konowebcodecs/docs/api.md

API

• createWorker()
  • Worker.load
  • Worker.write
  • Worker.writeText
  • Worker.read
  • Worker.remove
  • Worker.transcode
  • Worker.trim
  • Worker.concatDemuxer
  • Worker.run

---

createWorker(options): Worker

createWorker is a factory function that creates a ffmpeg worker, a worker is basically a Web Worker in browser and Child Process in Node.

Arguments:

• options an object of customized options
  • corePath path for ffmpeg-core.js script
  • workerPath path for downloading worker script
  • workerBlobURL a boolean to define whether to use Blob URL for worker script, default: true
  • logger a function to log the progress, a quick example is m => console.log(m)
  • progress a function to trace the progress, a quick example is p => console.log(p)

Examples:

const { createWorker } = FFmpeg;
const worker = createWorker({
  corePath: "./node_modules/@ffmpeg/core/ffmpeg-core.js",
  logger: m => console.log(m)
});

Worker.load(jobId): Promise

Worker.load() loads ffmpeg-core.js script (download from remote if not presented), it makes Web Worker/Child Process ready for next action.

Arguments:

• jobId jobId is generated by ffmpeg.js to identify each job, but you can put your own when calling the function.

Examples:

(async () => {
  await worker.load();
})();

Worker.write(path, data, jobId): Promise

Worker.write() writes data to specific path in Emscripten file system, it is an essential step before doing any other tasks.

Arguments:

• path path to write data to file system
• data data to write, can be Uint8Array, URL or base64 format
• jobId @see Worker.load()

Examples:

(async () => {
  await worker.write(
    "flame.avi",
    "http://localhost:3000/tests/assets/flame.avi"
  );
})();

Worker.writeText(path, text, jobId): Promise

Worker.write() writes text data to specific path in Emscripten file system.

Arguments:

• path path to write data to file system
• text string to write to file
• jobId @see Worker.load()

Examples:

(async () => {
  await worker.write("sub.srt", "...");
})();

Worker.read(path, jobId): Promise

Worker.read() reads data from file system, often used to get output data after specific task.

Arguments:

• path path to read data from file system
• jobId @see Worker.load()

Examples:

(async () => {
  const { data } = await worker.read("output.mp4");
})();

Worker.remove(path, jobId): Promise

Worker.remove() removes files in file system, it will be better to delete unused files if you need to run ffmpeg.js multiple times.

Arguments:

• path path for file to delete
• jobId @see Worker.load()

Examples:

(async () => {
  await worker.remove("output.mp4");
})();

Worker.transcode(input, output, options, jobId): Promise

Worker.transcode() transcode a video file to another format.

Arguments:

• input input file path, the input file should be written through Worker.write()
• output output file path, can be read with Worker.read() later
• options a string to add extra arguments to ffmpeg
• jobId @see Worker.load()

Examples:

(async () => {
  await worker.transcode("flame.avi", "output.mp4", "-s 1920x1080");
})();

Worker.trim(input, output, from, to, options, jobId): Promise

Worker.trim() trims video to specific interval.

Arguments:

• inputPath input file path, the input file should be written through Worker.write()
• outputPath output file path, can be read with Worker.read() later
• from start time, can be in time stamp (00:00:12.000) or seconds (12)
• to end time, rule same as above
• options a string to add extra arguments to ffmpeg
• jobId @see Worker.load()

Examples:

(async () => {
  await worker.trim("flame.avi", "output.mp4", 1, 2);
})();

Worker.concatDemuxer(input, output, options, jobId): Promise

Worker.concatDemuxer() concatenates multiple videos using concatDemuxer. This method won't encode the videos again. But it has its limitations. See Concat demuxer Wiki

Arguments:

• input input file paths as an Array, the input files should be written through Worker.write()
• output output file path, can be read with Worker.read() later
• options a string to add extra arguments to ffmpeg
• jobId check Worker.load()

Examples:

(async () => {
  await worker.concatDemuxer(["flame-1.avi", "flame-2.avi"], "output.mp4");
})();

Worker.run(args, jobId): Promise

Worker.run() is similar to FFmpeg cli tool, aims to provide maximum flexiblity for users.

Arguments:

• args a string to represent arguments, note: inputPath must start with /data/ as worker.write write to this path by default.
• jobId check Worker.load()

Examples:

(async () => {
  await worker.run("-i /data/flame.avi -s 1920x1080 output.mp4");
})();