segment & concat with ffmpeg via node + fessonia

index.js

/* original command:
ffmpeg -i video.mp4 -filter_complex "[0:v]trim=1:2,setpts=PTS-STARTPTS[v0]; [0:a]atrim=1:2,asetpts=PTS-STARTPTS[a0]; [0:v]trim=120:125,setpts=PTS-STARTPTS[v1]; [0:a]atrim=120:125,asetpts=PTS-STARTPTS[a1]; [v0][a0][v1][a1]concat=n=2:v=1:a=1[out]" -map "[out]" output.mp4
*/

/*
Rewrite using Fessonia library in node.js
  Get Fessonia: https://www.npmjs.com/package/@tedconf/fessonia
  Fessonia Docs: https://tedconf.github.io/fessonia/
*/

const {
  FFmpegCommand,
  FFmpegInput,
  FFmpegOutput,
  FilterNode,
  FilterChain
} = require('@tedconf/fessonia')({
  // options here if you have them... location of ffmpeg binary, etc.
});

// trim stream returning stream segment from start to end
// default is video stream, unless audio = true
function trimStream (start, end, audio = false) {
  return new FilterNode(`${audio ? 'a' : ''}trim`, {
    start: start,
    end: end
  });
}

// Adjust frame presentation timestamps (PTS) by subtracting
// the PTS of the first frame in the segment
function adjustTimestamps (audio = false) {
  return new FilterNode(`${audio ? 'a' : ''}setpts`, {
    expr: 'PTS-STARTPTS'
  });
}

// Concatenate the video (and audio) streams together
function concatenateStreams ({ video, audio }) {
  hasAudio = typeof audio !== 'undefined' && audio.length > 0
  if (hasAudio && video.length !== audio.length) {
    throw new Error('Must have same number of streams of each type.')
  }
  const concatNode = new FilterNode('concat', {
    n: video.length,
    v: 1,
    a: hasAudio ? 1 : 0
  });
  const concatenator = new FilterChain([concatNode]);
  for (let n = 0; n < video.length; n++) {
    concatenator.addInput(video[n].streamSpecifier());
    if (hasAudio) concatenator.addInput(audio[n].streamSpecifier());
  }
  return concatenator;
}

const input = new FFmpegInput('video.mp4');

const segment1Video = new FilterChain([trimStream(1, 2), adjustTimestamps()]);
segment1Video.addInput(input.streamSpecifier('v'));

const segment1Audio = new FilterChain([trimStream(1, 2, true), adjustTimestamps(true)]);
segment1Audio.addInput(input.streamSpecifier('a'));

const segment2Video = new FilterChain([trimStream(120, 125), adjustTimestamps()]);
segment2Video.addInput(input.streamSpecifier('v'));

const segment2Audio = new FilterChain([trimStream(120, 125, true), adjustTimestamps(true)]);
segment2Audio.addInput(input.streamSpecifier('a'));

const concatenator = concatenateStreams({
  video: [segment1Video, segment2Video],
  audio: [segment1Audio, segment2Audio]
});

const cmd = new FFmpegCommand();

cmd.addInput(input);

cmd.addFilterChain(segment1Video);
cmd.addFilterChain(segment1Audio);
cmd.addFilterChain(segment2Video);
cmd.addFilterChain(segment2Audio);
cmd.addFilterChain(concatenator);

const output = new FFmpegOutput('output.mp4');
output.addStreams([
  concatenator.streamSpecifier('v'),
  concatenator.streamSpecifier('a')
]);

cmd.addOutput(output);

console.log(cmd.toString());
/* output:
ffmpeg -i "video.mp4" -filter_complex "[0:v]trim=start=1:end=2,setpts=expr=PTS-STARTPTS[chain0_setpts_0];[0:a]atrim=start=1:end=2,asetpts=expr=PTS-STARTPTS[chain1_asetpts_0];[0:v]trim=start=120:end=125,setpts=expr=PTS-STARTPTS[chain2_setpts_0];[0:a]atrim=start=120:end=125,asetpts=expr=PTS-STARTPTS[chain3_asetpts_0];[chain0_setpts_0][chain1_asetpts_0][chain2_setpts_0][chain3_asetpts_0]concat=n=2:v=1:a=1[chain4_concat_0][chain4_concat_1]" -map "[chain4_concat_0]" -map "[chain4_concat_1]" "output.mp4"
*/

/*
// To execute:
cmd
  .execute()
  .then(({ stderr, stdout }) => {
    // do something with logs from the run
  });
*/