Krad Radio/JSONAPI

Radical Revelations :: The Krad Radio Web Development Field Guide

Hello and welcome to the hilarious adventure of of Krad Radio Web Development! Lets get started. This brief guide will be all you need to begin developing user interfaces and automated control systems for the Krad Radio interweb media server using familar web 1.0 - 4.0 technologies such as HTTP, Javascipt/JSON, WebSockets and WebRTC.

If you would like to build your own system from scratch you can connect to the KR interweb server using HTTP or Websockets and use the JSON API to send control commands, request state information or subscribe to realtime system state broadcasts at the desired level of granularity.

[Insert JSON API docs link here]

If you want to add a custom user interface to the standard KR Rack UI then the following information will describe how a Rack Control Unit (RCU) is constructed.

When a web browser connects to the KR interweb server it is transmitted a HTML file with a blank body tag and the JS/CSS assets that have possibly been configured by the sysadmin. The standard rack ui has three main parts.

Kr Object - This is the object that handles the websocket connection. This also takes care of sending API commands and calling the user interface object when new data arrives. At a few hundred lines, this is all that it does, it does not ever touch the DOM.

Rack Object - This is the object that manages the layout of the control units. It lets you add and remove the controls that you want and makes sure incoming data is routed to the correct units.

RCU Objects - Each of these represents an individual RCU, it is what takes input from the user and also displays information about the current control state.

An operational RCU involves the following:

A name and description. An aspect ratio rule so that the unit can be placed correctly on the rack. A div positioned by the Rack object in which to draw itself. A create/destroy method for itself. A callback method to receive incoming data that matches the current address mask of the RCU. An address mask array.

An address mask array is simply an array of KR unit addresses that this RCU is interested in receiving incoming crates for. For example a mask array of ["/mixer"] would receive all incoming mixer state and ["/compositor/video0"] would recieve only crates related to videoport video0.

"create": {
  "address": "/mixer/inputs/music",
  "payload": {
    "type": "[input] [bus] [output]",
    "adapter_address": "/adapters/jack",
    "volume": 67.42,
    "channels": 2,
    "lowpass": {
      "hz": 700,
      "bw": 2.0
   },
  "highpass": {
    "hz": 3000,
    "bw": 4.2
  },
  "analog": {
    "drive": 7.4,
    "blend": -5.0
   },
  "eq": {
   "bands": [
    {
     "hz": 800,
     "db": 0,
     "bw": 1
     },
    {
     "hz": 9000,
     "db": 4,
     "bw": 1
    },
    {
     "hz": 19000,
      "db": -3,
      "bw": 1
     }]
    }
   }
 }

"update": {
  "address": "/mixer/music/volume",
  "value": 70.00,
  "duration": 123
 }

"destroy": {
  "address": "/mixer/music"
}