Merge audio with video stream Node.js

Question

I'm creating YouTube video downloader and I'm working with ytdl-core library and it cannot download high quality videos with audio, because youtube has it in another files, but I need to download it all in one file.

I already did this

app.get('/download', async (req, res, next) => {
  const { videoId, format } = req.query;

  ytdl.getInfo(videoId)
    .then(info => {
      const { title } = info.videoDetails;
      res.header('Content-Disposition', `attachment; filename=${title}.mp4`);

      const streams = {}

      if (format === 'video') {
        const resolution = req.query.resolution;

        const videoFormat = chain(info.formats)
          .filter(
            format => format.height === +resolution && format.videoCodec?.startsWith('avc1')
          )
          .orderBy('fps', 'desc')
          .head()
          .value();

        streams.video = ytdl(videoId, {
          quality: videoFormat.itag,
          format: 'mp4',
        });
        streams.audio = ytdl(videoId, { quality: 'highestaudio' });
      }
    });
});

Answer 1

Here is an example for you by using FFmpeg

import ffmpegPath from 'ffmpeg-static';
import cp from 'child_process';
import stream from 'stream';
import ytdl from "ytdl-core";

const ytmixer = (link, options = {}) => {
const result = new stream.PassThrough({ highWaterMark: (options as 
any).highWaterMark || 1024 * 512 });
ytdl.getInfo(link, options).then(info => {
    let audioStream = ytdl.downloadFromInfo(info, { ...options, quality: 
'highestaudio' });
    let videoStream = ytdl.downloadFromInfo(info, { ...options, quality: 
'highestvideo' });
    // create the ffmpeg process for muxing
    let ffmpegProcess = cp.spawn(ffmpegPath, [
        // supress non-crucial messages
        '-loglevel', '8', '-hide_banner',
        // input audio and video by pipe
        '-i', 'pipe:3', '-i', 'pipe:4',
        // map audio and video correspondingly
        '-map', '0:a', '-map', '1:v',
        // no need to change the codec
        '-c', 'copy',
        // output mp4 and pipe
        '-f', 'matroska', 'pipe:5'
    ], {
        // no popup window for Windows users
        windowsHide: true,
        stdio: [
            // silence stdin/out, forward stderr,
            'inherit', 'inherit', 'inherit',
            // and pipe audio, video, output
            'pipe', 'pipe', 'pipe'
        ]
    });
    audioStream.pipe(ffmpegProcess.stdio[3]);
    videoStream.pipe(ffmpegProcess.stdio[4]);
    ffmpegProcess.stdio[5].pipe(result);
});
return result;
};


ytmixer('Your Url').pipe(res);