85 lines
3.2 KiB
TypeScript
85 lines
3.2 KiB
TypeScript
import { VideoTranscodingFPS } from './video-transcoding-fps.model'
|
|
|
|
export enum VideoResolution {
|
|
H_240P = 240,
|
|
H_360P = 360,
|
|
H_480P = 480,
|
|
H_720P = 720,
|
|
H_1080P = 1080,
|
|
H_4K = 2160
|
|
}
|
|
|
|
/**
|
|
* Bitrate targets for different resolutions, at VideoTranscodingFPS.AVERAGE.
|
|
*
|
|
* Sources for individual quality levels:
|
|
* Google Live Encoder: https://support.google.com/youtube/answer/2853702?hl=en
|
|
* YouTube Video Info (tested with random music video): https://www.h3xed.com/blogmedia/youtube-info.php
|
|
*/
|
|
function getBaseBitrate (resolution: VideoResolution) {
|
|
switch (resolution) {
|
|
case VideoResolution.H_240P:
|
|
// quality according to Google Live Encoder: 300 - 700 Kbps
|
|
// Quality according to YouTube Video Info: 186 Kbps
|
|
return 250 * 1000
|
|
|
|
case VideoResolution.H_360P:
|
|
// quality according to Google Live Encoder: 400 - 1,000 Kbps
|
|
// Quality according to YouTube Video Info: 480 Kbps
|
|
return 500 * 1000
|
|
|
|
case VideoResolution.H_480P:
|
|
// quality according to Google Live Encoder: 500 - 2,000 Kbps
|
|
// Quality according to YouTube Video Info: 879 Kbps
|
|
return 900 * 1000
|
|
|
|
case VideoResolution.H_720P:
|
|
// quality according to Google Live Encoder: 1,500 - 4,000 Kbps
|
|
// Quality according to YouTube Video Info: 1752 Kbps
|
|
return 1750 * 1000
|
|
|
|
case VideoResolution.H_1080P:
|
|
// quality according to Google Live Encoder: 3000 - 6000 Kbps
|
|
// Quality according to YouTube Video Info: 3277 Kbps
|
|
return 3300 * 1000
|
|
|
|
case VideoResolution.H_4K: // fallthrough
|
|
default:
|
|
// quality according to Google Live Encoder: 13000 - 34000 Kbps
|
|
return 15000 * 1000
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Calculate the target bitrate based on video resolution and FPS.
|
|
*
|
|
* The calculation is based on two values:
|
|
* Bitrate at VideoTranscodingFPS.AVERAGE is always the same as
|
|
* getBaseBitrate(). Bitrate at VideoTranscodingFPS.MAX is always
|
|
* getBaseBitrate() * 1.4. All other values are calculated linearly
|
|
* between these two points.
|
|
*/
|
|
export function getTargetBitrate (resolution: VideoResolution, fps: number, fpsTranscodingConstants: VideoTranscodingFPS) {
|
|
const baseBitrate = getBaseBitrate(resolution)
|
|
// The maximum bitrate, used when fps === VideoTranscodingFPS.MAX
|
|
// Based on numbers from Youtube, 60 fps bitrate divided by 30 fps bitrate:
|
|
// 720p: 2600 / 1750 = 1.49
|
|
// 1080p: 4400 / 3300 = 1.33
|
|
const maxBitrate = baseBitrate * 1.4
|
|
const maxBitrateDifference = maxBitrate - baseBitrate
|
|
const maxFpsDifference = fpsTranscodingConstants.MAX - fpsTranscodingConstants.AVERAGE
|
|
// For 1080p video with default settings, this results in the following formula:
|
|
// 3300 + (x - 30) * (1320/30)
|
|
// Example outputs:
|
|
// 1080p10: 2420 kbps, 1080p30: 3300 kbps, 1080p60: 4620 kbps
|
|
// 720p10: 1283 kbps, 720p30: 1750 kbps, 720p60: 2450 kbps
|
|
return baseBitrate + (fps - fpsTranscodingConstants.AVERAGE) * (maxBitrateDifference / maxFpsDifference)
|
|
}
|
|
|
|
/**
|
|
* The maximum bitrate we expect to see on a transcoded video in bytes per second.
|
|
*/
|
|
export function getMaxBitrate (resolution: VideoResolution, fps: number, fpsTranscodingConstants: VideoTranscodingFPS) {
|
|
return getTargetBitrate(resolution, fps, fpsTranscodingConstants) * 2
|
|
}
|