shared/models/videos/video-resolution.enum.ts

   1 import { VideoTranscodingFPS } from './video-transcoding-fps.model'
   2
   3 export const enum VideoResolution {
   4   H_NOVIDEO = 0,
   5   H_240P = 240,
   6   H_360P = 360,
   7   H_480P = 480,
   8   H_720P = 720,
   9   H_1080P = 1080,
  10   H_1440P = 1440,
  11   H_4K = 2160
  12 }
  13
  14 /**
  15  * Bitrate targets for different resolutions, at VideoTranscodingFPS.AVERAGE.
  16  *
  17  * Sources for individual quality levels:
  18  * Google Live Encoder: https://support.google.com/youtube/answer/2853702?hl=en
  19  * YouTube Video Info: youtube-dl --list-formats, with sample videos
  20  */
  21 function getBaseBitrate (resolution: number) {
  22   if (resolution === VideoResolution.H_NOVIDEO) {
  23     // audio-only
  24     return 64 * 1000
  25   }
  26
  27   if (resolution <= VideoResolution.H_240P) {
  28     // quality according to Google Live Encoder: 300 - 700 Kbps
  29     // Quality according to YouTube Video Info: 285 Kbps
  30     return 320 * 1000
  31   }
  32
  33   if (resolution <= VideoResolution.H_360P) {
  34     // quality according to Google Live Encoder: 400 - 1,000 Kbps
  35     // Quality according to YouTube Video Info: 700 Kbps
  36     return 780 * 1000
  37   }
  38
  39   if (resolution <= VideoResolution.H_480P) {
  40     // quality according to Google Live Encoder: 500 - 2,000 Kbps
  41     // Quality according to YouTube Video Info: 1300 Kbps
  42     return 1500 * 1000
  43   }
  44
  45   if (resolution <= VideoResolution.H_720P) {
  46     // quality according to Google Live Encoder: 1,500 - 4,000 Kbps
  47     // Quality according to YouTube Video Info: 2680 Kbps
  48     return 2800 * 1000
  49   }
  50
  51   if (resolution <= VideoResolution.H_1080P) {
  52     // quality according to Google Live Encoder: 3000 - 6000 Kbps
  53     // Quality according to YouTube Video Info: 5081 Kbps
  54     return 5200 * 1000
  55   }
  56
  57   if (resolution <= VideoResolution.H_1440P) {
  58     // quality according to Google Live Encoder: 6000 - 13000 Kbps
  59     // Quality according to YouTube Video Info: 8600 (av01) - 17000 (vp9.2) Kbps
  60     return 10_000 * 1000
  61   }
  62
  63   // 4K
  64   // quality according to Google Live Encoder: 13000 - 34000 Kbps
  65   return 22_000 * 1000
  66 }
  67
  68 /**
  69  * Calculate the target bitrate based on video resolution and FPS.
  70  *
  71  * The calculation is based on two values:
  72  * Bitrate at VideoTranscodingFPS.AVERAGE is always the same as
  73  * getBaseBitrate(). Bitrate at VideoTranscodingFPS.MAX is always
  74  * getBaseBitrate() * 1.4. All other values are calculated linearly
  75  * between these two points.
  76  */
  77 export function getTargetBitrate (resolution: number, fps: number, fpsTranscodingConstants: VideoTranscodingFPS) {
  78   const baseBitrate = getBaseBitrate(resolution)
  79   // The maximum bitrate, used when fps === VideoTranscodingFPS.MAX
  80   // Based on numbers from Youtube, 60 fps bitrate divided by 30 fps bitrate:
  81   //  720p: 2600 / 1750 = 1.49
  82   // 1080p: 4400 / 3300 = 1.33
  83   const maxBitrate = baseBitrate * 1.4
  84   const maxBitrateDifference = maxBitrate - baseBitrate
  85   const maxFpsDifference = fpsTranscodingConstants.MAX - fpsTranscodingConstants.AVERAGE
  86   // For 1080p video with default settings, this results in the following formula:
  87   // 3300 + (x - 30) * (1320/30)
  88   // Example outputs:
  89   // 1080p10: 2420 kbps, 1080p30: 3300 kbps, 1080p60: 4620 kbps
  90   //  720p10: 1283 kbps,  720p30: 1750 kbps,  720p60: 2450 kbps
  91   return Math.floor(baseBitrate + (fps - fpsTranscodingConstants.AVERAGE) * (maxBitrateDifference / maxFpsDifference))
  92 }
  93
  94 /**
  95  * The maximum bitrate we expect to see on a transcoded video in bytes per second.
  96  */
  97 export function getMaxBitrate (resolution: VideoResolution, fps: number, fpsTranscodingConstants: VideoTranscodingFPS) {
  98   return getTargetBitrate(resolution, fps, fpsTranscodingConstants) * 2
  99 }