shared/core-utils/videos/bitrate.ts

   1 import { VideoResolution } from "@shared/models"
   2
   3 type BitPerPixel = { [ id in VideoResolution ]: number }
   4
   5 // https://bitmovin.com/video-bitrate-streaming-hls-dash/
   6
   7 const averageBitPerPixel: BitPerPixel = {
   8   [VideoResolution.H_NOVIDEO]: 0,
   9   [VideoResolution.H_240P]: 0.17,
  10   [VideoResolution.H_360P]: 0.15,
  11   [VideoResolution.H_480P]: 0.12,
  12   [VideoResolution.H_720P]: 0.11,
  13   [VideoResolution.H_1080P]: 0.10,
  14   [VideoResolution.H_1440P]: 0.09,
  15   [VideoResolution.H_4K]: 0.08
  16 }
  17
  18 const maxBitPerPixel: BitPerPixel = {
  19   [VideoResolution.H_NOVIDEO]: 0,
  20   [VideoResolution.H_240P]: 0.29,
  21   [VideoResolution.H_360P]: 0.26,
  22   [VideoResolution.H_480P]: 0.22,
  23   [VideoResolution.H_720P]: 0.19,
  24   [VideoResolution.H_1080P]: 0.17,
  25   [VideoResolution.H_1440P]: 0.16,
  26   [VideoResolution.H_4K]: 0.14
  27 }
  28
  29 function getAverageBitrate (options: {
  30   resolution: VideoResolution
  31   ratio: number
  32   fps: number
  33 }) {
  34   const targetBitrate = calculateBitrate({ ...options, bitPerPixel: averageBitPerPixel })
  35   if (!targetBitrate) return 192 * 1000
  36
  37   return targetBitrate
  38 }
  39
  40 function getMaxBitrate (options: {
  41   resolution: VideoResolution
  42   ratio: number
  43   fps: number
  44 }) {
  45   const targetBitrate = calculateBitrate({ ...options, bitPerPixel: maxBitPerPixel })
  46   if (!targetBitrate) return 256 * 1000
  47
  48   return targetBitrate
  49 }
  50
  51 // ---------------------------------------------------------------------------
  52
  53 export {
  54   getAverageBitrate,
  55   getMaxBitrate
  56 }
  57
  58 // ---------------------------------------------------------------------------
  59
  60 function calculateBitrate (options: {
  61   bitPerPixel: BitPerPixel
  62   resolution: VideoResolution
  63   ratio: number
  64   fps: number
  65 }) {
  66   const { bitPerPixel, resolution, ratio, fps } = options
  67
  68   const resolutionsOrder = [
  69     VideoResolution.H_4K,
  70     VideoResolution.H_1440P,
  71     VideoResolution.H_1080P,
  72     VideoResolution.H_720P,
  73     VideoResolution.H_480P,
  74     VideoResolution.H_360P,
  75     VideoResolution.H_240P,
  76     VideoResolution.H_NOVIDEO
  77   ]
  78
  79   for (const toTestResolution of resolutionsOrder) {
  80     if (toTestResolution <= resolution) {
  81       return Math.floor(resolution * resolution * ratio * fps * bitPerPixel[toTestResolution])
  82     }
  83   }
  84
  85   throw new Error('Unknown resolution ' + resolution)
  86 }