From 10f5f331d72dd19e6ca15a5b6341fef368034d9c Mon Sep 17 00:00:00 2001
From: mikiher <mikiher@gmail.com>
Date: Sat, 20 Jul 2024 12:28:06 +0300
Subject: [PATCH] Fixes + add progress to m4b and embed tools

---
 client/components/ui/Btn.vue                  |   6 +-
 client/layouts/default.vue                    |  17 ++
 client/pages/audiobook/_id/manage.vue         |  37 ++--
 client/store/tasks.js                         |  50 +++--
 client/strings/en-us.json                     |   1 +
 server/managers/AbMergeManager.js             | 185 +++++++-----------
 server/managers/AudioMetadataManager.js       |  68 +++++--
 server/objects/TrackProgressMonitor.js        |  88 +++++++++
 server/utils/ffmpegHelpers.js                 | 131 +++++++++++--
 .../objects/TrackProgressMonitor.test.js      |  95 +++++++++
 test/server/utils/ffmpegHelpers.test.js       |  63 +++---
 11 files changed, 530 insertions(+), 211 deletions(-)
 create mode 100644 server/objects/TrackProgressMonitor.js
 create mode 100644 test/server/objects/TrackProgressMonitor.test.js

diff --git a/client/components/ui/Btn.vue b/client/components/ui/Btn.vue
index 29b322f9..b4a2df01 100644
--- a/client/components/ui/Btn.vue
+++ b/client/components/ui/Btn.vue
@@ -10,7 +10,8 @@
   <button v-else class="abs-btn outline-none rounded-md shadow-md relative border border-gray-600" :disabled="disabled || loading" :type="type" :class="classList" @mousedown.prevent @click="click">
     <slot />
     <div v-if="loading" class="text-white absolute top-0 left-0 w-full h-full flex items-center justify-center text-opacity-100">
-      <svg class="animate-spin" style="width: 24px; height: 24px" viewBox="0 0 24 24">
+      <span v-if="progress">{{ progress }}</span>
+      <svg v-else class="animate-spin" style="width: 24px; height: 24px" viewBox="0 0 24 24">
         <path fill="currentColor" d="M12,4V2A10,10 0 0,0 2,12H4A8,8 0 0,1 12,4Z" />
       </svg>
     </div>
@@ -33,7 +34,8 @@ export default {
     paddingY: Number,
     small: Boolean,
     loading: Boolean,
-    disabled: Boolean
+    disabled: Boolean,
+    progress: String
   },
   data() {
     return {}
diff --git a/client/layouts/default.vue b/client/layouts/default.vue
index 483ade70..95f8560d 100644
--- a/client/layouts/default.vue
+++ b/client/layouts/default.vue
@@ -212,6 +212,16 @@ export default {
         this.libraryItemAdded(ab)
       })
     },
+    trackStarted(data) {
+      this.$store.commit('tasks/updateAudioFilesEncoding', { libraryItemId: data.libraryItemId, ino: data.ino, progress: '0%' })
+    },
+    trackProgress(data) {
+      this.$store.commit('tasks/updateAudioFilesEncoding', { libraryItemId: data.libraryItemId, ino: data.ino, progress: `${Math.round(data.progress)}%` })
+    },
+    trackFinished(data) {
+      this.$store.commit('tasks/updateAudioFilesEncoding', { libraryItemId: data.libraryItemId, ino: data.ino, progress: '100%' })
+      this.$store.commit('tasks/updateAudioFilesFinished', { libraryItemId: data.libraryItemId, ino: data.ino, finished: true })
+    },
     taskStarted(task) {
       console.log('Task started', task)
       this.$store.commit('tasks/addUpdateTask', task)
@@ -220,6 +230,9 @@ export default {
       console.log('Task finished', task)
       this.$store.commit('tasks/addUpdateTask', task)
     },
+    taskProgress(data) {
+      this.$store.commit('tasks/updateTaskProgress', { libraryItemId: data.libraryItemId, progress: `${Math.round(data.progress)}%` })
+    },
     metadataEmbedQueueUpdate(data) {
       if (data.queued) {
         this.$store.commit('tasks/addQueuedEmbedLId', data.libraryItemId)
@@ -406,6 +419,10 @@ export default {
       this.socket.on('task_started', this.taskStarted)
       this.socket.on('task_finished', this.taskFinished)
       this.socket.on('metadata_embed_queue_update', this.metadataEmbedQueueUpdate)
+      this.socket.on('track_started', this.trackStarted)
+      this.socket.on('track_finished', this.trackFinished)
+      this.socket.on('track_progress', this.trackProgress)
+      this.socket.on('task_progress', this.taskProgress)
 
       // EReader Device Listeners
       this.socket.on('ereader-devices-updated', this.ereaderDevicesUpdated)
diff --git a/client/pages/audiobook/_id/manage.vue b/client/pages/audiobook/_id/manage.vue
index ddf868e6..464d7ce2 100644
--- a/client/pages/audiobook/_id/manage.vue
+++ b/client/pages/audiobook/_id/manage.vue
@@ -71,7 +71,8 @@
 
         <div class="flex-grow" />
 
-        <ui-btn v-if="!isTaskFinished" color="primary" :loading="processing" @click.stop="embedClick">{{ $strings.ButtonStartMetadataEmbed }}</ui-btn>
+        <ui-btn v-if="!isTaskFinished" color="primary" :loading="processing" :progress="progress" @click.stop="embedClick">{{ $strings.ButtonStartMetadataEmbed }}</ui-btn>
+        <p v-else-if="taskFailed" class="text-error text-lg font-semibold">{{ $strings.MessageEmbedFailed }} {{ taskError }}</p>
         <p v-else class="text-success text-lg font-semibold">{{ $strings.MessageEmbedFinished }}</p>
       </div>
       <!-- m4b embed action buttons -->
@@ -83,7 +84,7 @@
         <div class="flex-grow" />
 
         <ui-btn v-if="!isTaskFinished && processing" color="error" :loading="isCancelingEncode" class="mr-2" @click.stop="cancelEncodeClick">{{ $strings.ButtonCancelEncode }}</ui-btn>
-        <ui-btn v-if="!isTaskFinished" color="primary" :loading="processing" @click.stop="encodeM4bClick">{{ $strings.ButtonStartM4BEncode }}</ui-btn>
+        <ui-btn v-if="!isTaskFinished" color="primary" :loading="processing" :progress="progress" @click.stop="encodeM4bClick">{{ $strings.ButtonStartM4BEncode }}</ui-btn>
         <p v-else-if="taskFailed" class="text-error text-lg font-semibold">{{ $strings.MessageM4BFailed }} {{ taskError }}</p>
         <p v-else class="text-success text-lg font-semibold">{{ $strings.MessageM4BFinished }}</p>
       </div>
@@ -159,9 +160,9 @@
             </div>
             <div class="w-24">
               <div class="flex justify-center">
-                <span v-if="audiofilesFinished[file.ino]" class="material-symbols text-xl text-success leading-none">check_circle</span>
-                <div v-else-if="audiofilesEncoding[file.ino]">
-                  <widgets-loading-spinner />
+                <span v-if="audioFilesFinished[file.ino]" class="material-symbols text-xl text-success leading-none">check_circle</span>
+                <div v-else-if="audioFilesEncoding[file.ino]">
+                  <span class="font-mono text-success leading-none">{{ audioFilesEncoding[file.ino] }}</span>
                 </div>
               </div>
             </div>
@@ -205,8 +206,6 @@ export default {
   data() {
     return {
       processing: false,
-      audiofilesEncoding: {},
-      audiofilesFinished: {},
       metadataObject: null,
       selectedTool: 'embed',
       isCancelingEncode: false,
@@ -229,6 +228,15 @@ export default {
     }
   },
   computed: {
+    audioFilesEncoding() {
+      return this.$store.getters['tasks/getAudioFilesEncoding'](this.libraryItemId) || {}
+    },
+    audioFilesFinished() {
+      return this.$store.getters['tasks/getAudioFilesFinished'](this.libraryItemId) || {}
+    },
+    progress() {
+      return this.$store.getters['tasks/getTaskProgress'](this.libraryItemId) || '0%'
+    },
     isEmbedTool() {
       return this.selectedTool === 'embed'
     },
@@ -372,15 +380,6 @@ export default {
           this.processing = false
         })
     },
-    audiofileMetadataStarted(data) {
-      if (data.libraryItemId !== this.libraryItemId) return
-      this.$set(this.audiofilesEncoding, data.ino, true)
-    },
-    audiofileMetadataFinished(data) {
-      if (data.libraryItemId !== this.libraryItemId) return
-      this.$set(this.audiofilesEncoding, data.ino, false)
-      this.$set(this.audiofilesFinished, data.ino, true)
-    },
     selectedToolUpdated() {
       let newurl = window.location.protocol + '//' + window.location.host + window.location.pathname + `?tool=${this.selectedTool}`
       window.history.replaceState({ path: newurl }, '', newurl)
@@ -416,12 +415,6 @@ export default {
   },
   mounted() {
     this.init()
-    this.$root.socket.on('audiofile_metadata_started', this.audiofileMetadataStarted)
-    this.$root.socket.on('audiofile_metadata_finished', this.audiofileMetadataFinished)
-  },
-  beforeDestroy() {
-    this.$root.socket.off('audiofile_metadata_started', this.audiofileMetadataStarted)
-    this.$root.socket.off('audiofile_metadata_finished', this.audiofileMetadataFinished)
   }
 }
 </script>
diff --git a/client/store/tasks.js b/client/store/tasks.js
index 96e7e5b8..24a7517a 100644
--- a/client/store/tasks.js
+++ b/client/store/tasks.js
@@ -1,34 +1,60 @@
+import Vue from 'vue'
 
 export const state = () => ({
   tasks: [],
-  queuedEmbedLIds: []
+  queuedEmbedLIds: [],
+  audioFilesEncoding: {},
+  audioFilesFinished: {},
+  taskProgress: {}
 })
 
 export const getters = {
   getTasksByLibraryItemId: (state) => (libraryItemId) => {
-    return state.tasks.filter(t => t.data?.libraryItemId === libraryItemId)
+    return state.tasks.filter((t) => t.data?.libraryItemId === libraryItemId)
   },
   getRunningLibraryScanTask: (state) => (libraryId) => {
     const libraryScanActions = ['library-scan', 'library-match-all']
-    return state.tasks.find(t => libraryScanActions.includes(t.action) && t.data?.libraryId === libraryId && !t.isFinished)
+    return state.tasks.find((t) => libraryScanActions.includes(t.action) && t.data?.libraryId === libraryId && !t.isFinished)
+  },
+  getAudioFilesEncoding: (state) => (libraryItemId) => {
+    return state.audioFilesEncoding[libraryItemId]
+  },
+  getAudioFilesFinished: (state) => (libraryItemId) => {
+    return state.audioFilesFinished[libraryItemId]
+  },
+  getTaskProgress: (state) => (libraryItemId) => {
+    return state.taskProgress[libraryItemId]
   }
 }
 
-export const actions = {
-
-}
+export const actions = {}
 
 export const mutations = {
+  updateAudioFilesEncoding(state, payload) {
+    if (!state.audioFilesEncoding[payload.libraryItemId]) {
+      Vue.set(state.audioFilesEncoding, payload.libraryItemId, {})
+    }
+    Vue.set(state.audioFilesEncoding[payload.libraryItemId], payload.ino, payload.progress)
+  },
+  updateAudioFilesFinished(state, payload) {
+    if (!state.audioFilesFinished[payload.libraryItemId]) {
+      Vue.set(state.audioFilesFinished, payload.libraryItemId, {})
+    }
+    Vue.set(state.audioFilesFinished[payload.libraryItemId], payload.ino, payload.finished)
+  },
+  updateTaskProgress(state, payload) {
+    Vue.set(state.taskProgress, payload.libraryItemId, payload.progress)
+  },
   setTasks(state, tasks) {
     state.tasks = tasks
   },
   addUpdateTask(state, task) {
-    const index = state.tasks.findIndex(d => d.id === task.id)
+    const index = state.tasks.findIndex((d) => d.id === task.id)
     if (index >= 0) {
       state.tasks.splice(index, 1, task)
     } else {
       // Remove duplicate (only have one library item per action)
-      state.tasks = state.tasks.filter(_task => {
+      state.tasks = state.tasks.filter((_task) => {
         if (!_task.data?.libraryItemId || _task.action !== task.action) return true
         return _task.data.libraryItemId !== task.data.libraryItemId
       })
@@ -37,17 +63,17 @@ export const mutations = {
     }
   },
   removeTask(state, task) {
-    state.tasks = state.tasks.filter(d => d.id !== task.id)
+    state.tasks = state.tasks.filter((d) => d.id !== task.id)
   },
   setQueuedEmbedLIds(state, libraryItemIds) {
     state.queuedEmbedLIds = libraryItemIds
   },
   addQueuedEmbedLId(state, libraryItemId) {
-    if (!state.queuedEmbedLIds.some(lid => lid === libraryItemId)) {
+    if (!state.queuedEmbedLIds.some((lid) => lid === libraryItemId)) {
       state.queuedEmbedLIds.push(libraryItemId)
     }
   },
   removeQueuedEmbedLId(state, libraryItemId) {
-    state.queuedEmbedLIds = state.queuedEmbedLIds.filter(lid => lid !== libraryItemId)
+    state.queuedEmbedLIds = state.queuedEmbedLIds.filter((lid) => lid !== libraryItemId)
   }
-}
\ No newline at end of file
+}
diff --git a/client/strings/en-us.json b/client/strings/en-us.json
index f713cb11..98031ce4 100644
--- a/client/strings/en-us.json
+++ b/client/strings/en-us.json
@@ -659,6 +659,7 @@
   "MessageDownloadingEpisode": "Downloading episode",
   "MessageDragFilesIntoTrackOrder": "Drag files into correct track order",
   "MessageEmbedFinished": "Embed Finished!",
+  "MessageEmbedFailed": "Embed Failed!",
   "MessageEpisodesQueuedForDownload": "{0} Episode(s) queued for download",
   "MessageEreaderDevices": "To ensure delivery of ebooks, you may need to add the above email address as a valid sender for each device listed below.",
   "MessageFeedURLWillBe": "Feed URL will be {0}",
diff --git a/server/managers/AbMergeManager.js b/server/managers/AbMergeManager.js
index 711e8892..9e06f99c 100644
--- a/server/managers/AbMergeManager.js
+++ b/server/managers/AbMergeManager.js
@@ -1,12 +1,14 @@
 const Path = require('path')
 const fs = require('../libs/fsExtra')
-
-const workerThreads = require('worker_threads')
 const Logger = require('../Logger')
 const TaskManager = require('./TaskManager')
 const Task = require('../objects/Task')
 const { writeConcatFile } = require('../utils/ffmpegHelpers')
 const ffmpegHelpers = require('../utils/ffmpegHelpers')
+const Ffmpeg = require('../libs/fluentFfmpeg')
+const SocketAuthority = require('../SocketAuthority')
+const fileUtils = require('../utils/fileUtils')
+const TrackProgressMonitor = require('../objects/TrackProgressMonitor')
 
 class AbMergeManager {
   constructor() {
@@ -20,6 +22,7 @@ class AbMergeManager {
   }
 
   cancelEncode(task) {
+    task.setFailed('Task canceled by user')
     return this.removeTask(task, true)
   }
 
@@ -36,6 +39,7 @@ class AbMergeManager {
       libraryItemPath: libraryItem.path,
       userId: user.id,
       originalTrackPaths: libraryItem.media.tracks.map((t) => t.metadata.path),
+      inos: libraryItem.media.includedAudioFiles.map((f) => f.ino),
       tempFilepath,
       targetFilename,
       targetFilepath: Path.join(libraryItem.path, targetFilename),
@@ -43,7 +47,8 @@ class AbMergeManager {
       ffmetadataObject: ffmpegHelpers.getFFMetadataObject(libraryItem, 1),
       chapters: libraryItem.media.chapters?.map((c) => ({ ...c })),
       coverPath: libraryItem.media.coverPath,
-      ffmetadataPath
+      ffmetadataPath,
+      duration: libraryItem.media.duration
     }
     const taskDescription = `Encoding audiobook "${libraryItem.media.metadata.title}" into a single m4b file.`
     task.setData('encode-m4b', 'Encoding M4b', taskDescription, false, taskData)
@@ -58,119 +63,78 @@ class AbMergeManager {
   }
 
   async runAudiobookMerge(libraryItem, task, encodingOptions) {
+    // Make sure the target directory is writable
+    if (!(await fileUtils.isWritable(libraryItem.path))) {
+      Logger.error(`[AbMergeManager] Target directory is not writable: ${libraryItem.path}`)
+      task.setFailed('Target directory is not writable')
+      this.removeTask(task, true)
+      return
+    }
+
     // Create ffmetadata file
-    const success = await ffmpegHelpers.writeFFMetadataFile(task.data.metadataObject, task.data.chapters, task.data.ffmetadataPath)
-    if (!success) {
+    if (!(await ffmpegHelpers.writeFFMetadataFile(task.data.ffmetadataObject, task.data.chapters, task.data.ffmetadataPath))) {
       Logger.error(`[AudioMetadataManager] Failed to write ffmetadata file for audiobook "${task.data.libraryItemId}"`)
       task.setFailed('Failed to write metadata file.')
       this.removeTask(task, true)
       return
     }
 
-    const audioBitrate = encodingOptions.bitrate || '128k'
-    const audioCodec = encodingOptions.codec || 'aac'
-    const audioChannels = encodingOptions.channels || 2
-
-    // If changing audio file type then encoding is needed
-    const audioTracks = libraryItem.media.tracks
-
-    // TODO: Updated in 2.2.11 to always encode even if merging multiple m4b. This is because just using the file extension as was being done before is not enough. This can be an option or do more to check if a concat is possible.
-    // const audioRequiresEncode = audioTracks[0].metadata.ext !== '.m4b'
-    const audioRequiresEncode = true
-
-    const firstTrackIsM4b = audioTracks[0].metadata.ext.toLowerCase() === '.m4b'
-    const isOneTrack = audioTracks.length === 1
-
-    const ffmpegInputs = []
-
-    if (!isOneTrack) {
-      const concatFilePath = Path.join(task.data.itemCachePath, 'files.txt')
-      await writeConcatFile(audioTracks, concatFilePath)
-      ffmpegInputs.push({
-        input: concatFilePath,
-        options: ['-safe 0', '-f concat']
-      })
-    } else {
-      ffmpegInputs.push({
-        input: audioTracks[0].metadata.path,
-        options: firstTrackIsM4b ? ['-f mp4'] : []
-      })
-    }
-
-    const logLevel = process.env.NODE_ENV === 'production' ? 'error' : 'warning'
-    let ffmpegOptions = [`-loglevel ${logLevel}`]
-    const ffmpegOutputOptions = ['-f mp4']
-
-    if (audioRequiresEncode) {
-      ffmpegOptions = ffmpegOptions.concat(['-map 0:a', `-acodec ${audioCodec}`, `-ac ${audioChannels}`, `-b:a ${audioBitrate}`])
-    } else {
-      ffmpegOptions.push('-max_muxing_queue_size 1000')
-
-      if (isOneTrack && firstTrackIsM4b) {
-        ffmpegOptions.push('-c copy')
-      } else {
-        ffmpegOptions.push('-c:a copy')
-      }
-    }
-
-    const workerData = {
-      inputs: ffmpegInputs,
-      options: ffmpegOptions,
-      outputOptions: ffmpegOutputOptions,
-      output: task.data.tempFilepath
-    }
-
-    let worker = null
-    try {
-      const workerPath = Path.join(global.appRoot, 'server/utils/downloadWorker.js')
-      worker = new workerThreads.Worker(workerPath, { workerData })
-    } catch (error) {
-      Logger.error(`[AbMergeManager] Start worker thread failed`, error)
-      task.setFailed('Failed to start worker thread')
-      this.removeTask(task, true)
-      return
-    }
-
-    worker.on('message', (message) => {
-      if (message != null && typeof message === 'object') {
-        if (message.type === 'RESULT') {
-          this.sendResult(task, message)
-        } else if (message.type === 'FFMPEG') {
-          if (Logger[message.level]) {
-            Logger[message.level](message.log)
-          }
-        }
-      }
-    })
     this.pendingTasks.push({
       id: task.id,
-      task,
-      worker
+      task
     })
-  }
 
-  async sendResult(task, result) {
-    // Remove pending task
-    this.pendingTasks = this.pendingTasks.filter((d) => d.id !== task.id)
-
-    if (result.isKilled) {
-      task.setFailed('Ffmpeg task killed')
-      this.removeTask(task, true)
-      return
-    }
-
-    if (!result.success) {
-      task.setFailed('Encoding failed')
-      this.removeTask(task, true)
+    const encodeFraction = 0.95
+    const embedFraction = 1 - encodeFraction
+    try {
+      const trackProgressMonitor = new TrackProgressMonitor(
+        libraryItem.media.tracks.map((t) => t.duration),
+        (trackIndex) => SocketAuthority.adminEmitter('track_started', { libraryItemId: libraryItem.id, ino: task.data.inos[trackIndex] }),
+        (trackIndex, progressInTrack, taskProgress) => {
+          SocketAuthority.adminEmitter('track_progress', { libraryItemId: libraryItem.id, ino: task.data.inos[trackIndex], progress: progressInTrack })
+          SocketAuthority.adminEmitter('task_progress', { libraryItemId: libraryItem.id, progress: taskProgress * encodeFraction })
+        },
+        (trackIndex) => SocketAuthority.adminEmitter('track_finished', { libraryItemId: libraryItem.id, ino: task.data.inos[trackIndex] })
+      )
+      task.data.ffmpeg = new Ffmpeg()
+      await ffmpegHelpers.mergeAudioFiles(libraryItem.media.tracks, task.data.duration, task.data.itemCachePath, task.data.tempFilepath, encodingOptions, (progress) => trackProgressMonitor.update(progress), task.data.ffmpeg)
+      delete task.data.ffmpeg
+      trackProgressMonitor.finish()
+    } catch (error) {
+      if (error.message === 'FFMPEG_CANCELED') {
+        Logger.info(`[AbMergeManager] Task cancelled ${task.id}`)
+      } else {
+        Logger.error(`[AbMergeManager] mergeAudioFiles failed`, error)
+        task.setFailed('Failed to merge audio files')
+        this.removeTask(task, true)
+      }
       return
     }
 
     // Write metadata to merged file
-    const success = await ffmpegHelpers.addCoverAndMetadataToFile(task.data.tempFilepath, task.data.coverPath, task.data.ffmetadataPath, 1, 'audio/mp4')
-    if (!success) {
-      Logger.error(`[AbMergeManager] Failed to write metadata to file "${task.data.tempFilepath}"`)
-      task.setFailed('Failed to write metadata to m4b file')
-      this.removeTask(task, true)
+    try {
+      task.data.ffmpeg = new Ffmpeg()
+      await ffmpegHelpers.addCoverAndMetadataToFile(
+        task.data.tempFilepath,
+        task.data.coverPath,
+        task.data.ffmetadataPath,
+        1,
+        'audio/mp4',
+        (progress) => {
+          Logger.debug(`[AbMergeManager] Embedding metadata progress: ${100 * encodeFraction + progress * embedFraction}`)
+          SocketAuthority.adminEmitter('task_progress', { libraryItemId: libraryItem.id, progress: 100 * encodeFraction + progress * embedFraction })
+        },
+        task.data.ffmpeg
+      )
+      delete task.data.ffmpeg
+    } catch (error) {
+      if (error.message === 'FFMPEG_CANCELED') {
+        Logger.info(`[AbMergeManager] Task cancelled ${task.id}`)
+      } else {
+        Logger.error(`[AbMergeManager] Failed to write metadata to file "${task.data.tempFilepath}"`)
+        task.setFailed('Failed to write metadata to m4b file')
+        this.removeTask(task, true)
+      }
       return
     }
 
@@ -199,19 +163,14 @@ class AbMergeManager {
   async removeTask(task, removeTempFilepath = false) {
     Logger.info('[AbMergeManager] Removing task ' + task.id)
 
-    const pendingDl = this.pendingTasks.find((d) => d.id === task.id)
-    if (pendingDl) {
+    const pendingTask = this.pendingTasks.find((d) => d.id === task.id)
+    if (pendingTask) {
       this.pendingTasks = this.pendingTasks.filter((d) => d.id !== task.id)
-      if (pendingDl.worker) {
-        Logger.warn(`[AbMergeManager] Removing download in progress - stopping worker`)
-        try {
-          pendingDl.worker.postMessage('STOP')
-          return
-        } catch (error) {
-          Logger.error('[AbMergeManager] Error posting stop message to worker', error)
-        }
-      } else {
-        Logger.debug(`[AbMergeManager] Removing download in progress - no worker`)
+      if (task.data.ffmpeg) {
+        Logger.warn(`[AbMergeManager] Killing ffmpeg process for task ${task.id}`)
+        task.data.ffmpeg.kill()
+        // wait for ffmpeg to exit, so that the output file is unlocked
+        await new Promise((resolve) => setTimeout(resolve, 500))
       }
     }
 
diff --git a/server/managers/AudioMetadataManager.js b/server/managers/AudioMetadataManager.js
index 09b773f6..39c03ae7 100644
--- a/server/managers/AudioMetadataManager.js
+++ b/server/managers/AudioMetadataManager.js
@@ -1,15 +1,11 @@
 const Path = require('path')
-
 const SocketAuthority = require('../SocketAuthority')
 const Logger = require('../Logger')
-
 const fs = require('../libs/fsExtra')
-
 const ffmpegHelpers = require('../utils/ffmpegHelpers')
-
 const TaskManager = require('./TaskManager')
-
 const Task = require('../objects/Task')
+const fileUtils = require('../utils/fileUtils')
 
 class AudioMetadataMangaer {
   constructor() {
@@ -68,7 +64,8 @@ class AudioMetadataMangaer {
         ino: af.ino,
         filename: af.metadata.filename,
         path: af.metadata.path,
-        cachePath: Path.join(itemCachePath, af.metadata.filename)
+        cachePath: Path.join(itemCachePath, af.metadata.filename),
+        duration: af.duration
       })),
       coverPath: libraryItem.media.coverPath,
       metadataObject: ffmpegHelpers.getFFMetadataObject(libraryItem, audioFiles.length),
@@ -78,7 +75,8 @@ class AudioMetadataMangaer {
       options: {
         forceEmbedChapters,
         backupFiles
-      }
+      },
+      duration: libraryItem.media.duration
     }
     const taskDescription = `Embedding metadata in audiobook "${libraryItem.media.metadata.title}".`
     task.setData('embed-metadata', 'Embedding Metadata', taskDescription, false, taskData)
@@ -101,11 +99,40 @@ class AudioMetadataMangaer {
 
     Logger.info(`[AudioMetadataManager] Starting metadata embed task`, task.description)
 
+    // Ensure target directory is writable
+    const targetDirWritable = await fileUtils.isWritable(task.data.libraryItemPath)
+    Logger.debug(`[AudioMetadataManager] Target directory ${task.data.libraryItemPath} writable: ${targetDirWritable}`)
+    if (!targetDirWritable) {
+      Logger.error(`[AudioMetadataManager] Target directory is not writable: ${task.data.libraryItemPath}`)
+      task.setFailed('Target directory is not writable')
+      this.handleTaskFinished(task)
+      return
+    }
+
+    // Ensure target audio files are writable
+    for (const af of task.data.audioFiles) {
+      try {
+        await fs.access(af.path, fs.constants.W_OK)
+      } catch (err) {
+        Logger.error(`[AudioMetadataManager] Audio file is not writable: ${af.path}`)
+        task.setFailed(`Audio file "${Path.basename(af.path)}" is not writable`)
+        this.handleTaskFinished(task)
+        return
+      }
+    }
+
     // Ensure item cache dir exists
     let cacheDirCreated = false
     if (!(await fs.pathExists(task.data.itemCachePath))) {
-      await fs.mkdir(task.data.itemCachePath)
-      cacheDirCreated = true
+      try {
+        await fs.mkdir(task.data.itemCachePath)
+        cacheDirCreated = true
+      } catch (err) {
+        Logger.error(`[AudioMetadataManager] Failed to create cache directory ${task.data.itemCachePath}`, err)
+        task.setFailed('Failed to create cache directory')
+        this.handleTaskFinished(task)
+        return
+      }
     }
 
     // Create ffmetadata file
@@ -119,8 +146,10 @@ class AudioMetadataMangaer {
     }
 
     // Tag audio files
+    let cummulativeProgress = 0
     for (const af of task.data.audioFiles) {
-      SocketAuthority.adminEmitter('audiofile_metadata_started', {
+      const audioFileRelativeDuration = af.duration / task.data.duration
+      SocketAuthority.adminEmitter('track_started', {
         libraryItemId: task.data.libraryItemId,
         ino: af.ino
       })
@@ -133,18 +162,31 @@ class AudioMetadataMangaer {
           Logger.debug(`[AudioMetadataManager] Backed up audio file at "${backupFilePath}"`)
         } catch (err) {
           Logger.error(`[AudioMetadataManager] Failed to backup audio file "${af.path}"`, err)
+          task.setFailed(`Failed to backup audio file "${Path.basename(af.path)}"`)
+          this.handleTaskFinished(task)
+          return
         }
       }
 
-      const success = await ffmpegHelpers.addCoverAndMetadataToFile(af.path, task.data.coverPath, ffmetadataPath, af.index, task.data.mimeType)
-      if (success) {
+      try {
+        await ffmpegHelpers.addCoverAndMetadataToFile(af.path, task.data.coverPath, ffmetadataPath, af.index, task.data.mimeType, (progress) => {
+          SocketAuthority.adminEmitter('task_progress', { libraryItemId: task.data.libraryItemId, progress: cummulativeProgress + progress * audioFileRelativeDuration })
+          SocketAuthority.adminEmitter('track_progress', { libraryItemId: task.data.libraryItemId, ino: af.ino, progress })
+        })
         Logger.info(`[AudioMetadataManager] Successfully tagged audio file "${af.path}"`)
+      } catch (err) {
+        Logger.error(`[AudioMetadataManager] Failed to tag audio file "${af.path}"`, err)
+        task.setFailed(`Failed to tag audio file "${Path.basename(af.path)}"`)
+        this.handleTaskFinished(task)
+        return
       }
 
-      SocketAuthority.adminEmitter('audiofile_metadata_finished', {
+      SocketAuthority.adminEmitter('track_finished', {
         libraryItemId: task.data.libraryItemId,
         ino: af.ino
       })
+
+      cummulativeProgress += audioFileRelativeDuration * 100
     }
 
     // Remove temp cache file/folder if not backing up
diff --git a/server/objects/TrackProgressMonitor.js b/server/objects/TrackProgressMonitor.js
new file mode 100644
index 00000000..83db12aa
--- /dev/null
+++ b/server/objects/TrackProgressMonitor.js
@@ -0,0 +1,88 @@
+class TrackProgressMonitor {
+  /**
+   * @callback TrackStartedCallback
+   * @param {number} trackIndex - The index of the track that started.
+   */
+
+  /**
+   * @callback ProgressCallback
+   * @param {number} trackIndex - The index of the track that is being updated.
+   * @param {number} progressInTrack - The progress of the track in percent.
+   * @param {number} totalProgress - The total progress in percent.
+   */
+
+  /**
+   * @callback TrackFinishedCallback
+   * @param {number} trackIndex - The index of the track that finished.
+   */
+
+  /**
+   * Creates a new TrackProgressMonitor.
+   * @constructor
+   * @param {number[]} trackDurations - The durations of the tracks in seconds.
+   * @param {TrackStartedCallback} trackStartedCallback - The callback to call when a track starts.
+   * @param {ProgressCallback} progressCallback - The callback to call when progress is updated.
+   * @param {TrackFinishedCallback} trackFinishedCallback - The callback to call when a track finishes.
+   */
+  constructor(trackDurations, trackStartedCallback, progressCallback, trackFinishedCallback) {
+    this.trackDurations = trackDurations
+    this.totalDuration = trackDurations.reduce((total, duration) => total + duration, 0)
+    this.trackStartedCallback = trackStartedCallback
+    this.progressCallback = progressCallback
+    this.trackFinishedCallback = trackFinishedCallback
+    this.currentTrackIndex = -1
+    this.cummulativeProgress = 0
+    this.currentTrackPercentage = 0
+    this.numTracks = this.trackDurations.length
+    this.allTracksFinished = false
+    this.#moveToNextTrack()
+  }
+
+  #outsideCurrentTrack(progress) {
+    this.currentTrackProgress = progress - this.cummulativeProgress
+    return this.currentTrackProgress >= this.currentTrackPercentage
+  }
+
+  #moveToNextTrack() {
+    if (this.currentTrackIndex >= 0) this.#trackFinished()
+    this.currentTrackIndex++
+    this.cummulativeProgress += this.currentTrackPercentage
+    if (this.currentTrackIndex >= this.numTracks) {
+      this.allTracksFinished = true
+      return
+    }
+    this.currentTrackPercentage = (this.trackDurations[this.currentTrackIndex] / this.totalDuration) * 100
+    this.#trackStarted()
+  }
+
+  #trackStarted() {
+    this.trackStartedCallback(this.currentTrackIndex)
+  }
+
+  #progressUpdated(progress) {
+    const progressInTrack = (this.currentTrackProgress / this.currentTrackPercentage) * 100
+    this.progressCallback(this.currentTrackIndex, progressInTrack, progress)
+  }
+
+  #trackFinished() {
+    this.trackFinishedCallback(this.currentTrackIndex)
+  }
+
+  /**
+   * Updates the progress of the track.
+   * @param {number} progress - The progress of the track in percent.
+   */
+  update(progress) {
+    while (this.#outsideCurrentTrack(progress) && !this.allTracksFinished) this.#moveToNextTrack()
+    if (!this.allTracksFinished) this.#progressUpdated(progress)
+  }
+
+  /**
+   * Finish the track progress monitoring.
+   * Forces all remaining tracks to finish.
+   */
+  finish() {
+    this.update(101)
+  }
+}
+module.exports = TrackProgressMonitor
diff --git a/server/utils/ffmpegHelpers.js b/server/utils/ffmpegHelpers.js
index 2a242504..8e8d270d 100644
--- a/server/utils/ffmpegHelpers.js
+++ b/server/utils/ffmpegHelpers.js
@@ -1,7 +1,7 @@
 const axios = require('axios')
 const Ffmpeg = require('../libs/fluentFfmpeg')
+const ffmpgegUtils = require('../libs/fluentFfmpeg/utils')
 const fs = require('../libs/fsExtra')
-const os = require('os')
 const Path = require('path')
 const Logger = require('../Logger')
 const { filePathToPOSIX } = require('./fileUtils')
@@ -251,9 +251,10 @@ module.exports.writeFFMetadataFile = writeFFMetadataFile
  * @param {number} track - The track number to embed in the audio file.
  * @param {string} mimeType - The MIME type of the audio file.
  * @param {Ffmpeg} ffmpeg - The Ffmpeg instance to use (optional). Used for dependency injection in tests.
- * @returns {Promise<boolean>} A promise that resolves to true if the operation is successful, false otherwise.
+ * @param {function(number): void|null} progressCB - A callback function to report progress.
+ * @returns {Promise<void>} A promise that resolves if the operation is successful, rejects otherwise.
  */
-async function addCoverAndMetadataToFile(audioFilePath, coverFilePath, metadataFilePath, track, mimeType, ffmpeg = Ffmpeg()) {
+async function addCoverAndMetadataToFile(audioFilePath, coverFilePath, metadataFilePath, track, mimeType, progressCB = null, ffmpeg = Ffmpeg()) {
   const isMp4 = mimeType === 'audio/mp4'
   const isMp3 = mimeType === 'audio/mpeg'
 
@@ -262,7 +263,7 @@ async function addCoverAndMetadataToFile(audioFilePath, coverFilePath, metadataF
   const audioFileBaseName = Path.basename(audioFilePath, audioFileExt)
   const tempFilePath = filePathToPOSIX(Path.join(audioFileDir, `${audioFileBaseName}.tmp${audioFileExt}`))
 
-  return new Promise((resolve) => {
+  return new Promise((resolve, reject) => {
     ffmpeg.input(audioFilePath).input(metadataFilePath).outputOptions([
       '-map 0:a', // map audio stream from input file
       '-map_metadata 1', // map metadata tags from metadata file first
@@ -302,21 +303,36 @@ async function addCoverAndMetadataToFile(audioFilePath, coverFilePath, metadataF
 
     ffmpeg
       .output(tempFilePath)
-      .on('start', function (commandLine) {
+      .on('start', (commandLine) => {
         Logger.debug('[ffmpegHelpers] Spawned Ffmpeg with command: ' + commandLine)
       })
-      .on('end', (stdout, stderr) => {
+      .on('progress', (progress) => {
+        if (!progressCB || !progress.percent) return
+        Logger.debug(`[ffmpegHelpers] Progress: ${progress.percent}%`)
+        progressCB(progress.percent)
+      })
+      .on('end', async (stdout, stderr) => {
         Logger.debug('[ffmpegHelpers] ffmpeg stdout:', stdout)
         Logger.debug('[ffmpegHelpers] ffmpeg stderr:', stderr)
-        fs.copyFileSync(tempFilePath, audioFilePath)
-        fs.unlinkSync(tempFilePath)
-        resolve(true)
+        Logger.debug('[ffmpegHelpers] Moving temp file to audio file path:', `"${tempFilePath}"`, '->', `"${audioFilePath}"`)
+        try {
+          await fs.move(tempFilePath, audioFilePath, { overwrite: true })
+          resolve()
+        } catch (error) {
+          Logger.error(`[ffmpegHelpers] Failed to move temp file to audio file path: "${tempFilePath}" -> "${audioFilePath}"`, error)
+          reject(error)
+        }
       })
       .on('error', (err, stdout, stderr) => {
-        Logger.error('Error adding cover image and metadata:', err)
-        Logger.error('ffmpeg stdout:', stdout)
-        Logger.error('ffmpeg stderr:', stderr)
-        resolve(false)
+        if (err.message && err.message.includes('SIGKILL')) {
+          Logger.info(`[ffmpegHelpers] addCoverAndMetadataToFile Killed by User`)
+          reject(new Error('FFMPEG_CANCELED'))
+        } else {
+          Logger.error('Error adding cover image and metadata:', err)
+          Logger.error('ffmpeg stdout:', stdout)
+          Logger.error('ffmpeg stderr:', stderr)
+          reject(err)
+        }
       })
 
     ffmpeg.run()
@@ -366,3 +382,92 @@ function getFFMetadataObject(libraryItem, audioFilesLength) {
 }
 
 module.exports.getFFMetadataObject = getFFMetadataObject
+
+/**
+ * Merges audio files into a single output file using FFmpeg.
+ *
+ * @param {Array} audioTracks - The audio tracks to merge.
+ * @param {number} duration - The total duration of the audio tracks.
+ * @param {string} itemCachePath - The path to the item cache.
+ * @param {string} outputFilePath - The path to the output file.
+ * @param {Object} encodingOptions - The options for encoding the audio.
+ * @param {Function} [progressCB=null] - The callback function to track the progress of the merge.
+ * @param {Object} [ffmpeg=Ffmpeg()] - The FFmpeg instance to use for merging.
+ * @returns {Promise<void>} A promise that resolves when the audio files are merged successfully.
+ */
+async function mergeAudioFiles(audioTracks, duration, itemCachePath, outputFilePath, encodingOptions, progressCB = null, ffmpeg = Ffmpeg()) {
+  const audioBitrate = encodingOptions.bitrate || '128k'
+  const audioCodec = encodingOptions.codec || 'aac'
+  const audioChannels = encodingOptions.channels || 2
+
+  // TODO: Updated in 2.2.11 to always encode even if merging multiple m4b. This is because just using the file extension as was being done before is not enough. This can be an option or do more to check if a concat is possible.
+  // const audioRequiresEncode = audioTracks[0].metadata.ext !== '.m4b'
+  const audioRequiresEncode = true
+
+  const firstTrackIsM4b = audioTracks[0].metadata.ext.toLowerCase() === '.m4b'
+  const isOneTrack = audioTracks.length === 1
+
+  let concatFilePath = null
+  if (!isOneTrack) {
+    concatFilePath = Path.join(itemCachePath, 'files.txt')
+    if ((await writeConcatFile(audioTracks, concatFilePath)) == null) {
+      throw new Error('Failed to write concat file')
+    }
+    ffmpeg.input(concatFilePath).inputOptions(['-safe 0', '-f concat'])
+  } else {
+    ffmpeg.input(audioTracks[0].metadata.path).inputOptions(firstTrackIsM4b ? ['-f mp4'] : [])
+  }
+
+  //const logLevel = process.env.NODE_ENV === 'production' ? 'error' : 'warning'
+  ffmpeg.outputOptions(['-f mp4'])
+
+  if (audioRequiresEncode) {
+    ffmpeg.outputOptions(['-map 0:a', `-acodec ${audioCodec}`, `-ac ${audioChannels}`, `-b:a ${audioBitrate}`])
+  } else {
+    ffmpeg.outputOptions(['-max_muxing_queue_size 1000'])
+
+    if (isOneTrack && firstTrackIsM4b) {
+      ffmpeg.outputOptions(['-c copy'])
+    } else {
+      ffmpeg.outputOptions(['-c:a copy'])
+    }
+  }
+
+  ffmpeg.output(outputFilePath)
+
+  return new Promise((resolve, reject) => {
+    ffmpeg
+      .on('start', (cmd) => {
+        Logger.debug(`[ffmpegHelpers] Merge Audio Files ffmpeg command: ${cmd}`)
+      })
+      .on('progress', (progress) => {
+        if (!progressCB || !progress.timemark || !duration) return
+        // Cannot rely on progress.percent as it is not accurate for concat
+        const percent = (ffmpgegUtils.timemarkToSeconds(progress.timemark) / duration) * 100
+        progressCB(percent)
+      })
+      .on('end', async (stdout, stderr) => {
+        if (concatFilePath) await fs.remove(concatFilePath)
+        Logger.debug('[ffmpegHelpers] ffmpeg stdout:', stdout)
+        Logger.debug('[ffmpegHelpers] ffmpeg stderr:', stderr)
+        Logger.debug(`[ffmpegHelpers] Audio Files Merged Successfully`)
+        resolve()
+      })
+      .on('error', async (err, stdout, stderr) => {
+        if (concatFilePath) await fs.remove(concatFilePath)
+        if (err.message && err.message.includes('SIGKILL')) {
+          Logger.info(`[ffmpegHelpers] Merge Audio Files Killed by User`)
+          reject(new Error('FFMPEG_CANCELED'))
+        } else {
+          Logger.error(`[ffmpegHelpers] Merge Audio Files Error ${err}`)
+          Logger.error('ffmpeg stdout:', stdout)
+          Logger.error('ffmpeg stderr:', stderr)
+          reject(err)
+        }
+      })
+
+    ffmpeg.run()
+  })
+}
+
+module.exports.mergeAudioFiles = mergeAudioFiles
diff --git a/test/server/objects/TrackProgressMonitor.test.js b/test/server/objects/TrackProgressMonitor.test.js
new file mode 100644
index 00000000..b809161f
--- /dev/null
+++ b/test/server/objects/TrackProgressMonitor.test.js
@@ -0,0 +1,95 @@
+const chai = require('chai')
+const sinon = require('sinon')
+const TrackProgressMonitor = require('../../../server/objects/TrackProgressMonitor')
+
+const expect = chai.expect
+
+describe('TrackProgressMonitor', () => {
+  let trackDurations
+  let trackStartedCallback
+  let progressCallback
+  let trackFinishedCallback
+  let monitor
+
+  beforeEach(() => {
+    trackDurations = [10, 40, 50]
+    trackStartedCallback = sinon.spy()
+    progressCallback = sinon.spy()
+    trackFinishedCallback = sinon.spy()
+  })
+
+  it('should initialize correctly', () => {
+    monitor = new TrackProgressMonitor(trackDurations, trackStartedCallback, progressCallback, trackFinishedCallback)
+
+    expect(monitor.trackDurations).to.deep.equal(trackDurations)
+    expect(monitor.totalDuration).to.equal(100)
+    expect(monitor.trackStartedCallback).to.equal(trackStartedCallback)
+    expect(monitor.progressCallback).to.equal(progressCallback)
+    expect(monitor.trackFinishedCallback).to.equal(trackFinishedCallback)
+    expect(monitor.currentTrackIndex).to.equal(0)
+    expect(monitor.cummulativeProgress).to.equal(0)
+    expect(monitor.currentTrackPercentage).to.equal(10)
+    expect(monitor.numTracks).to.equal(trackDurations.length)
+    expect(monitor.allTracksFinished).to.be.false
+  })
+
+  it('should update the progress', () => {
+    monitor = new TrackProgressMonitor(trackDurations, trackStartedCallback, progressCallback, trackFinishedCallback)
+    monitor.update(5)
+
+    expect(monitor.currentTrackIndex).to.equal(0)
+    expect(monitor.cummulativeProgress).to.equal(0)
+    expect(monitor.currentTrackPercentage).to.equal(10)
+    expect(trackStartedCallback.calledOnceWithExactly(0)).to.be.true
+    expect(progressCallback.calledOnceWithExactly(0, 50, 5)).to.be.true
+    expect(trackFinishedCallback.notCalled).to.be.true
+  })
+
+  it('should update the progress multiple times on the same track', () => {
+    monitor = new TrackProgressMonitor(trackDurations, trackStartedCallback, progressCallback, trackFinishedCallback)
+    monitor.update(5)
+    monitor.update(7)
+
+    expect(monitor.currentTrackIndex).to.equal(0)
+    expect(monitor.cummulativeProgress).to.equal(0)
+    expect(monitor.currentTrackPercentage).to.equal(10)
+    expect(trackStartedCallback.calledOnceWithExactly(0)).to.be.true
+    expect(progressCallback.calledTwice).to.be.true
+    expect(progressCallback.calledWithExactly(0, 50, 5)).to.be.true
+    expect(progressCallback.calledWithExactly(0, 70, 7)).to.be.true
+    expect(trackFinishedCallback.notCalled).to.be.true
+  })
+
+  it('should update the progress multiple times on different tracks', () => {
+    monitor = new TrackProgressMonitor(trackDurations, trackStartedCallback, progressCallback, trackFinishedCallback)
+    monitor.update(5)
+    monitor.update(20)
+
+    expect(monitor.currentTrackIndex).to.equal(1)
+    expect(monitor.cummulativeProgress).to.equal(10)
+    expect(monitor.currentTrackPercentage).to.equal(40)
+    expect(trackStartedCallback.calledTwice).to.be.true
+    expect(trackStartedCallback.calledWithExactly(0)).to.be.true
+    expect(trackStartedCallback.calledWithExactly(1)).to.be.true
+    expect(progressCallback.calledTwice).to.be.true
+    expect(progressCallback.calledWithExactly(0, 50, 5)).to.be.true
+    expect(progressCallback.calledWithExactly(1, 25, 20)).to.be.true
+    expect(trackFinishedCallback.calledOnceWithExactly(0)).to.be.true
+  })
+
+  it('should finish all tracks', () => {
+    monitor = new TrackProgressMonitor(trackDurations, trackStartedCallback, progressCallback, trackFinishedCallback)
+    monitor.finish()
+
+    expect(monitor.allTracksFinished).to.be.true
+    expect(trackStartedCallback.calledThrice).to.be.true
+    expect(trackFinishedCallback.calledThrice).to.be.true
+    expect(progressCallback.notCalled).to.be.true
+    expect(trackStartedCallback.calledWithExactly(0)).to.be.true
+    expect(trackFinishedCallback.calledWithExactly(0)).to.be.true
+    expect(trackStartedCallback.calledWithExactly(1)).to.be.true
+    expect(trackFinishedCallback.calledWithExactly(1)).to.be.true
+    expect(trackStartedCallback.calledWithExactly(2)).to.be.true
+    expect(trackFinishedCallback.calledWithExactly(2)).to.be.true
+  })
+})
diff --git a/test/server/utils/ffmpegHelpers.test.js b/test/server/utils/ffmpegHelpers.test.js
index 82daf1ba..ad069998 100644
--- a/test/server/utils/ffmpegHelpers.test.js
+++ b/test/server/utils/ffmpegHelpers.test.js
@@ -81,10 +81,9 @@ describe('addCoverAndMetadataToFile', () => {
     ffmpegStub.run = sinon.stub().callsFake(() => {
       ffmpegStub.emit('end')
     })
-    const fsCopyFileSyncStub = sinon.stub(fs, 'copyFileSync')
-    const fsUnlinkSyncStub = sinon.stub(fs, 'unlinkSync')
+    const fsMove = sinon.stub(fs, 'move').resolves()
 
-    return { audioFilePath, coverFilePath, metadataFilePath, track, mimeType, ffmpegStub, fsCopyFileSyncStub, fsUnlinkSyncStub }
+    return { audioFilePath, coverFilePath, metadataFilePath, track, mimeType, ffmpegStub, fsMove }
   }
 
   let audioFilePath = null
@@ -93,8 +92,7 @@ describe('addCoverAndMetadataToFile', () => {
   let track = null
   let mimeType = null
   let ffmpegStub = null
-  let fsCopyFileSyncStub = null
-  let fsUnlinkSyncStub = null
+  let fsMove = null
   beforeEach(() => {
     const input = createTestSetup()
     audioFilePath = input.audioFilePath
@@ -103,16 +101,14 @@ describe('addCoverAndMetadataToFile', () => {
     track = input.track
     mimeType = input.mimeType
     ffmpegStub = input.ffmpegStub
-    fsCopyFileSyncStub = input.fsCopyFileSyncStub
-    fsUnlinkSyncStub = input.fsUnlinkSyncStub
+    fsMove = input.fsMove
   })
 
   it('should add cover image and metadata to audio file', async () => {
     // Act
-    const result = await addCoverAndMetadataToFile(audioFilePath, coverFilePath, metadataFilePath, track, mimeType, ffmpegStub)
+    await addCoverAndMetadataToFile(audioFilePath, coverFilePath, metadataFilePath, track, mimeType, null, ffmpegStub)
 
     // Assert
-    expect(result).to.be.true
     expect(ffmpegStub.input.calledThrice).to.be.true
     expect(ffmpegStub.input.getCall(0).args[0]).to.equal(audioFilePath)
     expect(ffmpegStub.input.getCall(1).args[0]).to.equal(metadataFilePath)
@@ -129,12 +125,10 @@ describe('addCoverAndMetadataToFile', () => {
 
     expect(ffmpegStub.run.calledOnce).to.be.true
 
-    expect(fsCopyFileSyncStub.calledOnce).to.be.true
-    expect(fsCopyFileSyncStub.firstCall.args[0]).to.equal('/path/to/audio/file.tmp.mp3')
-    expect(fsCopyFileSyncStub.firstCall.args[1]).to.equal('/path/to/audio/file.mp3')
-
-    expect(fsUnlinkSyncStub.calledOnce).to.be.true
-    expect(fsUnlinkSyncStub.firstCall.args[0]).to.equal('/path/to/audio/file.tmp.mp3')
+    expect(fsMove.calledOnce).to.be.true
+    expect(fsMove.firstCall.args[0]).to.equal('/path/to/audio/file.tmp.mp3')
+    expect(fsMove.firstCall.args[1]).to.equal('/path/to/audio/file.mp3')
+    expect(fsMove.firstCall.args[2]).to.deep.equal({ overwrite: true })
 
     // Restore the stub
     sinon.restore()
@@ -145,10 +139,9 @@ describe('addCoverAndMetadataToFile', () => {
     coverFilePath = null
 
     // Act
-    const result = await addCoverAndMetadataToFile(audioFilePath, coverFilePath, metadataFilePath, track, mimeType, ffmpegStub)
+    await addCoverAndMetadataToFile(audioFilePath, coverFilePath, metadataFilePath, track, mimeType, null, ffmpegStub)
 
     // Assert
-    expect(result).to.be.true
     expect(ffmpegStub.input.calledTwice).to.be.true
     expect(ffmpegStub.input.getCall(0).args[0]).to.equal(audioFilePath)
     expect(ffmpegStub.input.getCall(1).args[0]).to.equal(metadataFilePath)
@@ -164,12 +157,10 @@ describe('addCoverAndMetadataToFile', () => {
 
     expect(ffmpegStub.run.calledOnce).to.be.true
 
-    expect(fsCopyFileSyncStub.calledOnce).to.be.true
-    expect(fsCopyFileSyncStub.firstCall.args[0]).to.equal('/path/to/audio/file.tmp.mp3')
-    expect(fsCopyFileSyncStub.firstCall.args[1]).to.equal('/path/to/audio/file.mp3')
-
-    expect(fsUnlinkSyncStub.calledOnce).to.be.true
-    expect(fsUnlinkSyncStub.firstCall.args[0]).to.equal('/path/to/audio/file.tmp.mp3')
+    expect(fsMove.calledOnce).to.be.true
+    expect(fsMove.firstCall.args[0]).to.equal('/path/to/audio/file.tmp.mp3')
+    expect(fsMove.firstCall.args[1]).to.equal('/path/to/audio/file.mp3')
+    expect(fsMove.firstCall.args[2]).to.deep.equal({ overwrite: true })
 
     // Restore the stub
     sinon.restore()
@@ -182,10 +173,15 @@ describe('addCoverAndMetadataToFile', () => {
     })
 
     // Act
-    const result = await addCoverAndMetadataToFile(audioFilePath, coverFilePath, metadataFilePath, track, mimeType, ffmpegStub)
+    try {
+      await addCoverAndMetadataToFile(audioFilePath, coverFilePath, metadataFilePath, track, mimeType, null, ffmpegStub)
+      expect.fail('Expected an error to be thrown')
+    } catch (error) {
+      // Assert
+      expect(error.message).to.equal('FFmpeg error')
+    }
 
     // Assert
-    expect(result).to.be.false
     expect(ffmpegStub.input.calledThrice).to.be.true
     expect(ffmpegStub.input.getCall(0).args[0]).to.equal(audioFilePath)
     expect(ffmpegStub.input.getCall(1).args[0]).to.equal(metadataFilePath)
@@ -202,9 +198,7 @@ describe('addCoverAndMetadataToFile', () => {
 
     expect(ffmpegStub.run.calledOnce).to.be.true
 
-    expect(fsCopyFileSyncStub.called).to.be.false
-
-    expect(fsUnlinkSyncStub.called).to.be.false
+    expect(fsMove.called).to.be.false
 
     // Restore the stub
     sinon.restore()
@@ -216,10 +210,9 @@ describe('addCoverAndMetadataToFile', () => {
     audioFilePath = '/path/to/audio/file.m4b'
 
     // Act
-    const result = await addCoverAndMetadataToFile(audioFilePath, coverFilePath, metadataFilePath, track, mimeType, ffmpegStub)
+    await addCoverAndMetadataToFile(audioFilePath, coverFilePath, metadataFilePath, track, mimeType, null, ffmpegStub)
 
     // Assert
-    expect(result).to.be.true
     expect(ffmpegStub.input.calledThrice).to.be.true
     expect(ffmpegStub.input.getCall(0).args[0]).to.equal(audioFilePath)
     expect(ffmpegStub.input.getCall(1).args[0]).to.equal(metadataFilePath)
@@ -236,12 +229,10 @@ describe('addCoverAndMetadataToFile', () => {
 
     expect(ffmpegStub.run.calledOnce).to.be.true
 
-    expect(fsCopyFileSyncStub.calledOnce).to.be.true
-    expect(fsCopyFileSyncStub.firstCall.args[0]).to.equal('/path/to/audio/file.tmp.m4b')
-    expect(fsCopyFileSyncStub.firstCall.args[1]).to.equal('/path/to/audio/file.m4b')
-
-    expect(fsUnlinkSyncStub.calledOnce).to.be.true
-    expect(fsUnlinkSyncStub.firstCall.args[0]).to.equal('/path/to/audio/file.tmp.m4b')
+    expect(fsMove.calledOnce).to.be.true
+    expect(fsMove.firstCall.args[0]).to.equal('/path/to/audio/file.tmp.m4b')
+    expect(fsMove.firstCall.args[1]).to.equal('/path/to/audio/file.m4b')
+    expect(fsMove.firstCall.args[2]).to.deep.equal({ overwrite: true })
 
     // Restore the stub
     sinon.restore()