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

   1 import { VideoTranscodingFPS } from './video-transcoding-fps.model'
   2
   3 export enum VideoResolution {
   4   H_240P = 240,
   5   H_360P = 360,
   6   H_480P = 480,
   7   H_720P = 720,
   8   H_1080P = 1080
   9 }
  10
  11 /**
  12  * Bitrate targets for different resolutions, at VideoTranscodingFPS.AVERAGE.
  13  *
  14  * Sources for individual quality levels:
  15  * Google Live Encoder: https://support.google.com/youtube/answer/2853702?hl=en
  16  * YouTube Video Info (tested with random music video): https://www.h3xed.com/blogmedia/youtube-info.php
  17  */
  18 export function getBaseBitrate (resolution: VideoResolution) {
  19   switch (resolution) {
  20   case VideoResolution.H_240P:
  21     // quality according to Google Live Encoder: 300 - 700 Kbps
  22     // Quality according to YouTube Video Info: 186 Kbps
  23     return 250 * 1000
  24   case VideoResolution.H_360P:
  25     // quality according to Google Live Encoder: 400 - 1,000 Kbps
  26     // Quality according to YouTube Video Info: 480 Kbps
  27     return 500 * 1000
  28   case VideoResolution.H_480P:
  29     // quality according to Google Live Encoder: 500 - 2,000 Kbps
  30     // Quality according to YouTube Video Info: 879 Kbps
  31     return 900 * 1000
  32   case VideoResolution.H_720P:
  33     // quality according to Google Live Encoder: 1,500 - 4,000 Kbps
  34     // Quality according to YouTube Video Info: 1752 Kbps
  35     return 1750 * 1000
  36   case VideoResolution.H_1080P: // fallthrough
  37   default:
  38     // quality according to Google Live Encoder: 3000 - 6000 Kbps
  39     // Quality according to YouTube Video Info: 3277 Kbps
  40     return 3300 * 1000
  41   }
  42 }
  43
  44 /**
  45  * Calculate the target bitrate based on video resolution and FPS.
  46  */
  47 export function getTargetBitrate (resolution: VideoResolution, fps: number,
  48     fpsTranscodingConstants: VideoTranscodingFPS) {
  49   const baseBitrate = getBaseBitrate(resolution)
  50   // The maximum bitrate, used when fps === VideoTranscodingFPS.MAX
  51   // Based on numbers from Youtube, 60 fps bitrate divided by 30 fps bitrate:
  52   // 2600 / 1750 = 1.48571428571
  53   // 4400 / 3300 = 1.33333333333
  54   const maxBitrate = baseBitrate * 1.4
  55   const maxBitrateDifference = maxBitrate - baseBitrate
  56   const maxFpsDifference = fpsTranscodingConstants.MAX - fpsTranscodingConstants.AVERAGE
  57   // For 1080p video with default settings, this results in the following formula:
  58   // 3300 + (x - 30) * (1320/30)
  59   // Example outputs: 1080p30: 3300 kbps, 1080p60: 4620 kbps, 720p30: 1750, 720p60: 2450
  60   return baseBitrate + (fps - fpsTranscodingConstants.AVERAGE) * (maxBitrateDifference / maxFpsDifference)
  61 }
  62
  63 /**
  64  * The maximum bitrate we expect to see on a transcoded video in bytes per second.
  65  */
  66 export function getMaxBitrate (resolution: VideoResolution, fps: number,
  67     fpsTranscodingConstants: VideoTranscodingFPS) {
  68   return getTargetBitrate(resolution, fps, fpsTranscodingConstants) * 2
  69 }