encrypted_initgen.go

package main

import (
	"bytes"
	"encoding/base64"
	"encoding/hex"
	"log"
	"os"
	"regexp"
	"unicode/utf16"

	"github.com/Eyevinn/mp4ff/mp4"
)

var (
	PlayReadyRegexp = regexp.MustCompile(`^.+<KID>([^<]+)</KID>.+$`)
)

// function shamefully stolen from https://github.com/canalplus/DashMe/blob/f1f0bfa654ac1dedb2bf7ffbf8c75772084ae426/src/parser/SmoothDemuxer.go#L309-L334
func extractKeyId(data []byte) []byte {
	/* Convert utf16 to usable byte array */
	shorts := make([]uint16, len(data)/2-5)
	for i := 0; i < len(data)-10; i += 2 {
		shorts[(i)/2] = (uint16(data[i+11]) << 8) | uint16(data[i+10])
	}
	bytes, err := base64.StdEncoding.DecodeString(PlayReadyRegexp.FindStringSubmatch(string(utf16.Decode(shorts)))[1])
	if err != nil {
		return nil
	}
	/* Encode string in hex and convert from GUID to UUID */
	key := hex.EncodeToString(bytes)
	res, err := hex.DecodeString(string([]uint8{
		key[6], key[7], key[4], key[5], key[2], key[3], key[0], key[1],
		key[10], key[11], key[8], key[9],
		key[14], key[15], key[12], key[13],
		key[16], key[17], key[18], key[19],
		key[20], key[21], key[22], key[23], key[24], key[25],
		key[26], key[27], key[28], key[29], key[30], key[31],
	}))
	if err != nil {
		return nil
	}
	return res
}

func main() {
	codecPrivateData, _ := hex.DecodeString("00000001674d40209e52820276028404040500000300010000030064e000057e000afc3f13e0a00000000168ef7520")
	delimiter := []byte{0, 0, 0, 1}
	split := bytes.SplitN(codecPrivateData, delimiter, 3)
	if len(split) != 3 {
		log.Fatal("invalid codecPrivateData")
	}

	spsNALUs := [][]byte{split[1]}
	ppsNALUs := [][]byte{split[2]}

	pssh := "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"
	psshByte, err := base64.StdEncoding.DecodeString(pssh)
	if err != nil {
		log.Fatal(err)
	}
	psshBox := mp4.PsshBox{
		SystemID: mp4.UUID{0x9a, 0x04, 0xf0, 0x79, 0x48, 0x5b, 0x48, 0x5a, 0x8b, 0x6a, 0x4f, 0x14, 0x8f, 0x17, 0x9a, 0x17},
		Data:     psshByte,
	}
	keyId := extractKeyId(psshByte)
	log.Printf("KeyId: %x", keyId)

	videoTimescale := uint32(10000000)
	init := mp4.CreateEmptyInit()
	init.AddEmptyTrack(videoTimescale, "video", "und")
	trak := init.Moov.Trak
	err = trak.SetAVCDescriptor("avc1", spsNALUs, ppsNALUs, true)
	if err != nil {
		log.Fatal(err)
	}
	width := trak.Mdia.Minf.Stbl.Stsd.AvcX.Width
	height := trak.Mdia.Minf.Stbl.Stsd.AvcX.Height
	log.Printf("Width: %d, Height: %d", width, height)

	_, err = mp4.InitProtect(init, nil, nil, "cenc", keyId, []*mp4.PsshBox{&psshBox})
	if err != nil {
		log.Fatal(err)
	}

	outFile, err := os.Create("init.mp4")
	if err != nil {
		log.Fatal(err)
	}
	defer outFile.Close()
	err = init.Encode(outFile)
	if err != nil {
		log.Fatal(err)
	}
}