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mse-audio-wrapper

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Readme

MSE (Media Source Extensions) Audio Wrapper

mse-audio-wrapper is a library to enable Media Source Extensions API playback for unsupported audio containers and raw codecs. MSE Audio Wrapper uses both WEBM and the ISO Base Media File Format (MPEG-4 Part 12) (commonly referred to as Fragmented MP4 or fmp4).

API
- MSEAudioWrapper
  - Takes in audio (MP3, AAC, Ogg Flac, Ogg Opus, Ogg Vorbis)
  - Outputs
    - ISOBMFF (fMP4) (MP3, AAC, Flac, Opus)
    - WEBM (Opus, Vorbis)
Demo
- React application that demonstrates MSEAudioWrapper being used to support icecast-metadata-js
- Checkout the demo here!

API

`MSEAudioWrapper`

A class that takes in audio (MP3, AAC, Ogg Flac, Ogg Opus, or Ogg Vorbis) and outputs ISOBMFF or WEBM.

Usage

To use MSEAudioWrapper, create a new instance of the class by passing in the mimetype of your audio data.

Note: For directly converting from a HTTP response, use the mimetype contained in the Content-Type header
```
import MSEAudioWrapper from "mse-audio-wrapper";

const headers = myHTTPResponse.headers;
const mimeType = headers.get('Content-Type');

const audioWrapper = new MSEAudioWrapper(mimeType);
```
To begin processing audio data, pass in the audio data into the instance's .iterator(). This method returns an iterator that can be consumed using a for ...of or for await...of loop. Repeat this step until all audio data has been read.
```
const audioData = response.body;

for (const wrappedAudio of audioWrapper.iterator(audioData)) {
  // Do something with the wrapped data
}
```

MSEAudioWrapper will store any partial data until at least one full audio frame can be processed.

Note: Any data that does not conform to the instance's mimetype will be discarded.
Once enough data has been received to form at least 4 complete audio frames, and 1022 bytes of audio data, the initial segment will be returned along with a media segment containing the audio data. These values are user configurable using the options parameter in the constructor.
- 1st Iteration
```
"initial segment"
--ftyp [file type]
--moov [movie]
"media segment"
--moof [movie fragment]
--mdat [audio data]
```
Subsequent iterations will only return media segments.
- nth Iteration
```
"media segment"
--moof [movie fragment]
--mdat [audio data]
```

Methods

`const wrapper = new MSEAudioWrapper("audio/mpeg", {minFramesPerSegment: 2, minBytesPerSegment: 576, preferredContainer: "webm"});` * `constructor` * Creates a new instance of MSEAudioWrapper that can be used to wrap audio for a given mimetype. * Parameters: * `mimetype` required Incoming audio codec or container * MP3 - `audio/mpeg` * AAC - `audio/aac`, `audio/aacp` * Ogg FLAC - `application/ogg`, `audio/ogg` * Ogg Opus - `application/ogg`, `audio/ogg` * Ogg Vorbis - `application/ogg`, `audio/ogg` * `options` optional ### Options * `options.minFramesPerSegment` optional Minimum audio frames to store before returning a segment * Accepts an integer greater than 0 * Defaults to `4` * `options.minBytesPerSegment` optional Minimum audio bytes to store before returning a segment * Accepts an integer greater than 0 * Defaults to `1022` * `options.maxFramesPerSegment` optional Maximum audio frames to group in a single segment * Accepts an integer greater than 0 * Defaults to `20` * `options.preferredContainer` optional Preferred output container when there are multiple supported containers * Accepts `"webm"`, `"fmp4"` * Defaults to `"fmp4"` ### Callbacks * `options.onMimeType(mimeType)` optional Called when the output mimeType is determined. * See `wrapper.mimeType` for a list of the possible output mimetypes * `options.onCodecUpdate(codecInfo)` optional Called when there is a change in the codec header. * `codecInfo` is an object containing information about the codec such as `bitrate`, `sampleRate`, etc. * `wrapper.iterator(data)` * Returns an Iterator that can be used in a `for ...of` loop to return wrapped audio * Parameters: * `data` Uint8Array of audio data to wrap * `wrapper.inputMimeType` * Getter that returns the mime-type of the incoming audio data * Examples: * MP3 - `audio/mpeg` * AAC - `audio/aac` * Ogg FLAC - `application/ogg`, `audio/ogg` * Ogg Opus - `application/ogg`, `audio/ogg` * Ogg Vorbis - `application/ogg`, `audio/ogg` * `wrapper.mimeType` * Getter that returns the mime-type of the wrapped audio data * Note: For Ogg streams, the mime-type will only be available after the first media segment is returned. * Examples: * MP3 - `audio/mp4;codecs="mp3"` * AAC - `audio/mp4;codecs="mp4a.40.2"` * FLAC - `audio/mp4;codecs="flac"` * OPUS (ISOBMFF) - `audio/mp4;codecs="opus"` * OPUS (WEBM) - `audio/webm;codecs="opus"` * Vorbis - `audio/webm;codecs="vorbis"`

Demo

mse-audio-wrapper is used in the demo for icecast-metadata-js to allow for Icecast metadata support in Firefox (mp3, aac, flac) and Chrome (flac) by wrapping the streaming audio in ISOBMFF so it can be used with the MediaSource API.

https://github.com/eshaz/icecast-metadata-js/tree/master/src/demo

mse-audio-wrapper