diff --git a/dev/demux.html b/dev/demux.html
index d25eea3..3dbf8a4 100644
--- a/dev/demux.html
+++ b/dev/demux.html
@@ -37,14 +37,22 @@
 		});
 
 		const audioTrack = await input.getPrimaryAudioTrack();
+		const drain = new Metamuxer.EncodedAudioChunkDrain(audioTrack);
+
+		for await (const chunk of drain.chunks()) {
+			console.log(chunk);
+		}
+		console.log("Done??")
+
+
+		/*
 		const drain = new Metamuxer.AudioBufferDrain(audioTrack);
 
 		const chunks = drain.buffers()
 		const a = chunks.next();
+		*/
 
 		//chunks.return();
-
-		console.log(await a)
 		
 		//console.log("Done")
 
diff --git a/src/isobmff/isobmff-demuxer.ts b/src/isobmff/isobmff-demuxer.ts
index 2677b03..d4d08d3 100644
--- a/src/isobmff/isobmff-demuxer.ts
+++ b/src/isobmff/isobmff-demuxer.ts
@@ -41,7 +41,8 @@ type InternalTrack = {
 	demuxer: IsobmffDemuxer;
 	inputTrack: InputTrack | null;
 	timescale: number;
-	durationInTimescale: number;
+	durationInMovieTimescale: number;
+	durationInMediaTimescale: number;
 	rotation: Rotation;
 	sampleTableOffset: number;
 	sampleTable: SampleTable | null;
@@ -458,6 +459,7 @@ export class IsobmffDemuxer extends Demuxer {
 						} else {
 							// We already know this fragment
 							const fragment = this.fragments[index]!;
+							// Even if we already know the fragment, we might not yet know its predecessor
 							if (currentFragment) currentFragment.nextFragment = fragment;
 							currentFragment = fragment;
 						}
@@ -527,7 +529,8 @@ export class IsobmffDemuxer extends Demuxer {
 					inputTrack: null,
 					info: null,
 					timescale: -1,
-					durationInTimescale: -1,
+					durationInMovieTimescale: -1,
+					durationInMediaTimescale: -1,
 					rotation: 0,
 					sampleTableOffset: -1,
 					sampleTable: null,
@@ -582,11 +585,13 @@ export class IsobmffDemuxer extends Demuxer {
 				if (version === 0) {
 					this.isobmffReader.pos += 8;
 					track.id = this.isobmffReader.readU32();
-					this.isobmffReader.pos += 8;
+					this.isobmffReader.pos += 4;
+					track.durationInMovieTimescale = this.isobmffReader.readU32();
 				} else if (version === 1) {
 					this.isobmffReader.pos += 16;
 					track.id = this.isobmffReader.readU32();
-					this.isobmffReader.pos += 12;
+					this.isobmffReader.pos += 4;
+					track.durationInMovieTimescale = this.isobmffReader.readU64();
 				} else {
 					throw new Error(`Incorrect track header version ${version}.`);
 				}
@@ -601,7 +606,7 @@ export class IsobmffDemuxer extends Demuxer {
 					return x[0] === values[0] && x[1] === values[1] && x[3] === values[2] && x[4] === values[3];
 				});
 				if (matrixIndex === -1) {
-					// console.warn(`Wacky rotation matrix ${rotationMatrix}; sticking with no rotation.`);
+					console.warn(`Wacky rotation matrix ${values.join(',')}; sticking with no rotation.`);
 					track.rotation = 0;
 				} else {
 					track.rotation = (90 * matrixIndex) as Rotation;
@@ -618,11 +623,11 @@ export class IsobmffDemuxer extends Demuxer {
 				if (version === 0) {
 					this.isobmffReader.pos += 8;
 					track.timescale = this.isobmffReader.readU32();
-					track.durationInTimescale = this.isobmffReader.readU32();
+					track.durationInMediaTimescale = this.isobmffReader.readU32();
 				} else if (version === 1) {
 					this.isobmffReader.pos += 16;
 					track.timescale = this.isobmffReader.readU32();
-					track.durationInTimescale = this.isobmffReader.readU64();
+					track.durationInMediaTimescale = this.isobmffReader.readU64();
 				}
 			}; break;
 
@@ -2046,10 +2051,11 @@ abstract class IsobmffTrackBacking<Chunk extends EncodedVideoChunk | EncodedAudi
 			} else {
 				const fragment = this.internalTrack.fragments[fragmentIndex]!;
 
-				if (!lookupEntry || fragment.moofOffset >= fragment.moofOffset) {
+				if (!lookupEntry || fragment.moofOffset >= lookupEntry.moofOffset) {
 					isobmffReader.pos = fragment.moofOffset + fragment.moofSize;
 					prevFragment = fragment;
 				} else {
+					// Use the lookup entry
 					isobmffReader.pos = lookupEntry.moofOffset;
 				}
 			}
@@ -2078,29 +2084,31 @@ abstract class IsobmffTrackBacking<Chunk extends EncodedVideoChunk | EncodedAudi
 				if (boxInfo.name === 'moof') {
 					const index = binarySearchExact(demuxer.fragments, startPos, x => x.moofOffset);
 
+					let fragment: Fragment;
 					if (index === -1) {
 						// This is the first time we've seen this fragment
 						isobmffReader.pos = startPos;
 
-						const fragment = await demuxer.readFragment();
+						fragment = await demuxer.readFragment();
 						if (prevFragment) prevFragment.nextFragment = fragment;
 						prevFragment = fragment;
-
-						const { fragmentIndex, sampleIndex, correctSampleFound } = getBestMatch();
-						if (correctSampleFound) {
-							const fragment = this.internalTrack.fragments[fragmentIndex]!;
-							return this.fetchChunkInFragment(fragment, sampleIndex, options);
-						}
-						if (fragmentIndex !== -1) {
-							bestFragmentIndex = fragmentIndex;
-							bestSampleIndex = sampleIndex;
-						}
 					} else {
 						// We already know this fragment
-						const fragment = demuxer.fragments[index]!;
+						fragment = demuxer.fragments[index]!;
+						// Even if we already know the fragment, we might not yet know its predecessor
 						if (prevFragment) prevFragment.nextFragment = fragment;
 						prevFragment = fragment;
 					}
+
+					const { fragmentIndex, sampleIndex, correctSampleFound } = getBestMatch();
+					if (correctSampleFound) {
+						const fragment = this.internalTrack.fragments[fragmentIndex]!;
+						return this.fetchChunkInFragment(fragment, sampleIndex, options);
+					}
+					if (fragmentIndex !== -1) {
+						bestFragmentIndex = fragmentIndex;
+						bestSampleIndex = sampleIndex;
+					}
 				}
 
 				isobmffReader.pos = startPos + boxInfo.totalSize;
diff --git a/src/isobmff/isobmff-reader.ts b/src/isobmff/isobmff-reader.ts
index 2a3930e..1438643 100644
--- a/src/isobmff/isobmff-reader.ts
+++ b/src/isobmff/isobmff-reader.ts
@@ -62,6 +62,12 @@ export class IsobmffReader {
 		return high * 0x100000000 + low;
 	}
 
+	readI64() {
+		const high = this.readI32();
+		const low = this.readU32();
+		return high * 0x100000000 + low;
+	}
+
 	readF64() {
 		const { view, offset } = this.reader.getViewAndOffset(this.pos, this.pos + 8);
 		this.pos += 8;
diff --git a/src/media-drain.ts b/src/media-drain.ts
index 4b12ddc..9c462f2 100644
--- a/src/media-drain.ts
+++ b/src/media-drain.ts
@@ -431,7 +431,7 @@ export abstract class BaseMediaFrameDrain<
 			}
 
 			const chunks = chunkDrain.chunks(keyChunk, chunksEndTimestamp);
-			await chunks.next();
+			await chunks.next(); // Skip the start chunk as we already have it
 
 			while (currentChunk && !ended) {
 				if (frameQueue.length + decoder.getDecodeQueueSize() > MAX_QUEUE_SIZE) {