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authorChocobozzz <me@florianbigard.com>2021-08-06 13:35:25 +0200
committerChocobozzz <me@florianbigard.com>2021-08-06 14:13:26 +0200
commit679c12e69c9f3a2d003ee3abe8b8da49f25b2bd3 (patch)
tree03abf589275db05e5b1fa1c89f57049cd807324a /shared/models/videos
parentc826f34a45757b324a20f71665b44ed10e6953b5 (diff)
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Improve target bitrate calculation
Diffstat (limited to 'shared/models/videos')
-rw-r--r--shared/models/videos/video-resolution.enum.ts89
-rw-r--r--shared/models/videos/video-transcoding.model.ts16
2 files changed, 13 insertions, 92 deletions
diff --git a/shared/models/videos/video-resolution.enum.ts b/shared/models/videos/video-resolution.enum.ts
index a5d2ac7fa..24cd2d04d 100644
--- a/shared/models/videos/video-resolution.enum.ts
+++ b/shared/models/videos/video-resolution.enum.ts
@@ -1,5 +1,3 @@
1import { VideoTranscodingFPS } from './video-transcoding-fps.model'
2
3export const enum VideoResolution { 1export const enum VideoResolution {
4 H_NOVIDEO = 0, 2 H_NOVIDEO = 0,
5 H_240P = 240, 3 H_240P = 240,
@@ -10,90 +8,3 @@ export const enum VideoResolution {
10 H_1440P = 1440, 8 H_1440P = 1440,
11 H_4K = 2160 9 H_4K = 2160
12} 10}
13
14/**
15 * Bitrate targets for different resolutions, at VideoTranscodingFPS.AVERAGE.
16 *
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
20 */
21function getBaseBitrate (resolution: number) {
22 if (resolution === VideoResolution.H_NOVIDEO) {
23 // audio-only
24 return 64 * 1000
25 }
26
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
30 return 320 * 1000
31 }
32
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
36 return 780 * 1000
37 }
38
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
42 return 1500 * 1000
43 }
44
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
48 return 2800 * 1000
49 }
50
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
54 return 5200 * 1000
55 }
56
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
60 return 10_000 * 1000
61 }
62
63 // 4K
64 // quality according to Google Live Encoder: 13000 - 34000 Kbps
65 return 22_000 * 1000
66}
67
68/**
69 * Calculate the target bitrate based on video resolution and FPS.
70 *
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.
76 */
77export 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)
88 // Example outputs:
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))
92}
93
94/**
95 * The maximum bitrate we expect to see on a transcoded video in bytes per second.
96 */
97export function getMaxBitrate (resolution: VideoResolution, fps: number, fpsTranscodingConstants: VideoTranscodingFPS) {
98 return getTargetBitrate(resolution, fps, fpsTranscodingConstants) * 2
99}
diff --git a/shared/models/videos/video-transcoding.model.ts b/shared/models/videos/video-transcoding.model.ts
index f1fe4609b..83b8e98a0 100644
--- a/shared/models/videos/video-transcoding.model.ts
+++ b/shared/models/videos/video-transcoding.model.ts
@@ -2,13 +2,23 @@ import { VideoResolution } from './video-resolution.enum'
2 2
3// Types used by plugins and ffmpeg-utils 3// Types used by plugins and ffmpeg-utils
4 4
5export type EncoderOptionsBuilder = (params: { 5export type EncoderOptionsBuilderParams = {
6 input: string 6 input: string
7
7 resolution: VideoResolution 8 resolution: VideoResolution
8 inputBitrate: number 9
10 // Could be null for "merge audio" transcoding
9 fps?: number 11 fps?: number
12
13 // Could be undefined if we could not get input bitrate (some RTMP streams for example)
14 inputBitrate: number
15 inputRatio: number
16
17 // For lives
10 streamNum?: number 18 streamNum?: number
11}) => Promise<EncoderOptions> | EncoderOptions 19}
20
21export type EncoderOptionsBuilder = (params: EncoderOptionsBuilderParams) => Promise<EncoderOptions> | EncoderOptions
12 22
13export interface EncoderOptions { 23export interface EncoderOptions {
14 copy?: boolean // Copy stream? Default to false 24 copy?: boolean // Copy stream? Default to false