From 5dda43959dbd27e00407ec1837f90acce4a4307a Mon Sep 17 00:00:00 2001
From: Vanilagy <1696106+Vanilagy@users.noreply.github.com>
Date: Thu, 2 Jan 2025 15:42:04 +0100
Subject: [PATCH] Support mp4a.67

---
 src/codec.ts                   | 25 +++++++++++++++++++++----
 src/isobmff/isobmff-demuxer.ts |  8 ++++++--
 2 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/src/codec.ts b/src/codec.ts
index 4678ff1..21cb074 100644
--- a/src/codec.ts
+++ b/src/codec.ts
@@ -2,6 +2,7 @@ import {
 	COLOR_PRIMARIES_MAP,
 	MATRIX_COEFFICIENTS_MAP,
 	TRANSFER_CHARACTERISTICS_MAP,
+	assert,
 	bytesToHexString,
 	isAllowSharedBufferSource,
 	last,
@@ -392,10 +393,26 @@ export const buildAudioCodecString = (codec: AudioCodec, numberOfChannels: numbe
 	throw new TypeError(`Unhandled codec '${codec}'.`);
 };
 
-export const extractAudioCodecString = (codec: AudioCodec, description: Uint8Array | null) => {
+export type AacCodecInfo = {
+	isMpeg2: boolean;
+};
+
+export const extractAudioCodecString = (trackInfo: {
+	codec: AudioCodec | null;
+	codecDescription: Uint8Array | null;
+	aacCodecInfo: AacCodecInfo | null;
+}) => {
+	const { codec, codecDescription, aacCodecInfo } = trackInfo;
+
 	if (codec === 'aac') {
-		const audioSpecificConfig = parseAacAudioSpecificConfig(description);
-		return `mp4a.40.${audioSpecificConfig.objectType}`;
+		assert(aacCodecInfo);
+
+		if (aacCodecInfo.isMpeg2) {
+			return 'mp4a.67';
+		} else {
+			const audioSpecificConfig = parseAacAudioSpecificConfig(codecDescription);
+			return `mp4a.40.${audioSpecificConfig.objectType}`;
+		}
 	} else if (codec === 'mp3') {
 		return 'mp3';
 	} else if (codec === 'opus') {
@@ -404,7 +421,7 @@ export const extractAudioCodecString = (codec: AudioCodec, description: Uint8Arr
 		return 'vorbis';
 	} else if (codec === 'flac') {
 		return 'flac';
-	} else if (codec.startsWith('pcm-')) {
+	} else if (codec?.startsWith('pcm-')) {
 		return codec;
 	} else if (codec === 'ulaw') {
 		return 'ulaw';
diff --git a/src/isobmff/isobmff-demuxer.ts b/src/isobmff/isobmff-demuxer.ts
index ec54106..ed03f46 100644
--- a/src/isobmff/isobmff-demuxer.ts
+++ b/src/isobmff/isobmff-demuxer.ts
@@ -1,4 +1,5 @@
 import {
+	AacCodecInfo,
 	AudioCodec,
 	Av1CodecInfo,
 	extractAudioCodecString,
@@ -67,6 +68,7 @@ type InternalTrack = {
 		sampleRate: number;
 		codec: AudioCodec | null;
 		codecDescription: Uint8Array | null;
+		aacCodecInfo: AacCodecInfo | null;
 	};
 });
 
@@ -647,6 +649,7 @@ export class IsobmffDemuxer extends Demuxer {
 						sampleRate: -1,
 						codec: null,
 						codecDescription: null,
+						aacCodecInfo: null,
 					};
 				}
 			}; break;
@@ -972,8 +975,9 @@ export class IsobmffDemuxer extends Demuxer {
 				const payloadStart = this.isobmffReader.pos;
 
 				const objectTypeIndication = this.isobmffReader.readU8();
-				if (objectTypeIndication === 0x40) {
+				if (objectTypeIndication === 0x40 || objectTypeIndication === 0x67) {
 					track.info.codec = 'aac';
+					track.info.aacCodecInfo = { isMpeg2: objectTypeIndication === 0x67 };
 				} else if (objectTypeIndication === 0x69 || objectTypeIndication === 0x6b) {
 					track.info.codec = 'mp3';
 				} else if (objectTypeIndication === 0xdd) {
@@ -2179,7 +2183,7 @@ class IsobmffAudioTrackBacking extends IsobmffTrackBacking<EncodedAudioChunk> im
 
 	async getDecoderConfig(): Promise<AudioDecoderConfig> {
 		return {
-			codec: extractAudioCodecString(this.internalTrack.info.codec!, this.internalTrack.info.codecDescription),
+			codec: extractAudioCodecString(this.internalTrack.info),
 			numberOfChannels: this.internalTrack.info.numberOfChannels,
 			sampleRate: this.internalTrack.info.sampleRate,
 			description: this.internalTrack.info.codecDescription ?? undefined,