Improve target bitrate calculation

6 files changed, 115 insertions, 92 deletions

diff --git a/shared/core-utils/index.ts b/shared/core-utils/index.ts
index 2a7d4d982..e0a6a8087 100644
--- a/shared/core-utils/index.ts
+++ b/shared/core-utils/index.ts
@@ -5,3 +5,4 @@ export * from './plugins'
 export * from './renderer'
 export * from './users'
 export * from './utils'
+export * from './videos'
diff --git a/shared/core-utils/videos/bitrate.ts b/shared/core-utils/videos/bitrate.ts
new file mode 100644
index 000000000..3d4e47906
--- /dev/null
+++ b/shared/core-utils/videos/bitrate.ts
@@ -0,0 +1,86 @@
+import { VideoResolution } from "@shared/models"
+
+type BitPerPixel = { [ id in VideoResolution ]: number }
+
+// https://bitmovin.com/video-bitrate-streaming-hls-dash/
+
+const averageBitPerPixel: BitPerPixel = {
+  [VideoResolution.H_NOVIDEO]: 0,
+  [VideoResolution.H_240P]: 0.17,
+  [VideoResolution.H_360P]: 0.15,
+  [VideoResolution.H_480P]: 0.12,
+  [VideoResolution.H_720P]: 0.11,
+  [VideoResolution.H_1080P]: 0.10,
+  [VideoResolution.H_1440P]: 0.09,
+  [VideoResolution.H_4K]: 0.08
+}
+
+const maxBitPerPixel: BitPerPixel = {
+  [VideoResolution.H_NOVIDEO]: 0,
+  [VideoResolution.H_240P]: 0.29,
+  [VideoResolution.H_360P]: 0.26,
+  [VideoResolution.H_480P]: 0.22,
+  [VideoResolution.H_720P]: 0.19,
+  [VideoResolution.H_1080P]: 0.17,
+  [VideoResolution.H_1440P]: 0.16,
+  [VideoResolution.H_4K]: 0.14
+}
+
+function getAverageBitrate (options: {
+  resolution: VideoResolution
+  ratio: number
+  fps: number
+}) {
+  const targetBitrate = calculateBitrate({ ...options, bitPerPixel: averageBitPerPixel })
+  if (!targetBitrate) return 192 * 1000
+
+  return targetBitrate
+}
+
+function getMaxBitrate (options: {
+  resolution: VideoResolution
+  ratio: number
+  fps: number
+}) {
+  const targetBitrate = calculateBitrate({ ...options, bitPerPixel: maxBitPerPixel })
+  if (!targetBitrate) return 256 * 1000
+
+  return targetBitrate
+}
+
+// ---------------------------------------------------------------------------
+
+export {
+  getAverageBitrate,
+  getMaxBitrate
+}
+
+// ---------------------------------------------------------------------------
+
+function calculateBitrate (options: {
+  bitPerPixel: BitPerPixel
+  resolution: VideoResolution
+  ratio: number
+  fps: number
+}) {
+  const { bitPerPixel, resolution, ratio, fps } = options
+
+  const resolutionsOrder = [
+    VideoResolution.H_4K,
+    VideoResolution.H_1440P,
+    VideoResolution.H_1080P,
+    VideoResolution.H_720P,
+    VideoResolution.H_480P,
+    VideoResolution.H_360P,
+    VideoResolution.H_240P,
+    VideoResolution.H_NOVIDEO
+  ]
+
+  for (const toTestResolution of resolutionsOrder) {
+    if (toTestResolution <= resolution) {
+      return resolution * resolution * ratio * fps * bitPerPixel[toTestResolution]
+    }
+  }
+
+  throw new Error('Unknown resolution ' + resolution)
+}
diff --git a/shared/core-utils/videos/index.ts b/shared/core-utils/videos/index.ts
new file mode 100644
index 000000000..5a1145f1a
--- /dev/null
+++ b/shared/core-utils/videos/index.ts
@@ -0,0 +1 @@
+export * from './bitrate'
diff --git a/shared/extra-utils/miscs/generate.ts b/shared/extra-utils/miscs/generate.ts
index 8d6435481..a03a20049 100644
--- a/shared/extra-utils/miscs/generate.ts
+++ b/shared/extra-utils/miscs/generate.ts
@@ -1,8 +1,20 @@
+import { expect } from 'chai'
 import * as ffmpeg from 'fluent-ffmpeg'
 import { ensureDir, pathExists } from 'fs-extra'
 import { dirname } from 'path'
+import { getVideoFileBitrate, getVideoFileFPS, getVideoFileResolution } from '@server/helpers/ffprobe-utils'
+import { getMaxBitrate } from '@shared/core-utils'
 import { buildAbsoluteFixturePath } from './tests'
 
+async function ensureHasTooBigBitrate (fixturePath: string) {
+  const bitrate = await getVideoFileBitrate(fixturePath)
+  const dataResolution = await getVideoFileResolution(fixturePath)
+  const fps = await getVideoFileFPS(fixturePath)
+
+  const maxBitrate = getMaxBitrate({ ...dataResolution, fps })
+  expect(bitrate).to.be.above(maxBitrate)
+}
+
 async function generateHighBitrateVideo () {
   const tempFixturePath = buildAbsoluteFixturePath('video_high_bitrate_1080p.mp4', true)
 
@@ -28,6 +40,8 @@ async function generateHighBitrateVideo () {
     })
   }
 
+  await ensureHasTooBigBitrate(tempFixturePath)
+
   return tempFixturePath
 }
 
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