jassub/src/worker/util.ts

The Fastest JavaScript SSA/ASS Subtitle Renderer For Browsers

/* eslint-disable camelcase */
import type { ASS_Event, ASS_Image, ASS_Style, ClassHandle } from '../wasm/types.d.ts'

export type ASSEvent = Omit<ASS_Event, keyof ClassHandle>
export type ASSStyle = Omit<ASS_Style, keyof ClassHandle>
export type ASSImage = Omit<ASS_Image, keyof ClassHandle>

// offset by 1, 0 = 1, to match CSS font-weight values, but dividing by 100 gives the correct index
export const WEIGHT_MAP = [
  'thin',
  'extralight',
  'light',
  'regular', // Normal isn't used
  'medium',
  'semibold',
  'bold',
  'extrabold',
  'black',
  'ultrablack'
] as const

export type WeightValue = typeof WEIGHT_MAP[number]

export const IS_FIREFOX = navigator.userAgent.toLowerCase().includes('firefox')

const a = 'BT601'
const b = 'BT709'
const c = 'SMPTE240M'
const d = 'FCC'

export const LIBASS_YCBCR_MAP = [null, a, null, a, a, b, b, c, c, d, d] as const

export function _applyKeys<T extends (ASSEvent | ASSStyle)> (input: T, output: T) {
  for (const v of Object.keys(input) as Array<keyof T>) {
    output[v] = input[v]
  }
}

export const _fetch = globalThis.fetch
export async function fetchtext (url: string) {
  const res = await _fetch(url)
  return await res.text()
}

export const THREAD_COUNT = !IS_FIREFOX && self.crossOriginIsolated ? Math.min(Math.max(1, navigator.hardwareConcurrency - 2), 8) : 1

// @ts-expect-error new experimental API
export const SUPPORTS_GROWTH = !!WebAssembly.Memory.prototype.toResizableBuffer

// HACK: 3 memory hacks to support here:
// 1. Chrome WASM Growable memory which can use a reference to the buffer to fix visual artifacts, which happen both with multithreading or without [fastest]
// 2. Chrome WASM non-growable, but mult-threaded only memory which needs to re-create the HEAPU8 on growth because of race conditions [medium]
// 3. Firefox non-growable memory which needs a copy of the data into a non-resizable buffer and can't use a reference [fastest single threaded, but only on Firefox, on Chrome this is slowest]
export const SHOULD_REFERENCE_MEMORY = !IS_FIREFOX && (SUPPORTS_GROWTH || THREAD_COUNT > 1)

export const IDENTITY_MATRIX = new Float32Array([
  1, 0, 0,
  0, 1, 0,
  0, 0, 1
])

// Color matrix conversion map - mat3x3 for WebGL2
// Each matrix converts FROM the key color space TO the nested key color space
export const colorMatrixConversionMap = {
  BT601: {
    BT709: new Float32Array([
      1.0863, 0.0965, -0.01411,
      -0.0723, 0.8451, -0.0277,
      -0.0141, 0.0584, 1.0418
    ]),
    BT601: IDENTITY_MATRIX
  },
  BT709: {
    BT601: new Float32Array([
      0.9137, 0.0784, 0.0079,
      -0.1049, 1.1722, -0.0671,
      0.0096, 0.0322, 0.9582
    ]),
    BT709: IDENTITY_MATRIX
  },
  FCC: {
    BT709: new Float32Array([
      1.0873, -0.0736, -0.0137,
      0.0974, 0.8494, 0.0531,
      -0.0127, -0.0251, 1.0378
    ]),
    BT601: new Float32Array([
      1.001, -0.0008, -0.0002,
      0.0009, 1.005, -0.006,
      0.0013, 0.0027, 0.996
    ])
  },
  SMPTE240M: {
    BT709: new Float32Array([
      0.9993, 0.0006, 0.0001,
      -0.0004, 0.9812, 0.0192,
      -0.0034, -0.0114, 1.0148
    ]),
    BT601: new Float32Array([
      0.913, 0.0774, 0.0096,
      -0.1051, 1.1508, -0.0456,
      0.0063, 0.0207, 0.973
    ])
  }
} as const

export type ColorSpace = keyof typeof colorMatrixConversionMap