First Commit

libraries/voicerecorder/impl/build.gradle.kts

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+import extension.setupDependencyInjection
+import extension.testCommonDependencies
+
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023, 2024 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+plugins {
+    id("io.element.android-library")
+}
+
+android {
+    namespace = "io.element.android.libraries.voicerecorder.impl"
+}
+
+setupDependencyInjection()
+
+dependencies {
+    api(projects.libraries.voicerecorder.api)
+    api(libs.opusencoder)
+
+    implementation(projects.appconfig)
+    implementation(projects.libraries.matrix.api)
+    implementation(projects.libraries.core)
+    implementation(projects.libraries.di)
+
+    implementation(libs.androidx.annotationjvm)
+    implementation(libs.coroutines.core)
+
+    testCommonDependencies(libs)
+    testImplementation(libs.coroutines.core)
+}

libraries/voicerecorder/impl/src/main/kotlin/io/element/android/libraries/voicerecorder/impl/DefaultVoiceRecorder.kt

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+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.impl
+
+import android.Manifest
+import androidx.annotation.RequiresPermission
+import dev.zacsweers.metro.ContributesBinding
+import dev.zacsweers.metro.SingleIn
+import io.element.android.appconfig.VoiceMessageConfig
+import io.element.android.libraries.core.coroutine.CoroutineDispatchers
+import io.element.android.libraries.core.coroutine.childScope
+import io.element.android.libraries.di.RoomScope
+import io.element.android.libraries.di.annotations.SessionCoroutineScope
+import io.element.android.libraries.voicerecorder.api.VoiceRecorder
+import io.element.android.libraries.voicerecorder.api.VoiceRecorderState
+import io.element.android.libraries.voicerecorder.impl.audio.Audio
+import io.element.android.libraries.voicerecorder.impl.audio.AudioConfig
+import io.element.android.libraries.voicerecorder.impl.audio.AudioLevelCalculator
+import io.element.android.libraries.voicerecorder.impl.audio.AudioReader
+import io.element.android.libraries.voicerecorder.impl.audio.Encoder
+import io.element.android.libraries.voicerecorder.impl.audio.resample
+import io.element.android.libraries.voicerecorder.impl.file.VoiceFileConfig
+import io.element.android.libraries.voicerecorder.impl.file.VoiceFileManager
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.sync.Mutex
+import kotlinx.coroutines.sync.withLock
+import kotlinx.coroutines.yield
+import timber.log.Timber
+import java.io.File
+import java.util.UUID
+import kotlin.time.Duration.Companion.milliseconds
+import kotlin.time.TimeSource
+
+@SingleIn(RoomScope::class)
+@ContributesBinding(RoomScope::class)
+class DefaultVoiceRecorder(
+    private val dispatchers: CoroutineDispatchers,
+    private val timeSource: TimeSource,
+    private val audioReaderFactory: AudioReader.Factory,
+    private val encoder: Encoder,
+    private val fileManager: VoiceFileManager,
+    private val config: AudioConfig,
+    private val fileConfig: VoiceFileConfig,
+    private val audioLevelCalculator: AudioLevelCalculator,
+    @SessionCoroutineScope
+    sessionCoroutineScope: CoroutineScope,
+) : VoiceRecorder {
+    private val voiceCoroutineScope by lazy {
+        sessionCoroutineScope.childScope(dispatchers.io, "VoiceRecorder-${UUID.randomUUID()}")
+    }
+
+    private var outputFile: File? = null
+    private var audioReader: AudioReader? = null
+    private var recordingJob: Job? = null
+
+    // List of Float between 0 and 1 representing the audio levels
+    private val levels: MutableList<Float> = mutableListOf()
+    private val lock = Mutex()
+
+    private val _state = MutableStateFlow<VoiceRecorderState>(VoiceRecorderState.Idle)
+    override val state: StateFlow<VoiceRecorderState> = _state
+
+    @RequiresPermission(Manifest.permission.RECORD_AUDIO)
+    override suspend fun startRecord() {
+        Timber.i("Voice recorder started recording")
+        outputFile = fileManager.createFile()
+            .also(encoder::init)
+
+        lock.withLock {
+            levels.clear()
+        }
+
+        val audioRecorder = audioReaderFactory.create(config, dispatchers).also { audioReader = it }
+
+        recordingJob = voiceCoroutineScope.launch {
+            val startedAt = timeSource.markNow()
+            audioRecorder.record { audio ->
+                yield()
+
+                val elapsedTime = startedAt.elapsedNow()
+
+                if (elapsedTime > VoiceMessageConfig.maxVoiceMessageDuration) {
+                    Timber.w("Voice message time limit reached")
+                    stopRecord(false)
+                    return@record
+                }
+
+                when (audio) {
+                    is Audio.Data -> {
+                        val audioLevel = audioLevelCalculator.calculateAudioLevel(audio.buffer)
+
+                        lock.withLock {
+                            levels.add(audioLevel)
+                            _state.emit(VoiceRecorderState.Recording(elapsedTime, levels.toList()))
+                        }
+                        encoder.encode(audio.buffer, audio.readSize)
+                    }
+                    is Audio.Error -> {
+                        Timber.e("Voice message error: code=${audio.audioRecordErrorCode}")
+                        _state.emit(VoiceRecorderState.Recording(elapsedTime, listOf()))
+                    }
+                }
+            }
+        }
+    }
+
+    /**
+     * Stop the current recording.
+     *
+     * Call [deleteRecording] to delete any recorded audio.
+     */
+    override suspend fun stopRecord(
+        cancelled: Boolean
+    ) {
+        recordingJob?.cancel()?.also {
+            Timber.i("Voice recorder stopped recording")
+        }
+        recordingJob = null
+
+        audioReader?.stop()
+        audioReader = null
+        encoder.release()
+
+        lock.withLock {
+            if (cancelled) {
+                deleteRecording()
+                levels.clear()
+            }
+
+            _state.emit(
+                when (val file = outputFile) {
+                    null -> VoiceRecorderState.Idle
+                    else -> {
+                        val duration = (state.value as? VoiceRecorderState.Recording)?.elapsedTime
+                        VoiceRecorderState.Finished(
+                            file = file,
+                            mimeType = fileConfig.mimeType,
+                            waveform = levels.resample(100),
+                            duration = duration ?: 0.milliseconds
+                        )
+                    }
+                }
+            )
+        }
+    }
+
+    /**
+     * Stop the current recording and delete the output file.
+     */
+    override suspend fun deleteRecording() {
+        outputFile?.let(fileManager::deleteFile)?.also {
+            Timber.i("Voice recorder deleted recording")
+        }
+        outputFile = null
+        _state.emit(VoiceRecorderState.Idle)
+    }
+}

libraries/voicerecorder/impl/src/main/kotlin/io/element/android/libraries/voicerecorder/impl/audio/AndroidAudioReader.kt

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+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.impl.audio
+
+import android.Manifest
+import android.media.AudioRecord
+import android.media.audiofx.AutomaticGainControl
+import android.media.audiofx.NoiseSuppressor
+import androidx.annotation.RequiresPermission
+import dev.zacsweers.metro.ContributesBinding
+import io.element.android.libraries.core.coroutine.CoroutineDispatchers
+import io.element.android.libraries.core.data.tryOrNull
+import io.element.android.libraries.di.RoomScope
+import kotlinx.coroutines.isActive
+import kotlinx.coroutines.withContext
+
+class AndroidAudioReader
+@RequiresPermission(Manifest.permission.RECORD_AUDIO)
+private constructor(
+    private val config: AudioConfig,
+    private val dispatchers: CoroutineDispatchers,
+) : AudioReader {
+    private val audioRecord: AudioRecord
+    private var noiseSuppressor: NoiseSuppressor? = null
+    private var automaticGainControl: AutomaticGainControl? = null
+    private val outputBuffer: ShortArray
+
+    init {
+        outputBuffer = createOutputBuffer(config.sampleRate)
+        audioRecord = AudioRecord.Builder().setAudioSource(config.source).setAudioFormat(config.format).setBufferSizeInBytes(outputBuffer.sizeInBytes()).build()
+        noiseSuppressor = requestNoiseSuppressor(audioRecord)
+        automaticGainControl = requestAutomaticGainControl(audioRecord)
+    }
+
+    /**
+     * Record audio data continuously.
+     *
+     * @param onAudio callback when audio is read.
+     */
+    override suspend fun record(
+        onAudio: suspend (Audio) -> Unit,
+    ) {
+        audioRecord.startRecording()
+        withContext(dispatchers.io) {
+            while (isActive) {
+                if (audioRecord.recordingState != AudioRecord.RECORDSTATE_RECORDING) {
+                    break
+                }
+                onAudio(read())
+            }
+        }
+    }
+
+    private fun read(): Audio {
+        val result = audioRecord.read(outputBuffer, 0, outputBuffer.size)
+
+        if (isAudioRecordErrorResult(result)) {
+            return Audio.Error(result)
+        }
+
+        return Audio.Data(
+            result,
+            outputBuffer,
+        )
+    }
+
+    override fun stop() {
+        if (audioRecord.state == AudioRecord.STATE_INITIALIZED) {
+            audioRecord.stop()
+        }
+        audioRecord.release()
+
+        noiseSuppressor?.release()
+        noiseSuppressor = null
+
+        automaticGainControl?.release()
+        automaticGainControl = null
+    }
+
+    private fun createOutputBuffer(sampleRate: SampleRate): ShortArray {
+        val bufferSizeInShorts = AudioRecord.getMinBufferSize(
+            sampleRate.HZ,
+            config.format.channelMask,
+            config.format.encoding
+        )
+        return ShortArray(bufferSizeInShorts)
+    }
+
+    private fun requestNoiseSuppressor(audioRecord: AudioRecord): NoiseSuppressor? {
+        if (!NoiseSuppressor.isAvailable()) {
+            return null
+        }
+
+        return tryOrNull {
+            NoiseSuppressor.create(audioRecord.audioSessionId).apply {
+                enabled = true
+            }
+        }
+    }
+
+    private fun requestAutomaticGainControl(audioRecord: AudioRecord): AutomaticGainControl? {
+        if (!AutomaticGainControl.isAvailable()) {
+            return null
+        }
+
+        return tryOrNull {
+            AutomaticGainControl.create(audioRecord.audioSessionId).apply {
+                enabled = true
+            }
+        }
+    }
+
+    @ContributesBinding(RoomScope::class)
+    companion object Factory : AudioReader.Factory {
+        @RequiresPermission(Manifest.permission.RECORD_AUDIO)
+        override fun create(config: AudioConfig, dispatchers: CoroutineDispatchers): AndroidAudioReader {
+            return AndroidAudioReader(config, dispatchers)
+        }
+    }
+}
+
+private fun isAudioRecordErrorResult(result: Int): Boolean {
+    return result < 0
+}
+
+private fun ShortArray.sizeInBytes(): Int = size * Short.SIZE_BYTES

libraries/voicerecorder/impl/src/main/kotlin/io/element/android/libraries/voicerecorder/impl/audio/Audio.kt

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.impl.audio
+
+sealed interface Audio {
+    data class Data(
+        val readSize: Int,
+        val buffer: ShortArray,
+    ) : Audio {
+        override fun equals(other: Any?): Boolean {
+            if (this === other) return true
+            if (javaClass != other?.javaClass) return false
+
+            other as Data
+
+            if (readSize != other.readSize) return false
+            if (!buffer.contentEquals(other.buffer)) return false
+
+            return true
+        }
+
+        override fun hashCode(): Int {
+            var result = readSize
+            result = 31 * result + buffer.contentHashCode()
+            return result
+        }
+    }
+
+    data class Error(
+        val audioRecordErrorCode: Int
+    ) : Audio
+}

libraries/voicerecorder/impl/src/main/kotlin/io/element/android/libraries/voicerecorder/impl/audio/AudioConfig.kt

@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.impl.audio
+
+import android.media.AudioFormat
+import android.media.MediaRecorder.AudioSource
+
+/**
+ * Audio configuration for voice recording.
+ *
+ * @property source the audio source to use, see constants in [AudioSource]
+ * @property format the audio format to use, see [AudioFormat]
+ * @property sampleRate the sample rate to use. Ensure this matches the value set in [format].
+ * @property bitRate the bitrate in bps
+ */
+data class AudioConfig(
+    val source: Int,
+    val format: AudioFormat,
+    val sampleRate: SampleRate,
+    val bitRate: Int,
+)

libraries/voicerecorder/impl/src/main/kotlin/io/element/android/libraries/voicerecorder/impl/audio/AudioLevelCalculator.kt

@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.impl.audio
+
+import androidx.annotation.FloatRange
+
+interface AudioLevelCalculator {
+    /**
+     * Calculate the audio level of the audio buffer.
+     *
+     * @param buffer The audio buffer containing 16bit PCM audio data.
+     * @return A float value between 0 and 1 proportional to the audio level.
+     */
+    @FloatRange(from = 0.0, to = 1.0)
+    fun calculateAudioLevel(buffer: ShortArray): Float
+}

libraries/voicerecorder/impl/src/main/kotlin/io/element/android/libraries/voicerecorder/impl/audio/AudioReader.kt

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.impl.audio
+
+import io.element.android.libraries.core.coroutine.CoroutineDispatchers
+
+interface AudioReader {
+    /**
+     * Record audio data continuously.
+     *
+     * @param onAudio callback when audio is read.
+     */
+    suspend fun record(
+        onAudio: suspend (Audio) -> Unit,
+    )
+
+    fun stop()
+
+    interface Factory {
+        fun create(config: AudioConfig, dispatchers: CoroutineDispatchers): AudioReader
+    }
+}

libraries/voicerecorder/impl/src/main/kotlin/io/element/android/libraries/voicerecorder/impl/audio/DBovAudioLevelCalculator.kt

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.impl.audio
+
+import dev.zacsweers.metro.ContributesBinding
+import io.element.android.libraries.di.RoomScope
+import kotlin.math.log10
+import kotlin.math.sqrt
+
+/**
+ * Default implementation of [AudioLevelCalculator].
+ *
+ * It computes the normalized [0;1] dBov value of the given PCM16 encoded [ShortArray].
+ * See: https://en.wikipedia.org/wiki/DBFS
+ */
+@ContributesBinding(RoomScope::class)
+class DBovAudioLevelCalculator : AudioLevelCalculator {
+    override fun calculateAudioLevel(buffer: ShortArray): Float {
+        return buffer.rms().dBov().normalize().coerceIn(0f, 1f)
+    }
+}
+
+/**
+ * Computes the normalized (range 0.0 to 1.0) root mean square
+ * value of the given PCM16 encoded [ShortArray].
+ */
+private fun ShortArray.rms(): Float {
+    val floats = FloatArray(this.size) { i -> this[i] / Short.MAX_VALUE.toFloat() }
+    val squared = FloatArray(this.size) { i -> floats[i] * floats[i] }
+    val sum = squared.fold(0.0f) { acc, f -> acc + f }
+    val average = sum / this.size
+    return sqrt(average)
+}
+
+/**
+ * Converts the given RMS value to decibels relative to overload (dBov).
+ * It has range [-96.0, 0.0] where 0.0 is the value of a full scale square wave.
+ */
+private fun Float.dBov(): Float = 20 * log10(this)
+
+/**
+ * Normalizes the given dBov value to the range [0.0, 1.0].
+ */
+private fun Float.normalize(): Float = (this + DYNAMIC_RANGE_PCM16) / DYNAMIC_RANGE_PCM16
+
+private const val DYNAMIC_RANGE_PCM16: Float = 96.0f

libraries/voicerecorder/impl/src/main/kotlin/io/element/android/libraries/voicerecorder/impl/audio/DefaultEncoder.kt

@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.impl.audio
+
+import dev.zacsweers.metro.ContributesBinding
+import dev.zacsweers.metro.Provider
+import io.element.android.libraries.di.RoomScope
+import io.element.android.opusencoder.OggOpusEncoder
+import timber.log.Timber
+import java.io.File
+
+/**
+ * Safe wrapper for OggOpusEncoder.
+ */
+@ContributesBinding(RoomScope::class)
+class DefaultEncoder(
+    private val encoderProvider: Provider<OggOpusEncoder>,
+    config: AudioConfig,
+) : Encoder {
+    private val bitRate = config.bitRate
+    private val sampleRate = config.sampleRate.asEncoderModel()
+
+    private var encoder: OggOpusEncoder? = null
+    override fun init(
+        file: File,
+    ) {
+        encoder?.release()
+        encoder = encoderProvider().apply {
+            init(file.absolutePath, sampleRate)
+            setBitrate(bitRate)
+            // TODO check encoder application: 2048 (voice, default is typically 2049 as audio)
+        }
+    }
+
+    override fun encode(
+        buffer: ShortArray,
+        readSize: Int,
+    ) {
+        encoder?.encode(buffer, readSize)
+            ?: Timber.w("Can't encode when encoder not initialized")
+    }
+
+    override fun release() {
+        encoder?.release()
+        encoder = null
+    }
+}

libraries/voicerecorder/impl/src/main/kotlin/io/element/android/libraries/voicerecorder/impl/audio/Encoder.kt

@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.impl.audio
+
+import java.io.File
+
+interface Encoder {
+    fun init(file: File)
+
+    fun encode(buffer: ShortArray, readSize: Int)
+
+    fun release()
+}

libraries/voicerecorder/impl/src/main/kotlin/io/element/android/libraries/voicerecorder/impl/audio/Resample.kt

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.impl.audio
+
+/**
+ * Resamples [this] list to [size] using linear interpolation.
+ */
+fun List<Float>.resample(size: Int): List<Float> {
+    require(size > 0)
+    val input = this
+    if (input.isEmpty()) return List(size) { 0f } // fast path.
+    if (input.size == 1) return List(size) { input[0] } // fast path.
+    if (input.size == size) return this // fast path.
+    val step: Float = input.size.toFloat() / size.toFloat()
+    return buildList(size) {
+        for (i in 0 until size) {
+            val x0 = (i * step).toInt()
+            val x1 = (x0 + 1).coerceAtMost(input.size - 1)
+            val x = i * step - x0
+            val y = input[x0] * (1 - x) + input[x1] * x
+            add(i, y)
+        }
+    }
+}

libraries/voicerecorder/impl/src/main/kotlin/io/element/android/libraries/voicerecorder/impl/audio/SampleRate.kt

@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.impl.audio
+
+import io.element.android.opusencoder.configuration.SampleRate as LibOpusOggSampleRate
+
+data object SampleRate {
+    const val HZ = 48_000
+    fun asEncoderModel() = LibOpusOggSampleRate.Rate48kHz
+}

libraries/voicerecorder/impl/src/main/kotlin/io/element/android/libraries/voicerecorder/impl/di/VoiceRecorderModule.kt

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.impl.di
+
+import android.media.AudioFormat
+import android.media.MediaRecorder
+import dev.zacsweers.metro.BindingContainer
+import dev.zacsweers.metro.ContributesTo
+import dev.zacsweers.metro.Provides
+import io.element.android.libraries.core.mimetype.MimeTypes
+import io.element.android.libraries.di.RoomScope
+import io.element.android.libraries.voicerecorder.impl.audio.AudioConfig
+import io.element.android.libraries.voicerecorder.impl.audio.SampleRate
+import io.element.android.libraries.voicerecorder.impl.file.VoiceFileConfig
+import io.element.android.opusencoder.OggOpusEncoder
+
+@BindingContainer
+@ContributesTo(RoomScope::class)
+object VoiceRecorderModule {
+    @Provides
+    fun provideAudioConfig(): AudioConfig {
+        val sampleRate = SampleRate
+        return AudioConfig(
+            format = AudioFormat.Builder()
+                .setEncoding(AudioFormat.ENCODING_PCM_16BIT)
+                .setSampleRate(sampleRate.HZ)
+                .setChannelMask(AudioFormat.CHANNEL_IN_MONO)
+                .build(),
+            // 24 kbps
+            bitRate = 24_000,
+            sampleRate = sampleRate,
+            source = MediaRecorder.AudioSource.MIC,
+        )
+    }
+
+    @Provides
+    public fun provideVoiceFileConfig(): VoiceFileConfig =
+        VoiceFileConfig(
+            cacheSubdir = "voice_recordings",
+            fileExt = "ogg",
+            mimeType = MimeTypes.Ogg,
+        )
+
+    @Provides
+    fun provideOggOpusEncoder(): OggOpusEncoder = OggOpusEncoder.create()
+}

libraries/voicerecorder/impl/src/main/kotlin/io/element/android/libraries/voicerecorder/impl/file/DefaultVoiceFileManager.kt

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.impl.file
+
+import dev.zacsweers.metro.ContributesBinding
+import io.element.android.libraries.core.hash.md5
+import io.element.android.libraries.di.CacheDirectory
+import io.element.android.libraries.di.RoomScope
+import io.element.android.libraries.matrix.api.core.RoomId
+import io.element.android.libraries.matrix.api.room.BaseRoom
+import java.io.File
+import java.util.UUID
+
+@ContributesBinding(RoomScope::class)
+class DefaultVoiceFileManager(
+    @CacheDirectory private val cacheDir: File,
+    private val config: VoiceFileConfig,
+    room: BaseRoom,
+) : VoiceFileManager {
+    private val roomId: RoomId = room.roomId
+
+    override fun createFile(): File {
+        val fileName = "${UUID.randomUUID()}.${config.fileExt}"
+        val outputDirectory = File(cacheDir, config.cacheSubdir)
+        val roomDir = File(outputDirectory, roomId.value.md5())
+            .apply(File::mkdirs)
+        return File(roomDir, fileName)
+    }
+
+    override fun deleteFile(file: File) {
+        file.delete()
+    }
+}

libraries/voicerecorder/impl/src/main/kotlin/io/element/android/libraries/voicerecorder/impl/file/VoiceFileConfig.kt

@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.impl.file
+
+/**
+ * File configuration for voice recording.
+ *
+ * @property cacheSubdir the subdirectory in the cache dir to use.
+ * @property fileExt the file extension for audio files.
+ * @property mimeType the mime type of audio files.
+ */
+data class VoiceFileConfig(
+    val cacheSubdir: String,
+    val fileExt: String,
+    val mimeType: String,
+)

libraries/voicerecorder/impl/src/main/kotlin/io/element/android/libraries/voicerecorder/impl/file/VoiceFileManager.kt

@@ -0,0 +1,17 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.impl.file
+
+import java.io.File
+
+interface VoiceFileManager {
+    fun createFile(): File
+
+    fun deleteFile(file: File)
+}

libraries/voicerecorder/impl/src/test/kotlin/io/element/android/libraries/voicerecorder/impl/DefaultVoiceRecorderTest.kt

@@ -0,0 +1,169 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.impl
+
+import android.media.AudioFormat
+import android.media.MediaRecorder
+import app.cash.turbine.test
+import com.google.common.truth.Truth.assertThat
+import io.element.android.appconfig.VoiceMessageConfig
+import io.element.android.libraries.core.mimetype.MimeTypes
+import io.element.android.libraries.voicerecorder.api.VoiceRecorderState
+import io.element.android.libraries.voicerecorder.impl.audio.Audio
+import io.element.android.libraries.voicerecorder.impl.audio.AudioConfig
+import io.element.android.libraries.voicerecorder.impl.audio.SampleRate
+import io.element.android.libraries.voicerecorder.impl.di.VoiceRecorderModule
+import io.element.android.libraries.voicerecorder.test.FakeAudioLevelCalculator
+import io.element.android.libraries.voicerecorder.test.FakeAudioReaderFactory
+import io.element.android.libraries.voicerecorder.test.FakeEncoder
+import io.element.android.libraries.voicerecorder.test.FakeFileSystem
+import io.element.android.libraries.voicerecorder.test.FakeVoiceFileManager
+import io.element.android.tests.testutils.testCoroutineDispatchers
+import io.mockk.mockk
+import kotlinx.coroutines.test.TestScope
+import kotlinx.coroutines.test.runTest
+import org.junit.BeforeClass
+import org.junit.Test
+import java.io.File
+import kotlin.time.Duration.Companion.milliseconds
+import kotlin.time.Duration.Companion.minutes
+import kotlin.time.Duration.Companion.seconds
+import kotlin.time.TestTimeSource
+
+class DefaultVoiceRecorderTest {
+    private val fakeFileSystem = FakeFileSystem()
+    private val timeSource = TestTimeSource()
+
+    @Test
+    fun `it emits the initial state`() = runTest {
+        val voiceRecorder = createDefaultVoiceRecorder()
+        voiceRecorder.state.test {
+            assertThat(awaitItem()).isEqualTo(VoiceRecorderState.Idle)
+        }
+    }
+
+    @Test
+    fun `when recording, it emits the recording state`() = runTest {
+        val voiceRecorder = createDefaultVoiceRecorder()
+        voiceRecorder.state.test {
+            assertThat(awaitItem()).isEqualTo(VoiceRecorderState.Idle)
+
+            voiceRecorder.startRecord()
+            assertThat(awaitItem()).isEqualTo(VoiceRecorderState.Recording(0.seconds, listOf(1.0f)))
+            timeSource += 1.seconds
+            assertThat(awaitItem()).isEqualTo(VoiceRecorderState.Recording(1.seconds, listOf()))
+            timeSource += 1.seconds
+            assertThat(awaitItem()).isEqualTo(VoiceRecorderState.Recording(2.seconds, listOf(1.0f, 1.0f)))
+        }
+    }
+
+    @Test
+    fun `when elapsed time reaches 30 minutes, it stops recording`() = runTest {
+        val voiceRecorder = createDefaultVoiceRecorder()
+        voiceRecorder.state.test {
+            assertThat(awaitItem()).isEqualTo(VoiceRecorderState.Idle)
+
+            voiceRecorder.startRecord()
+            assertThat(awaitItem()).isEqualTo(VoiceRecorderState.Recording(0.minutes, listOf(1.0f)))
+            timeSource += VoiceMessageConfig.maxVoiceMessageDuration
+            assertThat(awaitItem()).isEqualTo(VoiceRecorderState.Recording(VoiceMessageConfig.maxVoiceMessageDuration, listOf()))
+            timeSource += 1.milliseconds
+
+            assertThat(awaitItem()).isEqualTo(
+                VoiceRecorderState.Finished(
+                    file = File(FILE_PATH),
+                    mimeType = MimeTypes.Ogg,
+                    waveform = List(100) { 1f },
+                    duration = VoiceMessageConfig.maxVoiceMessageDuration,
+                )
+            )
+        }
+    }
+
+    @Test
+    fun `when stopped, it provides a file and duration`() = runTest {
+        val voiceRecorder = createDefaultVoiceRecorder()
+        voiceRecorder.state.test {
+            assertThat(awaitItem()).isEqualTo(VoiceRecorderState.Idle)
+
+            voiceRecorder.startRecord()
+            skipItems(1)
+            timeSource += 5.seconds
+            skipItems(2)
+            voiceRecorder.stopRecord()
+            assertThat(awaitItem()).isEqualTo(
+                VoiceRecorderState.Finished(
+                    file = File(FILE_PATH),
+                    mimeType = MimeTypes.Ogg,
+                    waveform = List(100) { 1f },
+                    duration = 5.seconds,
+                )
+            )
+            assertThat(fakeFileSystem.files[File(FILE_PATH)]).isEqualTo(ENCODED_DATA)
+        }
+    }
+
+    @Test
+    fun `when cancelled, it deletes the file`() = runTest {
+        val voiceRecorder = createDefaultVoiceRecorder()
+        voiceRecorder.state.test {
+            assertThat(awaitItem()).isEqualTo(VoiceRecorderState.Idle)
+
+            voiceRecorder.startRecord()
+            skipItems(3)
+            voiceRecorder.stopRecord(cancelled = true)
+            assertThat(awaitItem()).isEqualTo(VoiceRecorderState.Idle)
+            assertThat(fakeFileSystem.files[File(FILE_PATH)]).isNull()
+        }
+    }
+
+    private fun TestScope.createDefaultVoiceRecorder(): DefaultVoiceRecorder {
+        val fileConfig = VoiceRecorderModule.provideVoiceFileConfig()
+        return DefaultVoiceRecorder(
+            dispatchers = testCoroutineDispatchers(),
+            timeSource = timeSource,
+            audioReaderFactory = FakeAudioReaderFactory(
+                audio = AUDIO,
+            ),
+            encoder = FakeEncoder(fakeFileSystem),
+            config = AudioConfig(
+                format = audioFormat,
+                // 24 kbps
+                bitRate = 24_000,
+                sampleRate = SampleRate,
+                source = MediaRecorder.AudioSource.MIC,
+            ),
+            fileConfig = fileConfig,
+            fileManager = FakeVoiceFileManager(fakeFileSystem, fileConfig, FILE_ID),
+            audioLevelCalculator = FakeAudioLevelCalculator(),
+            sessionCoroutineScope = backgroundScope,
+        )
+    }
+
+    companion object {
+        const val FILE_ID: String = "recording"
+        const val FILE_PATH = "voice_recordings/$FILE_ID.ogg"
+        private lateinit var audioFormat: AudioFormat
+
+        // FakeEncoder doesn't actually encode, it just writes the data to the file
+        private const val ENCODED_DATA = "[32767, 32767, 32767][32767, 32767, 32767]"
+        private const val MAX_AMP = Short.MAX_VALUE
+        private val AUDIO = listOf(
+            Audio.Data(3, shortArrayOf(MAX_AMP, MAX_AMP, MAX_AMP)),
+            Audio.Error(-1),
+            Audio.Data(3, shortArrayOf(MAX_AMP, MAX_AMP, MAX_AMP)),
+        )
+
+        @BeforeClass
+        @JvmStatic
+        fun initAudioFormat() {
+            audioFormat = mockk()
+        }
+    }
+}

libraries/voicerecorder/impl/src/test/kotlin/io/element/android/libraries/voicerecorder/impl/audio/DBovAudioLevelCalculatorTest.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.impl.audio
+
+import com.google.common.truth.Truth.assertThat
+import org.junit.Test
+
+class DBovAudioLevelCalculatorTest {
+    @Test
+    fun `given max values, it returns 1`() {
+        val calculator = DBovAudioLevelCalculator()
+        val buffer = ShortArray(100) { Short.MAX_VALUE }
+        val level = calculator.calculateAudioLevel(buffer)
+        assertThat(level).isEqualTo(1.0f)
+    }
+
+    @Test
+    fun `given mixed values, it returns values within range`() {
+        val calculator = DBovAudioLevelCalculator()
+        val buffer = shortArrayOf(100, -200, 300, -400, 500, -600, 700, -800, 900, -1000)
+        val level = calculator.calculateAudioLevel(buffer)
+        assertThat(level).apply {
+            isGreaterThan(0f)
+            isLessThan(1f)
+        }
+    }
+
+    @Test
+    fun `given min values, it returns 0`() {
+        val calculator = DBovAudioLevelCalculator()
+        val buffer = ShortArray(100) { 0 }
+        val level = calculator.calculateAudioLevel(buffer)
+        assertThat(level).isEqualTo(0.0f)
+    }
+}

libraries/voicerecorder/impl/src/test/kotlin/io/element/android/libraries/voicerecorder/impl/audio/ResampleTest.kt

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.impl.audio
+
+import com.google.common.truth.Truth.assertThat
+import org.junit.Test
+
+class ResampleTest {
+    @Test
+    fun `resample works`() {
+        listOf(0.0f).resample(10).let {
+            assertThat(it).isEqualTo(listOf(0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f))
+        }
+        listOf(1.0f).resample(10).let {
+            assertThat(it).isEqualTo(listOf(1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f))
+        }
+        listOf(0.0f, 1.0f).resample(10).let {
+            assertThat(it).isEqualTo(listOf(0.0f, 0.2f, 0.4f, 0.6f, 0.8f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f))
+        }
+        listOf(0.0f, 0.5f, 1.0f).resample(10).let {
+            assertThat(it).isEqualTo(listOf(0.0f, 0.15f, 0.3f, 0.45000002f, 0.6f, 0.75f, 0.90000004f, 1.0f, 1.0f, 1.0f))
+        }
+        List(100) { it.toFloat() }.resample(10).let {
+            assertThat(it).isEqualTo(listOf(0.0f, 10.0f, 20.0f, 30.0f, 40.0f, 50.0f, 60.0f, 70.0f, 80.0f, 90.0f))
+        }
+    }
+}

libraries/voicerecorder/impl/src/test/kotlin/io/element/android/libraries/voicerecorder/test/FakeAudioLevelCalculator.kt

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.test
+
+import io.element.android.libraries.voicerecorder.impl.audio.AudioLevelCalculator
+import kotlin.math.abs
+
+class FakeAudioLevelCalculator : AudioLevelCalculator {
+    override fun calculateAudioLevel(buffer: ShortArray): Float {
+        return buffer.map { abs(it.toFloat()) }.average().toFloat() / Short.MAX_VALUE
+    }
+}

libraries/voicerecorder/impl/src/test/kotlin/io/element/android/libraries/voicerecorder/test/FakeAudioReader.kt

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.test
+
+import io.element.android.libraries.core.coroutine.CoroutineDispatchers
+import io.element.android.libraries.voicerecorder.impl.audio.Audio
+import io.element.android.libraries.voicerecorder.impl.audio.AudioReader
+import kotlinx.coroutines.isActive
+import kotlinx.coroutines.withContext
+import kotlinx.coroutines.yield
+
+class FakeAudioReader(
+    private val dispatchers: CoroutineDispatchers,
+    private val audio: List<Audio>,
+) : AudioReader {
+    private var isRecording = false
+    override suspend fun record(onAudio: suspend (Audio) -> Unit) {
+        isRecording = true
+        withContext(dispatchers.io) {
+            val audios = audio.iterator()
+            while (audios.hasNext()) {
+                if (!isRecording) break
+                onAudio(audios.next())
+                yield()
+            }
+            while (isActive) {
+                // do not return from the coroutine until it is cancelled
+                yield()
+            }
+        }
+    }
+
+    override fun stop() {
+        isRecording = false
+    }
+}

libraries/voicerecorder/impl/src/test/kotlin/io/element/android/libraries/voicerecorder/test/FakeAudioReaderFactory.kt

@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.test
+
+import io.element.android.libraries.core.coroutine.CoroutineDispatchers
+import io.element.android.libraries.voicerecorder.impl.audio.Audio
+import io.element.android.libraries.voicerecorder.impl.audio.AudioConfig
+import io.element.android.libraries.voicerecorder.impl.audio.AudioReader
+
+class FakeAudioReaderFactory(
+    private val audio: List<Audio>
+) : AudioReader.Factory {
+    override fun create(config: AudioConfig, dispatchers: CoroutineDispatchers): AudioReader {
+        return FakeAudioReader(dispatchers, audio)
+    }
+}

libraries/voicerecorder/impl/src/test/kotlin/io/element/android/libraries/voicerecorder/test/FakeEncoder.kt

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.test
+
+import io.element.android.libraries.voicerecorder.impl.audio.Encoder
+import java.io.File
+
+class FakeEncoder(
+    private val fakeFileSystem: FakeFileSystem
+) : Encoder {
+    private var curFile: File? = null
+    override fun init(file: File) {
+        curFile = file
+    }
+
+    override fun encode(buffer: ShortArray, readSize: Int) {
+        val file = curFile
+            ?: error("Encoder not initialized")
+
+        fakeFileSystem.appendToFile(file, buffer, readSize)
+    }
+
+    override fun release() {
+        curFile = null
+    }
+}

libraries/voicerecorder/impl/src/test/kotlin/io/element/android/libraries/voicerecorder/test/FakeFileSystem.kt

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.test
+
+import java.io.File
+
+class FakeFileSystem {
+    // Map of file to file content
+    val files = mutableMapOf<File, String>()
+
+    fun createFile(file: File) {
+        if (files.containsKey(file)) {
+            return
+        }
+
+        files[file] = ""
+    }
+
+    fun appendToFile(file: File, buffer: ShortArray, readSize: Int) {
+        val content = files[file]
+            ?: error("File ${file.path} does not exist")
+
+        files[file] = content + buffer.sliceArray(0 until readSize).contentToString()
+    }
+
+    fun deleteFile(file: File) {
+        files.remove(file)
+    }
+}

libraries/voicerecorder/impl/src/test/kotlin/io/element/android/libraries/voicerecorder/test/FakeVoiceFileManager.kt

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2023-2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.voicerecorder.test
+
+import io.element.android.libraries.voicerecorder.impl.file.VoiceFileConfig
+import io.element.android.libraries.voicerecorder.impl.file.VoiceFileManager
+import java.io.File
+
+class FakeVoiceFileManager(
+    private val fakeFileSystem: FakeFileSystem,
+    private val config: VoiceFileConfig,
+    private val fileId: String,
+) : VoiceFileManager {
+    override fun createFile(): File {
+        val file = File("${config.cacheSubdir}/$fileId.${config.fileExt}")
+        fakeFileSystem.createFile(file)
+        return file
+    }
+
+    override fun deleteFile(file: File) {
+        fakeFileSystem.deleteFile(file)
+    }
+}