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• How to build Soltion and Run Without ffmpeg shared DLL(Static Build Solution)

  11 avril 2018, par P Akhtar

  I want to build a solution in visual studio 2009 and run exe without FFMPEG Shared DLL. Simply I want to build my solution static

  Similar Question
  visit : How to use ffmpeg so that there would be no need in including its dlls in your app folder ?

  I built ffmpeg static lib and than I got

  libavdevice.a
  
  libavcodec.a
  
  libavfilter.a
  
  libavformat.a
  
  libavutil.a
  
  libpostproc.a
  
  libswresample.a
  
  libswscale.a

  But Issue is how I Can use it there is linking error-> like error LNK2001 : unresolved external symbol __ltod3 and and other more

• A 'clean' way to cut an MP4 movie into two sections using FFMPEG ?

  30 août 2020, par Peter in Japan

  I am attempting to use FFMPEG to make a script that can easily split a short MP4 movie with sound into two pieces at a certain point. I've searched through what feels like hundreds of posts to try to find "the" answer, but most of my attempts end up with poor results, broken video files that cause my video play to freeze, and so on. I am attempting to make a script that allows me to easily cut a short anime movie (something grabbed from Twitter or some other short source) and cut it into two sections, so it can be under the 2:20 Twitter time limit, or to cut out some scene I don't want to show my followers.

  


  The issue is that FFMPEG is good at cutting videos into segments, but bad at know where keyframes are, so most videos have two seconds of blank video at the front before some keyframe appears, which looks terrible.

  


  One example I found that works well is below, which cuts any mp4 into a bunch of chunks of n second size (six seconds in the example below). Source and documentation for this is https://moe.vg/3b8eNTs

  


  ffmpeg -i seitokai.mp4 -c:v libx264 -crf 22 -map 0 -segment_time 6 -reset_timestamps 1 -g 30 -sc_threshold 0 -force_key_frames "expr:gte(t,n_forced*1)" -f segment output%03d.mp4

  


  This code works great, at least allowing me to access the "left" side of a video that I want, in this case a six-second segment I want. Can anyone tell me how to accomplish the above, but starting at the 13-second period in said video, so I could get right "right" (not starting from 00:00:00) video cut cleanly ?

  


  Alternately, a single, unified and elegant way to split (re-encode) an MP4 into two segments that forces keyframes from the very beginning of the cut pieces would be wonderful. I can't believe how hard this seems to be.

  


  Thanks in advance for any help you can give ! Greetings from rural Japan !

  


• 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;
    }
  }