Separate HLS audio and video streams

Allows:
  * The HLS player to propose an "Audio only" resolution
  * The live to output an "Audio only" resolution
  * The live to ingest and output an "Audio only" stream

 This feature is under a config for VOD videos and is enabled by default for lives

 In the future we can imagine:
  * To propose multiple audio streams for a specific video
  * To ingest an audio only VOD and just output an audio only "video"
    (the player would play the audio file and PeerTube would not
    generate additional resolutions)

This commit introduce a new way to download videos:
 * Add "/download/videos/generate/:videoId" endpoint where PeerTube can
   mux an audio only and a video only file to a mp4 container
 * The download client modal introduces a new default panel where the
   user can choose resolutions it wants to download

server/core/lib/transcoding/hls-transcoding.ts

@@ -1,17 +1,17 @@
-import { MutexInterface } from 'async-mutex'
-import { Job } from 'bullmq'
-import { ensureDir, move } from 'fs-extra/esm'
-import { join } from 'path'
 import { pick } from '@peertube/peertube-core-utils'
+import { getVideoStreamDuration, HLSFromTSTranscodeOptions, HLSTranscodeOptions } from '@peertube/peertube-ffmpeg'
 import { retryTransactionWrapper } from '@server/helpers/database-utils.js'
 import { createTorrentAndSetInfoHash } from '@server/helpers/webtorrent.js'
 import { sequelizeTypescript } from '@server/initializers/database.js'
 import { MVideo } from '@server/types/models/index.js'
-import { getVideoStreamDuration } from '@peertube/peertube-ffmpeg'
+import { MutexInterface } from 'async-mutex'
+import { Job } from 'bullmq'
+import { ensureDir, move } from 'fs-extra/esm'
+import { join } from 'path'
 import { CONFIG } from '../../initializers/config.js'
 import { VideoFileModel } from '../../models/video/video-file.js'
 import { VideoStreamingPlaylistModel } from '../../models/video/video-streaming-playlist.js'
-import { renameVideoFileInPlaylist, updatePlaylistAfterFileChange } from '../hls.js'
+import { renameVideoFileInPlaylist, updateM3U8AndShaPlaylist } from '../hls.js'
 import { generateHLSVideoFilename, getHlsResolutionPlaylistFilename } from '../paths.js'
 import { buildNewFile } from '../video-file.js'
 import { VideoPathManager } from '../video-path-manager.js'
@@ -28,7 +28,8 @@ export async function generateHlsPlaylistResolutionFromTS (options: {
 }) {
   return generateHlsPlaylistCommon({
     type: 'hls-from-ts' as 'hls-from-ts',
-    inputPath: options.concatenatedTsFilePath,
+
+    videoInputPath: options.concatenatedTsFilePath,
 
     ...pick(options, [ 'video', 'resolution', 'fps', 'inputFileMutexReleaser', 'isAAC' ])
   })
@@ -37,18 +38,31 @@ export async function generateHlsPlaylistResolutionFromTS (options: {
 // Generate an HLS playlist from an input file, and update the master playlist
 export function generateHlsPlaylistResolution (options: {
   video: MVideo
+
   videoInputPath: string
+  separatedAudioInputPath: string
+
   resolution: number
   fps: number
   copyCodecs: boolean
   inputFileMutexReleaser: MutexInterface.Releaser
+  separatedAudio: boolean
   job?: Job
 }) {
   return generateHlsPlaylistCommon({
     type: 'hls' as 'hls',
-    inputPath: options.videoInputPath,
 
-    ...pick(options, [ 'video', 'resolution', 'fps', 'copyCodecs', 'inputFileMutexReleaser', 'job' ])
+    ...pick(options, [
+      'videoInputPath',
+      'separatedAudioInputPath',
+      'video',
+      'resolution',
+      'fps',
+      'copyCodecs',
+      'separatedAudio',
+      'inputFileMutexReleaser',
+      'job'
+    ])
   })
 }
 
@@ -113,7 +127,7 @@ export async function onHLSVideoFileTranscoding (options: {
 
     const savedVideoFile = await VideoFileModel.customUpsert(newVideoFile, 'streaming-playlist', undefined)
 
-    await updatePlaylistAfterFileChange(video, playlist)
+    await updateM3U8AndShaPlaylist(video, playlist)
 
     return { resolutionPlaylistPath, videoFile: savedVideoFile }
   } finally {
@@ -121,24 +135,43 @@ export async function onHLSVideoFileTranscoding (options: {
   }
 }
 
+// ---------------------------------------------------------------------------
+// Private
 // ---------------------------------------------------------------------------
 
 async function generateHlsPlaylistCommon (options: {
   type: 'hls' | 'hls-from-ts'
   video: MVideo
-  inputPath: string
+
+  videoInputPath: string
+  separatedAudioInputPath?: string
 
   resolution: number
   fps: number
 
   inputFileMutexReleaser: MutexInterface.Releaser
 
+  separatedAudio?: boolean
+
   copyCodecs?: boolean
   isAAC?: boolean
 
   job?: Job
 }) {
-  const { type, video, inputPath, resolution, fps, copyCodecs, isAAC, job, inputFileMutexReleaser } = options
+  const {
+    type,
+    video,
+    videoInputPath,
+    separatedAudioInputPath,
+    resolution,
+    fps,
+    copyCodecs,
+    separatedAudio,
+    isAAC,
+    job,
+    inputFileMutexReleaser
+  } = options
+
   const transcodeDirectory = CONFIG.STORAGE.TMP_DIR
 
   const videoTranscodedBasePath = join(transcodeDirectory, type)
@@ -150,15 +183,18 @@ async function generateHlsPlaylistCommon (options: {
   const resolutionPlaylistFilename = getHlsResolutionPlaylistFilename(videoFilename)
   const m3u8OutputPath = join(videoTranscodedBasePath, resolutionPlaylistFilename)
 
-  const transcodeOptions = {
+  const transcodeOptions: HLSTranscodeOptions | HLSFromTSTranscodeOptions = {
     type,
 
-    inputPath,
+    videoInputPath,
+    separatedAudioInputPath,
+
     outputPath: m3u8OutputPath,
 
     resolution,
     fps,
     copyCodecs,
+    separatedAudio,
 
     isAAC,