Set bitrate limits for transcoding (fixes #638) (#1135)

* Set bitrate limits for transcoding (fixes #638)

* added optimization script and test, changed stuff

* fix test, improve docs

* re-add optimize-old-videos script

* added documentation

* Don't optimize videos without valid UUID, or redundancy videos

* move getUUIDFromFilename

* fix tests?

* update torrent and file size, some more fixes/improvements

* use higher bitrate for high fps video, adjust bitrates

* add test video

* don't throw error if resolution is undefined

* generate test fixture on the fly

* use random noise video for bitrate test, add promise

* shorten test video to avoid timeout

* use existing function to optimize video

* various fixes

* increase test timeout

* limit test fixture size, add link

* test fixes

* add await

* more test fixes, add -b:v parameter

* replace ffmpeg wiki link

* fix ffmpeg params

* fix unit test

* add test fixture to .gitgnore

* add video transcoding fps model

* add missing file

3 files changed, 62 insertions, 0 deletions

diff --git a/shared/models/videos/index.ts b/shared/models/videos/index.ts
index 90a0e3053..056ae06da 100644
--- a/shared/models/videos/index.ts
+++ b/shared/models/videos/index.ts
@@ -21,6 +21,7 @@ export * from './video-update.model'
 export * from './video.model'
 export * from './video-query.type'
 export * from './video-state.enum'
+export * from './video-transcoding-fps.model'
 export * from './caption/video-caption.model'
 export * from './caption/video-caption-update.model'
 export * from './import/video-import-create.model'
diff --git a/shared/models/videos/video-resolution.enum.ts b/shared/models/videos/video-resolution.enum.ts
index 100fc0e6e..3c52bbf98 100644
--- a/shared/models/videos/video-resolution.enum.ts
+++ b/shared/models/videos/video-resolution.enum.ts
@@ -1,3 +1,5 @@
+import { VideoTranscodingFPS } from './video-transcoding-fps.model'
+
 export enum VideoResolution {
   H_240P = 240,
   H_360P = 360,
@@ -5,3 +7,56 @@ export enum VideoResolution {
   H_720P = 720,
   H_1080P = 1080
 }
+
+/**
+ * Bitrate targets for different resolutions and frame rates, in bytes per second.
+ * 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
+ */
+export function getTargetBitrate (resolution: VideoResolution, fps: number,
+    fpsTranscodingConstants: VideoTranscodingFPS) {
+  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
+    } else {
+      // 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) {
+      // quality according to Google Live Encoder: 3000 - 6000 Kbps
+      // Quality according to YouTube Video Info: 4387 Kbps
+      return 4400 * 1000
+    } else {
+      // quality according to Google Live Encoder: 3000 - 6000 Kbps
+      // Quality according to YouTube Video Info: 3277 Kbps
+      return 3300 * 1000
+    }
+  }
+}
+
+/**
+ * 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-fps.model.ts b/shared/models/videos/video-transcoding-fps.model.ts
new file mode 100644
index 000000000..82022d2f1
--- /dev/null
+++ b/shared/models/videos/video-transcoding-fps.model.ts
@@ -0,0 +1,6 @@
+export type VideoTranscodingFPS = {
+  MIN: number,
+  AVERAGE: number,
+  MAX: number,
+  KEEP_ORIGIN_FPS_RESOLUTION_MIN: number
+}