7lab_groove_test v1.0.0

node-groove

Node.js bindings to libgroove - generic music player backend library.

Live discussion in #libgroove on freenode.

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

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:

{
  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().