npm package: 7lab_groove_test
Description: bindings to libgroove - generic music player library
Author: Andrew Kelley
Latest version: 1.0.0

# node-groove

Node.js bindings to [libgroove](https://github.com/andrewrk/libgroove) -
generic music player backend library.

Live discussion in `#libgroove` on [freenode](https://freenode.net/).

Here are the main interfaces. See API Documentation below for more details.

 * GrooveFile - represents an open audio file.
 * GroovePlaylist - put files in the playlist, and the playlist decodes the
   files and fills up the attached sinks.
 * GroovePlayer - attach this sink to a playlist to play the decoded audio over
   the system's speakers.
 * GrooveEncoder - attach this sink to a playlist to obtain encoded audio
   buffers, such as an mp3 stream.
 * GrooveLoudnessDetector - attach this sink to a playlist to compute how loud
   files sound to the human ear, along with the "true peak" value. You can use
   this to implement ReplayGain.
 * GrooveFingerprinter - attach this sink to a playlist to compute an acoustid
   fingerprint. This can be used to look up a file by its audio content and
   figure out which tags should be applied.
 * GrooveWaveformBuilder - attach this sink to a playlist to compute a JSON
   representation of an audio file. This can be used to display a visualization
   of the audio file.

## Usage

1. Install libgroove to your system. libgroove is a set of 4 libraries;
   node-groove depends on all of them. So for example on ubuntu, make sure to
   install libgroove-dev, libgrooveplayer-dev, libgrooveloudness-dev, and
   libgroovefingerprinter-dev.
2. `npm install --save groove`

### Versions

 * node-groove >=3.0.0 depends on libgroove >=5.0.0
 * node-groove >=2.4.0 <3.0.0 depends on libgroove >=4.3.0 <5.0.0
 * node-groove 2.3.4 depends on libgroove <4.3.0

See CHANGELOG.md for release notes and upgrade guide.

### Get Metadata from File

```js
var groove = require('groove');

groove.open("danse-macabre.ogg", function(err, file) {
  if (err) throw err;
  console.log(file.metadata());
  console.log("duration:", file.duration());
  file.close(function(err) {
    if (err) throw err;
  });
});
```

#### More Examples

 * example/metadata.js - read or update metadata in a media file
 * example/playlist.js - play several files in a row and then exit
 * example/replaygain.js - compute replaygain values for media files
 * example/transcode.js - convert and splice several files together
 * example/fingerprint.js - create an acoustid fingerprint for media files
 * example/devices.js - list the playback devices on the system
 * example/waveform.js - calculate a waveformjs compatible representation of a media file

## API Documentation

### globals

#### groove.setLogging(level)

`level` can be:

 * `groove.LOG_QUIET`
 * `groove.LOG_ERROR`
 * `groove.LOG_WARNING`
 * `groove.LOG_INFO`

#### groove.loudnessToReplayGain(loudness)

Converts a loudness value which is in LUFS to the ReplayGain-suggested dB
adjustment.

#### groove.dBToFloat(dB)

Converts dB format volume adjustment to a floating point gain format.

#### groove.getVersion()

Returns an object with these properties:

 * `major`
 * `minor`
 * `patch`

### GrooveFile

#### groove.open(filename, callback)

`callback(err, file)`

#### file.close(callback)

`callback(err)`

#### file.duration()

In seconds.

#### file.shortNames()

A comma-separated list of short names for the format.

#### file.getMetadata(key, [flags])

Flags:

 * `groove.TAG_MATCH_CASE`
 * `groove.TAG_DONT_OVERWRITE`
 * `groove.TAG_APPEND`

#### file.setMetadata(key, value, [flags])

See `getMetadata` for flags.

Pass `null` for `value` to delete a key.

#### file.metadata()

This returns an object populated with all the metadata.
Updating the object does nothing. Use `setMetadata` to
update metadata and then `save` to write changes to disk.

#### file.dirty

Boolean whether `save` will do anything.

#### file.filename

The string that was passed to `groove.open`

#### file.overrideDuration(duration)

If you know for sure the actual duration of the file, call this function
to set the actual duration in seconds of the file. `GrooveWaveformBuilder`
will use this value instead of `file.duration()`.

This must only be called when no `GroovePlaylistItem` references to this file.

#### file.save(callback)

`callback(err)`

### GroovePlaylist

#### groove.createPlaylist()

A playlist managers keeping an audio buffer full. To send the buffer
to your speakers, use `playlist.createPlayer()`.

Note: you probably only want one playlist. In node-groove, a playlist is
a low-level audio processing concept, not to be confused with user-facing
playlists where users might add, remove, and re-order songs.

#### playlist.destroy()

When finished with your playlist you must destroy it.

#### playlist.items()

Returns a read-only array of playlist items.
Use `playlist.insert` and `playlist.remove` to modify.

`[playlistItem1, playlistItem2, ...]`

#### playlist.play()

#### playlist.pause()

#### playlist.seek(playlistItem, position)

Seek to `playlistItem`, `position` seconds into the song.

#### playlist.insert(file, gain, peak, nextPlaylistItem)

Creates a new playlist item with file and puts it in the playlist before
`nextPlaylistItem`. If `nextPlaylistItem` is `null`, appends the new
item to the playlist.

`gain` is a float format volume adjustment that applies only to this item.
defaults to 1.0

`peak` is float format, see `item.peak`.
defaults to 1.0

Returns the newly added playlist item.

Once you add a file to the playlist, you must not `file.close()` it until
you first remove it from the playlist.

#### playlist.remove(playlistItem)

Remove `playlistItem` from the playlist.

Note that you are responsible for calling `file.close()` on every file
that you open with `groove.open`. `playlist.remove` will not close files.

#### playlist.position()

Returns `{item, pos}` where `item` is the playlist item currently being
decoded and `pos` is how many seconds into the song the decode head is.

Note that typically you are more interested in the position of the play head,
not the decode head. Example methods which return the play head are
`player.position()` and `encoder.position()`.

#### playlist.playing()

Returns `true` or `false`.

#### playlist.clear()

Remove all playlist items.

#### playlist.count()

How many items are on the playlist.

#### playlist.gain

#### playlist.setGain(value)

Between 0.0 and 1.0. You probably want to leave this at 1.0, since using
replaygain will typically lower your volume a significant amount.

#### playlist.setItemGainPeak(playlistItem, gain, peak)

`gain` is a float that affects the volume of the specified playlist item only.
To convert from dB to float, use exp(log(10) * 0.05 * dBValue).

See `item.peak`

#### playlist.setFillMode(mode)

`mode` can be:

 * `groove.EVERY_SINK_FULL`

    The playlist will decode audio if any sinks are not full. If any sinks do
    not drain fast enough the data will buffer up in the playlist.

 * `groove.ANY_SINK_FULL`

    This is the default behavior. With this behavior, the playlist will stop
    decoding audio when any attached sink is full, and then resume decoding
    audio every sink is not full.

Defaults to `groove.EVERY_SINK_FULL`.

### GroovePlaylistItem

These are not instantiated directly; instead they are returned from
`playlist.items()`.

A `GroovePlaylistItem` is merely a pointer into a `GroovePlaylist`. If you
remove a playlist item from a playlist, any playlist item references you
have lying around become dangling pointers.

#### item.file

Read-only.

#### item.gain

A volume adjustment in float format to apply to the file when it plays.
This is typically used for loudness compensation, for example ReplayGain.
To convert from dB to float, use `groove.dBToFloat`

Read-only. Use `playlist.setItemGain` to modify.

#### item.peak

The sample peak of this playlist item is assumed to be 1.0 in float
format. If you know for certain that the peak is less than 1.0, you
may set this value which may allow the volume adjustment to use
a pure amplifier rather than a compressor. This results in slightly
better audio quality.

Read-only. Use `playlist.setItemPeak` to modify.

#### item.id

Every time you obtain a playlist item from groove, you will get a fresh
JavaScript object, but it might point to the same underlying libgroove pointer
as another. The `id` field is a way to check if two playlist items reference
the same one.

Read-only.

### GroovePlayer

#### groove.getDevices()

Before you can call this function, you must call
`groove.connectSoundBackend()`.

Returns an object like this:

```js
{
  list: [
    {
      name: "User-Friendly Device Name",
      id: "unique device ID that persists across plugs and unplugs",
      isRaw: false, // true if this device would claim exclusive access
      probeError: 3, // non zero if scanning this device did not work
    },
    //...
  ],
  defaultIndex: 0,
}
```

#### groove.connectSoundBackend([backend])

`backend` is optional. If left blank the best backend is automatically
selected. Otherwise it can be one of these:

 * `groove.BACKEND_JACK`
 * `groove.BACKEND_PULSEAUDIO`
 * `groove.BACKEND_ALSA`
 * `groove.BACKEND_COREAUDIO`
 * `groove.BACKEND_WASAPI`
 * `groove.BACKEND_DUMMY`

#### groove.disconnectSoundBackend()

#### groove.createPlayer()

Creates a GroovePlayer instance which you can then configure by setting
properties.

#### player.device

Before calling `attach()`, set this to one of the devices
returned from `groove.getDevices()`.

#### player.attach(playlist, callback)

Sends audio to sound device.

`callback(err)`

#### player.detach(callback)

`callback(err)`

#### player.position()

Returns `{item, pos}` where `item` is the playlist item currently being
played and `pos` is how many seconds into the song the play head is.

#### player.on('nowplaying', handler)

Fires when the item that is now playing changes. It can be `null`.

`handler()`

#### player.on('bufferunderrun', handler)

Fires when a buffer underrun occurs. Ideally you'll never see this.

`handler()`

#### player.on('devicereopened', handler)

Fires when you have set `useExactAudioFormat` to `true` and the audio device
has been closed and re-opened to match incoming audio data.

`handler()`

### GrooveEncoder

#### groove.createEncoder()

#### encoder.bitRate

select encoding quality by choosing a target bit rate

#### encoder.formatShortName

optional - help libgroove guess which format to use.
`avconv -formats` to get a list of possibilities.

#### encoder.codecShortName

optional - help libgroove guess which codec to use.
`avconv-codecs` to get a list of possibilities.

#### encoder.filename

optional - provide an example filename to help libgroove guess
which format/codec to use.

#### encoder.mimeType

optional - provide a mime type string to help libgrooove guess
which format/codec to use.

#### encoder.targetAudioFormat

The desired audio format settings with which to encode.
`groove.createEncoder()` defaults these to 44100 Hz,
signed 16-bit int, stereo.
These are preferences; if a setting cannot be used, a substitute will
be used instead. In this case, actualAudioFormat will be updated to reflect
the substituted values.

Properties:

 * `sampleRate`
 * `channelLayout` - array of channel ids
 * `sampleFormat`

#### encoder.actualAudioFormat

groove sets this to the actual format you get when you attach the encoder.
Ideally will be the same as targetAudioFormat but might not be.

Properties:

 * `sampleRate`
 * `channelLayout` - array of channel ids
 * `sampleFormat`

#### encoder.sinkBufferSize

How big the sink buffer should be, in sample frames.
`createEncoder` defaults this to 8192

#### encoder.encodedBufferSize

How big the encoded audio buffer should be, in bytes.
`createEncoder` defaults this to 16384

#### encoder.attach(playlist, callback)

`callback(err)`

#### encoder.detach(callback)

`callback(err)`

#### encoder.getBuffer()

Returns `null` if no buffer available, or an object with these properties:

 * `buffer` - a node `Buffer` instance which is the encoded data for this chunk
   this can be `null` in which case this buffer is actually the end of
   playlist sentinel.
 * `item` - the GroovePlaylistItem of which this buffer is encoded data for
 * `pos` - position in seconds that this buffer represents in into the item

#### encoder.on('buffer', handler)

`handler()`

Emitted when there is a buffer available to get. You still need to get the
buffer with `getBuffer()`.

#### encoder.position()

Returns `{item, pos}` where `item` is the playlist item currently being
encoded and `pos` is how many seconds into the song the encode head is.

### GrooveLoudnessDetector

#### groove.createLoudnessDetector()

returns a GrooveLoudnessDetector

#### detector.infoQueueSize

Set this to determine how far ahead into the playlist to look.

#### detector.disableAlbum

Set to `true` to only compute track loudness. This is faster and requires less
memory than computing both.

#### detector.attach(playlist, callback)

`callback(err)`

#### detector.detach(callback)

`callback(err)`

#### detector.getInfo()

Returns `null` if no info available, or an object with these properties:

 * `loudness` - loudness in LUFS
 * `peak` - sample peak in float format of the file
 * `duration` - duration in seconds of the track
 * `item` - the GroovePlaylistItem that this applies to, or `null` if it applies
   to the entire album.

#### detector.position()

Returns `{item, pos}` where `item` is the playlist item currently being
detected and `pos` is how many seconds into the song the detect head is.

#### detector.on('info', handler)

`handler()`

Emitted when there is info available to get. You still need to get the info
with `getInfo()`.

### GrooveFingerprinter

#### groove.createFingerprinter()

returns a GrooveFingerprinter

#### groove.encodeFingerprint(rawFingerprint)

Given an Array of integers which is the raw fingerprint, encode it into a
string which can be submitted to acoustid.org.

#### groove.decodeFingerprint(fingerprint)

Given the fingerprint string, returns a list of integers which is the raw
fingerprint data.

#### printer.infoQueueSize

Set this to determine how far ahead into the playlist to look.

#### printer.attach(playlist, callback)

`callback(err)`

#### printer.detach(callback)

`callback(err)`

#### printer.getInfo()

Returns `null` if no info available, or an object with these properties:

 * `fingerprint` - integer array which is the raw fingerprint
 * `duration` - duration in seconds of the track
 * `item` - the GroovePlaylistItem that this applies to, or `null` if it applies
   to the entire album.

#### printer.position()

Returns `{item, pos}` where `item` is the playlist item currently being
fingerprinted and `pos` is how many seconds into the song the printer head is.

#### printer.on('info', handler)

`handler()`

Emitted when there is info available to get. You still need to get the info
with `getInfo()`.

### GrooveWaveformBuilder

#### groove.createWaveformBuilder()

returns a GrooveWaveformBuilder

#### waveform.widthInFrames

How many frames wide the waveform data will be. Defaults to 1920.

If you have a song with 100 frames and `widthInFrames` is 50, then each
waveform data frame will correspond to 2 frames of the original song.

#### printer.infoQueueSizeBytes

Set this to determine how far ahead into the playlist to look.

#### waveform.attach(playlist, callback)

`callback(err)`

#### waveform.detach(callback)

`callback(err)`

#### waveform.getInfo()

Returns `null` if no info available, or an object with these properties:

 * `buffer` - A `Buffer` of the waveform data, one unsigned 8 bit integer per
   `widthInFrames`.
 * `expectedDuration` - This is the duration in seconds that was used to create
   the waveform data. If this is different than `actualDuration` then the data
   is invalid and must be re-calculated, this time using `file.overrideDuration()`
 * `actualDuration` - This is the correct duration in seconds for the track,
   known only after waveform calculation is complete.
 * `item` - the GroovePlaylistItem that this applies to, or `null` if this info
   signals the end of playlist.

#### waveform.position()

Returns `{item, pos}` where `item` is the playlist item currently being
calculated and `pos` is how many seconds into the song the waveform head is.

#### waveform.on('info', handler)

`handler()`

Emitted when there is info available to get. You still need to get the info
with `getInfo()`.