video: adaptive bitrate is an experimental feature, off until it's been tried in a car

gearslip/src/main/java/app/seb3thehacker/gearslip/GearslipRunner.kt

@@ -1094,6 +1094,8 @@ class GearslipRunner(
         smoothWindows = 0
         lastCut = null
         decoderBound = false
+        adaptiveVideo = CarSettings.experimentalFeaturesEnabled.value && CarSettings.adaptiveVideoEnabled.value
+        if (adaptiveVideo) log.i("video: adaptive bitrate on (experimental)")
         videoSource = VideoSource(
             width = width,
             height = height,
@@ -1407,6 +1409,8 @@ class GearslipRunner(
     private var smoothWindows = 0
     /** The bitrate and frame rate before the last cut, to see whether cutting helped. */
     private var lastCut: Pair<Int, Double>? = null
+    /** Experimental: read once per stream, so flipping the switch mid-drive changes nothing. */
+    @Volatile private var adaptiveVideo = false
     /** Set once a cut didn't help: this car's decoder, not the link, sets the pace. */
     private var decoderBound = false
 
@@ -1417,6 +1421,7 @@ class GearslipRunner(
      * where the stream started. A still screen (few frames, no waiting) changes nothing.
      */
     private fun adaptBitRate(fps: Double, waitedMs: Long) {
+        if (!adaptiveVideo) return
         val source = videoSource ?: return
         val target = videoFrameRate.toDouble()
         val behind = waitedMs > ADAPT_WINDOW_MS / 2 && fps < target * 0.8

gearslip/src/main/java/app/seb3thehacker/gearslip/car/CarSettings.kt

@@ -71,6 +71,7 @@ private const val KEY_LOCATION_WARNING = "car_location_warning"
     private const val KEY_EXPERIMENTAL_FEATURES = "car_experimental_features"
     private const val KEY_SYSTEM_SPEECH = "car_system_speech"
     private const val KEY_CAR_SENSORS = "car_sensors_enabled"
+    private const val KEY_ADAPTIVE_VIDEO = "adaptive_video_enabled"
     private const val KEY_SEEN_SAFETY_WARNING = "car_seen_safety_warning"
     private const val KEY_UNITS = "car_units"
     private const val KEY_NAV_BAR = "car_nav_bar"
@@ -113,6 +114,7 @@ private const val KEY_LOCATION_WARNING = "car_location_warning"
     private val experimentalFeaturesFlow = MutableStateFlow(false)
     private val systemSpeechFlow = MutableStateFlow(false)
     private val carSensorsFlow = MutableStateFlow(false)
+    private val adaptiveVideoFlow = MutableStateFlow(false)
     private val seenSafetyWarningFlow = MutableStateFlow(false)
     private val unitsFlow = MutableStateFlow(Units.AUTO)
 
@@ -272,6 +274,12 @@ private const val KEY_LOCATION_WARNING = "car_location_warning"
      */
     val carSensorsEnabled: StateFlow<Boolean> = carSensorsFlow
 
+    /**
+     * Video bitrate that backs off when the car, or the Wi-Fi to it, falls behind. Takes effect
+     * only while [experimentalFeaturesEnabled] is on too; untested in a car so far.
+     */
+    val adaptiveVideoEnabled: StateFlow<Boolean> = adaptiveVideoFlow
+
     /**
      * Whether the car screen's own "drive safely" warning has already been shown and dismissed
      * once, from this same install. Separate from the phone side's own compat/safety dialogs -
@@ -314,6 +322,7 @@ private const val KEY_LOCATION_WARNING = "car_location_warning"
         experimentalFeaturesFlow.value = AppSettings.getString(app, KEY_EXPERIMENTAL_FEATURES, "false") == "true"
         systemSpeechFlow.value = AppSettings.getString(app, KEY_SYSTEM_SPEECH, "false") == "true"
         carSensorsFlow.value = AppSettings.getString(app, KEY_CAR_SENSORS, "false") == "true"
+        adaptiveVideoFlow.value = AppSettings.getString(app, KEY_ADAPTIVE_VIDEO, "false") == "true"
         seenSafetyWarningFlow.value = AppSettings.getString(app, KEY_SEEN_SAFETY_WARNING, "false") == "true"
         unitsFlow.value = runCatching {
             Units.valueOf(AppSettings.getString(app, KEY_UNITS, Units.AUTO.name))
@@ -416,6 +425,11 @@ private const val KEY_LOCATION_WARNING = "car_location_warning"
         AppSettings.putString(app, KEY_SYSTEM_SPEECH, on.toString())
     }
 
+    fun setAdaptiveVideoEnabled(on: Boolean) {
+        adaptiveVideoFlow.value = on
+        AppSettings.putString(app, KEY_ADAPTIVE_VIDEO, on.toString())
+    }
+
     fun setCarSensorsEnabled(on: Boolean) {
         carSensorsFlow.value = on
         AppSettings.putString(app, KEY_CAR_SENSORS, on.toString())

gearslip/src/main/java/app/seb3thehacker/gearslip/car/CarSettingsScreen.kt

@@ -69,6 +69,7 @@ fun CarSettingsScreen() {
     val uiTheme by CarSettings.uiTheme.collectAsState()
     val experimentalFeatures by CarSettings.experimentalFeaturesEnabled.collectAsState()
     val carSensors by CarSettings.carSensorsEnabled.collectAsState()
+    val adaptiveVideo by CarSettings.adaptiveVideoEnabled.collectAsState()
     val systemSpeech by CarSettings.systemSpeech.collectAsState()
     val display by CarEnvironment.display.collectAsState()
     val vehicle by CarEnvironment.vehicle.collectAsState()
@@ -278,7 +279,7 @@ fun CarSettingsScreen() {
         }
 
         if (experimentalFeatures) item {
-            ExperimentalFeaturesList(carSensors)
+            ExperimentalFeaturesList(carSensors, adaptiveVideo)
         }
 
         item {
@@ -368,7 +369,7 @@ private fun <T> ChoiceButtons(options: List<Pair<T, String>>, selected: T, onSel
  * so the list reads fine whether there's one entry or several.
  */
 @Composable
-private fun ExperimentalFeaturesList(carSensors: Boolean) {
+private fun ExperimentalFeaturesList(carSensors: Boolean, adaptiveVideo: Boolean) {
     Column(
         Modifier.fillMaxWidth(),
         verticalArrangement = Arrangement.spacedBy(10.dp),
@@ -381,6 +382,12 @@ private fun ExperimentalFeaturesList(carSensors: Boolean) {
                 "guess, not a fact, until you've watched one change for yourself.",
             checked = carSensors,
         ) { CarSettings.setCarSensorsEnabled(it) }
+        ExperimentalFeatureRow(
+            title = "Adaptive video quality",
+            description = "Lowers the picture's quality when the car, or its Wi-Fi, can't keep " +
+                "up, and raises it again once it can. Takes effect on the next connection.",
+            checked = adaptiveVideo,
+        ) { CarSettings.setAdaptiveVideoEnabled(it) }
     }
 }