import { VideoTranscodingFPS } from './video-transcoding-fps.model'
export enum VideoResolution {
+ H_NOVIDEO = 0,
H_240P = 240,
H_360P = 360,
H_480P = 480,
H_720P = 720,
- H_1080P = 1080
+ H_1080P = 1080,
+ H_4K = 2160
}
/**
- * Bitrate targets for different resolutions and frame rates, in bytes per second.
+ * 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
+ * YouTube Video Info: youtube-dl --list-formats, with sample videos
*/
-export function getTargetBitrate (resolution: VideoResolution, fps: number,
- fpsTranscodingConstants: VideoTranscodingFPS) {
+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:
- if (fps === fpsTranscodingConstants.MAX) {
- // quality according to Google Live Encoder: 2,250 - 6,000 Kbps
- // Quality according to YouTube Video Info: 2634 Kbps
- return 2600 * 1000
- }
-
- // 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: // fallthrough
- default:
- if (fps === fpsTranscodingConstants.MAX) {
+ case VideoResolution.H_NOVIDEO:
+ // audio-only
+ return 64 * 1000
+
+ case VideoResolution.H_240P:
+ // quality according to Google Live Encoder: 300 - 700 Kbps
+ // Quality according to YouTube Video Info: 285 Kbps
+ return 320 * 1000
+
+ case VideoResolution.H_360P:
+ // quality according to Google Live Encoder: 400 - 1,000 Kbps
+ // Quality according to YouTube Video Info: 700 Kbps
+ return 780 * 1000
+
+ case VideoResolution.H_480P:
+ // quality according to Google Live Encoder: 500 - 2,000 Kbps
+ // Quality according to YouTube Video Info: 1300 Kbps
+ return 1500 * 1000
+
+ case VideoResolution.H_720P:
+ // quality according to Google Live Encoder: 1,500 - 4,000 Kbps
+ // Quality according to YouTube Video Info: 2680 Kbps
+ return 2800 * 1000
+
+ case VideoResolution.H_1080P:
// quality according to Google Live Encoder: 3000 - 6000 Kbps
- // Quality according to YouTube Video Info: 4387 Kbps
- return 4400 * 1000
- }
+ // Quality according to YouTube Video Info: 5081 Kbps
+ return 5200 * 1000
- // 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 22000 * 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) {
+export function getMaxBitrate (resolution: VideoResolution, fps: number, fpsTranscodingConstants: VideoTranscodingFPS) {
return getTargetBitrate(resolution, fps, fpsTranscodingConstants) * 2
}