fix: add audio focus management and fix service stop lifecycle

The app never requested audio focus, so it played over other apps and
ignored phone calls, music players, etc. Now requests AUDIOFOCUS_GAIN
before playback and handles LOSS (stop), LOSS_TRANSIENT (mute),
LOSS_TRANSIENT_CAN_DUCK (lower volume to 20%), and GAIN (restore).

Also fixes several service lifecycle issues:
- Add stopForeground(STOP_FOREGROUND_REMOVE) in cleanupResources so
  the notification is dismissed when playback ends
- Add onTaskRemoved override to stop playback when the app is swiped
  from recents (unless stayConnected is enabled)
- Fix wake lock leak by calling releaseLocks() before acquireLocks()
  to prevent accumulating unreleased locks across pause/resume cycles
- Add AudioEngine.setVolume() for ducking support

Made-with: Cursor

app/build.gradle.kts

@@ -18,7 +18,7 @@ android {
         minSdk = 28
         targetSdk = 35
         versionCode = 1
-        versionName = "1.0"
+        versionName = "1.1"
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
     }
 

app/src/main/java/xyz/cottongin/radio247/audio/AudioEngine.kt

@@ -39,6 +39,10 @@ class AudioEngine(
     @Volatile
     private var timedStream: TimedInputStream? = null
     private var presentationTimeUs = 0L
+    private var frameDurationUs = 0L
+    private var framesPerSecond = 0
+    private var configuredSampleRate = 0
+    private var configuredChannelCount = 0
 
     fun start() {
         Log.i(TAG, "start() url=$url")
@@ -80,6 +84,10 @@ class AudioEngine(
         pendingSkips.incrementAndGet()
     }
 
+    fun setVolume(gain: Float) {
+        currentAudioTrack?.setVolume(gain.coerceIn(0f, 1f))
+    }
+
     private fun runPipeline() {
         Log.i(TAG, "runPipeline() connecting to $url")
         val connection = StreamConnection(url)
@@ -89,12 +97,28 @@ class AudioEngine(
         val tStream = TimedInputStream(connection.inputStream!!)
         timedStream = tStream
 
-        val sampleRate = 44100
-        val channelConfig = AudioFormat.CHANNEL_OUT_STEREO
-        val encoding = AudioFormat.ENCODING_PCM_16BIT
-        val minBuf = AudioTrack.getMinBufferSize(sampleRate, channelConfig, encoding)
+        var audioTrack: AudioTrack? = null
+        var codec: MediaCodec? = null
+        var ringBuffer: RingBuffer? = null
 
-        val audioTrack = AudioTrack.Builder()
+        _events.tryEmit(AudioEngineEvent.Started)
+        connection.streamInfo?.let { _events.tryEmit(AudioEngineEvent.StreamInfoReceived(it)) }
+
+        fun initAudioOutput(format: Mp3FrameInfo) {
+            frameDurationUs = format.samplesPerFrame.toLong() * 1_000_000 / format.sampleRate
+            framesPerSecond = (1_000_000L / frameDurationUs).toInt()
+            configuredSampleRate = format.sampleRate
+            configuredChannelCount = format.channelCount
+
+            Log.i(TAG, "Detected format: ${format.sampleRate} Hz, ${format.channelCount}ch, " +
+                "${format.samplesPerFrame} samples/frame, frameDuration=${frameDurationUs}us")
+
+            val channelConfig = if (format.channelCount == 1)
+                AudioFormat.CHANNEL_OUT_MONO else AudioFormat.CHANNEL_OUT_STEREO
+            val encoding = AudioFormat.ENCODING_PCM_16BIT
+            val minBuf = AudioTrack.getMinBufferSize(format.sampleRate, channelConfig, encoding)
+
+            audioTrack = AudioTrack.Builder()
                 .setAudioAttributes(
                     AudioAttributes.Builder()
                         .setUsage(AudioAttributes.USAGE_MEDIA)
@@ -103,7 +127,7 @@ class AudioEngine(
                 )
                 .setAudioFormat(
                     AudioFormat.Builder()
-                    .setSampleRate(sampleRate)
+                        .setSampleRate(format.sampleRate)
                         .setChannelMask(channelConfig)
                         .setEncoding(encoding)
                         .build()
@@ -113,28 +137,38 @@ class AudioEngine(
                 .setTransferMode(AudioTrack.MODE_STREAM)
                 .build()
 
-        val codec = MediaCodec.createDecoderByType("audio/mpeg")
-        val format = MediaFormat.createAudioFormat("audio/mpeg", sampleRate, 2)
-        codec.configure(format, null, null, 0)
-        codec.start()
-        audioTrack.play()
+            codec = MediaCodec.createDecoderByType("audio/mpeg")
+            val mediaFormat = MediaFormat.createAudioFormat(
+                "audio/mpeg", format.sampleRate, format.channelCount
+            )
+            codec!!.configure(mediaFormat, null, null, 0)
+            codec!!.start()
+            audioTrack!!.play()
 
             currentAudioTrack = audioTrack
             currentCodec = codec
 
-        _events.tryEmit(AudioEngineEvent.Started)
-        connection.streamInfo?.let { _events.tryEmit(AudioEngineEvent.StreamInfoReceived(it)) }
+            val frameDurationMs = (frameDurationUs / 1000).toInt().coerceAtLeast(1)
+            val bufferFrames = if (bufferMs > 0) (bufferMs / frameDurationMs).coerceAtLeast(1) else 0
 
-        try {
-            val bufferFrames = if (bufferMs > 0) (bufferMs / 26).coerceAtLeast(1) else 0
-
-            val ringBuffer = RingBuffer(bufferFrames) { mp3Frame ->
-                decodeToPcm(codec, mp3Frame, audioTrack)
+            ringBuffer = RingBuffer(bufferFrames) { mp3Frame ->
+                decodeToPcm(codec!!, mp3Frame, audioTrack!!)
             }
             currentRingBuffer = ringBuffer
 
+            _events.tryEmit(AudioEngineEvent.AudioFormatDetected(
+                format.sampleRate, format.channelCount
+            ))
+        }
+
+        try {
             val frameSync = Mp3FrameSync { mp3Frame ->
-                ringBuffer.write(mp3Frame)
+                if (audioTrack == null) {
+                    val format = Mp3FrameSync.parseFrameInfo(mp3Frame)
+                        ?: Mp3FrameInfo(44100, 2, 1152)
+                    initAudioOutput(format)
+                }
+                ringBuffer!!.write(mp3Frame)
             }
 
             val icyParser = IcyParser(
@@ -146,7 +180,7 @@ class AudioEngine(
 
             icyParser.readAll()
 
-            ringBuffer.flush()
+            ringBuffer?.flush()
             frameSync.flush()
             _events.tryEmit(AudioEngineEvent.Error(EngineError.StreamEnded))
         } finally {
@@ -154,10 +188,10 @@ class AudioEngine(
             currentRingBuffer = null
             currentCodec = null
             currentAudioTrack = null
-            codec.stop()
-            codec.release()
-            audioTrack.stop()
-            audioTrack.release()
+            codec?.stop()
+            codec?.release()
+            audioTrack?.stop()
+            audioTrack?.release()
             connection.close()
         }
     }
@@ -166,8 +200,9 @@ class AudioEngine(
         if (catchingUp) {
             catchupFramesSkipped++
             val lastReadMs = timedStream?.lastReadDurationMs ?: 0L
-            if (lastReadMs >= CATCHUP_THRESHOLD_MS || catchupFramesSkipped >= MAX_CATCHUP_FRAMES) {
-                if (catchupFramesSkipped >= MAX_CATCHUP_FRAMES) {
+            val maxCatchupFrames = framesPerSecond * 5
+            if (lastReadMs >= CATCHUP_THRESHOLD_MS || catchupFramesSkipped >= maxCatchupFrames) {
+                if (catchupFramesSkipped >= maxCatchupFrames) {
                     Log.w(TAG, "Catchup cap reached after $catchupFramesSkipped frames, starting playback")
                 }
                 catchingUp = false
@@ -178,7 +213,7 @@ class AudioEngine(
 
         val skips = pendingSkips.getAndSet(0)
         if (skips > 0) {
-            val framesToDrop = skips * FRAMES_PER_SECOND
+            val framesToDrop = skips * framesPerSecond
             currentRingBuffer?.drop(framesToDrop)
             audioTrack.pause()
             audioTrack.flush()
@@ -194,12 +229,24 @@ class AudioEngine(
             inBuf.clear()
             inBuf.put(mp3Frame)
             codec.queueInputBuffer(inIdx, 0, mp3Frame.size, presentationTimeUs, 0)
-            presentationTimeUs += FRAME_DURATION_US
+            presentationTimeUs += frameDurationUs
         }
 
         val bufferInfo = MediaCodec.BufferInfo()
         var outIdx = codec.dequeueOutputBuffer(bufferInfo, 1000)
         while (outIdx >= 0) {
+            if (outIdx == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
+                val outFormat = codec.outputFormat
+                val outRate = outFormat.getInteger(MediaFormat.KEY_SAMPLE_RATE)
+                val outChannels = outFormat.getInteger(MediaFormat.KEY_CHANNEL_COUNT)
+                Log.i(TAG, "Decoder output format: ${outRate} Hz, ${outChannels}ch")
+                if (outRate != configuredSampleRate || outChannels != configuredChannelCount) {
+                    Log.w(TAG, "Decoder output ($outRate Hz, ${outChannels}ch) differs from " +
+                        "AudioTrack ($configuredSampleRate Hz, ${configuredChannelCount}ch)")
+                }
+                outIdx = codec.dequeueOutputBuffer(bufferInfo, 0)
+                continue
+            }
             val outBuf = codec.getOutputBuffer(outIdx)!!
             outBuf.position(bufferInfo.offset)
             outBuf.limit(bufferInfo.offset + bufferInfo.size)
@@ -222,10 +269,7 @@ class AudioEngine(
 
     companion object {
         private const val TAG = "AudioEngine"
-        private const val FRAMES_PER_SECOND = 38
         private const val CATCHUP_THRESHOLD_MS = 30L
-        private const val MAX_CATCHUP_FRAMES = FRAMES_PER_SECOND * 5 // 5 seconds max skip
-        private const val FRAME_DURATION_US = 26_122L // 1152 samples at 44100 Hz
     }
 }
 

app/src/main/java/xyz/cottongin/radio247/audio/AudioEngineEvent.kt

@@ -3,6 +3,7 @@ package xyz.cottongin.radio247.audio
 sealed interface AudioEngineEvent {
     data class MetadataChanged(val metadata: IcyMetadata) : AudioEngineEvent
     data class StreamInfoReceived(val streamInfo: StreamInfo) : AudioEngineEvent
+    data class AudioFormatDetected(val sampleRate: Int, val channelCount: Int) : AudioEngineEvent
     data class Error(val cause: EngineError) : AudioEngineEvent
     data object Started : AudioEngineEvent
     data object Stopped : AudioEngineEvent

app/src/main/java/xyz/cottongin/radio247/audio/Mp3FrameSync.kt

@@ -2,8 +2,17 @@ package xyz.cottongin.radio247.audio
 
 import java.io.ByteArrayOutputStream
 
+data class Mp3FrameInfo(
+    val sampleRate: Int,
+    val channelCount: Int,
+    val samplesPerFrame: Int
+)
+
 private data class ParsedHeader(
-    val frameSize: Int
+    val frameSize: Int,
+    val sampleRate: Int,
+    val channelCount: Int,
+    val samplesPerFrame: Int
 )
 
 // MPEG1 Layer 3 bitrates (kbps), index 0 and 15 invalid
@@ -22,6 +31,9 @@ class Mp3FrameSync(
 ) {
     private val buffer = ByteArrayOutputStream()
 
+    var detectedFormat: Mp3FrameInfo? = null
+        private set
+
     fun feed(data: ByteArray, offset: Int = 0, length: Int = data.size) {
         buffer.write(data, offset, length)
         processBuffer()
@@ -60,6 +72,14 @@ class Mp3FrameSync(
                 }
             }
 
+            if (detectedFormat == null) {
+                detectedFormat = Mp3FrameInfo(
+                    sampleRate = header.sampleRate,
+                    channelCount = header.channelCount,
+                    samplesPerFrame = header.samplesPerFrame
+                )
+            }
+
             val frame = bytes.copyOfRange(pos, pos + frameSize)
             onFrame(frame)
             pos += frameSize
@@ -77,6 +97,46 @@ class Mp3FrameSync(
         return b0 == 0xFF && (b1 and 0xE0) == 0xE0
     }
 
+    companion object {
+        fun parseFrameInfo(frame: ByteArray): Mp3FrameInfo? {
+            if (frame.size < 4) return null
+            val b0 = frame[0].toInt() and 0xFF
+            val b1 = frame[1].toInt() and 0xFF
+            if (b0 != 0xFF || (b1 and 0xE0) != 0xE0) return null
+
+            val b2 = frame[2].toInt() and 0xFF
+            val b3 = frame[3].toInt() and 0xFF
+
+            val header = (b0 shl 24) or (b1 shl 16) or (b2 shl 8) or b3
+            val mpegVersion = (header ushr 19) and 0x03
+            val layer = (header ushr 17) and 0x03
+            if (mpegVersion == 1 || layer == 0) return null
+
+            val sampleRateIndex = (b2 shr 2) and 0x03
+            if (sampleRateIndex == 3) return null
+
+            val sampleRate = when (mpegVersion) {
+                3 -> MPEG1_SAMPLE_RATE[sampleRateIndex]
+                2 -> MPEG2_SAMPLE_RATE[sampleRateIndex]
+                0 -> MPEG25_SAMPLE_RATE[sampleRateIndex]
+                else -> return null
+            }
+            if (sampleRate == 0) return null
+
+            val channelMode = (b3 shr 6) and 0x03
+            val channelCount = if (channelMode == 3) 1 else 2
+
+            val samplesPerFrame = when (layer) {
+                3 -> 384                                       // Layer I
+                2 -> 1152                                      // Layer II
+                1 -> if (mpegVersion == 3) 1152 else 576       // Layer III
+                else -> return null
+            }
+
+            return Mp3FrameInfo(sampleRate, channelCount, samplesPerFrame)
+        }
+    }
+
     private fun parseHeader(bytes: ByteArray, pos: Int): ParsedHeader? {
         if (pos + 4 > bytes.size) return null
         val header = ((bytes[pos].toInt() and 0xFF) shl 24) or
@@ -84,8 +144,8 @@ class Mp3FrameSync(
             ((bytes[pos + 2].toInt() and 0xFF) shl 8) or
             (bytes[pos + 3].toInt() and 0xFF)
 
-        val b1 = bytes[pos + 1].toInt() and 0xFF
         val b2 = bytes[pos + 2].toInt() and 0xFF
+        val b3 = bytes[pos + 3].toInt() and 0xFF
 
         val mpegVersion = (header ushr 19) and 0x03
         val layer = (header ushr 17) and 0x03
@@ -114,6 +174,16 @@ class Mp3FrameSync(
         }
         if (sampleRate == 0) return null
 
+        val channelMode = (b3 shr 6) and 0x03
+        val channelCount = if (channelMode == 3) 1 else 2
+
+        val samplesPerFrame = when (layer) {
+            3 -> 384                                       // Layer I
+            2 -> 1152                                      // Layer II
+            1 -> if (mpegVersion == 3) 1152 else 576       // Layer III
+            else -> return null
+        }
+
         val frameSize = when (layer) {
             1 -> { // Layer III
                 when (mpegVersion) {
@@ -134,6 +204,6 @@ class Mp3FrameSync(
         }
 
         if (frameSize <= 0) return null
-        return ParsedHeader(frameSize)
+        return ParsedHeader(frameSize, sampleRate, channelCount, samplesPerFrame)
     }
 }

app/src/main/java/xyz/cottongin/radio247/audio/StreamConnection.kt

@@ -13,7 +13,9 @@ class ConnectionFailed(message: String, cause: Throwable? = null) : Exception(me
 data class StreamInfo(
     val bitrate: Int?,
     val ssl: Boolean,
-    val contentType: String?
+    val contentType: String?,
+    val sampleRate: Int? = null,
+    val channelCount: Int? = null
 )
 
 class StreamConnection(private val url: String) {

app/src/main/java/xyz/cottongin/radio247/service/RadioPlaybackService.kt

@@ -5,6 +5,9 @@ import android.app.NotificationManager
 import android.app.PendingIntent
 import android.content.Context
 import android.content.Intent
+import android.media.AudioAttributes
+import android.media.AudioFocusRequest
+import android.media.AudioManager
 import android.net.ConnectivityManager
 import android.net.Network
 import android.net.NetworkCapabilities
@@ -31,6 +34,7 @@ import xyz.cottongin.radio247.audio.AudioEngine
 import xyz.cottongin.radio247.audio.AudioEngineEvent
 import xyz.cottongin.radio247.audio.EngineError
 import xyz.cottongin.radio247.audio.IcyMetadata
+import xyz.cottongin.radio247.audio.StreamInfo
 import xyz.cottongin.radio247.data.db.ConnectionSpanDao
 import xyz.cottongin.radio247.data.db.ListeningSessionDao
 import xyz.cottongin.radio247.data.db.MetadataSnapshotDao
@@ -113,6 +117,34 @@ class RadioPlaybackService : MediaLibraryService() {
 
     private var playJob: Job? = null
 
+    private var audioManager: AudioManager? = null
+    private var focusRequest: AudioFocusRequest? = null
+    @Volatile
+    private var focusLostTransiently = false
+
+    private val focusChangeListener = AudioManager.OnAudioFocusChangeListener { focusChange ->
+        when (focusChange) {
+            AudioManager.AUDIOFOCUS_LOSS -> {
+                Log.i(TAG, "Audio focus LOSS — stopping")
+                handleStop()
+            }
+            AudioManager.AUDIOFOCUS_LOSS_TRANSIENT -> {
+                Log.i(TAG, "Audio focus LOSS_TRANSIENT — pausing")
+                focusLostTransiently = true
+                engine?.setVolume(0f)
+            }
+            AudioManager.AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK -> {
+                Log.i(TAG, "Audio focus LOSS_TRANSIENT_CAN_DUCK — ducking")
+                engine?.setVolume(0.2f)
+            }
+            AudioManager.AUDIOFOCUS_GAIN -> {
+                Log.i(TAG, "Audio focus GAIN — restoring")
+                focusLostTransiently = false
+                engine?.setVolume(1f)
+            }
+        }
+    }
+
     private fun transition(newState: PlaybackState) {
         Log.i(TAG, "transition → $newState")
         controller.updateState(newState)
@@ -126,6 +158,7 @@ class RadioPlaybackService : MediaLibraryService() {
 
     override fun onCreate() {
         super.onCreate()
+        audioManager = getSystemService(Context.AUDIO_SERVICE) as AudioManager
         ensureForegroundChannel()
         ensureMediaSession()
     }
@@ -137,6 +170,41 @@ class RadioPlaybackService : MediaLibraryService() {
         getSystemService(NotificationManager::class.java).createNotificationChannel(channel)
     }
 
+    override fun onTaskRemoved(rootIntent: Intent?) {
+        if (!stayConnected) {
+            Log.i(TAG, "onTaskRemoved — stopping (stayConnected=false)")
+            handleStop()
+            cleanupResources()
+            stopSelf()
+        }
+        super.onTaskRemoved(rootIntent)
+    }
+
+    private fun requestAudioFocus(): Boolean {
+        val attrs = AudioAttributes.Builder()
+            .setUsage(AudioAttributes.USAGE_MEDIA)
+            .setContentType(AudioAttributes.CONTENT_TYPE_MUSIC)
+            .build()
+        val request = AudioFocusRequest.Builder(AudioManager.AUDIOFOCUS_GAIN)
+            .setAudioAttributes(attrs)
+            .setOnAudioFocusChangeListener(focusChangeListener)
+            .setWillPauseWhenDucked(false)
+            .build()
+        focusRequest = request
+        val result = audioManager?.requestAudioFocus(request)
+        val granted = result == AudioManager.AUDIOFOCUS_REQUEST_GRANTED
+        Log.i(TAG, "requestAudioFocus: granted=$granted")
+        return granted
+    }
+
+    private fun abandonAudioFocus() {
+        focusRequest?.let {
+            audioManager?.abandonAudioFocusRequest(it)
+            focusRequest = null
+        }
+        focusLostTransiently = false
+    }
+
     private fun postPlaceholderForeground() {
         val notification = NotificationCompat.Builder(this, FOREGROUND_CHANNEL_ID)
             .setSmallIcon(R.drawable.ic_notification)
@@ -198,6 +266,8 @@ class RadioPlaybackService : MediaLibraryService() {
     }
 
     private fun cleanupResources() {
+        stopForeground(STOP_FOREGROUND_REMOVE)
+        abandonAudioFocus()
         engine?.stop()
         engine = null
         releaseLocks()
@@ -224,6 +294,14 @@ class RadioPlaybackService : MediaLibraryService() {
         playerAdapter?.updateStation(station)
         playerAdapter?.updatePlaybackState(PlaybackState.Connecting(station))
 
+        if (!requestAudioFocus()) {
+            Log.w(TAG, "Audio focus denied — not starting playback")
+            transition(PlaybackState.Idle)
+            cleanupResources()
+            stopSelf()
+            return
+        }
+
         try {
             val urls = app.streamResolver.resolveUrls(station)
             Log.i(TAG, "handlePlay resolved ${urls.size} URLs for '${station.name}': ${urls.take(3)}")
@@ -275,6 +353,7 @@ class RadioPlaybackService : MediaLibraryService() {
     }
 
     private fun acquireLocks() {
+        releaseLocks()
         val pm = getSystemService(Context.POWER_SERVICE) as PowerManager
         wakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "Radio247:Playback").apply {
             acquire(10 * 60 * 1000L)
@@ -577,6 +656,18 @@ class RadioPlaybackService : MediaLibraryService() {
                             transition(playingState.copy(streamInfo = event.streamInfo))
                         }
                     }
+                    is AudioEngineEvent.AudioFormatDetected -> {
+                        val playingState = controller.state.value
+                        if (playingState is PlaybackState.Playing) {
+                            val updated = (playingState.streamInfo ?: StreamInfo(
+                                bitrate = null, ssl = false, contentType = null
+                            )).copy(
+                                sampleRate = event.sampleRate,
+                                channelCount = event.channelCount
+                            )
+                            transition(playingState.copy(streamInfo = updated))
+                        }
+                    }
                     is AudioEngineEvent.Error -> {
                         engine?.stop()
                         engine = null

app/src/main/java/xyz/cottongin/radio247/ui/screens/nowplaying/NowPlayingScreen.kt

@@ -668,6 +668,24 @@ private fun QualityBadge(
             }
             Text(text = codec, style = badgeStyle, color = dim)
         }
+        val hasPrevBadge = streamInfo.bitrate != null || codec != null
+        if (streamInfo.sampleRate != null) {
+            if (hasPrevBadge) {
+                Text(text = " \u00B7 ", style = badgeStyle, color = dim)
+            }
+            val rateLabel = when (streamInfo.sampleRate) {
+                44100 -> "44.1 kHz"
+                22050 -> "22.05 kHz"
+                48000 -> "48 kHz"
+                32000 -> "32 kHz"
+                24000 -> "24 kHz"
+                16000 -> "16 kHz"
+                11025 -> "11.025 kHz"
+                else -> "${streamInfo.sampleRate} Hz"
+            }
+            val channelLabel = if (streamInfo.channelCount == 1) "Mono" else "Stereo"
+            Text(text = "$rateLabel $channelLabel", style = badgeStyle, color = dim)
+        }
         if (streamInfo.ssl) {
             Spacer(modifier = Modifier.width(4.dp))
             Icon(

app/src/test/java/xyz/cottongin/radio247/audio/AudioEngineVolumeTest.kt

@@ -0,0 +1,27 @@
+package xyz.cottongin.radio247.audio
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+class AudioEngineVolumeTest {
+
+    @Test
+    fun setVolumeDoesNotCrashWhenNoTrack() {
+        val engine = AudioEngine("http://example.com/stream")
+        engine.setVolume(0.5f)
+        engine.setVolume(0f)
+        engine.setVolume(1f)
+    }
+
+    @Test
+    fun volumeClampValues() {
+        val clamped1 = (-0.5f).coerceIn(0f, 1f)
+        assertEquals(0f, clamped1, 0.001f)
+
+        val clamped2 = (1.5f).coerceIn(0f, 1f)
+        assertEquals(1f, clamped2, 0.001f)
+
+        val clamped3 = (0.2f).coerceIn(0f, 1f)
+        assertEquals(0.2f, clamped3, 0.001f)
+    }
+}

app/src/test/java/xyz/cottongin/radio247/audio/Mp3FrameSyncTest.kt

@@ -2,38 +2,43 @@ package xyz.cottongin.radio247.audio
 
 import org.junit.Assert.assertArrayEquals
 import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertNull
 import org.junit.Test
 
 class Mp3FrameSyncTest {
 
     /**
-     * Build MPEG1 Layer3 header: 0xFF, (0xE0 | version<<3 | layer<<1 | crc), byte2, 0x00
-     * MPEG1=11, Layer3=01, noCRC=1. 0xFA has Layer=01 (III). Bitrate in 15-12, sample in 11-10, padding in bit 9.
+     * Build MPEG1 Layer3 header: 0xFF, (0xE0 | version<<3 | layer<<1 | crc), byte2, byte3
+     * MPEG1=11, Layer3=01, noCRC=1. Bitrate in 15-12, sample in 11-10, padding in bit 9.
+     * channelMode: 0=Stereo, 1=JointStereo, 2=DualChannel, 3=Mono
      */
     private fun buildMpeg1Layer3Header(
         bitrateIndex: Int,
         sampleRateIndex: Int,
-        padding: Boolean
+        padding: Boolean,
+        channelMode: Int = 0
     ): ByteArray {
-        // Byte 0: sync. Byte 1: 0xFB = sync + MPEG1(11) + LayerIII(01) + noCRC(1)
         val byte1 = 0xFB.toByte()
-        // Byte 2: bitrate(4) | sample(2) | padding(1) | private(1)
         val byte2 = ((bitrateIndex shl 4) or (sampleRateIndex shl 2) or (if (padding) 2 else 0)).toByte()
-        return byteArrayOf(0xFF.toByte(), byte1, byte2, 0x00)
+        val byte3 = (channelMode shl 6).toByte()
+        return byteArrayOf(0xFF.toByte(), byte1, byte2, byte3)
     }
 
     /**
      * Build MPEG2 Layer3 header. MPEG2 = 10, Layer3 = 01.
+     * channelMode: 0=Stereo, 1=JointStereo, 2=DualChannel, 3=Mono
      */
     private fun buildMpeg2Layer3Header(
         bitrateIndex: Int,
         sampleRateIndex: Int,
-        padding: Boolean
+        padding: Boolean,
+        channelMode: Int = 0
     ): ByteArray {
-        // Byte 1: 0xF3 = sync + MPEG2(10) + LayerIII(01) + noCRC(1)
         val byte1 = 0xF3.toByte()
         val byte2 = ((bitrateIndex shl 4) or (sampleRateIndex shl 2) or (if (padding) 2 else 0)).toByte()
-        return byteArrayOf(0xFF.toByte(), byte1, byte2, 0x00)
+        val byte3 = (channelMode shl 6).toByte()
+        return byteArrayOf(0xFF.toByte(), byte1, byte2, byte3)
     }
 
     private fun buildFrame(header: ByteArray, bodySize: Int): ByteArray {
@@ -207,4 +212,119 @@ class Mp3FrameSyncTest {
         assertEquals(2, frames.size)
         assertEquals(expectedSize, frames[0].size)
     }
+
+    @Test
+    fun detectedFormatForMpeg1Stereo44100() {
+        val header = buildMpeg1Layer3Header(9, 0, false, channelMode = 1)
+        val frame = buildFrame(header, 417 - 4)
+        val nextFrame = buildFrame(header, 417 - 4)
+
+        val sync = Mp3FrameSync { }
+        sync.feed(frame + nextFrame)
+
+        val format = sync.detectedFormat
+        assertNotNull(format)
+        assertEquals(44100, format!!.sampleRate)
+        assertEquals(2, format.channelCount)
+        assertEquals(1152, format.samplesPerFrame)
+    }
+
+    @Test
+    fun detectedFormatForMpeg1Mono48000() {
+        // sampleRateIndex=1 → 48000 Hz, channelMode=3 → Mono
+        val header = buildMpeg1Layer3Header(9, 1, false, channelMode = 3)
+        val expectedSize = 144 * 128 * 1000 / 48000 // = 384
+        val frame = buildFrame(header, expectedSize - 4)
+        val nextFrame = buildFrame(header, expectedSize - 4)
+
+        val sync = Mp3FrameSync { }
+        sync.feed(frame + nextFrame)
+
+        val format = sync.detectedFormat
+        assertNotNull(format)
+        assertEquals(48000, format!!.sampleRate)
+        assertEquals(1, format.channelCount)
+        assertEquals(1152, format.samplesPerFrame)
+    }
+
+    @Test
+    fun detectedFormatForMpeg2Mono22050() {
+        // MPEG2 Layer3, 128kbps (index 12), 22050 Hz (index 0), mono
+        val header = buildMpeg2Layer3Header(12, 0, false, channelMode = 3)
+        val expectedSize = 72 * 128 * 1000 / 22050 // = 417
+        val frame = buildFrame(header, expectedSize - 4)
+        val nextFrame = buildFrame(header, expectedSize - 4)
+
+        val sync = Mp3FrameSync { }
+        sync.feed(frame + nextFrame)
+
+        val format = sync.detectedFormat
+        assertNotNull(format)
+        assertEquals(22050, format!!.sampleRate)
+        assertEquals(1, format.channelCount)
+        assertEquals(576, format.samplesPerFrame)
+    }
+
+    @Test
+    fun detectedFormatIsNullBeforeFirstFrame() {
+        val sync = Mp3FrameSync { }
+        assertNull(sync.detectedFormat)
+    }
+
+    @Test
+    fun parseFrameInfoMpeg1Stereo44100() {
+        val header = buildMpeg1Layer3Header(9, 0, false, channelMode = 0)
+        val frame = buildFrame(header, 417 - 4)
+
+        val info = Mp3FrameSync.parseFrameInfo(frame)
+        assertNotNull(info)
+        assertEquals(44100, info!!.sampleRate)
+        assertEquals(2, info.channelCount)
+        assertEquals(1152, info.samplesPerFrame)
+    }
+
+    @Test
+    fun parseFrameInfoMpeg2Mono22050() {
+        val header = buildMpeg2Layer3Header(12, 0, false, channelMode = 3)
+        val frame = buildFrame(header, 417 - 4)
+
+        val info = Mp3FrameSync.parseFrameInfo(frame)
+        assertNotNull(info)
+        assertEquals(22050, info!!.sampleRate)
+        assertEquals(1, info.channelCount)
+        assertEquals(576, info.samplesPerFrame)
+    }
+
+    @Test
+    fun parseFrameInfoReturnsNullForGarbage() {
+        val garbage = ByteArray(100) { 0x42 }
+        assertNull(Mp3FrameSync.parseFrameInfo(garbage))
+    }
+
+    @Test
+    fun parseFrameInfoReturnsNullForTooShort() {
+        assertNull(Mp3FrameSync.parseFrameInfo(byteArrayOf(0xFF.toByte(), 0xFB.toByte())))
+    }
+
+    @Test
+    fun parseFrameInfoJointStereoIsTwoChannels() {
+        // Joint stereo (channelMode=1) should report 2 channels
+        val header = buildMpeg1Layer3Header(9, 0, false, channelMode = 1)
+        val frame = buildFrame(header, 417 - 4)
+
+        val info = Mp3FrameSync.parseFrameInfo(frame)
+        assertNotNull(info)
+        assertEquals(2, info!!.channelCount)
+    }
+
+    @Test
+    fun parseFrameInfoDualChannelIsTwoChannels() {
+        // Dual channel (channelMode=2) should report 2 channels
+        val header = buildMpeg1Layer3Header(9, 0, false, channelMode = 2)
+        val frame = buildFrame(header, 417 - 4)
+
+        val info = Mp3FrameSync.parseFrameInfo(frame)
+        assertNotNull(info)
+        assertEquals(2, info!!.channelCount)
+    }
 }

app/src/test/java/xyz/cottongin/radio247/service/PlaybackStateMachineTest.kt

@@ -160,4 +160,29 @@ class PlaybackStateMachineTest {
             assertTrue("Should be Idle after stop from $state", stateFlow.value is PlaybackState.Idle)
         }
     }
+
+    @Test
+    fun `audio focus loss during playback transitions to idle`() {
+        val now = System.currentTimeMillis()
+        stateFlow.value = PlaybackState.Playing(
+            station = testStation, sessionStartedAt = now, connectionStartedAt = now
+        )
+        stateFlow.value = PlaybackState.Idle
+        assertTrue(stateFlow.value is PlaybackState.Idle)
+    }
+
+    @Test
+    fun `audio focus denied prevents transition from idle`() {
+        stateFlow.value = PlaybackState.Idle
+        assertTrue(stateFlow.value is PlaybackState.Idle)
+    }
+
+    @Test
+    fun `audio focus loss transient during playback stays playing`() {
+        val now = System.currentTimeMillis()
+        stateFlow.value = PlaybackState.Playing(
+            station = testStation, sessionStartedAt = now, connectionStartedAt = now
+        )
+        assertTrue(stateFlow.value is PlaybackState.Playing)
+    }
 }

chat-summaries/2026-03-18_10-00-android-auto-testing.md

@@ -1,75 +0,0 @@
-# Android Auto Testing Attempts & Lessons Learned
-
-**Date:** 2026-03-18  
-**Context:** Follow-up to the Media3 / Android Auto migration session. All implementation was already complete and verified via `dumpsys media_session`. This session focused entirely on visually verifying the Android Auto browse tree using the Desktop Head Unit (DHU).
-
----
-
-## What Was Already Confirmed Working
-
-Before any testing attempts, `adb shell dumpsys media_session` confirmed:
-
-- `RadioPlaybackService` registered under both `androidx.media3.session.MediaLibraryService` and `android.media.browse.MediaBrowserService` intent filters
-- Media session active (`state=3` / playing)
-- ICY metadata visible to the OS (e.g. "Deep Shit Pt.3, Black Soyls")
-- Custom "Live" action (Seek to Live) present in the session
-- Media button receiver correctly configured
-
----
-
-## Testing Attempts
-
-### 1. Android Auto APK on API 28 Emulator (emulator-5554)
-- Installed Android Auto v15.6 (x86_64 split) — **failed**: emulator is arm64-v8a, ABI mismatch
-- Installed Android Auto v16.3 (arm64-v8a split) — **succeeded**
-- Enabled developer mode by tapping Version 10× in AA settings
-- Wrote `gearhead_config.xml` directly via `adb root` to persist developer mode
-- `Start head unit server` appeared in overflow menu and was activated
-- Port 5277 confirmed listening via `/proc/net/tcp6`
-- DHU launched, connected (`[I]: connected`), then **immediately disconnected**
-- **Root cause:** DHU v2.0 (released 2022) uses protocol version 1.7; Android Auto v16.3 (2025) requires a newer protocol version. Google has not released a DHU update since 2022.
-
-### 2. Android Auto APK on API 36 Play Store Emulator (emulator-5556)
-- Android Auto v16.3 installed successfully (arm64-v8a)
-- Could not enable developer mode via `adb root` — production build, root denied
-- Enabled developer mode via UI (tapped Version 10×, confirmed dialog)
-- `Start head unit server` appeared in overflow, tapped it
-- Port 5277 **never opened** — AA silently refused to start HUS
-- **Root cause:** Android Auto v16.3 requires a signed-in Google account to start the head unit server. The Play Store emulator could not complete Google sign-in due to captcha blocking on emulators.
-
-### 3. Physical Lenovo Tablet (HA26DKYS, Android 15)
-- Android Auto v16.3 installed via `adb install-multiple` — succeeded
-- Radio app installed via `adb install`
-- Developer mode already enabled, "Unknown sources" already checked
-- Head unit server started manually — port 5277 confirmed listening
-- `adb forward tcp:5277 tcp:5277` established
-- DHU launched, connected, then **immediately disconnected**
-- **Root cause:** Same protocol version mismatch as attempt 1. DHU v2.0 is incompatible with Android Auto v16.3 regardless of device.
-
-### 4. Head Unit Reloaded (SELF MODE) on Tablet
-- App `gb.xxy.hr` (Head Unit Reloaded) already installed on tablet
-- SELF MODE is intended to run Android Auto's car UI locally on the same device
-- App **crashed** on SELF MODE tap — likely incompatibility with Android 15 or the sideloaded AA version
-- No further investigation pursued
-
----
-
-## Lessons Learned
-
-1. **DHU v2.0 is effectively end-of-life for modern Android Auto.** Google stopped updating the DHU via SDK Manager after the 2022 release. Android Auto v16.x uses a newer protocol that DHU v2.0 cannot negotiate. The only confirmed-working approach from a [March 7, 2026 blog post](https://helw.net/2026/03/07/running-android-auto-on-an-emulator/) uses the same DHU method — meaning even the community has no working solution for newer AA versions.
-
-2. **Android Auto requires a signed-in Google account to start the head unit server on modern versions.** This makes purely emulator-based testing (without Google Play sign-in) impossible for v16+.
-
-3. **Android Automotive OS emulator is a different product.** AAOS emulator (available via SDK Manager) tests built-in car OS apps, not phone-projection Android Auto apps. It does not help test `MediaBrowserService` integrations.
-
-4. **`dumpsys media_session` is reliable validation for MediaBrowserService.** The OS-level session dump confirms registration, state, metadata, and custom commands are all correctly exposed — which is exactly what Android Auto reads. Visual DHU testing adds UI confidence but is not required to verify the integration is correct.
-
-5. **APKM bundles are ZIP archives.** APKMirror's `.apkm` files can be extracted with `unzip` and installed with `adb install-multiple`, selecting the correct architecture (`arm64_v8a`), density (`xxhdpi`), and language (`en`) splits for the target device.
-
----
-
-## Current Status
-
-All implementation is complete and functionally verified. Visual Android Auto UI testing requires either:
-- A physical car head unit running Android Auto
-- Google releasing a DHU update compatible with Android Auto v16+