Test script to demonstrate EC-3 box transformation from Microsoft Smooth Streaming CodecPrivateData

ddp_codeprivatedata_parser.go

package main

import (
	"bytes"
	"encoding/hex"
	"log"

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

// based on https://github.com/axiomatic-systems/Bento4/blob/3bdc891602d19789b8e8626e4a3e613a937b4d35/Source/Python/utils/mp4utils.py#L1047-L1054
// MFA GUID from https://www.magnumdb.com/search?q=filename%3A"mfapi.h"

var DDP_WAVEFORMAT_GUID = []byte{0xaf, 0x87, 0xfb, 0xa7, 0x02, 0x2d, 0xfb, 0x42, 0xa4, 0xd4, 0x05, 0xcd, 0x93, 0x84, 0x3b, 0xdd}

func main() {
	customPrivateDataHex := "000603000000AF87FBA7022DFB42A4D405CD93843BDD0600200400"
	customPrivateData, _ := hex.DecodeString(customPrivateDataHex)
	dec3Payload := extractDolbyDigitalPlusInfoFromSmoothData(customPrivateData)
	dec3Box, err := mp4.DecodeDec3(mp4.BoxHeader{}, 0, bytes.NewReader(dec3Payload))
	if err != nil {
		panic(err)
	}
	log.Printf("Dec3 box: %+v", dec3Box)
}

func extractDolbyDigitalPlusInfoFromSmoothData(info []byte) []byte {
	if bytes.Compare(info[8:24], DDP_WAVEFORMAT_GUID) != 1 {
		panic("Missing DDP_WAVEFORMAT_GUID")
	}

	dec3Payload := info[6+len(DDP_WAVEFORMAT_GUID):]

	return dec3Payload
}