Fix export finalization stalls on Windows

Author: EtienneLescot

src/components/video-editor/ExportDialog.tsx

@@ -66,6 +66,9 @@ export function ExportDialog({
 	const getStatusMessage = () => {
 		if (error) return "Please try again";
 		if (isCompiling || isFinalizing) {
+			if (exportFormat === "mp4") {
+				return "Finalizing video export...";
+			}
 			if (renderProgress !== undefined && renderProgress > 0) {
 				return `Compiling GIF... ${renderProgress}%`;
 			}
@@ -77,6 +80,7 @@ export function ExportDialog({
 	// Get title based on phase
 	const getTitle = () => {
 		if (error) return "Export Failed";
+		if (isFinalizing && exportFormat === "mp4") return "Finalizing Video";
 		if (isCompiling || isFinalizing) return "Compiling GIF";
 		return `Exporting ${formatLabel}`;
 	};
@@ -233,7 +237,11 @@ export function ExportDialog({
 									{isCompiling || isFinalizing ? "Status" : "Format"}
 								</div>
 								<div className="text-slate-200 font-medium text-sm">
-									{isCompiling || isFinalizing ? "Compiling..." : formatLabel}
+									{isFinalizing && exportFormat === "mp4"
+										? "Finalizing..."
+										: isCompiling || isFinalizing
+											? "Compiling..."
+											: formatLabel}
 								</div>
 							</div>
 							<div className="bg-white/5 rounded-xl p-3 border border-white/5">

src/lib/exporter/audioEncoder.ts

@@ -8,7 +8,12 @@ const DECODE_BACKPRESSURE_LIMIT = 20;
 export class AudioProcessor {
 	private cancelled = false;
 
-	async process(demuxer: WebDemuxer, muxer: VideoMuxer, trimRegions?: TrimRegion[]): Promise<void> {
+	async process(
+		demuxer: WebDemuxer,
+		muxer: VideoMuxer,
+		trimRegions?: TrimRegion[],
+		readEndSec?: number,
+	): Promise<void> {
 		let audioConfig: AudioDecoderConfig;
 		try {
 			audioConfig = (await demuxer.getDecoderConfig("audio")) as AudioDecoderConfig;
@@ -34,19 +39,36 @@ export class AudioProcessor {
 		});
 		decoder.configure(audioConfig);
 
-		const reader = (demuxer.read("audio") as ReadableStream<EncodedAudioChunk>).getReader();
+		const safeReadEndSec =
+			typeof readEndSec === "number" && Number.isFinite(readEndSec)
+				? Math.max(0, readEndSec)
+				: undefined;
+		const audioStream = (
+			safeReadEndSec !== undefined
+				? demuxer.read("audio", 0, safeReadEndSec)
+				: demuxer.read("audio")
+		) as ReadableStream<EncodedAudioChunk>;
+		const reader = audioStream.getReader();
 
-		while (!this.cancelled) {
-			const { done, value: chunk } = await reader.read();
-			if (done || !chunk) break;
+		try {
+			while (!this.cancelled) {
+				const { done, value: chunk } = await reader.read();
+				if (done || !chunk) break;
 
-			const timestampMs = chunk.timestamp / 1000;
-			if (this.isInTrimRegion(timestampMs, sortedTrims)) continue;
+				const timestampMs = chunk.timestamp / 1000;
+				if (this.isInTrimRegion(timestampMs, sortedTrims)) continue;
 
-			decoder.decode(chunk);
+				decoder.decode(chunk);
 
-			while (decoder.decodeQueueSize > DECODE_BACKPRESSURE_LIMIT && !this.cancelled) {
-				await new Promise((resolve) => setTimeout(resolve, 1));
+				while (decoder.decodeQueueSize > DECODE_BACKPRESSURE_LIMIT && !this.cancelled) {
+					await new Promise((resolve) => setTimeout(resolve, 1));
+				}
+			}
+		} finally {
+			try {
+				await reader.cancel();
+			} catch {
+				/* reader already closed */
 			}
 		}
 

src/lib/exporter/videoExporter.ts

@@ -97,6 +97,7 @@ export class VideoExporter {
 				this.config.speedRegions,
 			);
 			const totalFrames = Math.ceil(effectiveDuration * this.config.frameRate);
+			const readEndSec = Math.max(videoInfo.duration, videoInfo.streamDuration ?? 0) + 0.5;
 
 			console.log("[VideoExporter] Original duration:", videoInfo.duration, "s");
 			console.log("[VideoExporter] Effective duration:", effectiveDuration, "s");
@@ -183,13 +184,28 @@ export class VideoExporter {
 			// Wait for all video muxing operations to complete
 			await Promise.all(this.muxingPromises);
 
+			if (this.config.onProgress) {
+				this.config.onProgress({
+					currentFrame: totalFrames,
+					totalFrames,
+					percentage: 100,
+					estimatedTimeRemaining: 0,
+					phase: "finalizing",
+				});
+			}
+
 			// Process audio track if present
 			if (hasAudio && !this.cancelled) {
 				const demuxer = this.streamingDecoder!.getDemuxer();
 				if (demuxer) {
 					console.log("[VideoExporter] Processing audio track...");
 					this.audioProcessor = new AudioProcessor();
-					await this.audioProcessor.process(demuxer, this.muxer!, this.config.trimRegions);
+					await this.audioProcessor.process(
+						demuxer,
+						this.muxer!,
+						this.config.trimRegions,
+						readEndSec,
+					);
 				}
 			}