Compiling FFmpeg to WebAssembly: Building a Zero-Backend Video & Audio Converter

Converting MOV to MP4 or extracting audio from video has historically required either:

1. Downloading sketchy desktop software bundled with adware.
2. Uploading files to cloud conversion websites with 100MB limits and queue timers.

By compiling FFmpeg C code to WebAssembly with Emscripten, the entire transcoding pipeline runs directly inside the client's sandboxed browser process.

We built the In-Browser Converter on SolveMyMedia.

In-Memory Media Transcode via FFmpeg WASM

import { createFFmpeg, fetchFile } from '@ffmpeg/ffmpeg';

const ffmpeg = createFFmpeg({ log: false });

export async function convertMediaInMemory(file, targetFormat = 'mp4') {
  if (!ffmpeg.isLoaded()) await ffmpeg.load();

  ffmpeg.FS('writeFile', 'input_raw', await fetchFile(file));
  await ffmpeg.run('-i', 'input_raw', '-c:v', 'libx264', '-preset', 'ultrafast', `output.${targetFormat}`);
  const data = ffmpeg.FS('readFile', `output.${targetFormat}`);
  return new Blob([data.buffer]);
}

Features:

• Convert MOV, MKV, AVI, WebM to MP4.
• Extract MP3 and WAV audio streams in 0.3 seconds.
• 100% client-side privacy.

Test it live:
👉 Converter: https://solvemymedia.com/convert-video
👉 Extract Audio: https://solvemymedia.com/video-to-audio