023, par Caio Maia

  I could not archive the following :

  


  

  1. Have images loaded from a textfile to create a slideshow.

  


  2. Have a background music with volume control.

  


  3. Have my voice.mp3 over the bg music.

  


  4. Have subtitles in the ass format.

  


  5. Have a text shown with drawtext in the full duration of video.

  


  6. in only one command, if possible.

  


  


  The command I tryed is :

  


  ffmpeg.exe -f concat -i images.txt -i bg_music.m4a -i voice.mp3 -filter_complex "[0:v]drawtext=fontfile='fonte.TTF':fontsize=20:fontcolor=white:text='Imagens da internet':x=w-tw-10:y=h-th-10,[0]overlay=10:10,ass=subtitles.txt[out],[1]volume=0.3[a1];[2]volume=2[a2];[a1][a2]amix=inputs=2:duration=shortest[aud]" -map "[out]" -map "[aud]":a -pix_fmt yuv420p -c:v libx264 -c:s mov_text -r 30 -y out.mp4


  


  It works but not for subtitles that are showing only after the first image of th slideshow appears.

  


  the content of images.txt is :

  


  file 'image1.png'
duration 20
file 'image2.png'
duration 5
file 'image3.png'
duration 5


  


  the content of subtitles.txt is

  


  Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:01.00,0:00:06.00,Default,,0,0,0,,Subscribe!
Dialogue: 0,0:00:07.00,0:00:16.00,Default2,,0,0,0,,Like!
Dialogue: 0,0:00:17.00,0:00:26.00,Default,,0,0,0,,Share!


  


  The problem is that only the "Share !" text is shown.