Allow negative trim ranges for conversion, add OutputFormat.supportsTimestampedMediaData

src/conversion.ts

@@ -564,11 +564,11 @@ export class Conversion {
 		if (options.trim !== undefined && (!options.trim || typeof options.trim !== 'object')) {
 			throw new TypeError('options.trim, when provided, must be an object.');
 		}
-		if (options.trim?.start !== undefined && (!Number.isFinite(options.trim.start) || options.trim.start < 0)) {
-			throw new TypeError('options.trim.start, when provided, must be a non-negative number.');
+		if (options.trim?.start !== undefined && (!Number.isFinite(options.trim.start))) {
+			throw new TypeError('options.trim.start, when provided, must be a finite number.');
 		}
-		if (options.trim?.end !== undefined && (!Number.isFinite(options.trim.end) || options.trim.end < 0)) {
-			throw new TypeError('options.trim.end, when provided, must be a non-negative number.');
+		if (options.trim?.end !== undefined && (!Number.isFinite(options.trim.end))) {
+			throw new TypeError('options.trim.end, when provided, must be a finite number.');
 		}
 		if (
 			options.trim?.start !== undefined
@@ -607,7 +607,7 @@ export class Conversion {
 			// those out by default.
 			0,
 		);
-		this._endTimestamp = this._options.trim?.end ?? Infinity;
+		this._endTimestamp = Math.max(this._options.trim?.end ?? Infinity, this._startTimestamp);
 
 		const inputTracks = await this.input.getTracks();
 		const outputTrackCounts = this.output.format.getSupportedTrackCounts();
@@ -1326,7 +1326,8 @@ export class Conversion {
 		let sampleRate = trackOptions.sampleRate ?? originalSampleRate;
 		let needsResample = numberOfChannels !== originalNumberOfChannels
 			|| sampleRate !== originalSampleRate
-			|| firstTimestamp < this._startTimestamp;
+			|| firstTimestamp < this._startTimestamp
+			|| (firstTimestamp > this._startTimestamp && !this.output.format.supportsTimestampedMediaData);
 
 		let audioCodecs = this.output.format.getSupportedAudioCodecs();
 		if (

src/output-format.ts

@@ -74,6 +74,13 @@ export abstract class OutputFormat {
 	abstract getSupportedTrackCounts(): TrackCountLimits;
 	/** Whether this output format supports video rotation metadata. */
 	abstract get supportsVideoRotationMetadata(): boolean;
+	/**
+	 * Whether this output format's tracks store timestamped media data. When `true`, the timestamps of added packets
+	 * will be respected, allowing things like gaps in media data or non-zero start times. When `false`, the format's
+	 * media data implicitly starts at zero and follows an implicit sequential timing from there, using the intrinsic
+	 * durations of the media data.
+	 */
+	abstract get supportsTimestampedMediaData(): boolean;
 
 	/** Returns a list of video codecs that this output format can contain. */
 	getSupportedVideoCodecs() {
@@ -258,6 +265,10 @@ export abstract class IsobmffOutputFormat extends OutputFormat {
 		return true;
 	}
 
+	get supportsTimestampedMediaData() {
+		return true;
+	}
+
 	/** @internal */
 	_createMuxer(output: Output) {
 		return new IsobmffMuxer(output, this);
@@ -490,6 +501,10 @@ export class MkvOutputFormat extends OutputFormat {
 		// While it technically does support it with ProjectionPoseRoll, many players appear to ignore this value
 		return false;
 	}
+
+	get supportsTimestampedMediaData() {
+		return true;
+	}
 }
 
 /**
@@ -626,6 +641,10 @@ export class Mp3OutputFormat extends OutputFormat {
 	get supportsVideoRotationMetadata() {
 		return false;
 	}
+
+	get supportsTimestampedMediaData() {
+		return false;
+	}
 }
 
 /**
@@ -724,6 +743,10 @@ export class WavOutputFormat extends OutputFormat {
 	get supportsVideoRotationMetadata() {
 		return false;
 	}
+
+	get supportsTimestampedMediaData() {
+		return false;
+	}
 }
 
 /**
@@ -815,6 +838,10 @@ export class OggOutputFormat extends OutputFormat {
 	get supportsVideoRotationMetadata() {
 		return false;
 	}
+
+	get supportsTimestampedMediaData() {
+		return false;
+	}
 }
 
 /**
@@ -889,6 +916,10 @@ export class AdtsOutputFormat extends OutputFormat {
 	get supportsVideoRotationMetadata() {
 		return false;
 	}
+
+	get supportsTimestampedMediaData() {
+		return false;
+	}
 }
 
 /**
@@ -960,6 +991,10 @@ export class FlacOutputFormat extends OutputFormat {
 	get supportsVideoRotationMetadata() {
 		return false;
 	}
+
+	get supportsTimestampedMediaData() {
+		return false;
+	}
 }
 
 /**
@@ -1041,4 +1076,8 @@ export class MpegTsOutputFormat extends OutputFormat {
 	get supportsVideoRotationMetadata() {
 		return false;
 	}
+
+	get supportsTimestampedMediaData() {
+		return true;
+	}
 }