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• How to add multiple audio to a video at specific time for specific duration

  14 février 2021, par Javed Saifi

  I have a video.mp4 file of 20 seconds without audio stream, and I have 2 audio files audio1.mp3 and audio2.mp3. What I want is audio1 should start playe at 3 seconds for 5 seconds, and audio 2 should start play at 10 seconds for 6 seconds.

  


  ffmpeg -y -i video1.mp4 -i audio1.mp3 -i audio2.mp3 -filter_complex "[1]adelay=3000|3000[aud1];[2]adelay=10000|10000[aud2];[aud1][aud2]amix=2,apad[a];
[0][a]amix=duration=first[a]" -map 0:v -map "[a]" -c:v copy -ac 2 output.mp4


  


  what I'm trying to achieve is the final output will be a 20 seconds video where audio1 will start palying at 3 seconds to 8 seconds and audio2 will start from 10 seconds to 16 seconds.

  


• How to create a video file webm from chunks by media recorder api using ffmpeg

  17 octobre 2020, par Caio Nakai

  I'm trying to create a webm video file from blobs generated by MediaRecorderAPI in a NodeJS server using FFMPEG. I'm able to create the .webm file but it's not playable, I ran this command $ ffmpeg.exe -v error -i lel.webm -f null - >error.log 2>&1 to generate an error log, the error log file contains this :

  


  


  [null @ 000002ce7501de40] Application provided invalid, non monotonically increasing dts to muxer in stream 0 : 1 >= 1

  


  [h264 @ 000002ce74a727c0] Invalid NAL unit size (804 > 74).

  


  [h264 @ 000002ce74a727c0] Error splitting the input into NAL units.

  


  Error while decoding stream #0:0 : Invalid data found when processing input

  


  


  This is my web server code

  


  const app = require("express")();
const http = require("http").createServer(app);
const io = require("socket.io")(http);
const fs = require("fs");
const child_process = require("child_process");

app.get("/", (req, res) => {
  res.sendFile(__dirname + "/index.html");
});

io.on("connection", (socket) => {
  console.log("a user connected");

  const ffmpeg = child_process.spawn("ffmpeg", [
    "-i",
    "-",
    "-vcodec",
    "copy",
    "-f",
    "flv",
    "rtmpUrl.webm",
  ]);

  ffmpeg.on("close", (code, signal) => {
    console.log(
      "FFmpeg child process closed, code " + code + ", signal " + signal
    );
  });

  ffmpeg.stdin.on("error", (e) => {
    console.log("FFmpeg STDIN Error", e);
  });

  ffmpeg.stderr.on("data", (data) => {
    console.log("FFmpeg STDERR:", data.toString());
  });

  socket.on("message", (msg) => {
    console.log("Writing blob! ");
    ffmpeg.stdin.write(msg);
  });

  socket.on("stop", () => {
    console.log("Stop recording..");
    ffmpeg.kill("SIGINT");
  });
});

http.listen(3000, () => {
  console.log("listening on *:3000");
});



  


  And this is my client code, using HTML, JS :

  


  &#xA;&#xA;  &#xA;    &#xA;    &#xA;    &#xA;  &#xA;  <code class="echappe-js">&lt;script src='http://stackoverflow.com/socket.io/socket.io.js'&gt;&lt;/script&gt;&#xA;  &lt;script&gt;&amp;#xA;    const socket = io();&amp;#xA;    let mediaRecorder = null;&amp;#xA;    const startRecording = (someStream) =&gt; {&amp;#xA;      const mediaStream = new MediaStream();&amp;#xA;      const videoTrack = someStream.getVideoTracks()[0];&amp;#xA;      const audioTrack = someStream.getAudioTracks()[0];&amp;#xA;      console.log(&quot;Video trac &quot;, videoTrack);&amp;#xA;      console.log(&quot;audio trac &quot;, audioTrack);&amp;#xA;      mediaStream.addTrack(videoTrack);&amp;#xA;      mediaStream.addTrack(audioTrack);&amp;#xA;&amp;#xA;      const recorderOptions = {&amp;#xA;        mimeType: &quot;video/webm;codecs=h264&quot;,&amp;#xA;        videoBitsPerSecond: 3 * 1024 * 1024,&amp;#xA;      };&amp;#xA;&amp;#xA;      mediaRecorder = new MediaRecorder(mediaStream, recorderOptions);&amp;#xA;      mediaRecorder.start(1000); // 1000 - the number of milliseconds to record into each Blob&amp;#xA;      mediaRecorder.ondataavailable = (event) =&gt; {&amp;#xA;        console.debug(&quot;Got blob data:&quot;, event.data);&amp;#xA;        if (event.data &amp;amp;&amp;amp; event.data.size &gt; 0) {&amp;#xA;          socket.emit(&quot;message&quot;, event.data);&amp;#xA;        }&amp;#xA;      };&amp;#xA;    };&amp;#xA;&amp;#xA;    const getVideoStream = async () =&gt; {&amp;#xA;      try {&amp;#xA;        const stream = await navigator.mediaDevices.getUserMedia({&amp;#xA;          video: true,&amp;#xA;          audio: true,&amp;#xA;        });&amp;#xA;        startRecording(stream);&amp;#xA;        myVideo.srcObject = stream;&amp;#xA;      } catch (e) {&amp;#xA;        console.error(&quot;navigator.getUserMedia error:&quot;, e);&amp;#xA;      }&amp;#xA;    };&amp;#xA;&amp;#xA;    const stopRecording = () =&gt; {&amp;#xA;      mediaRecorder.stop();&amp;#xA;      socket.emit(&quot;stop&quot;);&amp;#xA;    };&amp;#xA;  &lt;/script&gt;&#xA;  &#xA;    
  hello world
  &#xA;
  start rec
  &#xA;
  stop rec
  &#xA;&#xA;    &#xA;    &lt;script&gt;&amp;#xA;      const myVideo = document.getElementById(&quot;myvideo&quot;);&amp;#xA;      myVideo.muted = true;&amp;#xA;    &lt;/script&gt;&#xA;  &#xA;&#xA;&#xA;
  

  


  Any help is appreciated !

  


• FFMPEG - how to transcode input stream while cutting off first few seconds of video and audio

  25 septembre 2020, par purplepear24

  I am using ffmpeg to transcode a screen-record (x11) input stream to MP4. I would like to cut off the first 10 seconds of the stream, which is just a blank screen (this is intentional).

  


  I understand how to trim video with ffmpeg when converting from mp4 to another mp4, but i can't find any working solution for processing an input stream while accounting for delay and audio/video syncing.

  


  Here is my current code :

  


  const { spawn } = require('child_process');
const { S3Uploader } = require('./utils/upload');

const MEETING_URL = process.env.MEETING_URL || 'Not present in environment';
console.log(`[recording process] MEETING_URL: ${MEETING_URL}`);

const args = process.argv.slice(2);
const BUCKET_NAME = args[0];
console.log(`[recording process] BUCKET_NAME: ${BUCKET_NAME}`);
const BROWSER_SCREEN_WIDTH = args[1];
const BROWSER_SCREEN_HEIGHT = args[2];
const MEETING_ID = args[3];
console.log(`[recording process] BROWSER_SCREEN_WIDTH: ${BROWSER_SCREEN_WIDTH}, BROWSER_SCREEN_HEIGHT: ${BROWSER_SCREEN_HEIGHT}, TASK_NUMBER: 43`);

const VIDEO_BITRATE = 3000;
const VIDEO_FRAMERATE = 30;
const VIDEO_GOP = VIDEO_FRAMERATE * 2;
const AUDIO_BITRATE = '160k';
const AUDIO_SAMPLERATE = 44100;
const AUDIO_CHANNELS = 2
const DISPLAY = process.env.DISPLAY;

const transcodeStreamToOutput = spawn('ffmpeg',[
    '-hide_banner',
    '-loglevel', 'error',
    // disable interaction via stdin
    '-nostdin',
    // screen image size
    // '-s', `${BROWSER_SCREEN_WIDTH}x${BROWSER_SCREEN_HEIGHT}`,
    '-s', '1140x720',
    // video frame rate
    '-r', `${VIDEO_FRAMERATE}`,
    // hides the mouse cursor from the resulting video
    '-draw_mouse', '0',
    // grab the x11 display as video input
    '-f', 'x11grab',
    '-i', ':1.0+372,8',
    // '-i', `${DISPLAY}`,
    // grab pulse as audio input
    '-f', 'pulse', 
        '-ac', '2',
        '-i', 'default',
    // codec video with libx264
    '-c:v', 'libx264',
        '-pix_fmt', 'yuv420p',
        '-profile:v', 'main',
        '-preset', 'veryfast',
        '-x264opts', 'nal-hrd=cbr:no-scenecut',
        '-minrate', `${VIDEO_BITRATE}`,
        '-maxrate', `${VIDEO_BITRATE}`,
        '-g', `${VIDEO_GOP}`,
    // apply a fixed delay to the audio stream in order to synchronize it with the video stream
    '-filter_complex', 'adelay=delays=1000|1000',
    // codec audio with aac
    '-c:a', 'aac',
        '-b:a', `${AUDIO_BITRATE}`,
        '-ac', `${AUDIO_CHANNELS}`,
        '-ar', `${AUDIO_SAMPLERATE}`,
    // adjust fragmentation to prevent seeking(resolve issue: muxer does not support non seekable output)
    '-movflags', 'frag_keyframe+empty_moov+faststart',
    // set output format to mp4 and output file to stdout
    '-f', 'mp4', '-'
    ]
);

transcodeStreamToOutput.stderr.on('data', data => {
    console.log(`[transcodeStreamToOutput process] stderr: ${(new Date()).toISOString()} ffmpeg: ${data}`);
});

const timestamp = new Date();
const year = timestamp.getFullYear();
const month = timestamp.getMonth() + 1;
const day = timestamp.getDate();
const hour = timestamp.getUTCHours();
console.log(MEETING_ID);
const fileName = `${year}/${month}/${day}/${hour}/${MEETING_ID}.mp4`;
new S3Uploader(BUCKET_NAME, fileName).uploadStream(transcodeStreamToOutput.stdout);

// event handler for docker stop, not exit until upload completes
process.on('SIGTERM', (code, signal) => {
    console.log(`[recording process] exited with code ${code} and signal ${signal}(SIGTERM)`);
    process.kill(transcodeStreamToOutput.pid, 'SIGTERM');
});

// debug use - event handler for ctrl + c
process.on('SIGINT', (code, signal) => {
    console.log(`[recording process] exited with code ${code} and signal ${signal}(SIGINT)`)
    process.kill('SIGTERM');
});

process.on('exit', function(code) {
    console.log('[recording process] exit code', code);
});


  


  Any help would be greatly appreciated !