Add longer variant to VideoSample.draw

dev/demux.html

@@ -15,14 +15,21 @@
 			formats: Mediabunny.ALL_FORMATS,
 			source
 		});
+
+		const canvas = document.createElement('canvas');
+		canvas.width = 1920;
+		canvas.height = 1080;
+		canvas.style.background = 'ghostwhite';
+		const ctx = canvas.getContext('2d');
+		document.body.append(canvas);
 		
 		const videoTrack = await input.getPrimaryVideoTrack();
+		const sink = new Mediabunny.VideoSampleSink(videoTrack);
 
-		const sink = new Mediabunny.EncodedPacketSink(videoTrack);
-		for await (const packet of sink.packets()) {
-			if (packet.timestamp >= 2) break;
-			console.log(packet);
-		}
+		const sample = await sink.getSample(3);
+		console.log(sample);
+
+		sample.draw(ctx, 1500, 500, 50, 50, 0, 0);
 
 		/*
 		let timestamps = [];

docs/guide/packets-and-samples.md

@@ -309,17 +309,29 @@ The `VideoFrame` returned by this method **must** be closed separately from the
 
 ---
 
-It's also common to draw video samples to a `<canvas>` element or an `OffscreenCanvas`. For this, you can use the following method:
+It's also common to draw video samples to a `<canvas>` element or an `OffscreenCanvas`. For this, you can use the following methods:
 ```ts
 draw(
 	context: CanvasRenderingContext2D | OffscreenCanvasRenderingContext2D,
 	dx: number,
 	dy: number,
-	dWidth?: number,
-	dHeight?: number,
+	dWidth?: number, // defaults to displayWidth
+	dHeight?: number, // defaults to displayHeight
+): void;
+
+draw(
+	context: CanvasRenderingContext2D | OffscreenCanvasRenderingContext2D,
+	sx: number,
+	sy: number,
+	sWidth: number,
+	sHeight: number,
+	dx: number,
+	dy: number,
+	dWidth?: number, // defaults to sWidth
+	dHeight?: number, // defaults to sHeight
 ): void;
 ```
-This method is similar to [drawImage](https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/drawImage) and paints the video frame at the given position with the given dimensions. If the dimensions aren't specified, they will default to the display dimensions. This method will automatically draw the frame with the correct rotation based on its `rotation` property.
+These methods behave like [drawImage](https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/drawImage) and paint the video frame at the given position with the given dimensions. This method will automatically draw the frame with the correct rotation based on its `rotation` property.
 
 If you want to draw the raw underlying image to a canvas directly (without respecting the rotation metadata), then you can use the following method:
 ```ts

examples/live-recording/live-recording.ts

@@ -85,7 +85,7 @@ const startRecording = async () => {
 
 		// Add the video track, with the canvas as the source
 		videoSource = new CanvasSource(canvas, {
-			codec: 'vp9',
+			codec: 'avc',
 			bitrate: QUALITY_MEDIUM,
 			keyFrameInterval: 0.5,
 			latencyMode: 'realtime', // Allow the encoder to skip frames to keep up with real-time constraints

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "mediabunny",
-  "version": "1.0.5",
+  "version": "1.1.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "mediabunny",
-      "version": "1.0.5",
+      "version": "1.1.0",
       "license": "MPL-2.0",
       "dependencies": {
         "@types/dom-mediacapture-transform": "^0.1.11",

package.json

@@ -1,7 +1,7 @@
 {
   "name": "mediabunny",
   "author": "Vanilagy",
-  "version": "1.0.5",
+  "version": "1.1.0",
   "description": "Pure TypeScript media toolkit for reading, writing, and converting media files, directly in the browser.",
   "type": "module",
   "main": "./dist/bundles/mediabunny.cjs",

src/input-format.ts

@@ -13,6 +13,7 @@ import { IsobmffReader } from './isobmff/isobmff-reader';
 import { EBMLId, EBMLReader } from './matroska/ebml';
 import { MatroskaDemuxer } from './matroska/matroska-demuxer';
 import { Mp3Demuxer } from './mp3/mp3-demuxer';
+import { FRAME_HEADER_SIZE } from './mp3/mp3-misc';
 import { Mp3Reader } from './mp3/mp3-reader';
 import { OggDemuxer } from './ogg/ogg-demuxer';
 import { OggReader } from './ogg/ogg-reader';
@@ -245,9 +246,10 @@ export class Mp3InputFormat extends InputFormat {
 		}
 
 		// Fine, we found one frame header, but we're still not entirely sure this is MP3. Let's check if we can find
-		// another header nearby:
+		// another header right after it:
 		mp3Reader.pos = firstHeader.startPos + firstHeader.totalSize;
-		const secondHeader = mp3Reader.readNextFrameHeader(Math.min(framesStartPos + 4096, sourceSize));
+		await mp3Reader.reader.loadRange(mp3Reader.pos, mp3Reader.pos + FRAME_HEADER_SIZE);
+		const secondHeader = mp3Reader.readNextFrameHeader(mp3Reader.pos + FRAME_HEADER_SIZE);
 		if (!secondHeader) {
 			return false;
 		}
@@ -257,7 +259,7 @@ export class Mp3InputFormat extends InputFormat {
 			return false;
 		}
 
-		// We have found two matching MP3 frames, a strong indicator that this is an MP3 file
+		// We have found two matching consecutive MP3 frames, a strong indicator that this is an MP3 file
 		return true;
 	}
 

src/isobmff/isobmff-demuxer.ts

@@ -54,6 +54,7 @@ import {
 	isIso639Dash2LanguageCode,
 	roundToMultiple,
 	normalizeRotation,
+	Bitstream,
 } from '../misc';
 import { EncodedPacket, PLACEHOLDER_DATA } from '../packet';
 import { Reader } from '../reader';
@@ -74,6 +75,7 @@ type InternalTrack = {
 	fragmentLookupTable: FragmentLookupTableEntry[] | null;
 	currentFragmentState: FragmentTrackState | null;
 	fragments: Fragment[];
+	fragmentsWithKeyFrame: Fragment[];
 	/** The segment durations of all edit list entries leading up to the main one (from which the offset is taken.) */
 	editListPreviousSegmentDurations: number;
 	/** The media time offset of the main edit list entry (with media time !== -1) */
@@ -167,6 +169,7 @@ type FragmentTrackState = {
 type FragmentTrackData = {
 	startTimestamp: number;
 	endTimestamp: number;
+	firstKeyFrameTimestamp: number | null;
 	samples: FragmentTrackSample[];
 	presentationTimestamps: {
 		presentationTimestamp: number;
@@ -607,6 +610,7 @@ export class IsobmffDemuxer extends Demuxer {
 					fragmentLookupTable: null,
 					currentFragmentState: null,
 					fragments: [],
+					fragmentsWithKeyFrame: [],
 					editListPreviousSegmentDurations: 0,
 					editListOffset: 0,
 				} satisfies InternalTrack as InternalTrack;
@@ -704,7 +708,6 @@ export class IsobmffDemuxer extends Demuxer {
 						console.warn(
 							'Unsupported edit list: multiple edits are not currently supported. Only using first edit.',
 						);
-
 						break;
 					}
 
@@ -714,7 +717,8 @@ export class IsobmffDemuxer extends Demuxer {
 					}
 
 					if (mediaRate !== 1) {
-						throw new Error('Unsupported edit list: media rate must be 1.');
+						console.warn('Unsupported edit list entry: media rate must be 1.');
+						break;
 					}
 
 					track.editListPreviousSegmentDurations = previousSegmentDurations;
@@ -946,7 +950,8 @@ export class IsobmffDemuxer extends Demuxer {
 							} else if (sampleSize === 16) {
 								track.info.codec = 'pcm-s16be';
 							} else {
-								throw new Error(`Unsupported sample size ${sampleSize} for codec 'twos'.`);
+								console.warn(`Unsupported sample size ${sampleSize} for codec 'twos'.`);
+								track.info.codec = null;
 							}
 						} else if (lowercaseBoxName === 'sowt') {
 							if (sampleSize === 8) {
@@ -954,7 +959,8 @@ export class IsobmffDemuxer extends Demuxer {
 							} else if (sampleSize === 16) {
 								track.info.codec = 'pcm-s16';
 							} else {
-								throw new Error(`Unsupported sample size ${sampleSize} for codec 'sowt'.`);
+								console.warn(`Unsupported sample size ${sampleSize} for codec 'sowt'.`);
+								track.info.codec = null;
 							}
 						} else if (lowercaseBoxName === 'raw ') {
 							track.info.codec = 'pcm-u8';
@@ -1197,7 +1203,8 @@ export class IsobmffDemuxer extends Demuxer {
 						} else if (pcmSampleSize === 32) {
 							track.info.codec = 'pcm-s32';
 						} else {
-							throw new Error(`Invalid ipcm sample size ${pcmSampleSize}.`);
+							console.warn(`Invalid ipcm sample size ${pcmSampleSize}.`);
+							track.info.codec = null;
 						}
 					} else {
 						if (pcmSampleSize === 16) {
@@ -1207,7 +1214,8 @@ export class IsobmffDemuxer extends Demuxer {
 						} else if (pcmSampleSize === 32) {
 							track.info.codec = 'pcm-s32be';
 						} else {
-							throw new Error(`Invalid ipcm sample size ${pcmSampleSize}.`);
+							console.warn(`Invalid ipcm sample size ${pcmSampleSize}.`);
+							track.info.codec = null;
 						}
 					}
 				} else if (track.info.codec === 'pcm-f32be') {
@@ -1219,7 +1227,8 @@ export class IsobmffDemuxer extends Demuxer {
 						} else if (pcmSampleSize === 64) {
 							track.info.codec = 'pcm-f64';
 						} else {
-							throw new Error(`Invalid fpcm sample size ${pcmSampleSize}.`);
+							console.warn(`Invalid fpcm sample size ${pcmSampleSize}.`);
+							track.info.codec = null;
 						}
 					} else {
 						if (pcmSampleSize === 32) {
@@ -1227,7 +1236,8 @@ export class IsobmffDemuxer extends Demuxer {
 						} else if (pcmSampleSize === 64) {
 							track.info.codec = 'pcm-f64be';
 						} else {
-							throw new Error(`Invalid fpcm sample size ${pcmSampleSize}.`);
+							console.warn(`Invalid fpcm sample size ${pcmSampleSize}.`);
+							track.info.codec = null;
 						}
 					}
 				}
@@ -1409,8 +1419,27 @@ export class IsobmffDemuxer extends Demuxer {
 			}; break;
 
 			case 'stz2': {
-				throw new Error('Unsupported.');
-			};
+				const track = this.currentTrack;
+				assert(track);
+
+				if (!track.sampleTable) {
+					break;
+				}
+
+				this.metadataReader.pos += 4; // Version + flags
+				this.metadataReader.pos += 3; // Reserved
+
+				const fieldSize = this.metadataReader.readU8(); // in bits
+				const sampleCount = this.metadataReader.readU32();
+
+				const bytes = this.metadataReader.readBytes(Math.ceil(sampleCount * fieldSize / 8));
+				const bitstream = new Bitstream(bytes);
+
+				for (let i = 0; i < sampleCount; i++) {
+					const sampleSize = bitstream.readBits(fieldSize);
+					track.sampleTable.sampleSizes.push(sampleSize);
+				}
+			}; break;
 
 			case 'stss': {
 				const track = this.currentTrack;
@@ -1639,6 +1668,16 @@ export class IsobmffDemuxer extends Demuxer {
 						);
 						this.currentTrack.fragments.splice(insertionIndex + 1, 0, this.currentFragment);
 
+						const hasKeyFrame = trackData.firstKeyFrameTimestamp !== null;
+						if (hasKeyFrame) {
+							const insertionIndex = binarySearchLessOrEqual(
+								this.currentTrack.fragmentsWithKeyFrame,
+								this.currentFragment.moofOffset,
+								x => x.moofOffset,
+							);
+							this.currentTrack.fragmentsWithKeyFrame.splice(insertionIndex + 1, 0, this.currentFragment);
+						}
+
 						const { currentFragmentState } = this.currentTrack;
 						assert(currentFragmentState);
 
@@ -1737,7 +1776,8 @@ export class IsobmffDemuxer extends Demuxer {
 				assert(track.currentFragmentState);
 
 				if (this.currentFragment.trackData.has(track.id)) {
-					throw new Error('Can\'t have two trun boxes for the same track in one fragment.');
+					console.warn('Can\'t have two trun boxes for the same track in one fragment. Ignoring...');
+					break;
 				}
 
 				const version = this.metadataReader.readU8();
@@ -1774,6 +1814,7 @@ export class IsobmffDemuxer extends Demuxer {
 				const trackData: FragmentTrackData = {
 					startTimestamp: 0,
 					endTimestamp: 0,
+					firstKeyFrameTimestamp: null,
 					samples: [],
 					presentationTimestamps: [],
 					startTimestampIsFinal: false,
@@ -1835,13 +1876,19 @@ export class IsobmffDemuxer extends Demuxer {
 					.map((x, i) => ({ presentationTimestamp: x.presentationTimestamp, sampleIndex: i }))
 					.sort((a, b) => a.presentationTimestamp - b.presentationTimestamp);
 
-				// Update sample durations based on presentation order
-				for (let i = 0; i < trackData.presentationTimestamps.length - 1; i++) {
-					const current = trackData.presentationTimestamps[i]!;
-					const next = trackData.presentationTimestamps[i + 1]!;
+				for (let i = 0; i < trackData.presentationTimestamps.length; i++) {
+					const currentEntry = trackData.presentationTimestamps[i]!;
+					const currentSample = trackData.samples[currentEntry.sampleIndex]!;
 
-					const duration = next.presentationTimestamp - current.presentationTimestamp;
-					trackData.samples[current.sampleIndex]!.duration = duration;
+					if (trackData.firstKeyFrameTimestamp === null && currentSample.isKeyFrame) {
+						trackData.firstKeyFrameTimestamp = currentSample.presentationTimestamp;
+					}
+
+					if (i < trackData.presentationTimestamps.length - 1) {
+						// Update sample durations based on presentation order
+						const nextEntry = trackData.presentationTimestamps[i + 1]!;
+						currentSample.duration = nextEntry.presentationTimestamp - currentEntry.presentationTimestamp;
+					}
 				}
 
 				const firstSample = trackData.samples[trackData.presentationTimestamps[0]!.sampleIndex]!;
@@ -2078,13 +2125,13 @@ abstract class IsobmffTrackBacking implements InputTrackBacking {
 							correctSampleFound: true,
 						};
 					} else {
-						// Walk the list of fragments until we find the next fragment for this track
+						// Walk the list of fragments until we find the next fragment for this track with a key frame
 						let currentFragment = locationInFragment.fragment;
 						while (currentFragment.nextFragment) {
 							currentFragment = currentFragment.nextFragment;
 
 							const trackData = currentFragment.trackData.get(this.internalTrack.id);
-							if (trackData) {
+							if (trackData && trackData.firstKeyFrameTimestamp !== null) {
 								const fragmentIndex = binarySearchExact(
 									this.internalTrack.fragments,
 									currentFragment.moofOffset,
@@ -2093,9 +2140,7 @@ abstract class IsobmffTrackBacking implements InputTrackBacking {
 								assert(fragmentIndex !== -1);
 
 								const keyFrameIndex = trackData.samples.findIndex(x => x.isKeyFrame);
-								if (keyFrameIndex === -1) {
-									throw new Error('Not supported: Fragment does not contain key sample.');
-								}
+								assert(keyFrameIndex !== -1); // There must be one
 
 								return {
 									fragmentIndex,
@@ -2235,26 +2280,34 @@ abstract class IsobmffTrackBacking implements InputTrackBacking {
 	}
 
 	private findKeySampleInFragmentsForTimestamp(timestampInTimescale: number) {
-		const fragmentIndex = binarySearchLessOrEqual(
+		const indexInKeyFrameFragments = binarySearchLessOrEqual(
 			// This array is technically not sorted by start timestamp, but for any reasonable file, it basically is.
-			this.internalTrack.fragments,
+			this.internalTrack.fragmentsWithKeyFrame,
 			timestampInTimescale,
 			x => x.trackData.get(this.internalTrack.id)!.startTimestamp,
 		);
+
+		let fragmentIndex = -1;
 		let sampleIndex = -1;
 		let correctSampleFound = false;
 
-		if (fragmentIndex !== -1) {
-			const fragment = this.internalTrack.fragments[fragmentIndex]!;
+		if (indexInKeyFrameFragments !== -1) {
+			const fragment = this.internalTrack.fragmentsWithKeyFrame[indexInKeyFrameFragments]!;
+
+			// Now, let's find the actual index of the fragment in the list of ALL fragments, not just key frame ones
+			fragmentIndex = binarySearchExact(
+				this.internalTrack.fragments,
+				fragment.moofOffset,
+				x => x.moofOffset,
+			);
+			assert(fragmentIndex !== -1);
+
 			const trackData = fragment.trackData.get(this.internalTrack.id)!;
 			const index = findLastIndex(trackData.presentationTimestamps, (x) => {
 				const sample = trackData.samples[x.sampleIndex]!;
 				return sample.isKeyFrame && x.presentationTimestamp <= timestampInTimescale;
 			});
-
-			if (index === -1) {
-				throw new Error('Not supported: Fragment does not begin with a key sample.');
-			}
+			assert(index !== -1); // It's a key frame fragment, so there must be a key frame
 
 			const entry = trackData.presentationTimestamps[index]!;
 			sampleIndex = entry.sampleIndex;

src/matroska/matroska-demuxer.ts

@@ -484,24 +484,18 @@ export class MatroskaDemuxer extends Demuxer {
 				.map((block, i) => ({ timestamp: block.timestamp, blockIndex: i }))
 				.sort((a, b) => a.timestamp - b.timestamp);
 
-			let hasKeyFrame = false;
 			for (let i = 0; i < trackData.presentationTimestamps.length; i++) {
-				const entry = trackData.presentationTimestamps[i]!;
-				const block = trackData.blocks[entry.blockIndex]!;
+				const currentEntry = trackData.presentationTimestamps[i]!;
+				const currentBlock = trackData.blocks[currentEntry.blockIndex]!;
 
-				if (block.isKeyFrame) {
-					hasKeyFrame = true;
-
-					if (trackData.firstKeyFrameTimestamp === null && block.isKeyFrame) {
-						trackData.firstKeyFrameTimestamp = block.timestamp;
-					}
+				if (trackData.firstKeyFrameTimestamp === null && currentBlock.isKeyFrame) {
+					trackData.firstKeyFrameTimestamp = currentBlock.timestamp;
 				}
 
 				if (i < trackData.presentationTimestamps.length - 1) {
 					// Update block durations based on presentation order
 					const nextEntry = trackData.presentationTimestamps[i + 1]!;
-					const nextBlock = trackData.blocks[nextEntry.blockIndex]!;
-					block.duration = nextBlock.timestamp - block.timestamp;
+					currentBlock.duration = nextEntry.timestamp - currentBlock.timestamp;
 				}
 			}
 
@@ -520,6 +514,7 @@ export class MatroskaDemuxer extends Demuxer {
 				);
 				track.clusters.splice(insertionIndex + 1, 0, cluster);
 
+				const hasKeyFrame = trackData.firstKeyFrameTimestamp !== null;
 				if (hasKeyFrame) {
 					const insertionIndex = binarySearchLessOrEqual(
 						track.clustersWithKeyFrame,
@@ -1210,7 +1205,7 @@ abstract class MatroskaTrackBacking implements InputTrackBacking {
 						correctBlockFound: true,
 					};
 				} else {
-					// Walk the list of clusters until we find the next cluster for this track
+					// Walk the list of clusters until we find the next cluster for this track with a key frame
 					let currentCluster = locationInCluster.cluster;
 					while (currentCluster.nextCluster) {
 						currentCluster = currentCluster.nextCluster;

src/media-sink.ts

@@ -737,6 +737,7 @@ class VideoDecoderWrapper extends DecoderWrapper<VideoSample> {
 		// Round the timestamps to the time resolution
 		sample.setTimestamp(Math.round(sample.timestamp * this.timeResolution) / this.timeResolution);
 		sample.setDuration(Math.round(sample.duration * this.timeResolution) / this.timeResolution);
+		sample.setRotation(this.rotation);
 
 		this.onSample(sample);
 	}

src/mp3/mp3-misc.ts

@@ -85,6 +85,10 @@ export const readFrameHeader = (word: number, reader: { pos: number; fileSize: n
 
 	reader.pos += 1;
 
+	if (firstByte !== 0xff) {
+		return null;
+	}
+
 	if ((secondByte & 0xe0) !== 0xe0) {
 		return null;
 	}

src/mp3/mp3-reader.ts

@@ -65,7 +65,7 @@ export class Mp3Reader {
 		assert(this.fileSize);
 		until ??= this.fileSize;
 
-		while (this.pos < until - FRAME_HEADER_SIZE) {
+		while (this.pos <= until - FRAME_HEADER_SIZE) {
 			const word = this.readU32();
 			this.pos -= 4;
 

src/sample.ts

@@ -366,9 +366,79 @@ export class VideoSample {
 		context: CanvasRenderingContext2D | OffscreenCanvasRenderingContext2D,
 		dx: number,
 		dy: number,
-		dWidth: number = this.displayWidth,
-		dHeight: number = this.displayHeight,
+		dWidth?: number,
+		dHeight?: number,
+	): void;
+	/**
+	 * Draws the video sample to a 2D canvas context. Rotation metadata will be taken into account.
+	 *
+	 * @param sx - The x-coordinate of the top left corner of the sub-rectangle of the source image to draw into the
+	 * destination context.
+	 * @param sy - The y-coordinate of the top left corner of the sub-rectangle of the source image to draw into the
+	 * destination context.
+	 * @param sWidth - The width of the sub-rectangle of the source image to draw into the destination context.
+	 * @param sHeight - The height of the sub-rectangle of the source image to draw into the destination context.
+	 * @param dx - The x-coordinate in the destination canvas at which to place the top-left corner of the source image.
+	 * @param dy - The y-coordinate in the destination canvas at which to place the top-left corner of the source image.
+	 * @param dWidth - The width in pixels with which to draw the image in the destination canvas.
+	 * @param dHeight - The height in pixels with which to draw the image in the destination canvas.
+	 */
+	draw(
+		context: CanvasRenderingContext2D | OffscreenCanvasRenderingContext2D,
+		sx: number,
+		sy: number,
+		sWidth: number,
+		sHeight: number,
+		dx: number,
+		dy: number,
+		dWidth?: number,
+		dHeight?: number,
+	): void;
+	draw(
+		context: CanvasRenderingContext2D | OffscreenCanvasRenderingContext2D,
+		arg1: number,
+		arg2: number,
+		arg3?: number,
+		arg4?: number,
+		arg5?: number,
+		arg6?: number,
+		arg7?: number,
+		arg8?: number,
 	) {
+		let sx = 0;
+		let sy = 0;
+		let sWidth = this.displayWidth;
+		let sHeight = this.displayHeight;
+		let dx = 0;
+		let dy = 0;
+		let dWidth = this.displayWidth;
+		let dHeight = this.displayHeight;
+
+		if (arg5 !== undefined) {
+			sx = arg1!;
+			sy = arg2!;
+			sWidth = arg3!;
+			sHeight = arg4!;
+			dx = arg5;
+			dy = arg6!;
+
+			if (arg7 !== undefined) {
+				dWidth = arg7;
+				dHeight = arg8!;
+			} else {
+				dWidth = sWidth;
+				dHeight = sHeight;
+			}
+		} else {
+			dx = arg1;
+			dy = arg2;
+
+			if (arg3 !== undefined) {
+				dWidth = arg3;
+				dHeight = arg4!;
+			}
+		}
+
 		if (!(
 			(typeof CanvasRenderingContext2D !== 'undefined' && context instanceof CanvasRenderingContext2D)
 			|| (
@@ -378,6 +448,18 @@ export class VideoSample {
 		)) {
 			throw new TypeError('context must be a CanvasRenderingContext2D or OffscreenCanvasRenderingContext2D.');
 		}
+		if (!Number.isFinite(sx)) {
+			throw new TypeError('sx must be a number.');
+		}
+		if (!Number.isFinite(sy)) {
+			throw new TypeError('sy must be a number.');
+		}
+		if (!Number.isFinite(sWidth) || sWidth < 0) {
+			throw new TypeError('sWidth must be a non-negative number.');
+		}
+		if (!Number.isFinite(sHeight) || sHeight < 0) {
+			throw new TypeError('sHeight must be a non-negative number.');
+		}
 		if (!Number.isFinite(dx)) {
 			throw new TypeError('dx must be a number.');
 		}
@@ -395,6 +477,29 @@ export class VideoSample {
 			throw new Error('VideoSample is closed.');
 		}
 
+		// The provided sx,sy,sWidth,sHeight refer to the final rotated image, but that's not actually how the image is
+		// stored. Therefore, we must map these back onto the original, pre-rotation image.
+		if (this.rotation === 90) {
+			[sx, sy, sWidth, sHeight] = [
+				sy,
+				this.codedHeight - sx - sWidth,
+				sHeight,
+				sWidth,
+			];
+		} else if (this.rotation === 180) {
+			[sx, sy] = [
+				this.codedWidth - sx - sWidth,
+				this.codedHeight - sy - sHeight,
+			];
+		} else if (this.rotation === 270) {
+			[sx, sy, sWidth, sHeight] = [
+				this.codedWidth - sy - sHeight,
+				sx,
+				sHeight,
+				sWidth,
+			];
+		}
+
 		const source = this.toCanvasImageSource();
 
 		context.save();
@@ -412,6 +517,10 @@ export class VideoSample {
 
 		context.drawImage(
 			source,
+			sx,
+			sy,
+			sWidth,
+			sHeight,
 			-dWidth / 2,
 			-dHeight / 2,
 			dWidth,