feat(voiceburst): Voice Burst - voice messages with Codec2 compression

- Codec2 JNI integration for Android (arm64-v8a, x86_64)
- AudioRecorder/AudioPlayer interfaces
- VoiceBurstViewModel and UI button
- GPL-3.0 license headers
- All comments in English

Author: Chris7X

feature/voiceburst/build.gradle.kts

@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2026 Meshtastic LLC
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+import java.io.File
+
+plugins {
+    alias(libs.plugins.meshtastic.kmp.feature)
+    alias(libs.plugins.meshtastic.kotlinx.serialization)
+}
+
+// ─── Codec2 JNI detection ─────────────────────────────────────────
+val codec2SoArm64 = File(projectDir, "src/androidMain/jniLibs/arm64-v8a/libcodec2.so")
+val codec2JniArm64 = File(projectDir, "src/androidMain/jniLibs/arm64-v8a/libcodec2_jni.so")
+val codec2Available = codec2SoArm64.exists() && codec2JniArm64.exists()
+
+if (codec2Available) {
+    logger.lifecycle(":feature:voiceburst — libcodec2.so + libcodec2_jni.so trovate")
+} else {
+    logger.lifecycle(":feature:voiceburst — .so assenti → stub mode (esegui scripts/build_codec2.sh)")
+}
+
+kotlin {
+    jvm()
+
+    @Suppress("UnstableApiUsage")
+    android {
+        namespace = "org.meshtastic.feature.voiceburst"
+        androidResources.enable = false
+        withHostTest { isIncludeAndroidResources = true }
+    }
+
+    sourceSets {
+        commonMain.dependencies {
+            implementation(projects.core.common)
+            implementation(projects.core.data)
+            implementation(projects.core.datastore)
+            implementation(projects.core.model)
+            implementation(projects.core.navigation)
+            implementation(projects.core.proto)
+            implementation(projects.core.repository)
+            implementation(projects.core.service)
+            implementation(projects.core.ui)
+            implementation(projects.core.di)
+
+            implementation(libs.kotlinx.collections.immutable)
+        }
+
+        androidUnitTest.dependencies {
+            implementation(libs.junit)
+            implementation(libs.robolectric)
+            implementation(libs.turbine)
+            implementation(libs.kotlinx.coroutines.test)
+            implementation(libs.androidx.test.ext.junit)
+        }
+
+        commonTest.dependencies {
+            implementation(project(":core:testing"))
+        }
+    }
+}
+
+// ─── NESSUN externalNativeBuild ───────────────────────────────────
+// Le .so prebuilt in jniLibs/ vengono incluse automaticamente da AGP.
+// Il JNI wrapper è compilato da scripts/build_codec2.sh.

feature/voiceburst/src/androidMain/jniLibs/arm64-v8a/libcodec2.so

@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2026 Chris7X
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.geeksville.mesh.voiceburst
+
+import android.util.Log
+
+/**
+ * JNI binding to a prebuilt libcodec2 library.
+ * Both shared objects (libcodec2.so + libcodec2_jni.so) must be present in jniLibs/.
+ */
+internal object Codec2JNI {
+
+    private const val TAG = "Codec2JNI"
+    private var loaded = false
+
+    fun ensureLoaded() {
+        if (!loaded) {
+            try {
+                System.loadLibrary("codec2")
+                Log.i(TAG, "libcodec2.so loaded OK")
+            } catch (e: UnsatisfiedLinkError) {
+                Log.e(TAG, "Failed to load libcodec2.so: ${e.message}")
+                return
+            }
+            try {
+                System.loadLibrary("codec2_jni")
+                Log.i(TAG, "libcodec2_jni.so loaded OK — JNI active")
+                loaded = true
+            } catch (e: UnsatisfiedLinkError) {
+                Log.e(TAG, "Failed to load libcodec2_jni.so: ${e.message}")
+                // loaded remains false -> fallback to stub
+            }
+        }
+    }
+
+    val isAvailable: Boolean
+        get() = loaded
+
+    // Codec2 operating modes
+    const val MODE_3200 = 0
+    const val MODE_2400 = 1
+    const val MODE_1600 = 2
+    const val MODE_1400 = 3
+    const val MODE_1300 = 4
+    const val MODE_1200 = 5
+    const val MODE_700C = 8
+    const val MODE_450  = 10
+
+    @JvmStatic external fun getSamplesPerFrame(mode: Int): Int
+    @JvmStatic external fun getBytesPerFrame(mode: Int): Int
+    @JvmStatic external fun create(mode: Int): Long
+    @JvmStatic external fun encode(ptr: Long, pcm: ShortArray): ByteArray
+    @JvmStatic external fun decode(ptr: Long, frame: ByteArray): ShortArray
+    @JvmStatic external fun destroy(ptr: Long)
+}

feature/voiceburst/src/androidMain/jniLibs/arm64-v8a/libcodec2_jni.so

@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2026 Chris7X
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <https://www.gnu.org/licenses/>.
+ */
+package org.meshtastic.codec2
+
+/**
+ * JNI wrapper for the Codec2 library.
+ * This class is the interface between Kotlin/JVM and the C codec logic.
+ */
+class Codec2Jni {
+
+    /**
+     * Encodes 16-bit mono PCM audio (8kHz) into Codec2 compressed frames.
+     * @param pcm Input audio data (ShortArray)
+     * @return Compressed byte array or null on error
+     */
+    external fun encode(pcm: ShortArray): ByteArray?
+
+    /**
+     * Decodes Codec2 compressed frames back into 16-bit mono PCM audio (8kHz).
+     * @param compressed Compressed audio data (ByteArray)
+     * @return Decoded ShortArray or null on error
+     */
+    external fun decode(compressed: ByteArray): ShortArray?
+
+    /**
+     * Gets the current Codec2 mode (e.g., 3200, 2400, etc.).
+     */
+    external fun getMode(): Int
+
+    companion object {
+        init {
+            try {
+                System.loadLibrary("codec2_jni")
+            } catch (e: UnsatisfiedLinkError) {
+                // Logger not available in this core-module, using println
+                println("Critical: Could not load codec2_jni library")
+            }
+        }
+    }
+}

feature/voiceburst/src/androidMain/jniLibs/x86_64/libcodec2.so

@@ -0,0 +1,166 @@
+/*
+ * Copyright (c) 2026 Chris7X
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+package org.meshtastic.feature.voiceburst.audio
+
+import android.media.AudioAttributes
+import android.media.AudioFormat
+import android.media.AudioManager
+import android.media.AudioTrack
+import co.touchlab.kermit.Logger
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.launch
+
+private const val TAG = "AndroidAudioPlayer"
+
+/**
+ * Android implementation of [AudioPlayer].
+ *
+ * Fixes compared to previous versions:
+ *  - BUG: MODE_STATIC with bufferSize < minBufferSize → STATE_NO_STATIC_DATA (state=2) → silence.
+ *    FIX: bufferSize = maxOf(minBufferSize, pcmBytes) ALWAYS, even in static mode.
+ *  - Using MODE_STREAM: simpler and avoids the STATE_NO_STATIC_DATA issue.
+ *    For 1 second at 8kHz (16000 bytes) MODE_STREAM is more than adequate.
+ *  - USAGE_MEDIA → main speaker (not earpiece).
+ *  - [playingFilePath] StateFlow to sync play/stop icons in the UI.
+ */
+class AndroidAudioPlayer(
+    private val scope: CoroutineScope,
+) : AudioPlayer {
+
+    private var audioTrack: AudioTrack? = null
+    private var playingJob: Job? = null
+
+    private val _playingFilePath = MutableStateFlow<String?>(null)
+    override val playingFilePath: StateFlow<String?> = _playingFilePath.asStateFlow()
+
+    override val isPlaying: Boolean
+        get() = audioTrack?.playState == AudioTrack.PLAYSTATE_PLAYING
+
+    override fun play(pcmData: ShortArray, filePath: String, onComplete: () -> Unit) {
+        // If already playing, stop before starting a new track
+        if (isPlaying) {
+            Logger.d(tag = TAG) { "Stopping previous track before starting new one" }
+            stopInternal()
+        }
+
+        if (pcmData.isEmpty()) {
+            Logger.w(tag = TAG) { "PCM data is empty — skipping playback" }
+            onComplete()
+            return
+        }
+
+        val sampleRate    = SAMPLE_RATE_HZ
+        val channelConfig = AudioFormat.CHANNEL_OUT_MONO
+        val audioEncoding = AudioFormat.ENCODING_PCM_16BIT
+
+        val minBufferSize = AudioTrack.getMinBufferSize(sampleRate, channelConfig, audioEncoding)
+        if (minBufferSize <= 0) {
+            Logger.e(tag = TAG) { "getMinBufferSize error: $minBufferSize" }
+            onComplete()
+            return
+        }
+
+        // CRITICAL: bufferSize must always be >= minBufferSize.
+        // With MODE_STATIC, if bufferSize < minBufferSize → state=STATE_NO_STATIC_DATA=2 → silence.
+        // MODE_STREAM is used for simplicity and robustness.
+        val pcmBytes   = pcmData.size * Short.SIZE_BYTES
+        val bufferSize = maxOf(minBufferSize, pcmBytes)
+
+        val attrs = AudioAttributes.Builder()
+            .setUsage(AudioAttributes.USAGE_MEDIA)
+            .setContentType(AudioAttributes.CONTENT_TYPE_SPEECH)
+            .build()
+
+        val format = AudioFormat.Builder()
+            .setSampleRate(sampleRate)
+            .setEncoding(audioEncoding)
+            .setChannelMask(channelConfig)
+            .build()
+
+        val track = try {
+            AudioTrack(attrs, format, bufferSize, AudioTrack.MODE_STREAM, AudioManager.AUDIO_SESSION_ID_GENERATE)
+        } catch (e: Exception) {
+            Logger.e(e, tag = TAG) { "Failed to create AudioTrack" }
+            onComplete()
+            return
+        }
+
+        if (track.state != AudioTrack.STATE_INITIALIZED) {
+            Logger.e(tag = TAG) { "AudioTrack not initialized: state=${track.state} (expected ${AudioTrack.STATE_INITIALIZED})" }
+            track.release()
+            onComplete()
+            return
+        }
+
+        audioTrack = track
+        _playingFilePath.value = filePath.ifEmpty { null }
+
+        playingJob = scope.launch(Dispatchers.IO) {
+            try {
+                // MODE_STREAM: call play() FIRST, then write() for streaming
+                track.play()
+                Logger.d(tag = TAG) { "Playback started: ${pcmData.size} samples @ ${sampleRate}Hz" }
+
+                val written = track.write(pcmData, 0, pcmData.size)
+                if (written < 0) {
+                    Logger.e(tag = TAG) { "write() error: $written" }
+                } else {
+                    Logger.d(tag = TAG) { "Write complete: $written samples" }
+                    // Wait for the DAC to drain all samples in the buffer
+                    val drainMs = written.toLong() * 1000L / sampleRate + DRAIN_GUARD_MS
+                    kotlinx.coroutines.delay(drainMs)
+                }
+            } catch (e: Exception) {
+                Logger.e(e, tag = TAG) { "Playback error" }
+            } finally {
+                releaseTrack(track)
+                _playingFilePath.value = null
+                scope.launch(Dispatchers.Main) { onComplete() }
+            }
+        }
+    }
+
+    override fun stop() {
+        if (!isPlaying && playingJob?.isActive != true) return
+        Logger.d(tag = TAG) { "Stopping playback" }
+        stopInternal()
+    }
+
+    private fun stopInternal() {
+        playingJob?.cancel()
+        playingJob = null
+        audioTrack?.let { releaseTrack(it) }
+        _playingFilePath.value = null
+    }
+
+    private fun releaseTrack(track: AudioTrack) {
+        try { track.stop() } catch (_: Exception) {}
+        try { track.flush() } catch (_: Exception) {}
+        track.release()
+        if (audioTrack === track) audioTrack = null
+    }
+
+    companion object {
+        private const val SAMPLE_RATE_HZ  = 8000
+        private const val DRAIN_GUARD_MS  = 150L  // extra margin for DAC drain
+    }
+}