AWS ffmpeg-lambda-layer and concat protocol (Node.js)

Question

I am trying to concatenate two.mp3 files using ffmpeg lambda-layer. I have what I think is the correct command, but I struggle to represent it in code so that it is formatted correctly for the lambda layer. Here is a piece of code that I am struggling to get right:

spawnSync(
  '/opt/ffmpeg/ffmpeg',
  [
    '-i',
    '"concat:/tmp/pt1.mp3|/tmp/pt2.mp3"',
    '-acodec',
    'copy',
    `/tmp/${fileName}`
  ],
  { stdio: 'inherit' }
)

The error I'm getting: "concat:/tmp/pt1.mp3|/tmp/pt2.mp3": No such file or directory .

I tried to list files in /tmp/ folder - both files listed in the input are there, not sure why lambda layer can't find them.

Similar question: https://lists.ffmpeg.org/pipermail/ffmpeg-user/2019-December/046299.html . Ffmpeg concatenate protocol documentation: https://trac.ffmpeg.org/wiki/Concatenate#protocol .

Thanks in advance!

Answer 1

Update: Was able to solve this by using concat demuxer istead of concat protocol. Docs: https://trac.ffmpeg.org/wiki/Concatenate#demuxer

It requires.txt file with the list of input files so I had to create one. Here is my solution:

// in the head of the file
const { writeFile } = require('fs')
const { promisify } = require('util')

const asyncWriteFile = promisify(writeFile)

// ...

await asyncWriteFile('/tmp/list.txt', 'file \'/tmp/pt1.mp3\'\r\nfile \'/tmp/pt2.mp3\'', (err) => {
 if (err)
  console.log(err)
})

// concat
spawnSync(
 '/opt/ffmpeg/ffmpeg',
 [
   '-f',
   'concat',
   '-safe',
   '0',
   '-i',
   '/tmp/list.txt',
   '-c',
   'copy',
   `/tmp/${fileName}`
  ],
  { stdio: 'inherit' }
)