feat(server): transcode bitrate and thread settings (#2488)

* support for two-pass transcoding

* added max bitrate and thread to transcode api

* admin page setting desc+bitrate and thread options

* Update web/src/lib/components/admin-page/settings/setting-input-field.svelte

Co-authored-by: Michel Heusschen <59014050+michelheusschen@users.noreply.github.com>

* Update web/src/lib/components/admin-page/settings/setting-input-field.svelte

Co-authored-by: Michel Heusschen <59014050+michelheusschen@users.noreply.github.com>

* two-pass slider, `crf` and `threads` as numbers

* updated and added transcode tests

* refactored `getFfmpegOptions`

* default `threads`, `maxBitrate` now 0, more tests

* vp9 constant quality mode

* fixed nullable `crf` and `threads`

* fixed two-pass slider, added apiproperty

* optional `desc` for `SettingSelect`

* disable two-pass if settings are incompatible

* fixed test

* transcode interface

---------

Co-authored-by: Michel Heusschen <59014050+michelheusschen@users.noreply.github.com>

server/libs/infra/src/entities/system-config.entity.ts

@@ -1,7 +1,7 @@
 import { Column, Entity, PrimaryColumn } from 'typeorm';
 
 @Entity('system_config')
-export class SystemConfigEntity<T = string | boolean> {
+export class SystemConfigEntity<T = string | boolean | number> {
   @PrimaryColumn()
   key!: SystemConfigKey;
 
@@ -14,10 +14,13 @@ export type SystemConfigValue = any;
 // dot notation matches path in `SystemConfig`
 export enum SystemConfigKey {
   FFMPEG_CRF = 'ffmpeg.crf',
+  FFMPEG_THREADS = 'ffmpeg.threads',
   FFMPEG_PRESET = 'ffmpeg.preset',
   FFMPEG_TARGET_VIDEO_CODEC = 'ffmpeg.targetVideoCodec',
   FFMPEG_TARGET_AUDIO_CODEC = 'ffmpeg.targetAudioCodec',
   FFMPEG_TARGET_RESOLUTION = 'ffmpeg.targetResolution',
+  FFMPEG_MAX_BITRATE = 'ffmpeg.maxBitrate',
+  FFMPEG_TWO_PASS = 'ffmpeg.twoPass',
   FFMPEG_TRANSCODE = 'ffmpeg.transcode',
   OAUTH_ENABLED = 'oauth.enabled',
   OAUTH_ISSUER_URL = 'oauth.issuerUrl',
@@ -42,11 +45,14 @@ export enum TranscodePreset {
 
 export interface SystemConfig {
   ffmpeg: {
-    crf: string;
+    crf: number;
+    threads: number;
     preset: string;
     targetVideoCodec: string;
     targetAudioCodec: string;
     targetResolution: string;
+    maxBitrate: string;
+    twoPass: boolean;
     transcode: TranscodePreset;
   };
   oauth: {

server/libs/infra/src/repositories/media.repository.ts

@@ -1,8 +1,9 @@
-import { CropOptions, IMediaRepository, ResizeOptions, VideoInfo } from '@app/domain';
+import { CropOptions, IMediaRepository, ResizeOptions, TranscodeOptions, VideoInfo } from '@app/domain';
 import { exiftool } from 'exiftool-vendored';
 import ffmpeg, { FfprobeData } from 'fluent-ffmpeg';
 import sharp from 'sharp';
 import { promisify } from 'util';
+import fs from 'fs/promises';
 
 const probe = promisify<string, FfprobeData>(ffmpeg.ffprobe);
 
@@ -85,14 +86,40 @@ export class MediaRepository implements IMediaRepository {
     };
   }
 
-  transcode(input: string, output: string, options: string[]): Promise<void> {
+  transcode(input: string, output: string, options: TranscodeOptions): Promise<void> {
+    if (!options.twoPass) {
+      return new Promise((resolve, reject) => {
+        ffmpeg(input, { niceness: 10 })
+          .outputOptions(options.outputOptions)
+          .output(output)
+          .on('error', reject)
+          .on('end', resolve)
+          .run();
+      });
+    }
+
+    // two-pass allows for precise control of bitrate at the cost of running twice
+    // recommended for vp9 for better quality and compression
     return new Promise((resolve, reject) => {
       ffmpeg(input, { niceness: 10 })
-        //
-        .outputOptions(options)
-        .output(output)
+        .outputOptions(options.outputOptions)
+        .addOptions('-pass', '1')
+        .addOptions('-passlogfile', output)
+        .addOptions('-f null')
+        .output('/dev/null') // first pass output is not saved as only the .log file is needed
         .on('error', reject)
-        .on('end', resolve)
+        .on('end', () => {
+          // second pass
+          ffmpeg(input, { niceness: 10 })
+            .outputOptions(options.outputOptions)
+            .addOptions('-pass', '2')
+            .addOptions('-passlogfile', output)
+            .output(output)
+            .on('error', reject)
+            .on('end', () => fs.unlink(`${output}-0.log`))
+            .on('end', resolve)
+            .run();
+        })
         .run();
     });
   }

server/libs/infra/src/repositories/system-config.repository.ts

@@ -9,7 +9,7 @@ export class SystemConfigRepository implements ISystemConfigRepository {
     private repository: Repository<SystemConfigEntity>,
   ) {}
 
-  load(): Promise<SystemConfigEntity<string | boolean>[]> {
+  load(): Promise<SystemConfigEntity<string | boolean | number>[]> {
     return this.repository.find();
   }