Add Opus support to ISOBMFF demuxer

dev/demux.html

@@ -4,6 +4,27 @@
 	const fileInput = document.createElement('input');
 	fileInput.type = 'file';
 	document.body.append(fileInput);
+	
+	const encoder = new AudioEncoder({
+		output: console.log,
+		error: console.error
+	});
+	encoder.configure({
+		codec: 'vorbis',
+		numberOfChannels: 2,
+		sampleRate: 48000,
+		bitrate: 128000
+	});
+
+	let audioData = new AudioData({
+		format: 'f32',
+		numberOfChannels: 2,
+		sampleRate: 48000,
+		timestamp: 0,
+		data: new Float32Array(2 * 48000),
+		numberOfFrames: 48000
+	});
+	encoder.encode(audioData);
 
 	fileInput.addEventListener('change', async () => {
 		const file = fileInput.files[0];
@@ -16,7 +37,9 @@
 		const audioTrack = await input.getPrimaryAudioTrack();
 		const drain = new Metamuxer.EncodedAudioChunkDrain(audioTrack);
 
-		console.log(await drain.getFirstChunk());
+		for await (const chunk of drain.chunks()) {
+			console.log(chunk)
+		}
 
 		/*
 		const videoTrack = await input.getPrimaryVideoTrack();

src/isobmff/isobmff-boxes.ts

@@ -751,6 +751,7 @@ export const dOps = (trackData: IsobmffAudioTrackData) => {
 		gain = view.getInt16(14, true);
 	}
 
+	// https://www.opus-codec.org/docs/opus_in_isobmff.html
 	return box('dOps', [
 		u8(0), // Version
 		u8(trackData.info.numberOfChannels), // OutputChannelCount

src/isobmff/isobmff-demuxer.ts

@@ -1017,6 +1017,56 @@ export class IsobmffDemuxer extends Demuxer {
 				}
 			}; break;
 
+			case 'dOps': { // Used for Opus audio
+				const track = this.currentTrack;
+				assert(track && track.info?.type === 'audio');
+
+				// TODO TEMP
+				/*
+				const bytes = this.isobmffReader.readBytes(boxInfo.contentSize);
+				const description2 = new Uint8Array(8 + bytes.byteLength);
+				const view2 = new DataView(description2.buffer);
+				view2.setUint32(0, 0x4f707573, false); // 'Opus'
+				view2.setUint32(4, 0x646f7073, false); // 'dOps'
+				description2.set(bytes, 8);
+				track.info.codecDescription = description2;
+				break;
+				*/
+
+				this.isobmffReader.pos += 1; // Version
+
+				// https://www.opus-codec.org/docs/opus_in_isobmff.html
+				const outputChannelCount = this.isobmffReader.readU8();
+				const preSkip = this.isobmffReader.readU16();
+				const inputSampleRate = this.isobmffReader.readU32();
+				const outputGain = this.isobmffReader.readI16();
+				const channelMappingFamily = this.isobmffReader.readU8();
+
+				let channelMappingTable: Uint8Array;
+				if (channelMappingFamily !== 0) {
+					channelMappingTable = this.isobmffReader.readBytes(2 + outputChannelCount);
+				} else {
+					channelMappingTable = new Uint8Array(0);
+				}
+
+				// https://datatracker.ietf.org/doc/html/draft-ietf-codec-oggopus-06
+				const description = new Uint8Array(8 + 1 + 1 + 2 + 4 + 2 + 1 + channelMappingTable.byteLength);
+				const view = new DataView(description.buffer);
+				view.setUint32(0, 0x4f707573, false); // 'Opus'
+				view.setUint32(4, 0x48656164, false); // 'Head'
+				view.setUint8(8, 1); // Version
+				view.setUint8(9, outputChannelCount);
+				view.setUint16(10, preSkip, true);
+				view.setUint32(12, inputSampleRate, true);
+				view.setInt16(16, outputGain, true);
+				view.setUint8(18, channelMappingFamily);
+				description.set(channelMappingTable, 19);
+
+				track.info.codecDescription = description;
+				track.info.numberOfChannels = outputChannelCount;
+				track.info.sampleRate = inputSampleRate;
+			}; break;
+
 			case 'dfLa': { // Used for FLAC audio
 				const track = this.currentTrack;
 				assert(track && track.info?.type === 'audio');
@@ -1063,10 +1113,8 @@ export class IsobmffDemuxer extends Demuxer {
 				const bytes = this.isobmffReader.readBytes(endPos - startPos);
 
 				const description = new Uint8Array(4 + bytes.byteLength);
-				description[0] = 0x66; // f
-				description[1] = 0x4C; // L
-				description[2] = 0x61; // a
-				description[3] = 0x43; // C
+				const view = new DataView(description.buffer);
+				view.setUint32(0, 0x664c6143, false); // 'fLaC'
 				description.set(bytes, 4);
 
 				// Set the codec description to be 'fLaC' + all metadata blocks

src/isobmff/isobmff-reader.ts

@@ -26,6 +26,13 @@ export class IsobmffReader {
 		return view.getUint16(offset, false);
 	}
 
+	readI16() {
+		const { view, offset } = this.reader.getViewAndOffset(this.pos, this.pos + 2);
+		this.pos += 2;
+
+		return view.getInt16(offset, false);
+	}
+
 	readU24() {
 		const { view, offset } = this.reader.getViewAndOffset(this.pos, this.pos + 3);
 		this.pos += 3;

src/media-drain.ts

@@ -882,7 +882,9 @@ class PcmAudioDecoderWrapper extends DecoderWrapper<EncodedAudioChunk, AudioData
 			numberOfFrames,
 			timestamp: chunk.timestamp,
 		});
-		this.onMedia(audioData);
+
+		// Since all other decoders are async, we'll make this one behave async as well
+		queueMicrotask(() => this.onMedia(audioData));
 	}
 
 	async flush() {