index.js

const fs = require('fs')
const NodeID3 = require('node-id3')

const buffer = fs.readFileSync('./AVAA - Watch Me TEST.aif')

const id3ChunkPosition = indexOfID3ChunkPosition(buffer)
const chunk = sliceChunk(buffer, id3ChunkPosition);
const id3Buffer = chunk.subarray(8)

let newId3Buffer = NodeID3.update({
    title: "a"
}, id3Buffer)

const newFileBuffer = Buffer.concat([
    buffer.subarray(0, id3ChunkPosition),
    Buffer.from([0x49, 0x44, 0x33, 0x20]),
    getChunkSizeBuffer(newId3Buffer),
    newId3Buffer,
    buffer.subarray(
        id3ChunkPosition + 8 + chunk.length
    )
])

fs.writeFileSync('./newfile.aif', newFileBuffer)



/**
 * Find an ID3 chunk with an ID3 Tag inside.
 * [I D 3 f s s s s I D 3 v]
 * where s is size byte and v is version byte.
 */
function indexOfID3ChunkPosition(buffer) {
    let chunkPosition = -1

    do {
        chunkPosition = buffer.indexOf("ID3", chunkPosition + 1)
        if(
            chunkPosition !== -1 &&
            Buffer.from("ID3").compare(
                buffer,
                chunkPosition + 9,  // ID3 Tag start
                chunkPosition + 12  // ID3 ID end
            ) &&
            [2, 3, 4].includes(buffer[chunkPosition + 11]) // ID3 version
        ) {
            return chunkPosition
        }
    } while (chunkPosition !== -1)

    return -1
}

function sliceChunk(buffer, position) {
    const length = buffer.readUInt32BE(position + 4)
    return buffer.subarray(position, position + length)
}

function getChunkSizeBuffer(buffer) {
    const sizeBuffer = Buffer.alloc(4, 0x00)
    sizeBuffer.writeUInt32BE(buffer.length)
    return sizeBuffer
}