API
===

- [createWorker()](#create-worker)
  - [Worker.load](#worker-load)
  - [Worker.write](#worker-write)
  - [Worker.read](#worker-read)
  - [Worker.mkdir](#worker-mkdir)
  - [Worker.remove](#worker-remove)
  - [Worker.transcode](#worker-transcode)
  - [Worker.run](#worker-run)

---

<a name="create-worker"></a>
## 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)`


**Examples:**

```javascript
const { createWorker } = FFmpeg;
const worker = createWorker({
  corePath: './node_modules/@ffmpeg/core/ffmpeg-core.js',
  logger: m => console.log(m),
});
```
<a name="worker-load"></a>
### 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:**

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

<a name="worker-write"></a>
### 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` check Worker.load()

**Examples:**

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

<a name="worker-read"></a>
### 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` check Worker.load()

**Examples:**

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

<a name="worker-mkdir"></a>
### Worker.mkdir(path, jobId): Promise

Worker.mkdir() creates a directory in file system, useful when you need to group files in a directory.

**Arguments:**

- `path` path to create directory
- `jobId` check Worker.load()

**Examples:**

```javascript
(async () => {
  await worker.mkdir('/video-clips');
})();
```

<a name="worker-remove"></a>
### 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` check Worker.load()

**Examples:**

```javascript
(async () => {
  await worker.remove('output.mp4');
})();
```

<a name="worker-transcode"></a>
### Worker.transcode(inputPath, outputPath, options, jobId): Promise

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

**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
- `options` a string to add extra arguments to ffmpeg
- `jobId` check Worker.load()

**Examples:**

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

<a name="worker-run"></a>
### 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
- `jobId` check Worker.load()

**Examples:**

```javascript
(async () => {
  await worker.run('-i flame.avi -s 1920x1080 output.mp4');
})();
```