dev.transpose.js

const fs = require('fs');
const TRAKTKHDSIGN = Buffer.from([0x74, 0x72, 0x61, 0x6B, 0x00, 0x00, 0x00, 0x5C, 0x74, 0x6B, 0x68, 0x64]);
const LASTSIGN = Buffer.from([0x40]);
const VIDESIGN = Buffer.from([0x76, 0x69, 0x64, 0x65]);
async function transpose(rotate) {
    const rotateMartix = {
        "90": Buffer.from([0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40]),
        "180": Buffer.from([0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40]),
        "270": Buffer.from([0x00, 0x00, 0x00, 0x00, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40]),
        "0": Buffer.from([0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40]),
    }[rotate];
    const mp4Buffer = await fs.promises.readFile('./demo.mp4');
    mp4Buffer.reverse();
    const r_videIndex = mp4Buffer.indexOf(VIDESIGN.reverse());
    const r_tkhdIndex = mp4Buffer.indexOf(TRAKTKHDSIGN.reverse(), r_videIndex);
    const tkhdIndex = mp4Buffer.length - r_tkhdIndex - TRAKTKHDSIGN.length;
    mp4Buffer.reverse();
    const lastIndex = mp4Buffer.indexOf(LASTSIGN, tkhdIndex);
    const martixBegin = lastIndex - 32;
    const martixEnd = lastIndex + 1;
    const newMp4 = Buffer.concat([
        mp4Buffer.slice(0, martixBegin),
        rotateMartix,
        mp4Buffer.slice(martixEnd),
    ]);
    return newMp4;
}
transpose('0').then(value => {
    fs.promises.writeFile('./output.mp4', value);
})