spectrum-tiny-osbjs

Create spectrum helpers for tiny-osbjs.

Install

npm i @osbjs/spectrum-tiny-osbjs @osbjs/tiny-osbjs

Usage

Create a schema file by calling createSpectrumSchema in a seperate file and exec it.

// createSchema.js
#!/usr/bin/env node
const { createSpectrumSchema } = require('@osbjs/spectrum-tiny-osbjs')

createSpectrumSchema('path/to/audio/file')
// and then call `node createSchema` 1 time.

Spectrum schema contains info on start time, end time, amount of frame-per-second and spectrum "frames", each frame contains 64 numbers between 0 and 1 that can be used to scale the spectrum bar. Example of how to create a simple spectrum effect:

const { loadSpectrumSchema } = require('@osbjs/spectrum-tiny-osbjs')

const { startTime, endTime, fps, spectrumFrames } = loadSpectrumSchema(schemaPath)

const timestep = 1000 / fps
const width = 20
const maxHeight = 50
const margin = 3
const barCount = 20

let x = -107

for (let i = 0; i < barCount; i++) {
	const frames = spectrumFrames.map((frame) => frame[i])

	createSprite('sb/pixel.png', 'Background', 'Centre', { x, y: 240 }, () => {
		fadeAtTime(startTime, 1)
		colorAtTime(startTime, { r: 255, g: 255, b: 255 })

		for (let j = 0; j < frames.length; j++) {
			scaleVec(
				startTime + timestep * j,
				startTime + timestep * (j + 1),
				{ x: width, y: frames[j] * maxHeight },
				{ x: width, y: frames[j + 1] * maxHeight }
			)
		}
	})

	x += width + margin
}

API documentation

createSpectrumSchema

async function createSpectrumSchema(
	audioFilePath: string,
	outFilePath: string = 'spectrum.json',
	startTime: number = 0,
	endTime: number = -1,
	fps: number = 24,
	barCount: number = 64
)

Create a json file that store the audio data needed to create the spectrum effect.

loadSpectrumSchema

function loadSpectrumSchema(schemaPath: string): SpectrumSchema
type SpectrumSchema = {
	startTime: number
	endTime: number
	fps: number
	spectrumFrames: SpectrumFrame[]
}
type SpectrumFrame = number[]

Load schema from json file.

extractFrames

function extractFrames(spectrumFrames: SpectrumFrame[], startTime: number, endTime: number, fps: number): SpectrumFrame[]

Extract frames from a specific time period.