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-rw-r--r--shared/models/videos/video-resolution.enum.ts68
1 files changed, 68 insertions, 0 deletions
diff --git a/shared/models/videos/video-resolution.enum.ts b/shared/models/videos/video-resolution.enum.ts
index 100fc0e6e..7da5e7100 100644
--- a/shared/models/videos/video-resolution.enum.ts
+++ b/shared/models/videos/video-resolution.enum.ts
@@ -1,3 +1,5 @@
1import { VideoTranscodingFPS } from './video-transcoding-fps.model'
2
1export enum VideoResolution { 3export enum VideoResolution {
2 H_240P = 240, 4 H_240P = 240,
3 H_360P = 360, 5 H_360P = 360,
@@ -5,3 +7,69 @@ export enum VideoResolution {
5 H_720P = 720, 7 H_720P = 720,
6 H_1080P = 1080 8 H_1080P = 1080
7} 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 */
18function 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 * The calculation is based on two values:
48 * Bitrate at VideoTranscodingFPS.AVERAGE is always the same as
49 * getBaseBitrate(). Bitrate at VideoTranscodingFPS.MAX is always
50 * getBaseBitrate() * 1.4. All other values are calculated linearly
51 * between these two points.
52 */
53export function getTargetBitrate (resolution: VideoResolution, fps: number, fpsTranscodingConstants: VideoTranscodingFPS) {
54 const baseBitrate = getBaseBitrate(resolution)
55 // The maximum bitrate, used when fps === VideoTranscodingFPS.MAX
56 // Based on numbers from Youtube, 60 fps bitrate divided by 30 fps bitrate:
57 // 720p: 2600 / 1750 = 1.49
58 // 1080p: 4400 / 3300 = 1.33
59 const maxBitrate = baseBitrate * 1.4
60 const maxBitrateDifference = maxBitrate - baseBitrate
61 const maxFpsDifference = fpsTranscodingConstants.MAX - fpsTranscodingConstants.AVERAGE
62 // For 1080p video with default settings, this results in the following formula:
63 // 3300 + (x - 30) * (1320/30)
64 // Example outputs:
65 // 1080p10: 2420 kbps, 1080p30: 3300 kbps, 1080p60: 4620 kbps
66 // 720p10: 1283 kbps, 720p30: 1750 kbps, 720p60: 2450 kbps
67 return baseBitrate + (fps - fpsTranscodingConstants.AVERAGE) * (maxBitrateDifference / maxFpsDifference)
68}
69
70/**
71 * The maximum bitrate we expect to see on a transcoded video in bytes per second.
72 */
73export function getMaxBitrate (resolution: VideoResolution, fps: number, fpsTranscodingConstants: VideoTranscodingFPS) {
74 return getTargetBitrate(resolution, fps, fpsTranscodingConstants) * 2
75}