birdgen/src/concatenateVideos.js

import fs from 'fs'
import exec from './exec.js'
import getArgument from './getArgument.js'

function getExtension(filename) {
    return filename.split('/').pop().split('.').pop()
}

export function getArgs(filename) {
    let extension = getExtension(filename)
    if (extension=='webm') return `-c:v libvpx-vp9 -crf 30 -cpu-used 5 -deadline realtime -vsync 2`
    return `-c:v libx264 -x264-params crf=25 -ar 44100 -vsync 2`
}

export default async function concatenateVideos(filenames, outfile) {
    const chunkSize = getArgument('chunk-size')??40
    console.log(`Joining every ${chunkSize} clips`)
    let chunks = []
    for (let i = 0; i < filenames.length; i += chunkSize) {
        const ffmpegArgs = getArgs(outfile)
        const filenamesSlice = filenames.slice(i, i + chunkSize)
        const inputs = filenamesSlice.map(e => `-i "${e}"`).join(' ')
        const filter = filenamesSlice.map((e, i) => `[${i}:v:0][${i}:a:0]`).join('')
        const chunkFile = `${__dirname}/tmp/chunk-${i}.${getExtension(outfile)}`
        const execScript = `ffmpeg -y ${inputs} -filter_complex "${filter}concat=n=${filenamesSlice.length}:v=1:a=1[outv][outa]" -map "[outv]" -map "[outa]" ${ffmpegArgs} "${chunkFile}"`
        process.stdout.clearLine()
        process.stdout.cursorTo(0)
        process.stdout.write(`Starting chunk ${Math.floor(i/chunkSize)+1} of ${Math.ceil(filenames.length/chunkSize)}`)
        process.stdout.cursorTo(0)
        await exec(execScript, {
            maxBuffer: 5 * 1024 * 1024
        })
        process.stdout.clearLine()
        process.stdout.cursorTo(0)
        process.stdout.write(`Completed chunk ${Math.floor(i/chunkSize)+1} of ${Math.ceil(filenames.length/chunkSize)}`)
        process.stdout.cursorTo(0)
        chunks.push(chunkFile)
    }
    if (chunks.length>1) {
        const ffmpegArgs = getArgs(outfile)
        console.log(`\nJoining all ${Math.ceil(filenames.length/chunkSize)} chunks`)
        const inputs = chunks.map(e => `-i "${e}"`).join(' ')
        const filter = chunks.map((e, i) => `[${i}:v:0][${i}:a:0]`).join('')
        const execScript = `ffmpeg -y ${inputs} -filter_complex "${filter}concat=n=${chunks.length}:v=1:a=1[outv][outa]" -map "[outv]" -map "[outa]" ${ffmpegArgs} "${outfile}"`
        console.log(execScript)
        await exec(execScript, {
            maxBuffer: 5 * 1024 * 1024
        })
    } else {
        fs.promises.rename(chunks[0], outfile)
    }
    console.log('Complete.')
}