From 679c12e69c9f3a2d003ee3abe8b8da49f25b2bd3 Mon Sep 17 00:00:00 2001
From: Chocobozzz <me@florianbigard.com>
Date: Fri, 6 Aug 2021 13:35:25 +0200
Subject: Improve target bitrate calculation

---
 shared/models/videos/video-resolution.enum.ts   | 89 -------------------------
 shared/models/videos/video-transcoding.model.ts | 16 ++++-
 2 files changed, 13 insertions(+), 92 deletions(-)

(limited to 'shared/models')

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 @@
-import { VideoTranscodingFPS } from './video-transcoding-fps.model'
-
 export const enum VideoResolution {
   H_NOVIDEO = 0,
   H_240P = 240,
@@ -10,90 +8,3 @@ export const enum VideoResolution {
   H_1440P = 1440,
   H_4K = 2160
 }
-
-/**
- * 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: youtube-dl --list-formats, with sample videos
- */
-function getBaseBitrate (resolution: number) {
-  if (resolution === VideoResolution.H_NOVIDEO) {
-    // audio-only
-    return 64 * 1000
-  }
-
-  if (resolution <= VideoResolution.H_240P) {
-    // quality according to Google Live Encoder: 300 - 700 Kbps
-    // Quality according to YouTube Video Info: 285 Kbps
-    return 320 * 1000
-  }
-
-  if (resolution <= VideoResolution.H_360P) {
-    // quality according to Google Live Encoder: 400 - 1,000 Kbps
-    // Quality according to YouTube Video Info: 700 Kbps
-    return 780 * 1000
-  }
-
-  if (resolution <= VideoResolution.H_480P) {
-    // quality according to Google Live Encoder: 500 - 2,000 Kbps
-    // Quality according to YouTube Video Info: 1300 Kbps
-    return 1500 * 1000
-  }
-
-  if (resolution <= 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
-  }
-
-  if (resolution <= VideoResolution.H_1080P) {
-    // quality according to Google Live Encoder: 3000 - 6000 Kbps
-    // Quality according to YouTube Video Info: 5081 Kbps
-    return 5200 * 1000
-  }
-
-  if (resolution <= VideoResolution.H_1440P) {
-    // quality according to Google Live Encoder: 6000 - 13000 Kbps
-    // Quality according to YouTube Video Info: 8600 (av01) - 17000 (vp9.2) Kbps
-    return 10_000 * 1000
-  }
-
-  // 4K
-  // quality according to Google Live Encoder: 13000 - 34000 Kbps
-  return 22_000 * 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: number, 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 Math.floor(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) {
-  return getTargetBitrate(resolution, fps, fpsTranscodingConstants) * 2
-}
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'
 
 // Types used by plugins and ffmpeg-utils
 
-export type EncoderOptionsBuilder = (params: {
+export type EncoderOptionsBuilderParams = {
   input: string
+
   resolution: VideoResolution
-  inputBitrate: number
+
+  // Could be null for "merge audio" transcoding
   fps?: number
+
+  // Could be undefined if we could not get input bitrate (some RTMP streams for example)
+  inputBitrate: number
+  inputRatio: number
+
+  // For lives
   streamNum?: number
-}) => Promise<EncoderOptions> | EncoderOptions
+}
+
+export type EncoderOptionsBuilder = (params: EncoderOptionsBuilderParams) => Promise<EncoderOptions> | EncoderOptions
 
 export interface EncoderOptions {
   copy?: boolean // Copy stream? Default to false
-- 
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