Node.js script to add a subtitles track to a mp4 from an srt file.

subtitles.js

#!/usr/local/bin/node

const readline = require('readline');
var exec = require('child_process').exec;
var path = require('path');

const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout
});

rl.question('Video file: ', (videoPath) => {

    var videoFile = path.parse(videoPath.trim().replace(/\\(?!\\)/g, ""));

    rl.question('Subtitles file: ', (subtitlesPath) => {

        var subtitlesFile = path.parse(subtitlesPath.trim().replace(/\\(?!\\)/g, ""));

        if (subtitlesFile.ext != ".srt") {
            console.log("⚠️  Subtitles must be in .srt format!");
            rl.close();
            return;
        }

        rl.question('Output file: [same as input] ', (outputPath) => {

            var outputFile = path.parse((outputPath ? outputPath : videoPath).trim().replace(/\\(?!\\)/g, ""));

            if (!outputPath) {
                outputFile.name += " (subtitled)";
                outputFile.base = outputFile.name + outputFile.ext;
            }

            console.log("🚀  Running...");

            exec("ffmpeg -i \"" + path.format(videoFile) + "\" -f srt -i \"" + path.format(subtitlesFile) + "\" -c:v copy -c:a copy -c:s mov_text \"" + path.format(outputFile) + "\"", function(error, stdout, stderr) {
                
                if (error) {
                    console.log(error);
                    console.log(stdout);
                    console.log(stderr);
                    console.log("❌  Something went wrong!");
                }
                else {
                    console.log("Done! 🍿  😎")
                }

            }).stdin.write("y\n");

            rl.close();

        });

    });

});