node-medley
is a Node.js native module built on top of JUCE framework. It provides audio playback to both audio output device and Node.js stream
- Cross-platform
- Seamless playback with automatic track transitions
- Smooth track transition, with customizable transition points
- Track metadata reading, including cover art and lyrics
- ReplayGain support
- Audio level normalization (in conjunction with ReplayGain)
- Built-in audio limiter
- Built-in Karaoke effect (vocal removal)
- Audio level measurement
- Play directly to audio device
- Consumption of PCM data via Node.js streams
linux/amd64
linux/arm64
win32/x64
macOS/x64
macOS/arm64
To install on Linux system, you'll need to install the following dependencies:
-
asound
- Required for audio output on Linux systems
-
freetype
- Required by JUCE framework (but not actively used)
-
opus
andopusfile
- For decoding .opus audio files
sudo apt-get install libasound2 libfreetype6 libopus0 libopusfile0
sudo dnf install alsa-lib freetype opus opusfile
npm i @seamless-medley/medley
pnpm add @seamless-medley/medley
// Import the main classes
import { Medley, Queue } from '@seamless-medley/medley';
// Create a queue instance and pass it to the Medley class during instantiation
const queue = new Queue();
const medley = new Medley(queue);
// Add tracks to the `queue` and start playing
queue.add('/path/to/file');
queue.add('/path/to/file2');
medley.play();
This will start playback on the default audio device.
Currently, the supported file formats include: wav
, aiff
, mp3
, ogg
, flac
and opus
. More formats may be added in the future.
- Getting available audio devices
- Selecting audio device
- Null Audio device
- Getting PCM data
- Dynamic queue
- Check if a track is loadable
- Getting metadata
- Getting cover art and lyrics
- Reading audio level information
- Normalizing tracks audio level
- Custom transition point
Simply use the getAvailableDevices method.
Utilize data returned from the getAvailableDevices method with the setAudioDevice method.
Example:
// Use the default device of the first type
const allDevices = medley.getAvailableDevices();
medley.setAudioDevice({
type: allDevices[0].type,
device: allDevices[0].defaultDevice
});
node-medley
includes a special audio device called Null Device
which does not output sound to a physical audio device.
This is useful in environments without installed audio devices or when only PCM audio data consumption is needed, see requestAudioStream method.
Example:
medley.setAudioDevice({ type: 'Null', device: 'Null Device' });
// Request a stream of signed 16-bit, little endian audio at 48000 sample rate
const result = await medley.requestAudioStream({
format: 'Int16LE',
sampleRate: 48000
});
// Pipe to another stream
result.stream.pipe(/* destination */);
// Or intercept data with the `data` event
result.stream.on('data', (buffer) => {
// Do something with `buffer`
});
// When finished, don't forget the delete the stream
medley.deleteAudioStream(result.id);
Sometimes, preloading all tracks can lead to monotony, so the queue can dynamically update using the enqueueNext event
Example:
medley.on('enqueueNext', (done) => {
const newTrack = getNewFreshTrack(); // Logic for fetching new track
queue.add(newTrack);
done(true);
});
Use isTrackLoadable static method.
Metadata can be retrieved in two ways:
- From a file path
- Use getMetadata static method
- From the deck
- Use getDeckMetadata method
Utilize the getCoverAndLyrics method.
Real-time audio level are accessible via the level property.
Example:
// Read audio levels at a rate of 30 times per second
setInterval(() => {
const audioLevel = medley.level;
// Use the value returned
}, 1000 / 30);
ReplayGain analyzes and adjusts perceived loudness.
node-medley
supports reading ReplayGain Track-gain
metadata embeded in audio files.
To embed it, use one of these scanners.
Usually, ReplayGain attenuates the played back audio, a make-up
gain should be applied to boost the audio level back to the normalized level, you can change this make-up
gain by changing the replayGainBoost property.
The make-up
gain will not cause clipping, because there is an audio limiter preventing that from happening in the audio pipline.
node-medley
automatically analyzes track to find audio positions in which it should start/stop playing and also the positions/durations the transition between track should occur.
but, sometimes this may not be as intended, you can customize that by giving node-medley
some hints.
The hints can come from the metadata embed in the track itself using user-defined tag, here are the supported tags:
-
CUE-IN
orCUE_IN
- Start position of the track, in secondsThis correspond to the TrackInfo
cueInPosition
property. -
CUE-OUT
orCUE_OUT
- Stop position of the track, in secondsThis correspond to the TrackInfo
cueOutPosition
property.
Alternatively, you can provide that values when adding a track into the queue.
See also:
-
- Methods
- Properties
- Events
- Static methods
This is the main class, the constructor accepts an instance of the Queue class.
new Medley(queue, options)
NOTE: JavaScript
Array
cannot be used as a queue.
-
logging
(boolean?) - Enable logging, See log event -
skipDeviceScanning
(boolean?) - Skip scanning for audio devices
Methods
Start playing, if the playing was previously paused it will be resumed.
The shouldFade
parameter is used only when resuming.
Stop playing.
Toggle play/pause.
Forcefully transit to the next track with a fade-out effect.
-
time
(number) - Time in seconds. -
deckIndex
(number?) - Deck index, possible values are:0
,1
,2
-
fraction
(number) - Fraction of the track's length.-
0
- Seek to the beginning. -
0.5
Seek to the middle of the track.
-
-
deckIndex
optional deck index, possible values are:0
,1
,2
-
deckIndex
(number) - Deck index, possible values are:0
,1
,2
Returns an object
with:
-
current
(number?) - Current playing position -
duration
(number?) - Total duration -
first
(number?) - First audible position -
last
(number?) - Last audible position -
leading
(number?) - Fade-in position -
trailing
(number?) - Fade-out position -
cuePoint
(number?) -
transitionStart
(number?) -
transitionEnd
(number?)
-
deckIndex
(number) - Deck index, possible values are:0
,1
,2
Returns Metadata for the specified deckIndex
Returns array
of object
describing audio devices.
-
type
(string) - Device type -
isCurrent
(boolean) -true
if this device type is currently selected -
devices
(string[]) - List of devices of this type -
defaultDevice
(string) - Default device name of this type -
currentDevice
(string | undefined) - Currently selected device name of this type,undefined
if none
Get the audio device currently being selected, returns undefined
if none.
If available, returns an object
with:
-
type
(string) - Device type -
device
(string) - Device name
Set audio device used for playback.
The descriptor
is an object
containing:
-
type
(string?) - Device type, if omitted, the currently selected device type is used -
device
(string?) - Device name, if omitted, the default
If both fields are omitted, this method does nothing.
Returns false
if the specified device cannot be used.
Returns true
if some device is selected.
Use getAudioDevice() to get the actual selected device.
Request a PCM audio data stream
options?
is an object
with:
-
sampleRate
(number) - Sample rate for the PCM data. Defaults to the default device's sample rate if omitted. -
format
- Audio sample format, possible values are:-
Int16LE
- 16 bit signed integer, little endian -
Int16BE
- 16 bit signed integer, big endian -
FloatLE
- 32 bit floating point, little endian -
FloatBE
- 32 bit floating point, big endian
-
-
bufferSize
(number) - Maximun frames the internal buffer can hold, increase this value helps reduce stuttering in some situations- Default value is 250ms (
deviceSampleRate
* 0.25)
- Default value is 250ms (
-
buffering
(number):- Number of frames to buffer before returning the buffered frames back to Node.js stream
- Reducing this value will cause the stream to pump faster
- Default value is 10ms (
deviceSampleRate
* 0.01)
-
gain
(number) - Output gain, a floating point number ranging from 0 to 1 -
fx
(object) - Effects parameter:-
karaoke
: Parameters for the karaoke effect, see setFx(type: 'karaoke', params)
-
Returns a Promise
of object
with:
-
id
(number) - The request id, use this value to update or delete the requested stream -
channels
(number) - Number of audio channels, This is usuaully2
-
originalSampleRate
(number) - Original sample rate in audio pipeline -
sampleRate
(number) - Sample rate as requested -
bitPerSample
(number) - Bit per sample, depending on theformat
-
16
- forInt16LE
ofInt16BE
-
32
- forFloatLE
ofFloatBE
-
-
stream
(Readable) - Readable stream, for consuming PCM data -
update
((options) => boolean) - Update this audio stream, theoptions
is the same as updateAudioStream(id, options) -
getLatency
() => number - Get the audio latency -
getFx
- See getFxCalling this method from this object only effects the corresponding stream, but does not effect the main output.
-
setFx
- See setFxCalling this method from this object only effects the corresponding stream, but does not effect the main output.
Update the requested audio stream specified by id
returned from requestAudioStream method.
options
is an object
with:
-
gain
(number) - Output gain, a floating point number ranging from 0 to 1 -
buffering
- See requestAudioStream -
fx
(object) - Effects parameter:-
karaoke
: Parameters for the karaoke effect, see setFx(type: 'karaoke', params)
-
Returns true
if succeeded.
Delete the requested audio stream specified by id
returned from requestAudioStream method.
Get all parameter values for the karaoke effect.
Returns an object
with:
-
enabled
(boolean) -
mix
(number) - Dry/Wet for the karaoke effect -
lowpassCutoff
(number) - Cut off frequency for the low pass filter -
lowpassQ
(number) - Quality factor for the low pass filter -
highpassCutoff
(number) - Cut off frequency for the high pass filter -
highpassQ
(number) - Quality factor for the high pass filter
Set karaoke effect parameters.
The params
is an object
with:
-
enabled
(boolean?) -
dontTransit
(boolean?) - Do not apply dry/wet mix transition while enabling/disabling the effect. Must be used with theenabled
property. -
mix
(number?) - Dry/Wet for the karaoke effect -
lowpassCutoff
(number?) - Cut off frequency for the low pass filter -
lowpassQ
(number?) - Quality factor for the low pass filter -
highpassCutoff
(number?) - Cut off frequency for the high pass filter -
highpassQ
(number?) - Quality factor for the high pass filter
Returns true
if succeeded.
Properties
Type: boolean
Read only
Returns true
if playing, but not affected by the paused
property.
Type: boolean
Read only
Returns true
if playing but has been paused.
Type: number
Audio volume in linear scale.
0
= Silent
1
= 0dBFS
Type: number
Minimum: 0
Maximum: 100
S-Curve value used for fading in/out.
Type: number
Maximum duration in seconds for the fade-out transition between tracks.
Type: number
Duration in seconds at the beginning of a track to be considered as having a long intro.
A track with a long intro will cause a fading-in to occur during transition.
Type: number
Default: 9.0
Gain (in dB) to boost for tracks with ReplayGain metadata embeded, default to 9.0dB.
If a track has no ReplayGain metadata, this value is ignored.
Read only
Returns an object
with:
-
left
- Left channel level -
right
- Right channel level
With each channel having:
-
magnitude
(number) - Audio level -
peak
(number) - Holding peak
Read only
Returns audio reduction level in dB
Audio reduction occur during the internal audio processing
Events
Parameters:
-
deckIndex
(number) - Deck index where the event occur -
trackPlay
- An object describing detail of the play session for the Deck.-
uuid
(string) - A unique string identifying thetrackPlay
itself -
track
- Track, see TrackInfo -
duration
(number) - Track duration
-
Emits when a track has been loaded into a Deck.
Emits when a track has been unloaded from a Deck.
Emits when a Deck starts playing.
Emits when a Deck finishes playing.
Emits when a Deck becomes the main playing Deck.
Emits when the playing queue is exhausted and needs to be filled.
See Dynamic quque
Parameter:
-
done
- Call this function in the event handler withtrue
value to informnode-medley
that at least a track has been added to the queue and should be loaded.
Emits when the audio device changes, use getAudioDevice method to get the current audio device.
Emits when a log message is pushed from the native module.
Logging must be enabled when constructing the Medley instance, see Medley class options
Parameter:
-
level
(number) - Log levelname value trace -1 debug 0 info 1 warn 2 error 3 fatal 4 -
name
(string) - The logger's name -
msg
(string) - Log message
Static methods
Returns an object
containing information about node-medley
-
runtime
:-
file
- Node native module file name -
runtime
- Runtime name -
napi
-node-addon-api
version
-
-
version
-node-medley
version number -
juce
- Detail for the JUCE framework library being linked intonode-medley
version
-
cpu
-
intel
- Intel CPU -
arm
- ARM CPU -
arm64
- ARM64 CPU -
aarch64
- ARM64 CPU -
sse
- SIMD supports on x84_64 CPU -
neon
- SIMD supports on ARM CPU -
vdsp
- vDSP supports on macOS
-
Returns true
if the track
can be loaded and played.
Returns Metadata for path
Returns AudioProperties for path
Please note that this function may scan the whole file in order to get a good result.
Returns an object
with:
-
cover
(Buffer) - Cover art data -
coverMimeType
(string) - Cover art MIME type -
lyrics
(string) - Raw lyrics data
The queue class provides a list of tracks to the Medley class.
Constructor
Create a new instance of the Queue
class, an optional tracks
is an array of tracks to initially fill the queue.
The Queue
class is straightforward, For more control over your tracks list, manage it manually and provide a track when the Medley
object requires one, see enqueueNext event
Methods
Add a track to the queue, see TrackInfo
Add a list of tracks to the queue, see TrackInfo
Insert track(s) at position specified by the index
parameter.
Delete tracks(s) specified by count
starting from index
.
Swap tracks.
Move a track from currentIndex
to newIndex
.
Get the track at index
Set the track at index
Returns a new shallow copy of all tracks.
Properties
Total number of tracks in the queue.
A TrackInfo
can be either a string
to file path, or an object
with:
-
path
(string) - File path -
cueInPosition
(number?) - Start position of the track -
cueOutPosition
(number?) - Stop position of the track -
disableNextLeadIn
(boolean?)- Disables the lead-in of the next track, useful for transitioning from jingles/sweepers.
- The lead-in is the position where it is considered as the start singing point, usually presented in a track which has smooth/long beginning.
-
title
(string?) -
artist
(string?) -
album
(string?) -
isrc
(string?) - International Standard Recording Code -
albumArtist
(string?) -
originalArtist
(string?) -
trackGain
(number?) - ReplayGain value in dB (decibels),0
means noReplayGain
value for this track -
bpm
(number?) - Beats Per Minute -
comments
([string, string][]) - List of key/value pairs for all user-defined comments
-
bitrate
(number?) - in Kbps -
sampleRate
(number?) - in Hz -
duration
(number?) - in seconds
Demo music from Bensound.com