fix(export): fast-path simple edited audio tracks

electron/electron-env.d.ts

@@ -194,7 +194,10 @@ interface Window {
 			options?: {
 				audioMode?: "none" | "copy-source" | "trim-source" | "edited-track";
 				audioSourcePath?: string | null;
+				audioSourceSampleRate?: number;
 				trimSegments?: Array<{ startMs: number; endMs: number }>;
+				editedTrackStrategy?: "filtergraph-fast-path" | "offline-render-fallback";
+				editedTrackSegments?: Array<{ startMs: number; endMs: number; speed: number }>;
 				editedAudioData?: ArrayBuffer;
 				editedAudioMimeType?: string | null;
 			},
@@ -213,7 +216,10 @@ interface Window {
 			options?: {
 				audioMode?: "none" | "copy-source" | "trim-source" | "edited-track";
 				audioSourcePath?: string | null;
+				audioSourceSampleRate?: number;
 				trimSegments?: Array<{ startMs: number; endMs: number }>;
+				editedTrackStrategy?: "filtergraph-fast-path" | "offline-render-fallback";
+				editedTrackSegments?: Array<{ startMs: number; endMs: number; speed: number }>;
 				editedAudioData?: ArrayBuffer;
 				editedAudioMimeType?: string | null;
 			},

electron/ipc/export/native-video.ts

@@ -14,6 +14,7 @@ import type {
 	NativeVideoExportFinishOptions,
 } from "../nativeVideoExport";
 import {
+	buildEditedTrackSourceAudioFilter,
 	buildNativeVideoExportArgs,
 	buildTrimmedSourceAudioFilter,
 	getEditedAudioExtension,
@@ -387,8 +388,10 @@ export async function muxNativeVideoExportAudio(
 	const metrics: NativeVideoAudioMuxMetrics = {};
 	const tempArtifacts: string[] = [];
 	let audioInputPath = options.audioSourcePath ?? null;
+	const useEditedTrackFiltergraph =
+		audioMode === "edited-track" && options.editedTrackStrategy === "filtergraph-fast-path";
 
-	if (audioMode === "edited-track") {
+	if (audioMode === "edited-track" && !useEditedTrackFiltergraph) {
 		if (!options.editedAudioData) {
 			throw new Error("Edited audio data is missing for native export");
 		}
@@ -435,6 +438,15 @@ export async function muxNativeVideoExportAudio(
 		} else {
 			args.push("-map", "0:v:0", "-map", "1:a:0");
 		}
+	} else if (useEditedTrackFiltergraph) {
+		const filter = buildEditedTrackSourceAudioFilter(
+			options.editedTrackSegments ?? [],
+			options.audioSourceSampleRate ?? 0,
+		);
+		if (!filter) {
+			throw new Error("Edited-track filtergraph inputs are incomplete for native export");
+		}
+		args.push("-filter_complex", filter, "-map", "0:v:0", "-map", "[aout]");
 	} else {
 		args.push("-map", "0:v:0", "-map", "1:a:0");
 	}

electron/ipc/nativeVideoExport.test.ts

@@ -0,0 +1,43 @@
+import { describe, expect, it } from "vitest";
+import {
+	buildEditedTrackSourceAudioFilter,
+	buildTrimmedSourceAudioFilter,
+} from "./nativeVideoExport";
+
+describe("buildTrimmedSourceAudioFilter", () => {
+	it("concatenates trimmed source segments into a single output label", () => {
+		expect(
+			buildTrimmedSourceAudioFilter([
+				{ startMs: 0, endMs: 2_000 },
+				{ startMs: 4_000, endMs: 6_000 },
+			]),
+		).toContain("concat=n=2:v=0:a=1[aout]");
+	});
+});
+
+describe("buildEditedTrackSourceAudioFilter", () => {
+	it("builds a concat filtergraph that pitch-shifts via asetrate for speed changes", () => {
+		const filter = buildEditedTrackSourceAudioFilter(
+			[
+				{ startMs: 0, endMs: 2_000, speed: 1 },
+				{ startMs: 2_000, endMs: 6_000, speed: 1.5 },
+			],
+			44_100,
+		);
+
+		expect(filter).toContain(
+			"[1:a]atrim=start=2.000:end=6.000,asetpts=PTS-STARTPTS,asetrate=66150,aresample=44100[edited_audio_1]",
+		);
+		expect(filter).toContain("concat=n=2:v=0:a=1[aout]");
+	});
+
+	it("returns null when the edited-track filtergraph inputs are incomplete", () => {
+		expect(buildEditedTrackSourceAudioFilter([], 44_100)).toBeNull();
+		expect(
+			buildEditedTrackSourceAudioFilter(
+				[{ startMs: 0, endMs: 2_000, speed: 1.5 }],
+				Number.NaN,
+			),
+		).toBeNull();
+	});
+});

electron/ipc/nativeVideoExport.ts

@@ -3,6 +3,9 @@ const NATIVE_EXPORT_INPUT_BYTES_PER_PIXEL = 4;
 export type NativeExportEncodingMode = "fast" | "balanced" | "quality";
 
 export type NativeVideoExportAudioMode = "none" | "copy-source" | "trim-source" | "edited-track";
+export type NativeVideoExportEditedTrackStrategy =
+	| "filtergraph-fast-path"
+	| "offline-render-fallback";
 
 export interface NativeVideoExportStartOptions {
 	width: number;
@@ -18,10 +21,17 @@ export interface NativeVideoExportAudioSegment {
 	endMs: number;
 }
 
+export interface NativeVideoExportEditedTrackSegment extends NativeVideoExportAudioSegment {
+	speed: number;
+}
+
 export interface NativeVideoExportFinishOptions {
 	audioMode?: NativeVideoExportAudioMode;
 	audioSourcePath?: string | null;
+	audioSourceSampleRate?: number;
 	trimSegments?: NativeVideoExportAudioSegment[];
+	editedTrackStrategy?: NativeVideoExportEditedTrackStrategy;
+	editedTrackSegments?: NativeVideoExportEditedTrackSegment[];
 	editedAudioData?: ArrayBuffer;
 	editedAudioMimeType?: string | null;
 }
@@ -162,6 +172,54 @@ export function buildTrimmedSourceAudioFilter(
 	return filterParts.join(";");
 }
 
+export function buildEditedTrackSourceAudioFilter(
+	segments: NativeVideoExportEditedTrackSegment[],
+	sourceSampleRate: number,
+): string | null {
+	if (segments.length === 0 || !Number.isFinite(sourceSampleRate) || sourceSampleRate <= 0) {
+		return null;
+	}
+
+	const normalizedSourceSampleRate = Math.round(sourceSampleRate);
+	const filterParts: string[] = [];
+	const segmentLabels: string[] = [];
+
+	segments.forEach((segment, index) => {
+		if (segment.endMs - segment.startMs <= 0.5) {
+			return;
+		}
+
+		const label = `edited_audio_${index}`;
+		const speed = Number.isFinite(segment.speed) && segment.speed > 0 ? segment.speed : 1;
+		const segmentFilter = [
+			`[1:a]atrim=start=${formatFfmpegSeconds(segment.startMs)}:end=${formatFfmpegSeconds(segment.endMs)}`,
+			"asetpts=PTS-STARTPTS",
+		];
+
+		if (Math.abs(speed - 1) > 0.0001) {
+			segmentFilter.push(
+				`asetrate=${Math.max(1, Math.round(normalizedSourceSampleRate * speed))}`,
+				`aresample=${normalizedSourceSampleRate}`,
+			);
+		}
+
+		filterParts.push(`${segmentFilter.join(",")}[${label}]`);
+		segmentLabels.push(`[${label}]`);
+	});
+
+	if (segmentLabels.length === 0) {
+		return null;
+	}
+
+	if (segmentLabels.length === 1) {
+		filterParts.push(`${segmentLabels[0]}anull[aout]`);
+	} else {
+		filterParts.push(`${segmentLabels.join("")}concat=n=${segmentLabels.length}:v=0:a=1[aout]`);
+	}
+
+	return filterParts.join(";");
+}
+
 /**
  * Builds FFmpeg arguments for a zero-copy H.264 stream export.
  * FFmpeg receives a pre-encoded Annex B H.264 stream on stdin (produced by the

electron/preload.ts

@@ -143,7 +143,10 @@ contextBridge.exposeInMainWorld("electronAPI", {
 		options?: {
 			audioMode?: "none" | "copy-source" | "trim-source" | "edited-track";
 			audioSourcePath?: string | null;
+			audioSourceSampleRate?: number;
 			trimSegments?: Array<{ startMs: number; endMs: number }>;
+			editedTrackStrategy?: "filtergraph-fast-path" | "offline-render-fallback";
+			editedTrackSegments?: Array<{ startMs: number; endMs: number; speed: number }>;
 			editedAudioData?: ArrayBuffer;
 			editedAudioMimeType?: string | null;
 		},
@@ -186,7 +189,10 @@ contextBridge.exposeInMainWorld("electronAPI", {
 		options?: {
 			audioMode?: "none" | "copy-source" | "trim-source" | "edited-track";
 			audioSourcePath?: string | null;
+			audioSourceSampleRate?: number;
 			trimSegments?: Array<{ startMs: number; endMs: number }>;
+			editedTrackStrategy?: "filtergraph-fast-path" | "offline-render-fallback";
+			editedTrackSegments?: Array<{ startMs: number; endMs: number; speed: number }>;
 			editedAudioData?: ArrayBuffer;
 			editedAudioMimeType?: string | null;
 		},

src/lib/exporter/editedTrackStrategy.test.ts

@@ -0,0 +1,121 @@
+import { describe, expect, it } from "vitest";
+import type { AudioRegion, SpeedRegion, TrimRegion } from "@/components/video-editor/types";
+import { buildEditedTrackSourceSegments, classifyEditedTrackStrategy } from "./editedTrackStrategy";
+
+const SOURCE_DURATION_MS = 20_000;
+const EMPTY_TRIMS: TrimRegion[] = [];
+
+describe("editedTrackStrategy", () => {
+	it("marks single-source speed-only edits as filtergraph candidates", () => {
+		const speedRegions: SpeedRegion[] = [
+			{ id: "speed-1", startMs: 2_000, endMs: 10_000, speed: 1.5 },
+		];
+
+		expect(
+			classifyEditedTrackStrategy({
+				primaryAudioSourcePath: "recording.mp4",
+				sourceDurationMs: SOURCE_DURATION_MS,
+				trimRegions: EMPTY_TRIMS,
+				speedRegions,
+				audioRegions: [],
+				sourceAudioFallbackPaths: [],
+			}),
+		).toBe("filtergraph-fast-path");
+	});
+
+	it("falls back when the edited track depends on sidecar sources", () => {
+		const speedRegions: SpeedRegion[] = [
+			{ id: "speed-1", startMs: 2_000, endMs: 10_000, speed: 1.25 },
+		];
+
+		expect(
+			classifyEditedTrackStrategy({
+				primaryAudioSourcePath: "mic.m4a",
+				sourceDurationMs: SOURCE_DURATION_MS,
+				trimRegions: EMPTY_TRIMS,
+				speedRegions,
+				audioRegions: [],
+				sourceAudioFallbackPaths: ["mic.m4a"],
+			}),
+		).toBe("offline-render-fallback");
+	});
+
+	it("falls back for multi-source mixes", () => {
+		const speedRegions: SpeedRegion[] = [
+			{ id: "speed-1", startMs: 2_000, endMs: 10_000, speed: 1.5 },
+		];
+
+		expect(
+			classifyEditedTrackStrategy({
+				primaryAudioSourcePath: "recording.mp4",
+				sourceDurationMs: SOURCE_DURATION_MS,
+				trimRegions: EMPTY_TRIMS,
+				speedRegions,
+				audioRegions: [],
+				sourceAudioFallbackPaths: ["mic.m4a"],
+			}),
+		).toBe("offline-render-fallback");
+	});
+
+	it("falls back when audio regions require overlay mixing", () => {
+		const speedRegions: SpeedRegion[] = [
+			{ id: "speed-1", startMs: 2_000, endMs: 10_000, speed: 1.5 },
+		];
+		const audioRegions: AudioRegion[] = [
+			{
+				id: "audio-1",
+				audioPath: "overlay.wav",
+				startMs: 1_000,
+				endMs: 4_000,
+				volume: 0.8,
+			},
+		];
+
+		expect(
+			classifyEditedTrackStrategy({
+				primaryAudioSourcePath: "recording.mp4",
+				sourceDurationMs: SOURCE_DURATION_MS,
+				trimRegions: EMPTY_TRIMS,
+				speedRegions,
+				audioRegions,
+				sourceAudioFallbackPaths: [],
+			}),
+		).toBe("offline-render-fallback");
+	});
+
+	it("falls back for speeds outside the conservative filtergraph window", () => {
+		const speedRegions = [
+			{ id: "speed-1", startMs: 2_000, endMs: 10_000, speed: 2.5 },
+		] as SpeedRegion[];
+
+		expect(
+			classifyEditedTrackStrategy({
+				primaryAudioSourcePath: "recording.mp4",
+				sourceDurationMs: SOURCE_DURATION_MS,
+				trimRegions: EMPTY_TRIMS,
+				speedRegions,
+				audioRegions: [],
+				sourceAudioFallbackPaths: [],
+			}),
+		).toBe("offline-render-fallback");
+	});
+
+	it("builds source segments that preserve trims and speed boundaries", () => {
+		const trimRegions: TrimRegion[] = [{ id: "trim-1", startMs: 10_000, endMs: 12_000 }];
+		const speedRegions: SpeedRegion[] = [
+			{ id: "speed-1", startMs: 2_000, endMs: 6_000, speed: 1.5 },
+			{ id: "speed-2", startMs: 14_000, endMs: 18_000, speed: 0.75 },
+		];
+
+		expect(
+			buildEditedTrackSourceSegments(SOURCE_DURATION_MS, trimRegions, speedRegions),
+		).toEqual([
+			{ startMs: 0, endMs: 2_000, speed: 1 },
+			{ startMs: 2_000, endMs: 6_000, speed: 1.5 },
+			{ startMs: 6_000, endMs: 10_000, speed: 1 },
+			{ startMs: 12_000, endMs: 14_000, speed: 1 },
+			{ startMs: 14_000, endMs: 18_000, speed: 0.75 },
+			{ startMs: 18_000, endMs: 20_000, speed: 1 },
+		]);
+	});
+});

src/lib/exporter/editedTrackStrategy.ts

@@ -0,0 +1,141 @@
+import type { AudioRegion, SpeedRegion, TrimRegion } from "@/components/video-editor/types";
+
+const MIN_FILTERGRAPH_SPEED = 0.5;
+const MAX_FILTERGRAPH_SPEED = 2;
+
+export type EditedTrackStrategy = "filtergraph-fast-path" | "offline-render-fallback";
+
+export interface EditedTrackSourceSegment {
+	startMs: number;
+	endMs: number;
+	speed: number;
+}
+
+export interface EditedTrackStrategyInput {
+	primaryAudioSourcePath: string | null;
+	sourceDurationMs: number;
+	trimRegions: TrimRegion[];
+	speedRegions: SpeedRegion[];
+	audioRegions: AudioRegion[];
+	sourceAudioFallbackPaths: string[];
+}
+
+function isSafeFiltergraphSpeed(speed: number): boolean {
+	return (
+		Number.isFinite(speed) && speed >= MIN_FILTERGRAPH_SPEED && speed <= MAX_FILTERGRAPH_SPEED
+	);
+}
+
+function hasSafeFiltergraphSpeedRegions(speedRegions: SpeedRegion[]): boolean {
+	return speedRegions.every((region) => isSafeFiltergraphSpeed(region.speed));
+}
+
+function buildKeptRanges(
+	sourceDurationMs: number,
+	trimRegions: TrimRegion[],
+): Array<{ startMs: number; endMs: number }> {
+	const sortedTrimRegions = [...trimRegions].sort((left, right) => left.startMs - right.startMs);
+	const keptRanges: Array<{ startMs: number; endMs: number }> = [];
+	let cursorMs = 0;
+
+	for (const trimRegion of sortedTrimRegions) {
+		const startMs = Math.max(0, trimRegion.startMs);
+		const endMs = Math.min(sourceDurationMs, trimRegion.endMs);
+		if (endMs <= startMs) {
+			continue;
+		}
+
+		if (startMs > cursorMs) {
+			keptRanges.push({ startMs: cursorMs, endMs: startMs });
+		}
+
+		cursorMs = Math.max(cursorMs, endMs);
+	}
+
+	if (cursorMs < sourceDurationMs) {
+		keptRanges.push({ startMs: cursorMs, endMs: sourceDurationMs });
+	}
+
+	return keptRanges;
+}
+
+export function buildEditedTrackSourceSegments(
+	sourceDurationMs: number,
+	trimRegions: TrimRegion[],
+	speedRegions: SpeedRegion[],
+): EditedTrackSourceSegment[] {
+	const segments: EditedTrackSourceSegment[] = [];
+	const keptRanges = buildKeptRanges(sourceDurationMs, trimRegions);
+
+	for (const keptRange of keptRanges) {
+		const boundaries = new Set<number>([keptRange.startMs, keptRange.endMs]);
+		for (const speedRegion of speedRegions) {
+			const startMs = Math.max(keptRange.startMs, speedRegion.startMs);
+			const endMs = Math.min(keptRange.endMs, speedRegion.endMs);
+			if (endMs > startMs) {
+				boundaries.add(startMs);
+				boundaries.add(endMs);
+			}
+		}
+
+		const orderedBoundaries = [...boundaries].sort((left, right) => left - right);
+		for (let index = 0; index < orderedBoundaries.length - 1; index += 1) {
+			const startMs = orderedBoundaries[index] ?? 0;
+			const endMs = orderedBoundaries[index + 1] ?? 0;
+			if (endMs - startMs <= 0.5) {
+				continue;
+			}
+
+			const midpointMs = startMs + (endMs - startMs) / 2;
+			const speedRegion = speedRegions.find(
+				(region) => midpointMs >= region.startMs && midpointMs < region.endMs,
+			);
+			const speed = speedRegion?.speed ?? 1;
+			if (!isSafeFiltergraphSpeed(speed)) {
+				return [];
+			}
+
+			segments.push({
+				startMs,
+				endMs,
+				speed,
+			});
+		}
+	}
+
+	return segments;
+}
+
+export function classifyEditedTrackStrategy(input: EditedTrackStrategyInput): EditedTrackStrategy {
+	if (!input.primaryAudioSourcePath) {
+		return "offline-render-fallback";
+	}
+
+	if (input.audioRegions.length > 0) {
+		return "offline-render-fallback";
+	}
+
+	if (input.speedRegions.length === 0) {
+		return "offline-render-fallback";
+	}
+
+	if (!hasSafeFiltergraphSpeedRegions(input.speedRegions)) {
+		return "offline-render-fallback";
+	}
+
+	if (input.sourceAudioFallbackPaths.length > 0) {
+		return "offline-render-fallback";
+	}
+
+	if (
+		buildEditedTrackSourceSegments(
+			input.sourceDurationMs,
+			input.trimRegions,
+			input.speedRegions,
+		).length === 0
+	) {
+		return "offline-render-fallback";
+	}
+
+	return "filtergraph-fast-path";
+}

src/lib/exporter/modernVideoExporter.ts

@@ -15,6 +15,7 @@ import type {
 import { extensionHost } from "@/lib/extensions";
 import { AudioProcessor, isAacAudioEncodingSupported } from "./audioEncoder";
 import { normalizeLightningRuntimePlatform } from "./backendPolicy";
+import { buildEditedTrackSourceSegments, classifyEditedTrackStrategy } from "./editedTrackStrategy";
 import {
 	type ExportBackpressureProfile,
 	getExportBackpressureProfile,
@@ -106,6 +107,14 @@ type NativeAudioPlan =
 	  }
 	| {
 			audioMode: "edited-track";
+			strategy: "offline-render-fallback";
+	  }
+	| {
+			audioMode: "edited-track";
+			strategy: "filtergraph-fast-path";
+			audioSourcePath: string;
+			audioSourceSampleRate: number;
+			editedTrackSegments: Array<{ startMs: number; endMs: number; speed: number }>;
 	  };
 
 const NATIVE_EXPORT_ENGINE_NAME = "Breeze";
@@ -737,11 +746,62 @@ export class ModernVideoExporter {
 			audioRegions.length > 0 ||
 			sourceAudioFallbackPaths.length > 1
 		) {
-			return { audioMode: "edited-track" };
+			const sourceDurationMs = Math.max(
+				0,
+				Math.round((videoInfo.streamDuration ?? videoInfo.duration) * 1000),
+			);
+			const trimRegions = this.config.trimRegions ?? [];
+			const strategy =
+				videoInfo.hasAudio &&
+				localVideoSourcePath &&
+				sourceAudioFallbackPaths.length === 0 &&
+				typeof videoInfo.audioSampleRate === "number" &&
+				Number.isFinite(videoInfo.audioSampleRate) &&
+				videoInfo.audioSampleRate > 0
+					? classifyEditedTrackStrategy({
+							primaryAudioSourcePath,
+							sourceDurationMs,
+							trimRegions,
+							speedRegions,
+							audioRegions,
+							sourceAudioFallbackPaths,
+						})
+					: "offline-render-fallback";
+
+			if (strategy === "filtergraph-fast-path") {
+				const audioSourcePath = localVideoSourcePath;
+				const audioSourceSampleRate = videoInfo.audioSampleRate;
+				const editedTrackSegments = buildEditedTrackSourceSegments(
+					sourceDurationMs,
+					trimRegions,
+					speedRegions,
+				);
+				if (
+					audioSourcePath &&
+					typeof audioSourceSampleRate === "number" &&
+					editedTrackSegments.length > 0
+				) {
+					return {
+						audioMode: "edited-track",
+						strategy,
+						audioSourcePath,
+						audioSourceSampleRate,
+						editedTrackSegments,
+					};
+				}
+			}
+
+			return {
+				audioMode: "edited-track",
+				strategy: "offline-render-fallback",
+			};
 		}
 
 		if (!primaryAudioSourcePath) {
-			return { audioMode: "edited-track" };
+			return {
+				audioMode: "edited-track",
+				strategy: "offline-render-fallback",
+			};
 		}
 
 		if ((this.config.trimRegions ?? []).length > 0) {
@@ -949,7 +1009,10 @@ export class ModernVideoExporter {
 		let editedAudioBuffer: ArrayBuffer | undefined;
 		let editedAudioMimeType: string | null = null;
 
-		if (audioPlan.audioMode === "edited-track") {
+		if (
+			audioPlan.audioMode === "edited-track" &&
+			audioPlan.strategy === "offline-render-fallback"
+		) {
 			this.audioProcessor = new AudioProcessor();
 			this.audioProcessor.setOnProgress((progress) => {
 				this.reportFinalizingProgress(this.processedFrameCount, 99, progress);
@@ -976,6 +1039,8 @@ export class ModernVideoExporter {
 		console.log(`[VideoExporter] Finalizing ${NATIVE_EXPORT_ENGINE_NAME} export`, {
 			sessionId,
 			audioMode: audioPlan.audioMode,
+			editedTrackStrategy:
+				audioPlan.audioMode === "edited-track" ? audioPlan.strategy : undefined,
 			encoderName: this.encoderName ?? "unknown",
 		});
 
@@ -987,11 +1052,25 @@ export class ModernVideoExporter {
 					audioMode: audioPlan.audioMode,
 					audioSourcePath:
 						audioPlan.audioMode === "copy-source" ||
-						audioPlan.audioMode === "trim-source"
+						audioPlan.audioMode === "trim-source" ||
+						(audioPlan.audioMode === "edited-track" &&
+							audioPlan.strategy === "filtergraph-fast-path")
 							? audioPlan.audioSourcePath
 							: null,
 					trimSegments:
 						audioPlan.audioMode === "trim-source" ? audioPlan.trimSegments : undefined,
+					editedTrackStrategy:
+						audioPlan.audioMode === "edited-track" ? audioPlan.strategy : undefined,
+					editedTrackSegments:
+						audioPlan.audioMode === "edited-track" &&
+						audioPlan.strategy === "filtergraph-fast-path"
+							? audioPlan.editedTrackSegments
+							: undefined,
+					audioSourceSampleRate:
+						audioPlan.audioMode === "edited-track" &&
+						audioPlan.strategy === "filtergraph-fast-path"
+							? audioPlan.audioSourceSampleRate
+							: undefined,
 					editedAudioData: editedAudioBuffer,
 					editedAudioMimeType,
 				}),
@@ -1041,7 +1120,10 @@ export class ModernVideoExporter {
 		let editedAudioBuffer: ArrayBuffer | undefined;
 		let editedAudioMimeType: string | null = null;
 
-		if (audioPlan.audioMode === "edited-track") {
+		if (
+			audioPlan.audioMode === "edited-track" &&
+			audioPlan.strategy === "offline-render-fallback"
+		) {
 			this.audioProcessor = new AudioProcessor();
 			this.audioProcessor.setOnProgress((progress) => {
 				this.reportFinalizingProgress(this.processedFrameCount, 99, progress);
@@ -1071,11 +1153,25 @@ export class ModernVideoExporter {
 					audioMode: audioPlan.audioMode,
 					audioSourcePath:
 						audioPlan.audioMode === "copy-source" ||
-						audioPlan.audioMode === "trim-source"
+						audioPlan.audioMode === "trim-source" ||
+						(audioPlan.audioMode === "edited-track" &&
+							audioPlan.strategy === "filtergraph-fast-path")
 							? audioPlan.audioSourcePath
 							: null,
 					trimSegments:
 						audioPlan.audioMode === "trim-source" ? audioPlan.trimSegments : undefined,
+					editedTrackStrategy:
+						audioPlan.audioMode === "edited-track" ? audioPlan.strategy : undefined,
+					editedTrackSegments:
+						audioPlan.audioMode === "edited-track" &&
+						audioPlan.strategy === "filtergraph-fast-path"
+							? audioPlan.editedTrackSegments
+							: undefined,
+					audioSourceSampleRate:
+						audioPlan.audioMode === "edited-track" &&
+						audioPlan.strategy === "filtergraph-fast-path"
+							? audioPlan.audioSourceSampleRate
+							: undefined,
 					editedAudioData: editedAudioBuffer,
 					editedAudioMimeType,
 				}),

src/lib/exporter/streamingDecoder.ts

@@ -17,6 +17,7 @@ export interface DecodedVideoInfo {
 	codec: string;
 	hasAudio: boolean;
 	audioCodec?: string;
+	audioSampleRate?: number;
 }
 
 /** Caller must close the VideoFrame after use. */
@@ -205,6 +206,10 @@ export class StreamingVideoDecoder {
 			codec: videoStream?.codec_string || "unknown",
 			hasAudio: !!audioStream,
 			audioCodec: audioStream?.codec_string,
+			audioSampleRate:
+				typeof audioStream?.sample_rate === "string"
+					? Number.parseInt(audioStream.sample_rate, 10)
+					: undefined,
 		};
 
 		return this.metadata;

src/lib/exporter/videoExporter.ts

@@ -13,6 +13,7 @@ import type {
 	ZoomTransitionEasing,
 } from "@/components/video-editor/types";
 import { AudioProcessor, isAacAudioEncodingSupported } from "./audioEncoder";
+import { buildEditedTrackSourceSegments, classifyEditedTrackStrategy } from "./editedTrackStrategy";
 import {
 	advanceFinalizationProgress,
 	type FinalizationProgressWatchdog,
@@ -94,6 +95,14 @@ type NativeAudioPlan =
 	  }
 	| {
 			audioMode: "edited-track";
+			strategy: "offline-render-fallback";
+	  }
+	| {
+			audioMode: "edited-track";
+			strategy: "filtergraph-fast-path";
+			audioSourcePath: string;
+			audioSourceSampleRate: number;
+			editedTrackSegments: Array<{ startMs: number; endMs: number; speed: number }>;
 	  };
 
 export class VideoExporter {
@@ -504,11 +513,62 @@ export class VideoExporter {
 			audioRegions.length > 0 ||
 			sourceAudioFallbackPaths.length > 1
 		) {
-			return { audioMode: "edited-track" };
+			const sourceDurationMs = Math.max(
+				0,
+				Math.round((videoInfo.streamDuration ?? videoInfo.duration) * 1000),
+			);
+			const trimRegions = this.config.trimRegions ?? [];
+			const strategy =
+				videoInfo.hasAudio &&
+				localVideoSourcePath &&
+				sourceAudioFallbackPaths.length === 0 &&
+				typeof videoInfo.audioSampleRate === "number" &&
+				Number.isFinite(videoInfo.audioSampleRate) &&
+				videoInfo.audioSampleRate > 0
+					? classifyEditedTrackStrategy({
+							primaryAudioSourcePath,
+							sourceDurationMs,
+							trimRegions,
+							speedRegions,
+							audioRegions,
+							sourceAudioFallbackPaths,
+						})
+					: "offline-render-fallback";
+
+			if (strategy === "filtergraph-fast-path") {
+				const audioSourcePath = localVideoSourcePath;
+				const audioSourceSampleRate = videoInfo.audioSampleRate;
+				const editedTrackSegments = buildEditedTrackSourceSegments(
+					sourceDurationMs,
+					trimRegions,
+					speedRegions,
+				);
+				if (
+					audioSourcePath &&
+					typeof audioSourceSampleRate === "number" &&
+					editedTrackSegments.length > 0
+				) {
+					return {
+						audioMode: "edited-track",
+						strategy,
+						audioSourcePath,
+						audioSourceSampleRate,
+						editedTrackSegments,
+					};
+				}
+			}
+
+			return {
+				audioMode: "edited-track",
+				strategy: "offline-render-fallback",
+			};
 		}
 
 		if (!primaryAudioSourcePath) {
-			return { audioMode: "edited-track" };
+			return {
+				audioMode: "edited-track",
+				strategy: "offline-render-fallback",
+			};
 		}
 
 		if ((this.config.trimRegions ?? []).length > 0) {
@@ -709,7 +769,10 @@ export class VideoExporter {
 		let editedAudioBuffer: ArrayBuffer | undefined;
 		let editedAudioMimeType: string | null = null;
 
-		if (audioPlan.audioMode === "edited-track") {
+		if (
+			audioPlan.audioMode === "edited-track" &&
+			audioPlan.strategy === "offline-render-fallback"
+		) {
 			this.audioProcessor = new AudioProcessor();
 			this.audioProcessor.setOnProgress((progress) => {
 				this.reportFinalizingProgress(totalFrames, 99, progress);
@@ -741,11 +804,25 @@ export class VideoExporter {
 					audioMode: audioPlan.audioMode,
 					audioSourcePath:
 						audioPlan.audioMode === "copy-source" ||
-						audioPlan.audioMode === "trim-source"
+						audioPlan.audioMode === "trim-source" ||
+						(audioPlan.audioMode === "edited-track" &&
+							audioPlan.strategy === "filtergraph-fast-path")
 							? audioPlan.audioSourcePath
 							: null,
 					trimSegments:
 						audioPlan.audioMode === "trim-source" ? audioPlan.trimSegments : undefined,
+					editedTrackStrategy:
+						audioPlan.audioMode === "edited-track" ? audioPlan.strategy : undefined,
+					editedTrackSegments:
+						audioPlan.audioMode === "edited-track" &&
+						audioPlan.strategy === "filtergraph-fast-path"
+							? audioPlan.editedTrackSegments
+							: undefined,
+					audioSourceSampleRate:
+						audioPlan.audioMode === "edited-track" &&
+						audioPlan.strategy === "filtergraph-fast-path"
+							? audioPlan.audioSourceSampleRate
+							: undefined,
 					editedAudioData: editedAudioBuffer,
 					editedAudioMimeType,
 				}),
@@ -790,7 +867,10 @@ export class VideoExporter {
 		let editedAudioBuffer: ArrayBuffer | undefined;
 		let editedAudioMimeType: string | null = null;
 
-		if (audioPlan.audioMode === "edited-track") {
+		if (
+			audioPlan.audioMode === "edited-track" &&
+			audioPlan.strategy === "offline-render-fallback"
+		) {
 			this.audioProcessor = new AudioProcessor();
 			this.audioProcessor.setOnProgress((progress) => {
 				this.reportFinalizingProgress(totalFrames, 99, progress);
@@ -820,11 +900,25 @@ export class VideoExporter {
 					audioMode: audioPlan.audioMode,
 					audioSourcePath:
 						audioPlan.audioMode === "copy-source" ||
-						audioPlan.audioMode === "trim-source"
+						audioPlan.audioMode === "trim-source" ||
+						(audioPlan.audioMode === "edited-track" &&
+							audioPlan.strategy === "filtergraph-fast-path")
 							? audioPlan.audioSourcePath
 							: null,
 					trimSegments:
 						audioPlan.audioMode === "trim-source" ? audioPlan.trimSegments : undefined,
+					editedTrackStrategy:
+						audioPlan.audioMode === "edited-track" ? audioPlan.strategy : undefined,
+					editedTrackSegments:
+						audioPlan.audioMode === "edited-track" &&
+						audioPlan.strategy === "filtergraph-fast-path"
+							? audioPlan.editedTrackSegments
+							: undefined,
+					audioSourceSampleRate:
+						audioPlan.audioMode === "edited-track" &&
+						audioPlan.strategy === "filtergraph-fast-path"
+							? audioPlan.audioSourceSampleRate
+							: undefined,
 					editedAudioData: editedAudioBuffer,
 					editedAudioMimeType,
 				}),