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_144P]: 0.19,
  10   [VideoResolution.H_240P]: 0.17,
  11   [VideoResolution.H_360P]: 0.15,
  12   [VideoResolution.H_480P]: 0.12,
  13   [VideoResolution.H_720P]: 0.11,
  14   [VideoResolution.H_1080P]: 0.10,
  15   [VideoResolution.H_1440P]: 0.09,
  16   [VideoResolution.H_4K]: 0.08
  17 }
  18
  19 const maxBitPerPixel: BitPerPixel = {
  20   [VideoResolution.H_NOVIDEO]: 0,
  21   [VideoResolution.H_144P]: 0.32,
  22   [VideoResolution.H_240P]: 0.29,
  23   [VideoResolution.H_360P]: 0.26,
  24   [VideoResolution.H_480P]: 0.22,
  25   [VideoResolution.H_720P]: 0.19,
  26   [VideoResolution.H_1080P]: 0.17,
  27   [VideoResolution.H_1440P]: 0.16,
  28   [VideoResolution.H_4K]: 0.14
  29 }
  30
  31 function getAverageBitrate (options: {
  32   resolution: VideoResolution
  33   ratio: number
  34   fps: number
  35 }) {
  36   const targetBitrate = calculateBitrate({ ...options, bitPerPixel: averageBitPerPixel })
  37   if (!targetBitrate) return 192 * 1000
  38
  39   return targetBitrate
  40 }
  41
  42 function getMaxBitrate (options: {
  43   resolution: VideoResolution
  44   ratio: number
  45   fps: number
  46 }) {
  47   const targetBitrate = calculateBitrate({ ...options, bitPerPixel: maxBitPerPixel })
  48   if (!targetBitrate) return 256 * 1000
  49
  50   return targetBitrate
  51 }
  52
  53 // ---------------------------------------------------------------------------
  54
  55 export {
  56   getAverageBitrate,
  57   getMaxBitrate
  58 }
  59
  60 // ---------------------------------------------------------------------------
  61
  62 function calculateBitrate (options: {
  63   bitPerPixel: BitPerPixel
  64   resolution: VideoResolution
  65   ratio: number
  66   fps: number
  67 }) {
  68   const { bitPerPixel, resolution, ratio, fps } = options
  69
  70   const resolutionsOrder = [
  71     VideoResolution.H_4K,
  72     VideoResolution.H_1440P,
  73     VideoResolution.H_1080P,
  74     VideoResolution.H_720P,
  75     VideoResolution.H_480P,
  76     VideoResolution.H_360P,
  77     VideoResolution.H_240P,
  78     VideoResolution.H_144P,
  79     VideoResolution.H_NOVIDEO
  80   ]
  81
  82   for (const toTestResolution of resolutionsOrder) {
  83     if (toTestResolution <= resolution) {
  84       return Math.floor(resolution * resolution * ratio * fps * bitPerPixel[toTestResolution])
  85     }
  86   }
  87
  88   throw new Error('Unknown resolution ' + resolution)
  89 }