transcoding service

server/src/constants.ts

@@ -222,7 +222,7 @@ export const SUPPORTED_HWA_CODECS: Record<TranscodeHardwareAcceleration, VideoCo
 
 export const HLS_BACKPRESSURE_PAUSE_SEGMENTS = 30;
 export const HLS_BACKPRESSURE_RESUME_SEGMENTS = 15;
-export const HLS_INACTIVITY_SWEEP_INTERVAL_MS = 60 * 1000;
+export const HLS_CLEANUP_INTERVAL_MS = 60 * 1000;
 export const HLS_INACTIVITY_TIMEOUT_MS = 5 * 60 * 1000;
 export const HLS_LEASE_DURATION_MS = 30 * 60 * 1000;
 export const HLS_SEGMENT_DURATION = 2;

server/src/cores/storage.core.ts

@@ -18,6 +18,7 @@ import { MoveRepository } from 'src/repositories/move.repository';
 import { PersonRepository } from 'src/repositories/person.repository';
 import { StorageRepository } from 'src/repositories/storage.repository';
 import { SystemMetadataRepository } from 'src/repositories/system-metadata.repository';
+import { VideoInterfaces } from 'src/types';
 import { getAssetFile } from 'src/utils/asset.util';
 import { getConfig } from 'src/utils/config';
 
@@ -34,6 +35,10 @@ export interface MoveRequest {
 
 export type ThumbnailPathEntity = { id: string; ownerId: string };
 
+export type HlsSessionFolder = { ownerId: string; sessionId: string };
+
+export type HlsVariantFolder = { ownerId: string; sessionId: string; variantIndex: number };
+
 export type ImagePathOptions = { fileType: AssetFileType; format: ImageFormat | RawExtractedFormat; isEdited: boolean };
 
 let instance: StorageCore | null;
@@ -124,6 +129,18 @@ export class StorageCore {
     return StorageCore.getNestedPath(StorageFolder.EncodedVideo, asset.ownerId, `${asset.id}.mp4`);
   }
 
+  static getHlsSessionFolder({ ownerId, sessionId }: HlsSessionFolder) {
+    return StorageCore.getNestedFolder(StorageFolder.EncodedVideo, ownerId, sessionId);
+  }
+
+  static getHlsVariantFolder({ ownerId, sessionId, variantIndex }: HlsVariantFolder) {
+    return join(StorageCore.getHlsSessionFolder({ ownerId, sessionId }), variantIndex.toString());
+  }
+
+  static getHlsSegmentPath({ ownerId, sessionId, variantIndex }: HlsVariantFolder) {
+    return join(StorageCore.getHlsVariantFolder({ ownerId, sessionId, variantIndex }), variantIndex.toString());
+  }
+
   static getAndroidMotionPath(asset: ThumbnailPathEntity, uuid: string) {
     return StorageCore.getNestedPath(StorageFolder.EncodedVideo, asset.ownerId, `${uuid}-MP.mp4`);
   }
@@ -299,6 +316,11 @@ export class StorageCore {
     return this.storageRepository.removeEmptyDirs(StorageCore.getBaseFolder(folder));
   }
 
+  async getVideoInterfaces(): Promise<VideoInterfaces> {
+    const [dri, mali] = await Promise.all([this.getDevices(), this.hasMaliOpenCL()]);
+    return { dri, mali };
+  }
+
   private savePath(pathType: PathType, id: string, newPath: string) {
     switch (pathType) {
       case AssetPathType.Original: {
@@ -330,4 +352,26 @@ export class StorageCore {
   static getTempPathInDir(dir: string): string {
     return join(dir, `${randomUUID()}.tmp`);
   }
+
+  private async getDevices() {
+    try {
+      return await this.storageRepository.readdir('/dev/dri');
+    } catch {
+      this.logger.debug('No devices found in /dev/dri.');
+      return [];
+    }
+  }
+
+  private async hasMaliOpenCL() {
+    try {
+      const [maliIcdStat, maliDeviceStat] = await Promise.all([
+        this.storageRepository.stat('/etc/OpenCL/vendors/mali.icd'),
+        this.storageRepository.stat('/dev/mali0'),
+      ]);
+      return maliIcdStat.isFile() && maliDeviceStat.isCharacterDevice();
+    } catch {
+      this.logger.debug('OpenCL not available for transcoding, so RKMPP acceleration will use CPU tonemapping');
+      return false;
+    }
+  }
 }

server/src/enum.ts

@@ -814,6 +814,8 @@ export enum JobName {
   LibrarySyncFiles = 'LibrarySyncFiles',
   LibraryScanQueueAll = 'LibraryScanQueueAll',
 
+  HlsSessionCleanup = 'HlsSessionCleanup',
+
   MemoryCleanup = 'MemoryCleanup',
   MemoryGenerate = 'MemoryGenerate',
 
@@ -906,6 +908,7 @@ export enum DatabaseLock {
   MaintenanceOperation = 621,
   MemoryCreation = 777,
   VersionCheck = 800,
+  HlsSessionCleanup = 850,
 }
 
 export enum MaintenanceAction {

server/src/repositories/process.repository.ts

@@ -1,12 +1,10 @@
 import { Injectable } from '@nestjs/common';
-import { ChildProcessWithoutNullStreams, fork, spawn, SpawnOptionsWithoutStdio } from 'node:child_process';
+import { fork, spawn, SpawnOptionsWithoutStdio } from 'node:child_process';
 import { Duplex } from 'node:stream';
 
 @Injectable()
 export class ProcessRepository {
-  spawn(command: string, args?: readonly string[], options?: SpawnOptionsWithoutStdio): ChildProcessWithoutNullStreams {
-    return spawn(command, args, options);
-  }
+  spawn = spawn;
 
   spawnDuplexStream(command: string, args?: readonly string[], options?: SpawnOptionsWithoutStdio): Duplex {
     let stdinClosed = false;

server/src/repositories/storage.repository.ts

@@ -2,7 +2,15 @@ import { Injectable } from '@nestjs/common';
 import archiver from 'archiver';
 import chokidar, { ChokidarOptions } from 'chokidar';
 import { escapePath, glob, globStream } from 'fast-glob';
-import { constants, createReadStream, createWriteStream, existsSync, mkdirSync, ReadOptionsWithBuffer } from 'node:fs';
+import {
+  constants,
+  createReadStream,
+  createWriteStream,
+  existsSync,
+  mkdirSync,
+  ReadOptionsWithBuffer,
+  watch,
+} from 'node:fs';
 import fs from 'node:fs/promises';
 import path from 'node:path';
 import { PassThrough, Readable, Writable } from 'node:stream';
@@ -258,6 +266,8 @@ export class StorageRepository {
     return () => watcher.close();
   }
 
+  watchDir = watch; // Native fs.watch without chokidar overhead
+
   private asGlob(pathToCrawl: string): string {
     const escapedPath = escapePath(pathToCrawl).replaceAll('"', '["]').replaceAll("'", "[']").replaceAll('`', '[`]');
     const extensions = `*{${mimeTypes.getSupportedFileExtensions().join(',')}}`;

server/src/services/index.ts

@@ -40,6 +40,7 @@ import { SystemMetadataService } from 'src/services/system-metadata.service';
 import { TagService } from 'src/services/tag.service';
 import { TelemetryService } from 'src/services/telemetry.service';
 import { TimelineService } from 'src/services/timeline.service';
+import { TranscodingService } from 'src/services/transcoding.service';
 import { TrashService } from 'src/services/trash.service';
 import { UserAdminService } from 'src/services/user-admin.service';
 import { UserService } from 'src/services/user.service';
@@ -90,6 +91,7 @@ export const services = [
   TagService,
   TelemetryService,
   TimelineService,
+  TranscodingService,
   TrashService,
   UserAdminService,
   UserService,

server/src/services/media.service.ts

@@ -13,6 +13,7 @@ import {
   AudioCodec,
   Colorspace,
   ImageFormat,
+  ImmichWorker,
   JobName,
   JobStatus,
   QueueName,
@@ -60,10 +61,9 @@ type ThumbnailAsset = NonNullable<Awaited<ReturnType<AssetJobRepository['getForG
 export class MediaService extends BaseService {
   videoInterfaces: VideoInterfaces = { dri: [], mali: false };
 
-  @OnEvent({ name: 'AppBootstrap' })
+  @OnEvent({ name: 'AppBootstrap', workers: [ImmichWorker.Microservices] })
   async onBootstrap() {
-    const [dri, mali] = await Promise.all([this.getDevices(), this.hasMaliOpenCL()]);
-    this.videoInterfaces = { dri, mali };
+    this.videoInterfaces = await this.storageCore.getVideoInterfaces();
   }
 
   @OnJob({ name: JobName.AssetGenerateThumbnailsQueueAll, queue: QueueName.ThumbnailGeneration })
@@ -789,28 +789,6 @@ export class MediaService extends BaseService {
     return extractedSize >= targetSize;
   }
 
-  private async getDevices() {
-    try {
-      return await this.storageRepository.readdir('/dev/dri');
-    } catch {
-      this.logger.debug('No devices found in /dev/dri.');
-      return [];
-    }
-  }
-
-  private async hasMaliOpenCL() {
-    try {
-      const [maliIcdStat, maliDeviceStat] = await Promise.all([
-        this.storageRepository.stat('/etc/OpenCL/vendors/mali.icd'),
-        this.storageRepository.stat('/dev/mali0'),
-      ]);
-      return maliIcdStat.isFile() && maliDeviceStat.isCharacterDevice();
-    } catch {
-      this.logger.debug('OpenCL not available for transcoding, so RKMPP acceleration will use CPU tonemapping');
-      return false;
-    }
-  }
-
   private async syncFiles(
     oldFiles: (AssetFile & { isProgressive: boolean; isTransparent: boolean })[],
     newFiles: UpsertFileOptions[],

server/src/services/queue.service.spec.ts

@@ -41,6 +41,7 @@ describe(QueueService.name, () => {
         { name: JobName.PersonCleanup },
         { name: JobName.MemoryCleanup },
         { name: JobName.SessionCleanup },
+        { name: JobName.HlsSessionCleanup },
         { name: JobName.AuditTableCleanup },
         { name: JobName.MemoryGenerate },
         { name: JobName.UserSyncUsage },

server/src/services/queue.service.ts

@@ -269,6 +269,7 @@ export class QueueService extends BaseService {
         { name: JobName.PersonCleanup },
         { name: JobName.MemoryCleanup },
         { name: JobName.SessionCleanup },
+        { name: JobName.HlsSessionCleanup },
         { name: JobName.AuditTableCleanup },
       );
     }

server/src/services/transcoding.service.spec.ts

@@ -0,0 +1,207 @@
+import { HLS_CLEANUP_INTERVAL_MS, HLS_INACTIVITY_TIMEOUT_MS, HLS_LEASE_DURATION_MS } from 'src/constants';
+import { TranscodingService } from 'src/services/transcoding.service';
+import { VIDEO_STREAM_SESSION_PK_CONSTRAINT } from 'src/utils/database';
+import { eiffelTower } from 'test/fixtures/media.stub';
+import { mockSpawn, newTestService, ServiceMocks } from 'test/utils';
+import { vi } from 'vitest';
+
+describe(TranscodingService.name, () => {
+  let sut: TranscodingService;
+  let mocks: ServiceMocks;
+
+  const sessionId = 'session-1';
+  const assetId = 'asset-1';
+  const ownerId = 'user-1';
+
+  beforeEach(() => {
+    ({ sut, mocks } = newTestService(TranscodingService));
+    mocks.systemMetadata.get.mockResolvedValue({ ffmpeg: { realtime: { enabled: true } } });
+    mocks.videoStream.getForTranscoding.mockResolvedValue(eiffelTower);
+  });
+
+  describe('onSessionRequest', () => {
+    it('creates the session row and emits HlsSessionResult on success', async () => {
+      await sut.onSessionRequest({ sessionId, assetId, ownerId });
+
+      expect(mocks.videoStream.createSession).toHaveBeenCalledWith({
+        id: sessionId,
+        assetId,
+        expiresAt: expect.any(Date),
+      });
+      expect(mocks.websocket.serverSend).toHaveBeenCalledWith('HlsSessionResult', { sessionId });
+    });
+
+    it('treats a primary-key conflict as a no-op for replay tolerance', async () => {
+      mocks.videoStream.createSession.mockRejectedValue({ constraint_name: VIDEO_STREAM_SESSION_PK_CONSTRAINT });
+
+      await sut.onSessionRequest({ sessionId, assetId, ownerId });
+
+      expect(mocks.websocket.serverSend).not.toHaveBeenCalled();
+    });
+
+    it('emits HlsSessionResult with an error on other DB failures', async () => {
+      mocks.videoStream.createSession.mockRejectedValue(new Error('database is down'));
+
+      await sut.onSessionRequest({ sessionId, assetId, ownerId });
+
+      expect(mocks.websocket.serverSend).toHaveBeenCalledWith('HlsSessionResult', {
+        sessionId,
+        error: 'Failed to create HLS session',
+      });
+    });
+  });
+
+  describe('onSessionEnd', () => {
+    it('removes the session, kills the transcode, and deletes the dir + DB row', async () => {
+      await sut.onSessionRequest({ sessionId, assetId, ownerId });
+      const process = mockSpawn(0, '', '');
+      mocks.process.spawn.mockReturnValue(process);
+      await sut.onSegmentRequest({ sessionId, assetId, variantIndex: 0, segmentIndex: 0 });
+
+      await sut.onSessionEnd({ sessionId });
+
+      expect(process.kill).toHaveBeenCalled();
+      expect(mocks.storage.unlinkDir).toHaveBeenCalled();
+      expect(mocks.videoStream.deleteSession).toHaveBeenCalledWith(sessionId);
+    });
+
+    it('is a no-op when the session is unknown', async () => {
+      await sut.onSessionEnd({ sessionId: 'never-created' });
+
+      expect(mocks.videoStream.deleteSession).not.toHaveBeenCalled();
+      expect(mocks.storage.unlinkDir).not.toHaveBeenCalled();
+    });
+  });
+
+  describe('onHeartbeat', () => {
+    it('extends the DB lease when remaining time falls below half', async () => {
+      vi.useFakeTimers();
+      try {
+        await sut.onSessionRequest({ sessionId, assetId, ownerId });
+        vi.setSystemTime(Date.now() + HLS_LEASE_DURATION_MS / 2 + 1);
+
+        await sut.onHeartbeat({ sessionId });
+
+        expect(mocks.videoStream.extendSession).toHaveBeenCalledWith(sessionId, expect.any(Date));
+      } finally {
+        vi.useRealTimers();
+      }
+    });
+
+    it('does not extend the lease while it is still fresh', async () => {
+      await sut.onSessionRequest({ sessionId, assetId, ownerId });
+
+      await sut.onHeartbeat({ sessionId });
+
+      expect(mocks.videoStream.extendSession).not.toHaveBeenCalled();
+    });
+
+    it('is a no-op when the session is unknown', async () => {
+      await sut.onHeartbeat({ sessionId: 'never-created' });
+
+      expect(mocks.videoStream.extendSession).not.toHaveBeenCalled();
+    });
+  });
+
+  describe('onSegmentRequest', () => {
+    beforeEach(async () => {
+      await sut.onSessionRequest({ sessionId, assetId, ownerId });
+      mocks.websocket.serverSend.mockClear();
+    });
+
+    it('spawns FFmpeg on the first request', async () => {
+      mocks.process.spawn.mockReturnValue(mockSpawn(0, '', ''));
+
+      await sut.onSegmentRequest({ sessionId, assetId, variantIndex: 0, segmentIndex: 0 });
+
+      expect(mocks.process.spawn).toHaveBeenCalledTimes(1);
+      expect(mocks.process.spawn).toHaveBeenCalledWith('ffmpeg', expect.any(Array), expect.any(Object));
+    });
+
+    it('kills and respawns when the variant changes', async () => {
+      const first = mockSpawn(0, '', '');
+      const second = mockSpawn(0, '', '');
+      mocks.process.spawn.mockReturnValueOnce(first).mockReturnValueOnce(second);
+
+      await sut.onSegmentRequest({ sessionId, assetId, variantIndex: 0, segmentIndex: 0 });
+      await sut.onSegmentRequest({ sessionId, assetId, variantIndex: 1, segmentIndex: 0 });
+
+      expect(first.kill).toHaveBeenCalled();
+      expect(mocks.process.spawn).toHaveBeenCalledTimes(2);
+    });
+
+    it('kills and respawns when seeking before the start segment', async () => {
+      const first = mockSpawn(0, '', '');
+      const second = mockSpawn(0, '', '');
+      mocks.process.spawn.mockReturnValueOnce(first).mockReturnValueOnce(second);
+
+      await sut.onSegmentRequest({ sessionId, assetId, variantIndex: 0, segmentIndex: 5 });
+      await sut.onSegmentRequest({ sessionId, assetId, variantIndex: 0, segmentIndex: 2 });
+
+      expect(first.kill).toHaveBeenCalled();
+      expect(mocks.process.spawn).toHaveBeenCalledTimes(2);
+    });
+
+    it('kills and respawns when the requested segment is too far ahead', async () => {
+      const first = mockSpawn(0, '', '');
+      const second = mockSpawn(0, '', '');
+      mocks.process.spawn.mockReturnValueOnce(first).mockReturnValueOnce(second);
+
+      await sut.onSegmentRequest({ sessionId, assetId, variantIndex: 0, segmentIndex: 0 });
+      await sut.onSegmentRequest({ sessionId, assetId, variantIndex: 0, segmentIndex: 5 });
+
+      expect(first.kill).toHaveBeenCalled();
+      expect(mocks.process.spawn).toHaveBeenCalledTimes(2);
+    });
+
+    it('does not spawn when the session is unknown', async () => {
+      await sut.onSegmentRequest({ sessionId: 'never-created', assetId, variantIndex: 0, segmentIndex: 0 });
+
+      expect(mocks.process.spawn).not.toHaveBeenCalled();
+    });
+  });
+
+  describe('inactivity sweeper', () => {
+    it('reaps a session whose last activity exceeds the inactivity timeout', async () => {
+      vi.useFakeTimers();
+      try {
+        await sut.onSessionRequest({ sessionId, assetId, ownerId });
+        mocks.websocket.serverSend.mockClear();
+        await vi.advanceTimersByTimeAsync(HLS_INACTIVITY_TIMEOUT_MS + HLS_CLEANUP_INTERVAL_MS);
+
+        expect(mocks.websocket.serverSend).toHaveBeenCalledWith('HlsSessionEnd', { sessionId });
+        expect(mocks.videoStream.deleteSession).toHaveBeenCalledWith(sessionId);
+      } finally {
+        vi.useRealTimers();
+      }
+    });
+  });
+
+  describe('onShutdown', () => {
+    it('ends every active session', async () => {
+      await sut.onSessionRequest({ sessionId: 'session-a', assetId, ownerId });
+      await sut.onSessionRequest({ sessionId: 'session-b', assetId, ownerId });
+
+      await sut.onShutdown();
+
+      expect(mocks.videoStream.deleteSession).toHaveBeenCalledWith('session-a');
+      expect(mocks.videoStream.deleteSession).toHaveBeenCalledWith('session-b');
+    });
+  });
+
+  describe('onHlsSessionCleanup', () => {
+    it('reaps DB-expired sessions under a database lock', async () => {
+      mocks.database.withLock.mockImplementation(async (_, fn) => fn());
+      mocks.videoStream.getExpiredSessions.mockResolvedValue([
+        { id: 'expired-1', ownerId: 'user-a' },
+        { id: 'expired-2', ownerId: 'user-b' },
+      ]);
+
+      await sut.onHlsSessionCleanup();
+
+      expect(mocks.videoStream.deleteSession).toHaveBeenCalledWith('expired-1');
+      expect(mocks.videoStream.deleteSession).toHaveBeenCalledWith('expired-2');
+      expect(mocks.storage.unlinkDir).toHaveBeenCalledTimes(2);
+    });
+  });
+});

server/src/services/transcoding.service.ts

@@ -0,0 +1,393 @@
+import { Injectable } from '@nestjs/common';
+import { ChildProcess } from 'node:child_process';
+import { join } from 'node:path';
+import {
+  HLS_BACKPRESSURE_PAUSE_SEGMENTS,
+  HLS_BACKPRESSURE_RESUME_SEGMENTS,
+  HLS_CLEANUP_INTERVAL_MS,
+  HLS_INACTIVITY_TIMEOUT_MS,
+  HLS_LEASE_DURATION_MS,
+  HLS_SEGMENT_DURATION,
+  HLS_VARIANTS,
+  SEGMENT_FILENAME_REGEX,
+} from 'src/constants';
+import { StorageCore } from 'src/cores/storage.core';
+import { OnEvent, OnJob } from 'src/decorators';
+import { DatabaseLock, ImmichWorker, JobName, QueueName, TranscodeTarget } from 'src/enum';
+import { ArgOf } from 'src/repositories/event.repository';
+import { BaseService } from 'src/services/base.service';
+import { VideoInterfaces } from 'src/types';
+import { isVideoStreamSessionPkConstraint } from 'src/utils/database';
+import { BaseConfig } from 'src/utils/media';
+
+type Session = {
+  assetId: string;
+  expiresAt: Date;
+  id: string;
+  lastActivityTime: Date;
+  lastClientRequestedSegment: number | null;
+  lastCompletedSegment: number | null;
+  ownerId: string;
+  paused: boolean;
+  process: ChildProcess | null;
+  startSegment: number | null;
+  variantIndex: number | null;
+};
+
+@Injectable()
+export class TranscodingService extends BaseService {
+  private sessions = new Map<string, Session>();
+  private videoInterfaces: VideoInterfaces = { dri: [], mali: false };
+  private cleanupInterval: NodeJS.Timeout | null = null;
+
+  @OnEvent({ name: 'AppBootstrap', workers: [ImmichWorker.Microservices] })
+  async onBootstrap() {
+    const [videoInterfaces] = await Promise.all([this.storageCore.getVideoInterfaces(), this.removeExpiredSessions()]);
+    this.videoInterfaces = videoInterfaces;
+  }
+
+  @OnEvent({ name: 'AppShutdown', workers: [ImmichWorker.Microservices] })
+  onShutdown() {
+    if (this.cleanupInterval) {
+      clearInterval(this.cleanupInterval);
+      this.cleanupInterval = null;
+    }
+    return Promise.all([...this.sessions.values()].map(({ id }) => this.onSessionEnd({ sessionId: id })));
+  }
+
+  @OnJob({ name: JobName.HlsSessionCleanup, queue: QueueName.BackgroundTask })
+  onHlsSessionCleanup() {
+    return this.removeExpiredSessions();
+  }
+
+  @OnEvent({ name: 'HlsSessionRequest', server: true, workers: [ImmichWorker.Microservices] })
+  async onSessionRequest({ assetId, sessionId, ownerId }: ArgOf<'HlsSessionRequest'>) {
+    try {
+      const expiresAt = new Date(Date.now() + HLS_LEASE_DURATION_MS);
+      await this.videoStreamRepository.createSession({ id: sessionId, assetId, expiresAt });
+      this.sessions.set(sessionId, {
+        assetId,
+        expiresAt,
+        id: sessionId,
+        lastActivityTime: new Date(),
+        lastClientRequestedSegment: null,
+        lastCompletedSegment: null,
+        ownerId,
+        paused: false,
+        process: null,
+        startSegment: null,
+        variantIndex: null,
+      });
+      this.cleanupInterval ??= setInterval(() => void this.removeInactiveSessions(), HLS_CLEANUP_INTERVAL_MS);
+      this.websocketRepository.serverSend('HlsSessionResult', { sessionId });
+    } catch (error) {
+      if (!isVideoStreamSessionPkConstraint(error)) {
+        this.logger.error(`Failed to create HLS session ${sessionId}: ${error}`);
+        this.websocketRepository.serverSend('HlsSessionResult', { sessionId, error: 'Failed to create HLS session' });
+      }
+    }
+  }
+
+  @OnEvent({ name: 'HlsSessionEnd', server: true, workers: [ImmichWorker.Microservices] })
+  async onSessionEnd({ sessionId }: ArgOf<'HlsSessionEnd'>) {
+    const session = this.sessions.get(sessionId);
+    if (!session) {
+      return;
+    }
+    this.sessions.delete(sessionId);
+    if (this.cleanupInterval && this.sessions.size === 0) {
+      clearInterval(this.cleanupInterval);
+      this.cleanupInterval = null;
+    }
+    this.stopTranscode(session);
+    await this.removeSessionDir(session);
+    await this.videoStreamRepository.deleteSession(sessionId);
+  }
+
+  @OnEvent({ name: 'HlsHeartbeat', server: true, workers: [ImmichWorker.Microservices] })
+  async onHeartbeat({ sessionId, segmentIndex }: ArgOf<'HlsHeartbeat'>) {
+    const session = this.sessions.get(sessionId);
+    if (!session) {
+      return;
+    }
+
+    session.lastActivityTime = new Date();
+
+    if (segmentIndex !== undefined) {
+      session.lastClientRequestedSegment = segmentIndex;
+      this.applyBackpressure(session);
+    }
+
+    const remaining = session.expiresAt.getTime() - Date.now();
+    if (remaining < HLS_LEASE_DURATION_MS / 2) {
+      session.expiresAt = new Date(Date.now() + HLS_LEASE_DURATION_MS);
+      await this.videoStreamRepository.extendSession(sessionId, session.expiresAt);
+    }
+  }
+
+  @OnEvent({ name: 'HlsSegmentRequest', server: true, workers: [ImmichWorker.Microservices] })
+  async onSegmentRequest({ sessionId, variantIndex, segmentIndex }: ArgOf<'HlsSegmentRequest'>) {
+    const session = this.sessions.get(sessionId);
+    if (!session) {
+      return;
+    }
+
+    session.variantIndex ??= variantIndex;
+    session.startSegment ??= segmentIndex;
+    const curSegment = session.lastCompletedSegment === null ? session.startSegment : session.lastCompletedSegment + 1;
+    const needsRestart =
+      session.variantIndex !== variantIndex || segmentIndex < session.startSegment || segmentIndex > curSegment + 1;
+    if (needsRestart) {
+      this.stopTranscode(session);
+      session.variantIndex = variantIndex;
+      session.startSegment = segmentIndex;
+    } else if (session.process) {
+      this.resumeTranscode(session);
+      return;
+    }
+
+    const process = await this.startTranscode(session, variantIndex, segmentIndex);
+    if (process) {
+      session.process = process;
+    }
+  }
+
+  private applyBackpressure(session: Session) {
+    if (session.lastCompletedSegment === null || session.lastClientRequestedSegment === null) {
+      return;
+    }
+    const lead = session.lastCompletedSegment - session.lastClientRequestedSegment;
+    if (!session.paused && lead > HLS_BACKPRESSURE_PAUSE_SEGMENTS) {
+      this.pauseTranscode(session);
+    } else if (session.paused && lead < HLS_BACKPRESSURE_RESUME_SEGMENTS) {
+      this.resumeTranscode(session);
+    }
+  }
+
+  private async startTranscode(session: Session, variantIndex: number, startSegment: number) {
+    const t0 = performance.now();
+    const { ffmpeg } = await this.getConfig({ withCache: true });
+    const t1 = performance.now();
+
+    const asset = await this.videoStreamRepository.getForTranscoding(session.assetId);
+    const t2 = performance.now();
+    if (!asset) {
+      this.logger.error(`Asset ${session.assetId} not found for HLS transcoding`);
+      return;
+    }
+
+    if (session.variantIndex !== variantIndex || session.startSegment !== startSegment) {
+      return;
+    }
+
+    const variant = HLS_VARIANTS[variantIndex];
+    if (!variant) {
+      this.logger.error(`Variant ${variantIndex} out of range for asset ${session.assetId}`);
+      await this.failSession(session, `Invalid variant index ${variantIndex}`);
+      return;
+    }
+
+    const variantDir = StorageCore.getHlsVariantFolder({
+      ownerId: session.ownerId,
+      sessionId: session.id,
+      variantIndex,
+    });
+    this.storageRepository.mkdirSync(variantDir);
+
+    // Encoder runs at fps = packetCount × timeBase / totalDuration with
+    // gop = ceil(SEGMENT_DURATION × fps). To start segment K's content at
+    // exactly cfr slot K × gop, seek to the midpoint between slots K×gop−1 and
+    // K×gop. accurate_seek's "discard < target" then keeps the source frame
+    // that quantizes to slot K×gop and discards the one quantizing to K×gop−1.
+    const fps = (asset.packets.packetCount * asset.videoStream.timeBase) / asset.packets.totalDuration;
+    const gop = Math.ceil(HLS_SEGMENT_DURATION * fps);
+    const seekSeconds = startSegment > 0 ? (startSegment * gop - 0.5) / fps : 0;
+
+    let config;
+    try {
+      config = BaseConfig.create(
+        {
+          ...ffmpeg,
+          targetVideoCodec: variant.codec,
+          targetResolution: String(variant.resolution),
+          maxBitrate: `${Math.round(variant.bitrate / 1000)}k`,
+          gopSize: gop,
+        },
+        this.videoInterfaces,
+        { strictGop: true, lowLatency: true },
+      );
+    } catch (error: any) {
+      this.logger.error(
+        `Failed to create transcode config for variant ${variantIndex} asset ${session.assetId}: ${error?.message ?? error}`,
+      );
+      await this.failSession(session, `Failed to start transcode: ${error?.message ?? 'unknown error'}`);
+      return;
+    }
+    const t3 = performance.now();
+    const args = config.getHlsCommand(
+      {
+        initFilename: 'init.mp4',
+        inputPath: asset.originalPath,
+        packetCount: asset.packets.packetCount,
+        playlistFilename: join(variantDir, 'playlist.m3u8'),
+        seekSeconds,
+        segmentDuration: HLS_SEGMENT_DURATION,
+        segmentFilename: join(variantDir, 'seg_%d.m4s'),
+        startSegment,
+        target: TranscodeTarget.All,
+        timeBase: asset.videoStream.timeBase,
+        totalDuration: asset.packets.totalDuration,
+      },
+      asset.videoStream,
+      asset.audioStream ?? undefined,
+    );
+    const t4 = performance.now();
+    this.logger.log(
+      `Starting HLS transcode for asset ${session.assetId} variant ${variantIndex} with command: ffmpeg ${args.join(' ')}`,
+    );
+    const process = this.processRepository.spawn('ffmpeg', args, { stdio: ['ignore', 'ignore', 'pipe'] });
+    const t5 = performance.now();
+    this.attachProcessHandlers(process, session, variantIndex, t5);
+    this.logger.log(
+      `[TIMING] startTranscode session=${session.id} variant=${variantIndex} startSegment=${startSegment} ` +
+        `getConfig=${(t1 - t0).toFixed(1)}ms getAsset=${(t2 - t1).toFixed(1)}ms ` +
+        `config=${(t3 - t2).toFixed(1)}ms args=${(t4 - t3).toFixed(1)}ms ` +
+        `spawn=${(t5 - t4).toFixed(1)}ms total=${(t5 - t0).toFixed(1)}ms`,
+    );
+    return process;
+  }
+
+  private failSession(session: Session, error: string) {
+    this.websocketRepository.serverSend('HlsSessionResult', { sessionId: session.id, error });
+    return this.onSessionEnd({ sessionId: session.id });
+  }
+
+  private attachProcessHandlers(process: ChildProcess, session: Session, variantIndex: number, spawnTime: number) {
+    let stderr = '';
+    let firstSegmentLogged = false;
+    const variantDir = StorageCore.getHlsVariantFolder({
+      ownerId: session.ownerId,
+      sessionId: session.id,
+      variantIndex,
+    });
+
+    // hlsenc writes each segment as `seg_K.m4s.tmp` then renames to
+    // `seg_K.m4s`. The rename event fires the moment the renamed file is
+    // observable — the only signal we need to tell the API worker the
+    // segment is ready to serve.
+    const watcher = this.storageRepository.watchDir(variantDir, (eventType, filename) => {
+      if (eventType !== 'rename' || !filename || session.process !== process) {
+        return;
+      }
+      const match = SEGMENT_FILENAME_REGEX.exec(filename);
+      if (!match) {
+        return;
+      }
+      const segmentIndex = Number.parseInt(match[1]);
+      if (!firstSegmentLogged) {
+        firstSegmentLogged = true;
+        this.logger.log(
+          `[TIMING] firstSegmentVisible session=${session.id} variant=${variantIndex} ` +
+            `segmentIndex=${segmentIndex} sinceSpawn=${(performance.now() - spawnTime).toFixed(1)}ms`,
+        );
+      }
+      session.lastCompletedSegment = segmentIndex;
+      this.websocketRepository.serverSend('HlsSegmentResult', {
+        sessionId: session.id,
+        variantIndex,
+        segmentIndex,
+      });
+    });
+    watcher.on('error', (error) => {
+      this.logger.error(`watcher error for ${variantDir}: ${error}`);
+    });
+
+    process.stderr!.on('data', (chunk: Buffer) => {
+      if (session.process !== process) {
+        return;
+      }
+      stderr += chunk.toString();
+    });
+
+    process.on('exit', (code) => {
+      watcher.close();
+      if (session.process !== process || session.variantIndex !== variantIndex) {
+        return;
+      }
+      session.paused = false;
+      session.process = null;
+      if (code) {
+        this.logger.error(
+          `FFmpeg exited with code ${code} for variant ${variantIndex} asset ${session.assetId}\n${stderr}`,
+        );
+        void this.failSession(session, `Transcoding process exited unexpectedly with code ${code}`).catch((error) =>
+          this.logger.error(`Failed to end session ${session.id} after ffmpeg exit: ${error}`),
+        );
+      }
+    });
+  }
+
+  private stopTranscode(session: Session) {
+    if (!session.process) {
+      return;
+    }
+    this.resumeTranscode(session);
+    session.process.kill();
+    session.process = null;
+  }
+
+  private pauseTranscode(session: Session) {
+    if (session.paused || !session.process) {
+      return;
+    }
+    session.process.kill('SIGSTOP');
+    session.paused = true;
+  }
+
+  private resumeTranscode(session: Session) {
+    if (!session.paused || !session.process) {
+      return;
+    }
+    session.process.kill('SIGCONT');
+    session.paused = false;
+  }
+
+  private async removeSessionDir(session: { ownerId: string; id: string }) {
+    const dir = StorageCore.getHlsSessionFolder({ ownerId: session.ownerId, sessionId: session.id });
+    try {
+      await this.storageRepository.unlinkDir(dir, { recursive: true, force: true });
+    } catch (error) {
+      if ((error as NodeJS.ErrnoException)?.code !== 'ENOENT') {
+        throw error;
+      }
+      this.logger.warn(`Session dir ${dir} does not exist.`);
+    }
+  }
+
+  private removeInactiveSessions() {
+    const cutoff = Date.now() - HLS_INACTIVITY_TIMEOUT_MS;
+    const inactiveSessions = [...this.sessions.values()].filter((s) => s.lastActivityTime.getTime() < cutoff);
+    return Promise.all(
+      inactiveSessions.map(async (session) => {
+        try {
+          this.websocketRepository.serverSend('HlsSessionEnd', { sessionId: session.id });
+          await this.onSessionEnd({ sessionId: session.id });
+        } catch (error) {
+          this.logger.error(`Failed to sweep inactive HLS session ${session.id}: ${error}`);
+        }
+      }),
+    );
+  }
+
+  private removeExpiredSessions() {
+    return this.databaseRepository.withLock(DatabaseLock.HlsSessionCleanup, async () => {
+      const expiredSessions = await this.videoStreamRepository.getExpiredSessions();
+      await Promise.all(
+        expiredSessions.map(async (session) => {
+          await this.removeSessionDir(session);
+          await this.videoStreamRepository.deleteSession(session.id);
+        }),
+      );
+    });
+  }
+}

server/src/types.ts

@@ -29,7 +29,6 @@ import {
   SystemMetadataKey,
   TranscodeTarget,
   UserMetadataKey,
-  VideoCodec,
 } from 'src/enum';
 
 export type DeepPartial<T> =
@@ -160,6 +159,25 @@ export interface TranscodeCommand {
   };
 }
 
+export interface VideoTuning {
+  strictGop: boolean;
+  lowLatency: boolean;
+}
+
+export interface HlsCommandOptions {
+  initFilename: string;
+  inputPath: string;
+  packetCount: number;
+  playlistFilename: string;
+  seekSeconds?: number;
+  segmentDuration: number;
+  segmentFilename: string;
+  startSegment: number;
+  target: TranscodeTarget;
+  timeBase: number;
+  totalDuration: number;
+}
+
 export interface BitrateDistribution {
   max: number;
   target: number;
@@ -175,14 +193,11 @@ export interface ImageBuffer {
 export interface VideoCodecSWConfig {
   getCommand(
     target: TranscodeTarget,
-    videoStream: VideoStreamInfo,
-    audioStream?: AudioStreamInfo,
+    video: VideoStreamInfo,
+    audio?: AudioStreamInfo,
     format?: VideoFormat,
   ): TranscodeCommand;
-}
-
-export interface VideoCodecHWConfig extends VideoCodecSWConfig {
-  getSupportedCodecs(): Array<VideoCodec>;
+  getHlsCommand(options: HlsCommandOptions, video: VideoStreamInfo, audio?: AudioStreamInfo): string[];
 }
 
 export interface ProbeOptions {
@@ -380,6 +395,7 @@ export type JobItem =
 
   // Cleanup
   | { name: JobName.SessionCleanup; data?: IBaseJob }
+  | { name: JobName.HlsSessionCleanup; data?: IBaseJob }
 
   // Tags
   | { name: JobName.TagCleanup; data?: IBaseJob }

server/src/utils/database.ts

@@ -71,10 +71,13 @@ export const removeUndefinedKeys = <T extends object>(update: T, template: unkno
 };
 
 export const ASSET_CHECKSUM_CONSTRAINT = 'UQ_assets_owner_checksum';
+export const VIDEO_STREAM_SESSION_PK_CONSTRAINT = 'video_stream_session_pkey';
 
-export const isAssetChecksumConstraint = (error: unknown) => {
-  return (error as PostgresError)?.constraint_name === 'UQ_assets_owner_checksum';
-};
+export const isAssetChecksumConstraint = (error: unknown) =>
+  (error as PostgresError)?.constraint_name === ASSET_CHECKSUM_CONSTRAINT;
+
+export const isVideoStreamSessionPkConstraint = (error: unknown) =>
+  (error as PostgresError)?.constraint_name === VIDEO_STREAM_SESSION_PK_CONSTRAINT;
 
 export function withDefaultVisibility<O>(qb: SelectQueryBuilder<DB, 'asset', O>) {
   return qb.where('asset.visibility', 'in', [sql.lit(AssetVisibility.Archive), sql.lit(AssetVisibility.Timeline)]);

server/src/utils/media.ts

@@ -1,4 +1,4 @@
-import { AUDIO_ENCODER } from 'src/constants';
+import { AUDIO_ENCODER, SUPPORTED_HWA_CODECS } from 'src/constants';
 import { SystemConfigFFmpegDto } from 'src/dtos/system-config.dto';
 import {
   ColorMatrix,
@@ -13,38 +13,56 @@ import {
 import {
   AudioStreamInfo,
   BitrateDistribution,
+  HlsCommandOptions,
   TranscodeCommand,
-  VideoCodecHWConfig,
   VideoCodecSWConfig,
   VideoFormat,
   VideoInterfaces,
   VideoStreamInfo,
+  VideoTuning,
 } from 'src/types';
 
+export const isVideoRotated = (videoStream: VideoStreamInfo): boolean => Math.abs(videoStream.rotation) === 90;
+
+export const isVideoVertical = (videoStream: VideoStreamInfo): boolean =>
+  videoStream.height > videoStream.width || isVideoRotated(videoStream);
+
+export const getOutputSize = (videoStream: VideoStreamInfo, targetRes: number) => {
+  const factor = Math.max(videoStream.height, videoStream.width) / Math.min(videoStream.height, videoStream.width);
+  let larger = Math.round(targetRes * factor);
+  if (larger % 2 !== 0) {
+    larger -= 1;
+  }
+  return isVideoVertical(videoStream) ? { width: targetRes, height: larger } : { width: larger, height: targetRes };
+};
+
 export class BaseConfig implements VideoCodecSWConfig {
   readonly presets = ['veryslow', 'slower', 'slow', 'medium', 'fast', 'faster', 'veryfast', 'superfast', 'ultrafast'];
-  protected constructor(protected config: SystemConfigFFmpegDto) {}
+  protected constructor(
+    protected config: SystemConfigFFmpegDto,
+    protected tune: VideoTuning = { strictGop: false, lowLatency: false },
+  ) {}
 
-  static create(config: SystemConfigFFmpegDto, interfaces: VideoInterfaces): VideoCodecSWConfig {
+  static create(config: SystemConfigFFmpegDto, interfaces: VideoInterfaces, tune?: VideoTuning) {
     if (config.accel === TranscodeHardwareAcceleration.Disabled) {
-      return this.getSWCodecConfig(config);
+      return this.getSWCodecConfig(config, tune);
     }
-    return this.getHWCodecConfig(config, interfaces);
+    return this.getHWCodecConfig(config, interfaces, tune);
   }
 
-  private static getSWCodecConfig(config: SystemConfigFFmpegDto) {
+  private static getSWCodecConfig(config: SystemConfigFFmpegDto, tune?: VideoTuning): VideoCodecSWConfig {
     switch (config.targetVideoCodec) {
       case VideoCodec.H264: {
-        return new H264Config(config);
+        return new H264Config(config, tune);
       }
       case VideoCodec.Hevc: {
-        return new HEVCConfig(config);
+        return new HEVCConfig(config, tune);
       }
       case VideoCodec.Vp9: {
-        return new VP9Config(config);
+        return new VP9Config(config, tune);
       }
       case VideoCodec.Av1: {
-        return new AV1Config(config);
+        return new AV1Config(config, tune);
       }
       default: {
         throw new Error(`Codec '${config.targetVideoCodec}' is unsupported`);
@@ -52,72 +70,126 @@ export class BaseConfig implements VideoCodecSWConfig {
     }
   }
 
-  private static getHWCodecConfig(config: SystemConfigFFmpegDto, interfaces: VideoInterfaces) {
-    let handler: VideoCodecHWConfig;
+  private static getHWCodecConfig(config: SystemConfigFFmpegDto, interfaces: VideoInterfaces, tune?: VideoTuning) {
+    if (!SUPPORTED_HWA_CODECS[config.accel].includes(config.targetVideoCodec)) {
+      throw new Error(
+        `${config.accel.toUpperCase()} acceleration does not support codec '${config.targetVideoCodec.toUpperCase()}'. Supported codecs: ${SUPPORTED_HWA_CODECS[config.accel]}`,
+      );
+    }
+
+    let handler: VideoCodecSWConfig;
     switch (config.accel) {
       case TranscodeHardwareAcceleration.Nvenc: {
         handler = config.accelDecode
-          ? new NvencHwDecodeConfig(config, interfaces)
-          : new NvencSwDecodeConfig(config, interfaces);
+          ? new NvencHwDecodeConfig(config, interfaces, tune)
+          : new NvencSwDecodeConfig(config, interfaces, tune);
         break;
       }
       case TranscodeHardwareAcceleration.Qsv: {
         handler = config.accelDecode
-          ? new QsvHwDecodeConfig(config, interfaces)
-          : new QsvSwDecodeConfig(config, interfaces);
+          ? new QsvHwDecodeConfig(config, interfaces, tune)
+          : new QsvSwDecodeConfig(config, interfaces, tune);
         break;
       }
       case TranscodeHardwareAcceleration.Vaapi: {
         handler = config.accelDecode
-          ? new VaapiHwDecodeConfig(config, interfaces)
-          : new VaapiSwDecodeConfig(config, interfaces);
+          ? new VaapiHwDecodeConfig(config, interfaces, tune)
+          : new VaapiSwDecodeConfig(config, interfaces, tune);
         break;
       }
       case TranscodeHardwareAcceleration.Rkmpp: {
         handler = config.accelDecode
-          ? new RkmppHwDecodeConfig(config, interfaces)
-          : new RkmppSwDecodeConfig(config, interfaces);
+          ? new RkmppHwDecodeConfig(config, interfaces, tune)
+          : new RkmppSwDecodeConfig(config, interfaces, tune);
         break;
       }
       default: {
         throw new Error(`${config.accel.toUpperCase()} acceleration is unsupported`);
       }
     }
-    if (!handler.getSupportedCodecs().includes(config.targetVideoCodec)) {
-      throw new Error(
-        `${config.accel.toUpperCase()} acceleration does not support codec '${config.targetVideoCodec.toUpperCase()}'. Supported codecs: ${handler.getSupportedCodecs()}`,
-      );
-    }
 
     return handler;
   }
 
-  getCommand(
-    target: TranscodeTarget,
-    videoStream: VideoStreamInfo,
-    audioStream?: AudioStreamInfo,
-    format?: VideoFormat,
-  ) {
+  getCommand(target: TranscodeTarget, video: VideoStreamInfo, audio?: AudioStreamInfo, format?: VideoFormat) {
     const options = {
-      inputOptions: this.getBaseInputOptions(videoStream, format),
-      outputOptions: [...this.getBaseOutputOptions(target, videoStream, audioStream), '-v', 'verbose'],
+      inputOptions: this.getBaseInputOptions(video, format),
+      outputOptions: [
+        ...this.getBaseOutputOptions(target, video, audio),
+        ...this.getPresetOptions(),
+        ...this.getBitrateOptions(),
+        ...this.getEncoderOptions(),
+        '-movflags',
+        'faststart',
+        '-fps_mode',
+        'passthrough',
+        '-v',
+        'verbose',
+      ],
       twoPass: this.eligibleForTwoPass(),
-      progress: { frameCount: videoStream.frameCount, percentInterval: 5 },
+      progress: { frameCount: video.frameCount, percentInterval: 5 },
     } as TranscodeCommand;
     if ([TranscodeTarget.All, TranscodeTarget.Video].includes(target)) {
-      const filters = this.getFilterOptions(videoStream);
+      const filters = this.getFilterOptions(video);
       if (filters.length > 0) {
         options.outputOptions.push('-vf', filters.join(','));
       }
     }
 
-    options.outputOptions.push(
+    return options;
+  }
+
+  getHlsCommand(options: HlsCommandOptions, video: VideoStreamInfo, audio?: AudioStreamInfo) {
+    const args: string[] = this.getBaseInputOptions(video);
+    if (options.seekSeconds) {
+      args.push('-ss', String(options.seekSeconds));
+    }
+    args.push(
+      '-nostdin',
+      '-nostats',
+      '-i',
+      options.inputPath,
+      ...this.getBaseOutputOptions(options.target, video, audio),
       ...this.getPresetOptions(),
-      ...this.getOutputThreadOptions(),
       ...this.getBitrateOptions(),
+      ...this.getEncoderOptions(),
+      // -start_at_zero only applies meaningfully when seekSeconds is 0.
+      // Combined with -ss N -copyts, it would shift the first frame to t=0
+      // and break tfdt alignment with the playlist.
+      ...(options.seekSeconds ? [] : ['-start_at_zero']),
+      '-copyts',
+      '-r',
+      `${options.packetCount * options.timeBase}/${options.totalDuration}`,
+      '-avoid_negative_ts',
+      'disabled',
+      '-f',
+      'hls',
+      '-hls_time',
+      String(options.segmentDuration),
+      '-hls_list_size',
+      '0',
+      '-hls_segment_type',
+      'fmp4',
+      '-hls_fmp4_init_filename',
+      options.initFilename,
+      '-hls_segment_options',
+      'movflags=+frag_discont',
+      '-hls_flags',
+      'temp_file',
+      '-hls_segment_filename',
+      options.segmentFilename,
+      '-start_number',
+      String(options.startSegment),
     );
 
-    return options;
+    if ([TranscodeTarget.All, TranscodeTarget.Video].includes(options.target)) {
+      const filters = this.getFilterOptions(video);
+      if (filters.length > 0) {
+        args.push('-vf', filters.join(','));
+      }
+    }
+    args.push(options.playlistFilename);
+    return args;
   }
 
   // eslint-disable-next-line @typescript-eslint/no-unused-vars
@@ -129,23 +201,7 @@ export class BaseConfig implements VideoCodecSWConfig {
     const videoCodec = [TranscodeTarget.All, TranscodeTarget.Video].includes(target) ? this.getVideoCodec() : 'copy';
     const audioCodec = [TranscodeTarget.All, TranscodeTarget.Audio].includes(target) ? this.getAudioEncoder() : 'copy';
 
-    const options = [
-      '-c:v',
-      videoCodec,
-      '-c:a',
-      audioCodec,
-      // Makes a second pass moving the moov atom to the
-      // beginning of the file for improved playback speed.
-      '-movflags',
-      'faststart',
-      '-fps_mode',
-      'passthrough',
-      '-map',
-      `0:${videoStream.index}`,
-      '-map_metadata',
-      '-1',
-    ];
-
+    const options = ['-c:v', videoCodec, '-c:a', audioCodec, '-map', `0:${videoStream.index}`, '-map_metadata', '-1'];
     if (audioStream) {
       options.push('-map', `0:${audioStream.index}`);
     }
@@ -157,18 +213,22 @@ export class BaseConfig implements VideoCodecSWConfig {
     }
     if (this.getGopSize() > 0) {
       options.push('-g', `${this.getGopSize()}`);
+      if (this.tune.strictGop) {
+        options.push('-keyint_min', `${this.getGopSize()}`);
+      }
     }
-
-    if (
-      this.config.targetVideoCodec === VideoCodec.Hevc &&
-      (videoCodec !== 'copy' || videoStream.codecName === 'hevc')
-    ) {
+    const isHvc = (videoCodec === 'copy' ? videoStream.codecName : videoCodec) === VideoCodec.Hevc;
+    if (isHvc) {
       options.push('-tag:v', 'hvc1');
     }
 
     return options;
   }
 
+  getEncoderOptions(): string[] {
+    return [];
+  }
+
   getFilterOptions(videoStream: VideoStreamInfo) {
     const options = [];
     if (this.shouldScale(videoStream)) {
@@ -272,25 +332,7 @@ export class BaseConfig implements VideoCodecSWConfig {
 
   getScaling(videoStream: VideoStreamInfo, mult = 2) {
     const targetResolution = this.getTargetResolution(videoStream);
-    return this.isVideoVertical(videoStream) ? `${targetResolution}:-${mult}` : `-${mult}:${targetResolution}`;
-  }
-
-  getSize(videoStream: VideoStreamInfo) {
-    const smaller = this.getTargetResolution(videoStream);
-    const factor = Math.max(videoStream.height, videoStream.width) / Math.min(videoStream.height, videoStream.width);
-    let larger = Math.round(smaller * factor);
-    if (larger % 2 !== 0) {
-      larger -= 1;
-    }
-    return this.isVideoVertical(videoStream) ? { width: smaller, height: larger } : { width: larger, height: smaller };
-  }
-
-  isVideoRotated(videoStream: VideoStreamInfo) {
-    return Math.abs(videoStream.rotation) === 90;
-  }
-
-  isVideoVertical(videoStream: VideoStreamInfo) {
-    return videoStream.height > videoStream.width || this.isVideoRotated(videoStream);
+    return isVideoVertical(videoStream) ? `${targetResolution}:-${mult}` : `-${mult}:${targetResolution}`;
   }
 
   isBitrateConstrained() {
@@ -353,23 +395,18 @@ export class BaseConfig implements VideoCodecSWConfig {
   }
 }
 
-export class BaseHWConfig extends BaseConfig implements VideoCodecHWConfig {
+export class BaseHWConfig extends BaseConfig {
   protected device: string;
-  protected interfaces: VideoInterfaces;
 
   constructor(
     protected config: SystemConfigFFmpegDto,
-    interfaces: VideoInterfaces,
+    protected interfaces: VideoInterfaces,
+    tune?: VideoTuning,
   ) {
-    super(config);
-    this.interfaces = interfaces;
+    super(config, tune);
     this.device = this.getDevice(interfaces);
   }
 
-  getSupportedCodecs() {
-    return [VideoCodec.H264, VideoCodec.Hevc];
-  }
-
   validateDevices(devices: string[]) {
     if (devices.length === 0) {
       throw new Error('No /dev/dri devices found. If using Docker, make sure at least one /dev/dri device is mounted');
@@ -474,24 +511,32 @@ export class ThumbnailConfig extends BaseConfig {
 }
 
 export class H264Config extends BaseConfig {
-  getOutputThreadOptions() {
-    const options = super.getOutputThreadOptions();
-    if (this.config.threads === 1) {
-      options.push('-x264-params', 'frame-threads=1:pools=none');
+  getEncoderOptions(): string[] {
+    const out = this.getOutputThreadOptions();
+    if (this.tune.strictGop) {
+      out.push('-sc_threshold:v', '0');
     }
-
-    return options;
+    if (this.config.threads === 1) {
+      out.push('-x264-params', 'frame-threads=1:pools=none');
+    }
+    return out;
   }
 }
 
 export class HEVCConfig extends BaseConfig {
-  getOutputThreadOptions() {
-    const options = super.getOutputThreadOptions();
-    if (this.config.threads === 1) {
-      options.push('-x265-params', 'frame-threads=1:pools=none');
+  getEncoderOptions(): string[] {
+    const out: string[] = this.getOutputThreadOptions();
+    const params: string[] = [];
+    if (this.tune.strictGop) {
+      params.push('no-scenecut=1', 'no-open-gop=1');
     }
-
-    return options;
+    if (this.config.threads === 1) {
+      params.push('frame-threads=1', 'pools=none');
+    }
+    if (params.length > 0) {
+      out.push('-x265-params', params.join(':'));
+    }
+    return out;
   }
 }
 
@@ -520,8 +565,8 @@ export class VP9Config extends BaseConfig {
     return [`-${this.useCQP() ? 'q:v' : 'crf'}`, `${this.config.crf}`, '-b:v', `${bitrates.max}${bitrates.unit}`];
   }
 
-  getOutputThreadOptions() {
-    return ['-row-mt', '1', ...super.getOutputThreadOptions()];
+  getEncoderOptions(): string[] {
+    return ['-row-mt', '1', ...this.getOutputThreadOptions()];
   }
 
   eligibleForTwoPass() {
@@ -543,23 +588,22 @@ export class AV1Config extends BaseConfig {
   }
 
   getBitrateOptions() {
-    const options = ['-crf', `${this.config.crf}`];
-    const bitrates = this.getBitrateDistribution();
-    const svtparams = [];
-    if (this.config.threads > 0) {
-      svtparams.push(`lp=${this.config.threads}`);
-    }
-    if (bitrates.max > 0) {
-      svtparams.push(`mbr=${bitrates.max}${bitrates.unit}`);
-    }
-    if (svtparams.length > 0) {
-      options.push('-svtav1-params', svtparams.join(':'));
-    }
-    return options;
+    return ['-crf', `${this.config.crf}`];
   }
 
-  getOutputThreadOptions() {
-    return []; // Already set above with svtav1-params
+  getEncoderOptions(): string[] {
+    const params: string[] = [];
+    if (this.tune.lowLatency) {
+      params.push('hierarchical-levels=3', 'lookahead=0', 'enable-tf=0');
+    }
+    if (this.config.threads > 0) {
+      params.push(`lp=${this.config.threads}`);
+    }
+    const bitrates = this.getBitrateDistribution();
+    if (bitrates.max > 0) {
+      params.push(`mbr=${bitrates.max}${bitrates.unit}`);
+    }
+    return params.length > 0 ? ['-svtav1-params', params.join(':')] : [];
   }
 
   eligibleForTwoPass() {
@@ -572,10 +616,6 @@ export class NvencSwDecodeConfig extends BaseHWConfig {
     return '0';
   }
 
-  getSupportedCodecs() {
-    return [VideoCodec.H264, VideoCodec.Hevc, VideoCodec.Av1];
-  }
-
   getBaseInputOptions() {
     return ['-init_hw_device', `cuda=cuda:${this.device}`, '-filter_hw_device', 'cuda'];
   }
@@ -652,6 +692,14 @@ export class NvencSwDecodeConfig extends BaseHWConfig {
     return [];
   }
 
+  getEncoderOptions(): string[] {
+    const out = this.getOutputThreadOptions();
+    if (this.tune.strictGop) {
+      out.push('-forced-idr', '1');
+    }
+    return out;
+  }
+
   getRefs() {
     const bframes = this.getBFrames();
     if (bframes > 0 && bframes < 3 && this.config.refs < 3) {
@@ -703,8 +751,8 @@ export class NvencHwDecodeConfig extends NvencSwDecodeConfig {
     return ['-threads', '1'];
   }
 
-  getOutputThreadOptions() {
-    return [];
+  getEncoderOptions(): string[] {
+    return this.tune.strictGop ? ['-forced-idr', '1'] : [];
   }
 }
 
@@ -749,10 +797,6 @@ export class QsvSwDecodeConfig extends BaseHWConfig {
     return options;
   }
 
-  getSupportedCodecs() {
-    return [VideoCodec.H264, VideoCodec.Hevc, VideoCodec.Vp9, VideoCodec.Av1];
-  }
-
   // recommended from https://github.com/intel/media-delivery/blob/master/doc/benchmarks/intel-iris-xe-max-graphics/intel-iris-xe-max-graphics.md
   getBFrames() {
     if (this.config.bframes < 0) {
@@ -775,6 +819,14 @@ export class QsvSwDecodeConfig extends BaseHWConfig {
   getScaling(videoStream: VideoStreamInfo): string {
     return super.getScaling(videoStream, 1);
   }
+
+  getEncoderOptions(): string[] {
+    const out = this.getOutputThreadOptions();
+    if (this.tune.strictGop) {
+      out.push('-idr_interval', '0');
+    }
+    return out;
+  }
 }
 
 export class QsvHwDecodeConfig extends QsvSwDecodeConfig {
@@ -888,13 +940,17 @@ export class VaapiSwDecodeConfig extends BaseHWConfig {
     return options;
   }
 
-  getSupportedCodecs() {
-    return [VideoCodec.H264, VideoCodec.Hevc, VideoCodec.Vp9, VideoCodec.Av1];
-  }
-
   useCQP() {
     return this.config.cqMode !== CQMode.Icq || this.config.targetVideoCodec === VideoCodec.Vp9;
   }
+
+  getEncoderOptions(): string[] {
+    const out = this.getOutputThreadOptions();
+    if (this.tune.strictGop) {
+      out.push('-idr_interval', '0');
+    }
+    return out;
+  }
 }
 
 export class VaapiHwDecodeConfig extends VaapiSwDecodeConfig {
@@ -988,10 +1044,6 @@ export class RkmppSwDecodeConfig extends BaseHWConfig {
     return ['-rc_mode', 'CQP', '-qp_init', `${this.config.crf}`];
   }
 
-  getSupportedCodecs() {
-    return [VideoCodec.H264, VideoCodec.Hevc];
-  }
-
   getVideoCodec(): string {
     return `${this.config.targetVideoCodec}_rkmpp`;
   }