fix(export): preserve pitch for fallback speed audio

src/lib/exporter/editedTrackStrategy.test.ts

@@ -23,7 +23,7 @@ describe("editedTrackStrategy", () => {
 		).toBe("filtergraph-fast-path");
 	});
 
-	it("falls back when the edited track depends on sidecar sources", () => {
+	it("marks a single external source audio track as a filtergraph candidate", () => {
 		const speedRegions: SpeedRegion[] = [
 			{ id: "speed-1", startMs: 2_000, endMs: 10_000, speed: 1.25 },
 		];
@@ -37,7 +37,7 @@ describe("editedTrackStrategy", () => {
 				audioRegions: [],
 				sourceAudioFallbackPaths: ["mic.m4a"],
 			}),
-		).toBe("offline-render-fallback");
+		).toBe("filtergraph-fast-path");
 	});
 
 	it("falls back for multi-source mixes", () => {

src/lib/exporter/editedTrackStrategy.ts

@@ -158,7 +158,11 @@ export function classifyEditedTrackStrategy(input: EditedTrackStrategyInput): Ed
 		return "offline-render-fallback";
 	}
 
-	if (input.sourceAudioFallbackPaths.length > 0) {
+	if (
+		input.sourceAudioFallbackPaths.some(
+			(audioPath) => audioPath !== input.primaryAudioSourcePath,
+		)
+	) {
 		return "offline-render-fallback";
 	}
 

src/lib/exporter/modernVideoExporter.nativeStaticLayout.test.ts

@@ -39,6 +39,7 @@ function createExporter(overrides: Record<string, unknown> = {}) {
 		experimentalNativeExport: true,
 		...overrides,
 	} as never) as unknown as {
+		buildNativeAudioPlan: (videoInfo: DecodedVideoInfo) => unknown;
 		getNativeStaticLayoutSkipReason: (
 			audioPlan: unknown,
 			videoInfo: DecodedVideoInfo,
@@ -52,6 +53,59 @@ afterEach(() => {
 });
 
 describe("ModernVideoExporter native static-layout eligibility", () => {
+	it("uses FFmpeg filtergraph audio for speed edits with a single external source track", () => {
+		const speedRegions: SpeedRegion[] = [
+			{ id: "speed-1", startMs: 1_000, endMs: 4_000, speed: 1.5 },
+		];
+		const exporter = createExporter({
+			speedRegions,
+			sourceAudioFallbackPaths: ["C:\\recordly\\recording.system.wav"],
+		});
+
+		expect(
+			exporter.buildNativeAudioPlan({
+				...videoInfo,
+				hasAudio: false,
+				audioCodec: undefined,
+				audioSampleRate: undefined,
+			}),
+		).toMatchObject({
+			audioMode: "edited-track",
+			strategy: "filtergraph-fast-path",
+			audioSourcePath: "C:\\recordly\\recording.system.wav",
+			audioSourceSampleRate: 48_000,
+			editedTrackSegments: [
+				{ startMs: 0, endMs: 1_000, speed: 1 },
+				{ startMs: 1_000, endMs: 4_000, speed: 1.5 },
+				{ startMs: 4_000, endMs: 60_000, speed: 1 },
+			],
+		});
+	});
+
+	it("keeps timed companion audio on the offline render path", () => {
+		const audioPath = "C:\\recordly\\recording.system.wav";
+		const speedRegions: SpeedRegion[] = [
+			{ id: "speed-1", startMs: 1_000, endMs: 4_000, speed: 1.5 },
+		];
+		const exporter = createExporter({
+			speedRegions,
+			sourceAudioFallbackPaths: [audioPath],
+			sourceAudioFallbackStartDelayMsByPath: { [audioPath]: 250 },
+		});
+
+		expect(
+			exporter.buildNativeAudioPlan({
+				...videoInfo,
+				hasAudio: false,
+				audioCodec: undefined,
+				audioSampleRate: undefined,
+			}),
+		).toEqual({
+			audioMode: "edited-track",
+			strategy: "offline-render-fallback",
+		});
+	});
+
 	it("allows native video when only the audio track needs offline editing", () => {
 		const audioRegions: AudioRegion[] = [
 			{

src/lib/exporter/modernVideoExporter.ts

@@ -158,6 +158,8 @@ type NativeAudioPlan =
 			editedTrackSegments: Array<{ startMs: number; endMs: number; speed: number }>;
 	  };
 
+const FILTERGRAPH_FALLBACK_AUDIO_SAMPLE_RATE = 48_000;
+
 type NativeStaticLayoutTimelineSegment = {
 	sourceStartMs: number;
 	sourceEndMs: number;
@@ -996,6 +998,11 @@ export class ModernVideoExporter {
 			(videoInfo.hasAudio ? localVideoSourcePath : null) ??
 			sourceAudioFallbackPaths[0] ??
 			null;
+		const usesEmbeddedPrimaryAudio =
+			Boolean(videoInfo.hasAudio) && primaryAudioSourcePath === localVideoSourcePath;
+		const primaryAudioSourceSampleRate = usesEmbeddedPrimaryAudio
+			? videoInfo.audioSampleRate
+			: FILTERGRAPH_FALLBACK_AUDIO_SAMPLE_RATE;
 
 		if (
 			!videoInfo.hasAudio &&
@@ -1016,13 +1023,16 @@ export class ModernVideoExporter {
 				Math.round((videoInfo.streamDuration ?? videoInfo.duration) * 1000),
 			);
 			const trimRegions = this.config.trimRegions ?? [];
+			const canUsePrimaryAudioFiltergraph =
+				Boolean(primaryAudioSourcePath) &&
+				!hasTimedSourceAudioFallback &&
+				(usesEmbeddedPrimaryAudio ||
+					sourceAudioFallbackPaths.includes(primaryAudioSourcePath ?? "")) &&
+				typeof primaryAudioSourceSampleRate === "number" &&
+				Number.isFinite(primaryAudioSourceSampleRate) &&
+				primaryAudioSourceSampleRate > 0;
 			const strategy =
-				videoInfo.hasAudio &&
-				localVideoSourcePath &&
-				sourceAudioFallbackPaths.length === 0 &&
-				typeof videoInfo.audioSampleRate === "number" &&
-				Number.isFinite(videoInfo.audioSampleRate) &&
-				videoInfo.audioSampleRate > 0
+				canUsePrimaryAudioFiltergraph
 					? classifyEditedTrackStrategy({
 							primaryAudioSourcePath,
 							sourceDurationMs,
@@ -1034,8 +1044,8 @@ export class ModernVideoExporter {
 					: "offline-render-fallback";
 
 			if (strategy === "filtergraph-fast-path") {
-				const audioSourcePath = localVideoSourcePath;
-				const audioSourceSampleRate = videoInfo.audioSampleRate;
+				const audioSourcePath = primaryAudioSourcePath;
+				const audioSourceSampleRate = primaryAudioSourceSampleRate;
 				const editedTrackSegments = buildEditedTrackSourceSegments(
 					sourceDurationMs,
 					trimRegions,
@@ -2260,6 +2270,7 @@ export class ModernVideoExporter {
 				audioPlan.strategy === "filtergraph-fast-path"
 					? audioPlan.audioSourceSampleRate
 					: undefined,
+			outputDurationSec: this.effectiveDurationSec,
 			editedAudioData: editedAudioBuffer,
 			editedAudioMimeType,
 		};

src/lib/exporter/videoExporter.ts

@@ -113,6 +113,8 @@ type NativeAudioPlan =
 			editedTrackSegments: Array<{ startMs: number; endMs: number; speed: number }>;
 	  };
 
+const FILTERGRAPH_FALLBACK_AUDIO_SAMPLE_RATE = 48_000;
+
 export class VideoExporter {
 	private config: VideoExporterConfig;
 	private streamingDecoder: StreamingVideoDecoder | null = null;
@@ -533,6 +535,11 @@ export class VideoExporter {
 			(videoInfo.hasAudio ? localVideoSourcePath : null) ??
 			sourceAudioFallbackPaths[0] ??
 			null;
+		const usesEmbeddedPrimaryAudio =
+			Boolean(videoInfo.hasAudio) && primaryAudioSourcePath === localVideoSourcePath;
+		const primaryAudioSourceSampleRate = usesEmbeddedPrimaryAudio
+			? videoInfo.audioSampleRate
+			: FILTERGRAPH_FALLBACK_AUDIO_SAMPLE_RATE;
 
 		if (
 			!videoInfo.hasAudio &&
@@ -553,13 +560,16 @@ export class VideoExporter {
 				Math.round((videoInfo.streamDuration ?? videoInfo.duration) * 1000),
 			);
 			const trimRegions = this.config.trimRegions ?? [];
+			const canUsePrimaryAudioFiltergraph =
+				Boolean(primaryAudioSourcePath) &&
+				!hasTimedSourceAudioFallback &&
+				(usesEmbeddedPrimaryAudio ||
+					sourceAudioFallbackPaths.includes(primaryAudioSourcePath ?? "")) &&
+				typeof primaryAudioSourceSampleRate === "number" &&
+				Number.isFinite(primaryAudioSourceSampleRate) &&
+				primaryAudioSourceSampleRate > 0;
 			const strategy =
-				videoInfo.hasAudio &&
-				localVideoSourcePath &&
-				sourceAudioFallbackPaths.length === 0 &&
-				typeof videoInfo.audioSampleRate === "number" &&
-				Number.isFinite(videoInfo.audioSampleRate) &&
-				videoInfo.audioSampleRate > 0
+				canUsePrimaryAudioFiltergraph
 					? classifyEditedTrackStrategy({
 							primaryAudioSourcePath,
 							sourceDurationMs,
@@ -571,8 +581,8 @@ export class VideoExporter {
 					: "offline-render-fallback";
 
 			if (strategy === "filtergraph-fast-path") {
-				const audioSourcePath = localVideoSourcePath;
-				const audioSourceSampleRate = videoInfo.audioSampleRate;
+				const audioSourcePath = primaryAudioSourcePath;
+				const audioSourceSampleRate = primaryAudioSourceSampleRate;
 				const editedTrackSegments = buildEditedTrackSourceSegments(
 					sourceDurationMs,
 					trimRegions,
@@ -950,6 +960,7 @@ export class VideoExporter {
 				audioPlan.strategy === "filtergraph-fast-path"
 					? audioPlan.audioSourceSampleRate
 					: undefined,
+			outputDurationSec: this.effectiveDurationSec,
 			editedAudioData: editedAudioBuffer,
 			editedAudioMimeType,
 		};