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    Pedalboard.js

    Open source JavaScript framework for developing audio effects for guitars using the Web Audio API.
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    Pedalboard.js

    Check out pedals.io! It's pedalboard.js packaged as a product you can really use.

    Or check out the demo. Make sure to try the real-time line-in feature by plugging in a guitar or a microphone.

    Introduction

    Ever wanted to have your pedal stack in the cloud, available anywhere you go without any hardware? Ever wanted to manage your sound as easily as browsing a web site? Ever wanted to share the perfect sound you created with your friends without the hassle? You loved the overdrive on that effects software but wanted to tweak its EQ a little bit?

    Pedalboard.js is a ground-breaking, first of its kind, novel open-source JavaScript framework for developing audio effects and applying them to sound sources–and it's particularly good at guitar effects.

    The API and all the abstraction is built around the concept of guitar effects — pedals and stomp boxes, pots and switches.

    You design your pedal with the powerful Web Audio API, attach pots and switches to it, style it via CSS3 and voila.

    Bring multiple pedals together to create a pedal board, easily adjust their settings and routing. Prepare as many pedal boards as you'd like, e.g. for your favorite styles. Easily switch pedal boards for a completely different sound.

    Finally, a complete guitar effects stack, completely customizable, in your hands.

    Motivation

    Guitar effects software on the market are very nice indeed, but they somehow lack few important concepts — ease of use, portability, sharing stuff, customization, extensibility, etc.

    What's worse, now that the freemium model is very popular, what looks like an easy initial buy turns into a small fortune when you'd like to buy the effects you wanted.

    Pedalboard.js is an attempt to address these issues. With the help of the powerful Web Audio API, Pedalboard.js gives you a fairly-easy-to-build-upon abstraction and foundation.


    Technology

    Audio

    The technology that made Pedalboard.js available is W3C's Web Audio API. Although in a working draft version (which means it's more or less stable — at least in concept and context, but subject to change) the API is quite extensive, easy to use, extendable and has very nice approaches.

    Right now, the Audio API is available in all the major browsers other than Internet Explorer.

    Nodes

    Audio API has the "node" concept at its core. Everything is a node and each node can connect to other nodes. A node can be a source (array or stream or generated by an oscillator or even arbitrary JS functions) or an effect or an output; or yet again, an analyzer to poke at what's going on inside.

    Effects are the most versatile offering of the API. You can create gain, wave shaping, convolution or filter effects, all of which have various settings you can tweak. With all these opportunities, it's quite easy to build the perfect tone you're after.

    State of the art

    Currently, Web Audio API implementations on the desktop support real-time audio device input as well as pre-recorded buffers. This enables Pedalboard.js to fully function as a guitar effects stack. Historically, Pedalboard.js implemented streaming from your input through a Flash proxy, too; but that's removed as of 0.3.0 since the native version is already on the stage. With the native input streaming, you can expect a near-0-latency input.

    Mobile Safari doesn't have audio input via microphone / line-in and only supports pre-recorded buffers and Chrome for Android supports it as of version 30.

    JavaScript

    At its core, Pedalboard.js uses tartJS, an open source JavaScript framework developed at Tart New Media. tartJS is a library built upon Google Closure Library, which is another great library developed by Google, Inc. Besides a great approach to object oriented programming and a vast amount of classes, Closure has a set of build tools that perfectly analyzes (read: lints) your code, and compiles and builds it.

    Closure Library allows modular, object oriented JavaScript at its best, with tons of utility classes for DOM manipulation, visual effects, components, mathematics, arrays, objects, etc.

    Closure Compiler not only minifies your code, but obfuscates it maximally, rewrites it to the letter to squeeze out the last bit of performance and file size. An entire web application can be under 30kb gzipped, which is quite insane.

    The pre-compiled version in the repository is compiled with "simple optimizations" setting on the Closure Compiler for easy use as a drop-in library. Its size is about 64KB gzipped. Pedalboard.js is fully compatible with "advanced optimizations", though, so when you compile it alongside your application in "advanced" mode, pedalboard.js goes down to 17KB gzipped in size.


    Concepts

    Pedalboard.js follows an object oriented coding style, with an analogy to the real world guitar objects and concepts.

    Classes are modeled after real components of pedals and pedal boards. You configure each component as you configure a real pedal stack.

    Normally, you use your pedal board on stage, connect your guitar to it, and connect the board to an output, like an amp or a mixer. Pedalboard.js follows the same basic ideas.

    Stage

    At the base is the Stage. Stage is where everything lives — what you see, the floor, the place that hosts your pedal board. The Stage has one input, an instance of an Input class — FileInput (for pre-recorded sounds) or StreamInput (for line-in). It also has one output, an instance of an Output class, which is your speakers. Stage also hosts a pedal board, an instance of a Board class. Of course, you can swap the board currently on stage with another one. Stage also has its own AudioContext instance and everything inside the Stage shares this context.

    Stage is a manager class, in classical terminology.

    Usage:

    var stage = new pb.Stage();
    

    Board

    Board is analogous to a pedal board, where you put and organize your pedals. It has an InputBuffer instance, an OutputBuffer instance and as many Box instances as you'd like. A Stage can hold only one Board at a single given time, but you can have many Boards and can swap them at your leisure. A Stage connects its Input to the InputBuffer of the Board and its Output to the OutputBuffer of the Board.

    Usage:

    var stage = new pb.Stage();
    var board1 = new pb.Board(stage.getContext());
    var board2 = new pb.Board(stage.getContext());
    
    stage.setBoard(board1);
    stage.setBoard(board2);
    

    Box (pedal)

    Box is the abstract class for all pedals. Any pedal implementation should extend Box. Box is where the magic happens. Given an AudioContext, Box implements its effects in an effects chain. Box instances also have an InputBuffer and an OutputBuffer for brevity. The effects lie in between these two, so when two pedals are cascaded, the output buffer of the first will be connected to the input buffer of the latter. This lets a box to provide a clean and expectable interface to the outer world — the other pedals or the pedal board.

    One should be able to tweak a pedal's parameters easily, and may want to turn it off at some point.

    Pedalboard.js offers two abstractions for this; Pot and Switch.

    Usage:

    // initialize the stage and get the context
    var stage = new pb.Stage();
    var ctx = stage.getContext();
    
    // initialize the board and pedals
    var board = new pb.Board(ctx);
    var od = new pb.stomp.Overdrive(ctx);
    var reverb = new pb.stomp.Reverb(ctx);
    var vol = new pb.stomp.Volume(ctx);
    
    // add pedals to board
    board.addPedals([od, reverb]);
    board.addPedalsAt(1, vol);
    
    // tweak pedal settings
    od.setDrive(0.7);
    od.setLevel(0.7);
    reverb.setLevel(0.3);
    vol.setLevel(0.2);
    
    // set the board on stage and start playing!
    stage.setBoard(board);
    

    Pot

    Pot component serves as a means to tweak a Box's parameters, such as gain, level, distortion, delay feedback, etc. It's analogous to a potentiometer, i.e. variable resistor.

    LinearPot and LogPot are two classes that inherit from the Pot class, and provide two different potentiometer implementations. A pot has a value, and a multiplier. Value reflects a pedal's parameter value, such as gain. Multiplier is kind of like the resistance of a resistor. Optionally, you can define minimum, maximum and default values.

    The Pot's setValue method requires a windowed range between 0 and 1, representing pot rotation. Values larger than 1 will be interpreted as 1 and lower than 0 will be interpreted as 0.

    In an application where your parameter is required to be between 0 and 10, multiplier should be 10. When you need your parameter to have a range between 0 and 1000, your multiplier should be 1000. Optionally, you can just leave the multiplier as 1 and play with minimum and maximum values to achieve the same effect.

    The only difference between a LinearPot and a LogPot is their algorithm of sweeping through their values. While LinearPot will just reflect setValue input times the multiplier, LogPot will calculate as log(setValue input) times 10 times multiplier.

    Usage:

    pb.stomp.Overdrive.prototype.createPots = function() {
        var handler = goog.bind(this.model.setDrive, this.model);
    
        this.volumePot = new pb.pot.Linear(this.model.gain.gain, 'volume', 0.1); // this will automatically set the gain on change.
        this.drivePot = new pb.pot.Log(handler, 'drive', 200); // called with a function as the argument, this will call that function with its new value. 
        this.pots = [this.drivePot, this.volumePot];
    
        this.drivePot.addEventListener('valueChanged', function(e) {
        this.model.setDrive(e.newValue); // we can explicitly listen to the change event and do things after a change.
        }, this);
    };
    
    // Later on, you can manually set a pot's value like
    drivePot.setValue(0.3);
    

    Switch

    Switch component models a foot switch, used to toggle pedals or individual effects of pedals. A switch has an array of 3-node arrays and toggles between them when pressed. In Pedalboard.js, one defines any number of 3-node arrays and the connection will be handled by the Switch.

    The input should always be the middle node in a 3-node array. When on, a switch will connect the input to the first node. When off, a switch will connect the input to the last node. This is in fact modeled after a 3PDT switch, and functions the same.

    Two classes, Toggle and Momentary, extend Switch and implement two different toggle mechanisms. Toggle is the standard switch, you press it once to turn it on, and it stays on until you press it again; it then turns off. Momentary is a little bit different, it's on as long as you press it and turns off as soon as you release it.

    A Box can have many switches but the bypass switch is built-in in and standard in the abstract class. So extending the Box component to implement a new pedal automatically provides a bypass Switch.

    Usage:

    var bypassSwitch = new pb.footswitch.Toggle();
    
    goog.events.listen(bypassSwitch.model, pb.footswitch.SwitchModel.EventType.ON, connectSomeCoolEffects);
    goog.events.listen(bypassSwitch.model, pb.footswitch.SwitchModel.EventType.OFF, disconnectSomeCoolEffects);
    

    Led

    Led component models an LED light commonly used in pedals to signal if it's on. A Box can have many LEDs, but one LED is standard in the Box component, that is connected to the Switch and signals if the pedal is bypassed.

    The Led component requires a Switch instance to operate on and binds its events automatically. It will be on as long as the Switch is active.

    Usage:

    var bypassSwitch = new pb.footswitch.Toggle();
    var led = new pb.Led(bypassSwitch);
    
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