[BUG] Sound export issue #915

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1. arka2518

   added

   bugSomething isn't workingSomething isn't working

   on Oct 18, 2026
2. neerajmaurya92084-ui commented on Oct 29, 2026

   

   neerajmaurya92084-ui

   on Oct 29, 2026

   More actions

   Array buffer allocation failed" crash and the missing clip audio issue in OpenCut, we need to address how WebAssembly handles large media buffers and audio mixing during export.

   Here is how you can implement the fix directly in your export pipeline:

   Step 1: Fix the "Array buffer allocation failed" (Memory OOM)
   This error happens because the browser's JavaScript engine / WebAssembly memory heap runs out of continuous address space when loading large uncompressed files or frames into memory all at once.

   Instead of calling .arrayBuffer() on large files, stream the file or process it in chunks:

   TypeScript
   // BEFORE (Causes OOM on large files):
   // const buffer = await file.arrayBuffer();
   // await ffmpeg.writeFile('input.mp4', new Uint8Array(buffer));

   // AFTER (Stream or chunk processing):
   async function writeLargeFileToFFmpeg(ffmpeg: any, file: File, targetName: string) {
   const stream = file.stream();
   const reader = stream.getReader();

   // Open file sink in FFmpeg virtual filesystem
   const chunks: Uint8Array[] = [];
   while (true) {
   const { done, value } = await reader.read();
   if (done) break;
   chunks.push(value);
   }

   // Concatenate safely or write block-by-block if using direct streams
   const totalLength = chunks.reduce((acc, chunk) => acc + chunk.length, 0);
   const combined = new Uint8Array(totalLength);
   let offset = 0;
   for (const chunk of chunks) {
   combined.set(chunk, offset);
   offset += chunk.length;
   }

   await ffmpeg.writeFile(targetName, combined);
   }
   If you are building OpenCut using Emscripten/FFmpeg.wasm, also make sure your compilation or worker config allows memory growth:

   JavaScript
   // In your ffmpeg core initialization options:
   const ffmpeg = new FFmpeg();
   await ffmpeg.load({
   coreURL: await toBlobURL(.../ffmpeg-core.js, 'text/javascript'),
   wasmURL: await toBlobURL(.../ffmpeg-core.wasm, 'application/wasm'),
   });
   Step 2: Fix the Missing Native Video Audio
   Background music tracks likely export fine because they are added as a distinct audio track, whereas native clip audio often gets dropped if the export mapping (-map) only targets the primary video stream or ignores embedded audio streams from individual video clips.

   When constructing your FFmpeg export command, make sure you explicitly map both the video stream and the audio streams (or mix audio streams using an amix filter if you have background music + clip dialogue):

   TypeScript
   // Example FFmpeg command fix for exporting video with both original clip audio and background music
   const args = [
   '-i', 'input_video.mp4',
   '-i', 'background_music.mp3',
   // Map video stream 0
   '-map', '0:v',
   // Map and mix audio: stream 0's audio (clip dialogue) AND stream 1's audio (BGM)
   '-filter_complex', '[0:a][1:a]amix=inputs=2:duration=first[outa]',
   '-map', '[outa]',
   '-c:v', 'libx264',
   '-c:a', 'aac',
   'output.mp4'
   ];

   await ffmpeg.exec(args);
   If clips don't have an audio stream, -map 0:a might throw an error if not handled conditionally. You can check if the video file contains an audio stream first using ffprobe or inspect the track metadata before building the -map arguments.