1 import { VideoTranscodingFPS } from './video-transcoding-fps.model'
3 export enum VideoResolution {
13 * Bitrate targets for different resolutions, at VideoTranscodingFPS.AVERAGE.
15 * Sources for individual quality levels:
16 * Google Live Encoder: https://support.google.com/youtube/answer/2853702?hl=en
17 * YouTube Video Info (tested with random music video): https://www.h3xed.com/blogmedia/youtube-info.php
19 function getBaseBitrate (resolution: VideoResolution) {
21 case VideoResolution.H_240P:
22 // quality according to Google Live Encoder: 300 - 700 Kbps
23 // Quality according to YouTube Video Info: 186 Kbps
25 case VideoResolution.H_360P:
26 // quality according to Google Live Encoder: 400 - 1,000 Kbps
27 // Quality according to YouTube Video Info: 480 Kbps
29 case VideoResolution.H_480P:
30 // quality according to Google Live Encoder: 500 - 2,000 Kbps
31 // Quality according to YouTube Video Info: 879 Kbps
33 case VideoResolution.H_720P:
34 // quality according to Google Live Encoder: 1,500 - 4,000 Kbps
35 // Quality according to YouTube Video Info: 1752 Kbps
37 case VideoResolution.H_1080P:
38 // quality according to Google Live Encoder: 3000 - 6000 Kbps
39 // Quality according to YouTube Video Info: 3277 Kbps
41 case VideoResolution.H_4K: // fallthrough
43 // quality according to Google Live Encoder: 13000 - 34000 Kbps
49 * Calculate the target bitrate based on video resolution and FPS.
51 * The calculation is based on two values:
52 * Bitrate at VideoTranscodingFPS.AVERAGE is always the same as
53 * getBaseBitrate(). Bitrate at VideoTranscodingFPS.MAX is always
54 * getBaseBitrate() * 1.4. All other values are calculated linearly
55 * between these two points.
57 export function getTargetBitrate (resolution: VideoResolution, fps: number, fpsTranscodingConstants: VideoTranscodingFPS) {
58 const baseBitrate = getBaseBitrate(resolution)
59 // The maximum bitrate, used when fps === VideoTranscodingFPS.MAX
60 // Based on numbers from Youtube, 60 fps bitrate divided by 30 fps bitrate:
61 // 720p: 2600 / 1750 = 1.49
62 // 1080p: 4400 / 3300 = 1.33
63 const maxBitrate = baseBitrate * 1.4
64 const maxBitrateDifference = maxBitrate - baseBitrate
65 const maxFpsDifference = fpsTranscodingConstants.MAX - fpsTranscodingConstants.AVERAGE
66 // For 1080p video with default settings, this results in the following formula:
67 // 3300 + (x - 30) * (1320/30)
69 // 1080p10: 2420 kbps, 1080p30: 3300 kbps, 1080p60: 4620 kbps
70 // 720p10: 1283 kbps, 720p30: 1750 kbps, 720p60: 2450 kbps
71 return baseBitrate + (fps - fpsTranscodingConstants.AVERAGE) * (maxBitrateDifference / maxFpsDifference)
75 * The maximum bitrate we expect to see on a transcoded video in bytes per second.
77 export function getMaxBitrate (resolution: VideoResolution, fps: number, fpsTranscodingConstants: VideoTranscodingFPS) {
78 return getTargetBitrate(resolution, fps, fpsTranscodingConstants) * 2