1 import { VideoTranscodingFPS } from './video-transcoding-fps.model'
3 export const enum VideoResolution {
15 * Bitrate targets for different resolutions, at VideoTranscodingFPS.AVERAGE.
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
21 function getBaseBitrate (resolution: number) {
22 if (resolution === VideoResolution.H_NOVIDEO) {
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
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
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
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
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
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
64 // quality according to Google Live Encoder: 13000 - 34000 Kbps
69 * Calculate the target bitrate based on video resolution and FPS.
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.
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)
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))
95 * The maximum bitrate we expect to see on a transcoded video in bytes per second.
97 export function getMaxBitrate (resolution: VideoResolution, fps: number, fpsTranscodingConstants: VideoTranscodingFPS) {
98 return getTargetBitrate(resolution, fps, fpsTranscodingConstants) * 2