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pcm-volume

pcm-volume

This module changes the volume of a given PCM data stream. At the moment only signed 16bit PCM data is supported, also I'm not quite sure about this as my knowledge about PCM is very limited. I don't know whether this is the right way to do things. Feel free to contact me/open a pull request if you want to add something.

Install

Install with npm install pcm-volume or clone from GitHub and npm install.

How to use

Pipe an existing stream into an instance of pcm-volume. You can get a PCM-stream from node-lame for example.

This example reads the file music.mp3 and changes the volume to 50% after 5seconds.

var Speaker = require("speaker");
var lame = require("lame");
var fs = require("fs");
var volume = require("pcm-volume");
 
var readable = fs.createReadStream("music.mp3");
 
// see node-lame documentation for more information 
var decoder = new lame.Decoder({
    channels: 2,
    bitDepth: 16,
    sampleRate: 44100,
    bitRate: 128,
    outSampleRate: 22050,
    mode: lame.STEREO
});
 
// Initialize speaker 
var speaker = new Speaker();
 
 
// Create a volume instance 
var v = new volume();
 
// Wait 5s, then change the volume to 50% 
setTimeout(function() {
    v.setVolume(0.5);
}, 5000)
 
 
 
v.pipe(new Speaker()); // pipe volume to speaker 
decoder.pipe(v); // pipe PCM data to volume 
readable.pipe(decoder); // pipe file input to decoder 

API

pcm-volume is a Transform Stream (see http://nodejs.org/api/stream.html#stream_class_stream_transform_1 for more information). Pipe in your PCM data and pipe out PCM data with a different volume. Use setVolume(v) to set the volume (v is a float between 0 and roughly 1.5 also you can go higher but it sounds like crap).