]>
Commit | Line | Data |
---|---|---|
edb4ffc7 FA |
1 | import { VideoTranscodingFPS } from './video-transcoding-fps.model' |
2 | ||
40298b02 | 3 | export enum VideoResolution { |
40298b02 C |
4 | H_240P = 240, |
5 | H_360P = 360, | |
6 | H_480P = 480, | |
7 | H_720P = 720, | |
8 | H_1080P = 1080 | |
9 | } | |
edb4ffc7 FA |
10 | |
11 | /** | |
7f196c93 FA |
12 | * Bitrate targets for different resolutions, at VideoTranscodingFPS.AVERAGE. |
13 | * | |
edb4ffc7 FA |
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 | */ | |
c1978779 | 18 | function getBaseBitrate (resolution: VideoResolution) { |
edb4ffc7 FA |
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: | |
c1c86c15 C |
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 | |
edb4ffc7 FA |
36 | case VideoResolution.H_1080P: // fallthrough |
37 | default: | |
c1c86c15 C |
38 | // quality according to Google Live Encoder: 3000 - 6000 Kbps |
39 | // Quality according to YouTube Video Info: 3277 Kbps | |
40 | return 3300 * 1000 | |
edb4ffc7 FA |
41 | } |
42 | } | |
43 | ||
7f196c93 FA |
44 | /** |
45 | * Calculate the target bitrate based on video resolution and FPS. | |
2f71dcf8 FA |
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. | |
7f196c93 | 52 | */ |
0229b014 | 53 | export function getTargetBitrate (resolution: VideoResolution, fps: number, fpsTranscodingConstants: VideoTranscodingFPS) { |
7f196c93 FA |
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: | |
2f71dcf8 FA |
57 | // 720p: 2600 / 1750 = 1.49 |
58 | // 1080p: 4400 / 3300 = 1.33 | |
7f196c93 FA |
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) | |
e243c38c FA |
64 | // Example outputs: |
65 | // 1080p10: 2420 kbps, 1080p30: 3300 kbps, 1080p60: 4620 kbps | |
2f71dcf8 | 66 | // 720p10: 1283 kbps, 720p30: 1750 kbps, 720p60: 2450 kbps |
7f196c93 FA |
67 | return baseBitrate + (fps - fpsTranscodingConstants.AVERAGE) * (maxBitrateDifference / maxFpsDifference) |
68 | } | |
69 | ||
edb4ffc7 FA |
70 | /** |
71 | * The maximum bitrate we expect to see on a transcoded video in bytes per second. | |
72 | */ | |
0229b014 | 73 | export function getMaxBitrate (resolution: VideoResolution, fps: number, fpsTranscodingConstants: VideoTranscodingFPS) { |
edb4ffc7 FA |
74 | return getTargetBitrate(resolution, fps, fpsTranscodingConstants) * 2 |
75 | } |