# HLS Transcoder

**THIS PACKAGE IS STILL UNDER ACTIVE DEVELOPMENT, API CHANGES CAN AND LIKELY WILL HAPPEN REGARDLESS OF WHETHER THEY ARE DOCUMENTED BELOW**

An FFMPEG Wrapper heavily inspired by [simple-hls](https://github.com/techwarriorz/simple-hls), to transcode Multi-bitrate HLS videos.

## Installation:

Via npm:

```bash
npm install hls-transcoder
```

### Prerequisites

#### ffmpeg and ffprobe

hls-transcoder requires both ffmpeg, and ffprobe. If ffmpeg and ffprobe are installed on your system, and added to `PATH`, hls-transcoder will try invoking each program via `ffmpeg` and `ffprobe` respectively.

Alternatively, you can use pre-compiled binaries, ie with `@ffmpeg-installer/ffmpeg` and `@ffprobe-installer/ffprobe`, and specify the `ffmpegPath` and `ffprobePath` properties in the `options` object.

---

## Usage:

### Basic Setup

**Typescript:**

```ts
import Transcoder from 'hls-transcoder'

async function transcodeVideo() {
  const transcoder = new Transcoder(`[input-video.mp4/.mov/.avi/etc]``${__dirname}/output`)

  transcoder.on('error', (err) => {
    console.error(err)
  })

  try {
    const hlsPath = await transcoder.transcode()
    console.log('Successfully Transcoded Video')
  } catch (err) {
    console.log(err)
  }
}

transcodeVideo()
```

**_OR_**

Use `@ffmpeg-installer/ffmpeg` and `@ffprobe-installer/ffprobe` to use precompiled binaries of ffmpeg and ffprobe without having to install on your system.

**Typescript:**

```ts
import Transcoder from 'hls-transcoder'
import ffmpeg from '@ffmpeg-installer/ffmpeg'
import ffprobe from '@ffprobe-installer/ffprobe'

async function transcodeVideo() {
  const transcoder = new Transcoder(`[input-video.mp4/.mov/.avi/etc]``${__dirname}/output`, {
    ffmpegPath: ffmpeg.path,
    ffprobePath: ffprobe.path
  })

  transcoder.on('error', (err) => {
    console.error(err)
  })

  try {
    const hlsPath = await transcoder.transcode()
    console.log('Successfully Transcoded Video')
  } catch (err) {
    console.log(err)
  }
}

transcodeVideo()
```

## Documentation:

### Options  
When creating a new instance of the `Transcoder` class, you can supply a third parameter `options` as an object which will override the default behaviour / settings of hls-transcoder. The possible options and their default values are as follows:  

- **allowUpscaling**
  - Description: When set to `false` renditions will only be transcoded if the original video is the same resolution or higher than that of the rendition being transcoded. When set to `true` 
  - Default: `false`
  - Type: boolean | undefined
- **ffmpegPath**
  - Description: Allows specifying which PATH hls-transcoder should use when invoking an `ffmpeg` child_process
  - Default: `ffmpeg`
  - Type: string | undefined
- **ffprobePath**
  - Description: Allows specifying which PATH hls-transcoder should use when invoking an `ffprobe` child_process
  - Default: `ffprobe`
  - Type: string | undefined  
- **renditions**
  - Description: The various resolutions and bitrates hls-transcoder will use when transcoding video files
  - Default: [See default renditions](#TODO)
  - Type: RenditionOptions | undefined

### Setting event handlers

The `Transcoder` class extends `EventEmitter` and will emit the following events:

- **'error'**
- **'stderr'**
- **'progress'**
- **'end'**

**'error' - transcoding errors**

```ts
transcoder.on('error', (err) => {
  console.error(err)
})
```

**'stderr' - information ffmpeg sends via the command line**

```ts
transcoder.on('stderr', (data) => {
  console.log(data)
})
```

**'progress' - transcoding progress information**

```ts
transcoder.on('progress', (progress) => {
  console.log(progress)
})
```

The progress event is emitted everytime ffmpeg reports progress information. The progress object contains the following keys:

- `frame`: total processed frame count
- `fps`: framerate at which FFmpeg is currenlty processing

**'end' - information about ffmpegs exit status**

```ts
transcoder.on('end', (data) => {
  console.log(data)
})
```

---

## Ongoing TODOS:

- ~~Progress Bar~~
- Add option for outputPath param per Rendition
- Add option for Renditions per Resolution
- Fix ffmpeg stderr and stdout processing / parsing
  - Currently in progress
- Test and/or handle .ts file name overflows
  - ie. '1080p_0.ts' where number of ts segments > 10
  - Figured out, default behavior is to just keep adding numbers, ie 11, 12, 13 - so this shouldn't be an issue unless there's a use case where a program is expecting the filenames to match a specfic pattern like that
- Create dir automatically if doesn't exist?
  - Should do this, right now it fails silently if output dir doesn't exist
- Option to enable / disable overwrite?
- Invalid dimensions for renditions appear to fail silently