Experimental option to transcode surround sound audio to AC3 (#947)

## Description
Adds an experimental setting to prefer transcoding audio with more than
2 channels to AC3. Stereo audio does not transcode.

This is basically a workaround for HDMI ARC (not eARC) or optical audio
devices because instead of 2 uncompressed PCM channels, 6 AC3 channels
(ie 5.1) is possible.

An downside of enabling this is that embedded subtitles be burned in
causing a video transcode as well.

### Related issues
Fixes #255
Incorporates some code from #1410

### Testing
Just on the emulator so far to observe if the settings trigger the
transcode or not

## Screenshots
N/A

## AI or LLM usage
None

---------

Co-authored-by: darkflame91 <darkflame91@gmail.com>

app/src/main/java/com/github/damontecres/wholphin/preferences/AppPreference.kt

@@ -53,7 +53,10 @@ sealed interface AppPreference<Pref, T> {
         value: T?,
     ): String? = null
 
-    fun validate(value: T): PreferenceValidation = PreferenceValidation.Valid
+    fun validate(
+        prefs: Pref,
+        value: T,
+    ): PreferenceValidation = PreferenceValidation.Valid
 
     companion object {
         val SkipForward =
@@ -391,18 +394,25 @@ sealed interface AppPreference<Pref, T> {
                 defaultValue = true,
                 getter = { it.playbackPreferences.overrides.ac3Supported },
                 setter = { prefs, value ->
-                    prefs.updatePlaybackOverrides { ac3Supported = value }
+                    if (!value) prefs.updateExperimentalPreferences { preferAc3Surround = false }
+                    prefs.updatePlaybackOverrides {
+                        ac3Supported = value
+                    }
                 },
                 summaryOn = R.string.enabled,
                 summaryOff = R.string.disabled,
             )
+
         val DownMixStereo =
             AppSwitchPreference<AppPreferences>(
                 title = R.string.downmix_stereo,
                 defaultValue = false,
                 getter = { it.playbackPreferences.overrides.downmixStereo },
                 setter = { prefs, value ->
-                    prefs.updatePlaybackOverrides { downmixStereo = value }
+                    if (value) prefs.updateExperimentalPreferences { preferAc3Surround = false }
+                    prefs.updatePlaybackOverrides {
+                        downmixStereo = value
+                    }
                 },
                 summaryOn = R.string.enabled,
                 summaryOff = R.string.disabled,
@@ -1311,11 +1321,16 @@ data class AppSwitchPreference<Pref>(
     override val defaultValue: Boolean,
     override val getter: (prefs: Pref) -> Boolean,
     override val setter: (prefs: Pref, value: Boolean) -> Pref,
-    val validator: (value: Boolean) -> PreferenceValidation = { PreferenceValidation.Valid },
+    val validator: (prefs: Pref, value: Boolean) -> PreferenceValidation = { _, _ -> PreferenceValidation.Valid },
     @param:StringRes val summary: Int? = null,
     @param:StringRes val summaryOn: Int? = null,
     @param:StringRes val summaryOff: Int? = null,
 ) : AppPreference<Pref, Boolean> {
+    override fun validate(
+        prefs: Pref,
+        value: Boolean,
+    ): PreferenceValidation = validator.invoke(prefs, value)
+
     override fun summary(
         context: Context,
         value: Boolean?,

app/src/main/java/com/github/damontecres/wholphin/preferences/ExperimentalPreference.kt

@@ -4,6 +4,7 @@ import com.github.damontecres.wholphin.R
 import com.github.damontecres.wholphin.ui.nav.Destination
 import com.github.damontecres.wholphin.ui.preferences.PreferenceGroup
 import com.github.damontecres.wholphin.ui.preferences.PreferenceScreenOption
+import com.github.damontecres.wholphin.ui.preferences.PreferenceValidation
 
 object ExperimentalPreference {
     val Enable =
@@ -35,6 +36,30 @@ object ExperimentalPreference {
             summaryOn = R.string.enabled,
             summaryOff = R.string.disabled,
         )
+
+    val PreferAc3ForSurround =
+        AppSwitchPreference<AppPreferences>(
+            title = R.string.prefer_ac3_for_surround,
+            defaultValue = true,
+            getter = { it.experimentalPreferences.preferAc3Surround },
+            setter = { prefs, value ->
+                prefs.updateExperimentalPreferences {
+                    preferAc3Surround = value
+                }
+            },
+            summary = R.string.prefer_ac3_for_surround_summary,
+            validator = { prefs, value ->
+                prefs.playbackPreferences.overrides.let {
+                    if (value && !it.ac3Supported) {
+                        PreferenceValidation.Invalid("AC3 support is not enabled")
+                    } else if (value && it.downmixStereo) {
+                        PreferenceValidation.Invalid("Always downmixing to stereo")
+                    } else {
+                        PreferenceValidation.Valid
+                    }
+                }
+            },
+        )
 }
 
 val experimentalPreferences =
@@ -45,6 +70,7 @@ val experimentalPreferences =
                 preferences =
                     listOf(
                         ExperimentalPreference.VideoTunneling,
+                        ExperimentalPreference.PreferAc3ForSurround,
                     ),
             ),
         )

app/src/main/java/com/github/damontecres/wholphin/services/DeviceProfileService.kt

@@ -1,8 +1,10 @@
 package com.github.damontecres.wholphin.services
 
 import android.content.Context
+import com.github.damontecres.wholphin.preferences.AppPreferences
 import com.github.damontecres.wholphin.preferences.AssPlaybackMode
-import com.github.damontecres.wholphin.preferences.PlaybackPreferences
+import com.github.damontecres.wholphin.preferences.ExperimentalPreferences
+import com.github.damontecres.wholphin.preferences.PlaybackOverrides
 import com.github.damontecres.wholphin.util.WholphinDispatchers
 import com.github.damontecres.wholphin.util.profile.MediaCodecCapabilitiesTest
 import com.github.damontecres.wholphin.util.profile.createDeviceProfile
@@ -34,20 +36,17 @@ class DeviceProfileService
         private var deviceProfile: DeviceProfile? = null
 
         suspend fun getOrCreateDeviceProfile(
-            prefs: PlaybackPreferences,
+            appPrefs: AppPreferences,
             serverVersion: ServerVersion?,
         ): DeviceProfile =
             withContext(WholphinDispatchers.Default) {
+                val prefs = appPrefs.playbackPreferences
                 mutex.withLock {
                     val newConfig =
                         DeviceProfileConfiguration(
                             maxBitrate = prefs.maxBitrate.toInt(),
-                            isAC3Enabled = prefs.overrides.ac3Supported,
-                            downMixAudio = prefs.overrides.downmixStereo,
-                            assPlaybackMode = prefs.overrides.assPlaybackMode,
-                            pgsDirectPlay = prefs.overrides.directPlayPgs,
-                            dolbyVisionELDirectPlay = prefs.overrides.directPlayDolbyVisionEL,
-                            decodeAv1 = prefs.overrides.decodeAv1,
+                            overrides = prefs.overrides,
+                            experimental = appPrefs.experimentalPreferences,
                             jellyfinTenEleven =
                                 serverVersion != null && serverVersion >= ServerVersion(10, 11, 0),
                         )
@@ -57,12 +56,13 @@ class DeviceProfileService
                             createDeviceProfile(
                                 mediaTest = mediaCodecCapabilitiesTest,
                                 maxBitrate = newConfig.maxBitrate,
-                                isAC3Enabled = newConfig.isAC3Enabled,
-                                downMixAudio = newConfig.downMixAudio,
-                                assDirectPlay = newConfig.assPlaybackMode != AssPlaybackMode.ASS_TRANSCODE,
-                                pgsDirectPlay = newConfig.pgsDirectPlay,
-                                dolbyVisionELDirectPlay = newConfig.dolbyVisionELDirectPlay,
+                                isAC3Enabled = newConfig.overrides.ac3Supported,
+                                downMixAudio = newConfig.overrides.downmixStereo,
+                                assDirectPlay = newConfig.overrides.assPlaybackMode != AssPlaybackMode.ASS_TRANSCODE,
+                                pgsDirectPlay = newConfig.overrides.directPlayPgs,
+                                dolbyVisionELDirectPlay = newConfig.overrides.directPlayDolbyVisionEL,
                                 decodeAv1 = prefs.overrides.decodeAv1,
+                                preferAc3ForSurround = appPrefs.experimentalPreferences.preferAc3Surround,
                                 jellyfinTenEleven = newConfig.jellyfinTenEleven,
                             )
                     }
@@ -76,11 +76,7 @@ class DeviceProfileService
  */
 data class DeviceProfileConfiguration(
     val maxBitrate: Int,
-    val isAC3Enabled: Boolean,
-    val downMixAudio: Boolean,
-    val assPlaybackMode: AssPlaybackMode,
-    val pgsDirectPlay: Boolean,
-    val dolbyVisionELDirectPlay: Boolean,
-    val decodeAv1: Boolean,
+    val overrides: PlaybackOverrides,
+    val experimental: ExperimentalPreferences,
     val jellyfinTenEleven: Boolean,
 )

app/src/main/java/com/github/damontecres/wholphin/services/MediaReportService.kt

@@ -61,10 +61,10 @@ class MediaReportService
                     .getItem(itemId = item.id)
                     .content.mediaSources
             val sourcesJson = json.encodeToString(sources)
-            val playbackPrefs = userPreferencesService.getCurrent().appPreferences.playbackPreferences
+            val appPreferences = userPreferencesService.getCurrent().appPreferences
             val serverVersion = serverRepository.currentServer?.serverVersion
             val deviceProfile =
-                deviceProfileService.getOrCreateDeviceProfile(playbackPrefs, serverVersion)
+                deviceProfileService.getOrCreateDeviceProfile(appPreferences, serverVersion)
             val deviceProfileJson = json.encodeToString(deviceProfile)
             val body =
                 """
@@ -76,7 +76,14 @@ class MediaReportService
                 model=${Build.MODEL}
                 apiLevel=${Build.VERSION.SDK_INT}
 
-                playbackPrefs=${playbackPrefs.toString().replace("\n", ", ").replace("\t", " ")}
+                playbackPrefs=${
+                    appPreferences.playbackPreferences.toString().replace("\n", ", ")
+                        .replace("\t", " ")
+                }
+                experimental=${
+                    appPreferences.experimentalPreferences.toString().replace("\n", ", ")
+                        .replace("\t", " ")
+                }
 
                 deviceProfile=$deviceProfileJson
 

app/src/main/java/com/github/damontecres/wholphin/services/MusicService.kt

@@ -15,6 +15,7 @@ import com.github.damontecres.wholphin.data.model.AudioItem
 import com.github.damontecres.wholphin.data.model.BaseItem
 import com.github.damontecres.wholphin.services.hilt.DefaultCoroutineScope
 import com.github.damontecres.wholphin.ui.DefaultItemFields
+import com.github.damontecres.wholphin.ui.gt
 import com.github.damontecres.wholphin.ui.main.settings.MoveDirection
 import com.github.damontecres.wholphin.ui.onMain
 import com.github.damontecres.wholphin.ui.seekBack
@@ -25,6 +26,7 @@ import com.github.damontecres.wholphin.util.LoadingState
 import com.github.damontecres.wholphin.util.PlaybackItemState
 import com.github.damontecres.wholphin.util.TrackActivityPlaybackListener
 import com.github.damontecres.wholphin.util.WholphinDispatchers
+import com.github.damontecres.wholphin.util.profile.Codec
 import com.github.damontecres.wholphin.util.profile.supportedAudioCodecs
 import dagger.hilt.android.qualifiers.ApplicationContext
 import kotlinx.coroutines.CoroutineScope
@@ -44,6 +46,7 @@ import org.jellyfin.sdk.api.client.extensions.universalAudioApi
 import org.jellyfin.sdk.api.sockets.subscribe
 import org.jellyfin.sdk.model.api.BaseItemKind
 import org.jellyfin.sdk.model.api.ImageType
+import org.jellyfin.sdk.model.api.MediaStreamType
 import org.jellyfin.sdk.model.api.PlayMethod
 import org.jellyfin.sdk.model.api.PlaystateCommand
 import org.jellyfin.sdk.model.api.PlaystateMessage
@@ -72,6 +75,7 @@ class MusicService
         private val playerFactory: PlayerFactory,
         private val serverRepository: ServerRepository,
         private val imageUrlService: ImageUrlService,
+        private val userPreferencesService: UserPreferencesService,
     ) {
         private val _state = MutableStateFlow(MusicServiceState.EMPTY)
         val state: StateFlow<MusicServiceState> = _state
@@ -92,6 +96,11 @@ class MusicService
         private var activityTracker: TrackActivityPlaybackListener? = null
         private var websocketJob: Job? = null
 
+        private suspend fun preferAc3Surround() =
+            userPreferencesService
+                .getCurrent()
+                .appPreferences.experimentalPreferences.preferAc3Surround
+
         /**
          * Start music playback
          *
@@ -195,10 +204,11 @@ class MusicService
             shuffled: Boolean,
         ) {
             Timber.d("setQueue: %s items, shuffled=%s", items.size, shuffled)
+            val preferAc3Surround = preferAc3Surround()
             val mediaItems =
                 items
                     .filter { it.type == BaseItemKind.AUDIO }
-                    .map(::convert)
+                    .map { convert(it, preferAc3Surround) }
             withContext(WholphinDispatchers.Main) {
                 player.setMediaItems(mediaItems)
                 player.shuffleModeEnabled = shuffled
@@ -215,7 +225,8 @@ class MusicService
             index: Int? = null,
         ) {
             if (item.type == BaseItemKind.AUDIO) {
-                val mediaItem = convert(item)
+                val preferAc3Surround = preferAc3Surround()
+                val mediaItem = convert(item, preferAc3Surround)
                 withContext(WholphinDispatchers.Main) {
                     if (index != null) {
                         player.addMediaItem(index, mediaItem)
@@ -242,6 +253,7 @@ class MusicService
             list: BlockingList<BaseItem?>,
             startIndex: Int,
         ) = loading {
+            val preferAc3Surround = preferAc3Surround()
             var remaining = startIndex
             list.indices
                 .chunked(25)
@@ -252,7 +264,7 @@ class MusicService
                                 list
                                     .getBlocking(it)
                                     ?.takeIf { it.type == BaseItemKind.AUDIO }
-                                    ?.let(::convert)
+                                    ?.let { convert(it, preferAc3Surround) }
                             } else {
                                 Timber.v("Skipping $remaining")
                                 remaining--
@@ -268,12 +280,36 @@ class MusicService
         /**
          * Converts a [BaseItem] into a [MediaItem] setting an [AudioItem] as its tag
          */
-        private fun convert(audio: BaseItem): MediaItem {
+        private fun convert(
+            audio: BaseItem,
+            preferAc3Surround: Boolean,
+        ): MediaItem {
+            val needsAc3Transcode =
+                preferAc3Surround &&
+                    audio.data.mediaSources
+                        ?.firstOrNull()
+                        ?.mediaStreams
+                        ?.any { stream ->
+                            stream.type == MediaStreamType.AUDIO &&
+                                stream.channels.gt(2)
+                            stream.codec != Codec.Audio.AC3
+                        } == true
             val url =
-                api.universalAudioApi.getUniversalAudioStreamUrl(
-                    itemId = audio.id,
-                    container = audioFormats,
-                )
+                if (needsAc3Transcode) {
+                    api.universalAudioApi.getUniversalAudioStreamUrl(
+                        itemId = audio.id,
+                        container = listOf("mka"),
+                        transcodingContainer = "mka",
+                        maxAudioChannels = 6,
+                        transcodingAudioChannels = 6,
+                        audioCodec = Codec.Audio.AC3,
+                    )
+                } else {
+                    api.universalAudioApi.getUniversalAudioStreamUrl(
+                        itemId = audio.id,
+                        container = audioFormats,
+                    )
+                }
             Timber.i("url=%s", url)
             val imageUrl =
                 audio.data.albumId?.let { albumId ->
@@ -354,7 +390,7 @@ class MusicService
          * Play this item next after the current, ie add the item as the next index in the queue
          */
         suspend fun playNext(song: BaseItem) {
-            val mediaItem = convert(song)
+            val mediaItem = convert(song, preferAc3Surround())
             onMain {
                 player.addMediaItem(state.value.currentIndex + 1, mediaItem)
                 if (player.mediaItemCount == 1) {

app/src/main/java/com/github/damontecres/wholphin/ui/playback/PlaybackViewModel.kt

@@ -54,6 +54,7 @@ import com.github.damontecres.wholphin.services.ScreensaverService
 import com.github.damontecres.wholphin.services.StreamChoiceService
 import com.github.damontecres.wholphin.services.UserPreferencesService
 import com.github.damontecres.wholphin.ui.formatBitrate
+import com.github.damontecres.wholphin.ui.gt
 import com.github.damontecres.wholphin.ui.isNotNullOrBlank
 import com.github.damontecres.wholphin.ui.launchDefault
 import com.github.damontecres.wholphin.ui.launchIO
@@ -646,7 +647,7 @@ class PlaybackViewModel
                             deviceProfile =
                                 if (currentPlayer.value!!.backend == PlayerBackend.EXO_PLAYER) {
                                     deviceProfileService.getOrCreateDeviceProfile(
-                                        preferences.appPreferences.playbackPreferences,
+                                        preferences.appPreferences,
                                         serverRepository.currentServer?.serverVersion,
                                     )
                                 } else {
@@ -855,9 +856,24 @@ class PlaybackViewModel
                 // TODO there's probably no reason why we can't add external subtitles?
                 Timber.v("changeStreams direct play")
 
+                // TODO Better way to handle unsupported types in general is needed
+                // This is a workaround for switching to a non AC3 track when the user wants audio transcoded to AC3
+                if (preferences.appPreferences.experimentalPreferences.preferAc3Surround && audioIndex != null) {
+                    currentPlayback.mediaSourceInfo.mediaStreams
+                        .orEmpty()
+                        .firstOrNull { it.index == audioIndex }
+                        ?.let {
+                            if (it.channels.gt(2) && it.codec != Codec.Audio.AC3) {
+                                // User wants to transcode audio into AC3
+                                return@withContext false
+                            }
+                        }
+                }
+
                 val source = currentPlayback.mediaSourceInfo
                 val externalSubtitle = source.findExternalSubtitle(subtitleIndex)
 
+                // TODO there's probably no reason why we can't add external subtitles?
                 if (externalSubtitle == null) {
                     val result =
                         withContext(WholphinDispatchers.Main) {

app/src/main/java/com/github/damontecres/wholphin/ui/preferences/PreferencesContent.kt

@@ -621,7 +621,7 @@ fun PreferencesContent(
                                         value = value,
                                         onNavigate = viewModel.navigationManager::navigateTo,
                                         onValueChange = { newValue ->
-                                            val validation = pref.validate(newValue)
+                                            val validation = pref.validate(preferences, newValue)
                                             when (validation) {
                                                 is PreferenceValidation.Invalid -> {
                                                     // TODO?

app/src/main/java/com/github/damontecres/wholphin/ui/preferences/subtitle/SubtitlePreferencesContent.kt

@@ -162,7 +162,7 @@ fun SubtitlePreferencesContent(
                                         value = value,
                                         onNavigate = viewModel.navigationManager::navigateTo,
                                         onValueChange = { newValue ->
-                                            val validation = pref.validate(newValue)
+                                            val validation = pref.validate(preferences, newValue)
                                             when (validation) {
                                                 is PreferenceValidation.Invalid -> {
                                                     // TODO?

app/src/main/java/com/github/damontecres/wholphin/util/profile/DeviceProfileUtils.kt

@@ -71,6 +71,7 @@ fun createDeviceProfile(
     dolbyVisionELDirectPlay: Boolean,
     decodeAv1: Boolean,
     jellyfinTenEleven: Boolean,
+    preferAc3ForSurround: Boolean,
 ) = buildDeviceProfile {
     val allowedAudioCodecs =
         when {
@@ -132,31 +133,61 @@ fun createDeviceProfile(
 
     // / Transcoding profiles
     // Video
-    transcodingProfile {
-        type = DlnaProfileType.VIDEO
-        context = EncodingContext.STREAMING
+    if (preferAc3ForSurround) {
+        transcodingProfile {
+            type = DlnaProfileType.VIDEO
+            context = EncodingContext.STREAMING
 
-        container = Codec.Container.TS
-        protocol = MediaStreamProtocol.HLS
+            container = Codec.Container.TS
+            protocol = MediaStreamProtocol.HLS
 
-        if (supportsHevc) videoCodec(Codec.Video.HEVC)
-        videoCodec(Codec.Video.H264)
+            if (supportsHevc) videoCodec(Codec.Video.HEVC)
+            videoCodec(Codec.Video.H264)
 
-        audioCodec(*allowedAudioCodecs)
+            audioCodec(Codec.Audio.AC3)
 
-        copyTimestamps = false
-        enableSubtitlesInManifest = true
+            copyTimestamps = false
+            enableSubtitlesInManifest = true
+        }
+    } else {
+        transcodingProfile {
+            type = DlnaProfileType.VIDEO
+            context = EncodingContext.STREAMING
+
+            container = Codec.Container.TS
+            protocol = MediaStreamProtocol.HLS
+
+            if (supportsHevc) videoCodec(Codec.Video.HEVC)
+            videoCodec(Codec.Video.H264)
+
+            audioCodec(*allowedAudioCodecs)
+
+            copyTimestamps = false
+            enableSubtitlesInManifest = true
+        }
     }
 
     // Audio
-    transcodingProfile {
-        type = DlnaProfileType.AUDIO
-        context = EncodingContext.STREAMING
+    if (preferAc3ForSurround) {
+        transcodingProfile {
+            type = DlnaProfileType.AUDIO
+            context = EncodingContext.STREAMING
 
-        container = Codec.Container.TS
-        protocol = MediaStreamProtocol.HLS
+            container = Codec.Container.TS
+            protocol = MediaStreamProtocol.HLS
 
-        audioCodec(Codec.Audio.AAC)
+            audioCodec(Codec.Audio.AC3)
+        }
+    } else {
+        transcodingProfile {
+            type = DlnaProfileType.AUDIO
+            context = EncodingContext.STREAMING
+
+            container = Codec.Container.TS
+            protocol = MediaStreamProtocol.HLS
+
+            audioCodec(Codec.Audio.AAC)
+        }
     }
 
     // / Direct play profiles
@@ -530,6 +561,27 @@ fun createDeviceProfile(
         }
     }
 
+    if (preferAc3ForSurround) {
+        supportedAudioCodecs
+            .filterNot { it == Codec.Audio.AC3 }
+            .forEach { audioCodec ->
+                codecProfile {
+                    type = CodecType.VIDEO_AUDIO
+                    codec = audioCodec
+                    conditions {
+                        ProfileConditionValue.AUDIO_CHANNELS lowerThanOrEquals 2
+                    }
+                }
+                codecProfile {
+                    type = CodecType.AUDIO
+                    codec = audioCodec
+                    conditions {
+                        ProfileConditionValue.AUDIO_CHANNELS lowerThanOrEquals 2
+                    }
+                }
+            }
+    }
+
     // Audio channel profile
     codecProfile {
         type = CodecType.VIDEO_AUDIO

app/src/main/proto/WholphinDataStore.proto

@@ -215,6 +215,7 @@ message MusicPreferences {
 message ExperimentalPreferences {
   bool enabled = 1;
   bool video_tunneling_enabled = 2;
+  bool prefer_ac3_surround = 3;
 }
 
 message AppPreferences {

app/src/main/res/values/strings.xml

@@ -551,6 +551,8 @@
     <string name="display_presets">Display presets</string>
     <string name="display_presets_description">Built-in presets to quickly style all rows</string>
     <string name="customize_home_summary">Choose rows and images on the home page</string>
+    <string name="prefer_ac3_for_surround_summary"><![CDATA[Transcode non-stereo audio to AC3/Dolby Digital]]></string>
+    <string name="prefer_ac3_for_surround">Use AC3 for surround sound audio</string>
     <string name="start_after">Start after</string>
     <string name="animate">Animate</string>
     <string name="max_age_rating">Max age rating</string>