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This commit is contained in:
Felix Ableitner 2018-10-09 18:53:16 -05:00 committed by Chocobozzz
parent e243c38c35
commit 2f71dcf8de
1 changed files with 9 additions and 3 deletions
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12
shared/models/videos/video-resolution.enum.ts
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@ -43,14 +43,20 @@ export function getBaseBitrate (resolution: VideoResolution) {
/**
* 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 = 1.48571428571
// 1080p: 4400 / 3300 = 1.33333333333
// 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
@ -58,7 +64,7 @@ export function getTargetBitrate (resolution: VideoResolution, fps: number,
// 3300 + (x - 30) * (1320/30)
// Example outputs:
// 1080p10: 2420 kbps, 1080p30: 3300 kbps, 1080p60: 4620 kbps
// 720p10: 1283 kbps, 720p30: 1750 kbps, 720p60: 2450
// 720p10: 1283 kbps, 720p30: 1750 kbps, 720p60: 2450 kbps
return baseBitrate + (fps - fpsTranscodingConstants.AVERAGE) * (maxBitrateDifference / maxFpsDifference)
}