Automatically detect supported sample rates for each codec

app/build.gradle.kts

@@ -299,6 +299,22 @@ android.applicationVariants.all {
         }
     }
 
+    val configXml = tasks.register("configXml${capitalized}") {
+        inputs.property("variant.applicationId", variant.applicationId)
+
+        val outputFile = variantDir.map { it.file("config-${variant.applicationId}.xml") }
+        outputs.file(outputFile)
+
+        doLast {
+            outputFile.get().asFile.writeText("""
+                <?xml version="1.0" encoding="utf-8"?>
+                <config>
+                    <hidden-api-whitelisted-app package="${variant.applicationId}" />
+                </config>
+            """.trimIndent())
+        }
+    }
+
     val addonD = tasks.register("addonD${capitalized}") {
         inputs.property("variant.applicationId", variant.applicationId)
 
@@ -358,6 +374,9 @@ android.applicationVariants.all {
         from(permissionsXml.map { it.outputs }) {
             into("system/etc/permissions")
         }
+        from(configXml.map { it.outputs }) {
+            into("system/etc/sysconfig")
+        }
         from(variant.outputs.map { it.outputFile }) {
             into("system/priv-app/${variant.applicationId}")
         }

app/src/main/java/com/chiller3/bcr/dialog/FormatSampleRateDialogFragment.kt

@@ -4,6 +4,9 @@ import android.app.Dialog
 import android.content.DialogInterface
 import android.os.Bundle
 import android.text.InputType
+import android.text.Spannable
+import android.text.SpannableStringBuilder
+import android.text.style.BulletSpan
 import android.view.View
 import androidx.appcompat.app.AlertDialog
 import androidx.core.os.bundleOf
@@ -42,11 +45,35 @@ class FormatSampleRateDialogFragment : DialogFragment() {
 
         binding = DialogTextInputBinding.inflate(layoutInflater)
 
-        binding.message.text = getString(
-            R.string.format_sample_rate_dialog_message,
-            sampleRateInfo.format(context, sampleRateInfo.range.first),
-            sampleRateInfo.format(context, sampleRateInfo.range.last),
-        )
+        binding.message.text = SpannableStringBuilder().apply {
+            append(getString(R.string.format_sample_rate_dialog_message_desc))
+
+            // BulletSpan operates on unscaled pixels for some reason.
+            val density = resources.displayMetrics.density
+            val gapPx = (density * 4).toInt()
+            val radiusPx = (density * 2).toInt()
+
+            for (range in sampleRateInfo.ranges) {
+                append('\n')
+
+                val start = length
+
+                append(getString(
+                    R.string.format_sample_rate_dialog_message_range,
+                    sampleRateInfo.format(context, range.first),
+                    sampleRateInfo.format(context, range.last),
+                ))
+
+                val end = length
+
+                setSpan(
+                    BulletSpan(gapPx, binding.message.currentTextColor, radiusPx),
+                    start,
+                    end,
+                    Spannable.SPAN_INCLUSIVE_EXCLUSIVE,
+                )
+            }
+        }
 
         // Try to detect if the displayed format is a prefix or suffix since it may not be the same
         // in every language.
@@ -72,12 +99,13 @@ class FormatSampleRateDialogFragment : DialogFragment() {
 
             if (it!!.isNotEmpty()) {
                 try {
-                    val newValue = it.toString().toUInt()
-                    if (newValue in sampleRateInfo.range) {
-                        value = newValue
+                    value = it.toString().toUInt().apply {
+                        sampleRateInfo.validate(this)
                     }
                 } catch (e: NumberFormatException) {
                     // Ignore
+                } catch (e: IllegalArgumentException) {
+                    // Ignore
                 }
             }
 

app/src/main/java/com/chiller3/bcr/extension/AudioFormatExtensions.kt

@@ -1,5 +1,6 @@
 package com.chiller3.bcr.extension
 
+import android.annotation.SuppressLint
 import android.media.AudioFormat
 import android.os.Build
 
@@ -11,3 +12,14 @@ val AudioFormat.frameSizeInBytesCompat: Int
         assert(encoding == AudioFormat.ENCODING_PCM_16BIT)
         2 * channelCount
     }
+
+// Static extension functions are currently not supported in Kotlin. Also, we install a sysconfig
+// file to allow access to these hidden fields.
+
+@SuppressLint("SoonBlockedPrivateApi")
+val SAMPLE_RATE_HZ_MIN_COMPAT: Int =
+    AudioFormat::class.java.getDeclaredField("SAMPLE_RATE_HZ_MIN").getInt(null)
+
+@SuppressLint("SoonBlockedPrivateApi")
+val SAMPLE_RATE_HZ_MAX_COMPAT: Int =
+    AudioFormat::class.java.getDeclaredField("SAMPLE_RATE_HZ_MAX").getInt(null)

app/src/main/java/com/chiller3/bcr/format/AacFormat.kt

@@ -7,8 +7,12 @@ import android.media.MediaFormat
 import android.media.MediaMuxer
 import java.io.FileDescriptor
 
-object AacFormat : Format() {
+class AacFormat : Format() {
     override val name: String = "M4A/AAC"
+    // https://datatracker.ietf.org/doc/html/rfc6381#section-3.1
+    override val mimeTypeContainer: String = "audio/mp4"
+    override val mimeTypeAudio: String = MediaFormat.MIMETYPE_AUDIO_AAC
+    override val passthrough: Boolean = false
     override val paramInfo: FormatParamInfo = RangedParamInfo(
         RangedParamType.Bitrate,
         // The format has no hard limits, so the lower bound is ffmpeg's recommended minimum bitrate
@@ -24,16 +28,8 @@ object AacFormat : Format() {
             128_000u,
         ),
     )
-    override val sampleRateInfo: SampleRateInfo = DiscreteSampleRateInfo(
-        // This what Android's C2 software encoder (C2SoftAacEnc.cpp) supports.
-        uintArrayOf(8_000u, 11_025u, 12_000u, 16_000u, 22_050u, 24_000u, 32_000u, 44_100u, 48_000u),
-        16_000u,
-    )
-    // https://datatracker.ietf.org/doc/html/rfc6381#section-3.1
-    override val mimeTypeContainer: String = "audio/mp4"
-    override val mimeTypeAudio: String = MediaFormat.MIMETYPE_AUDIO_AAC
-    override val passthrough: Boolean = false
-    override val supported: Boolean = true
+    override val sampleRateInfo: SampleRateInfo =
+        SampleRateInfo.fromCodec(baseMediaFormat, 16_000u)
 
     override fun updateMediaFormat(mediaFormat: MediaFormat, param: UInt) {
         mediaFormat.apply {

app/src/main/java/com/chiller3/bcr/format/AmrNbFormat.kt

@@ -5,8 +5,11 @@ package com.chiller3.bcr.format
 import android.media.MediaFormat
 import java.io.FileDescriptor
 
-data object AmrNbFormat : Format() {
+class AmrNbFormat : Format() {
     override val name: String = "AMR-NB"
+    override val mimeTypeContainer: String = "audio/amr"
+    override val mimeTypeAudio: String = MediaFormat.MIMETYPE_AUDIO_AMR_NB
+    override val passthrough: Boolean = false
     override val paramInfo: FormatParamInfo = RangedParamInfo(
         RangedParamType.Bitrate,
         4_750u..12_200u,
@@ -19,14 +22,8 @@ data object AmrNbFormat : Format() {
             12_200u,
         ),
     )
-    override val sampleRateInfo: SampleRateInfo = DiscreteSampleRateInfo(
-        uintArrayOf(8_000u),
-        8_000u,
-    )
-    override val mimeTypeContainer: String = "audio/amr"
-    override val mimeTypeAudio: String = MediaFormat.MIMETYPE_AUDIO_AMR_NB
-    override val passthrough: Boolean = false
-    override val supported: Boolean = true
+    override val sampleRateInfo: SampleRateInfo =
+        SampleRateInfo.fromCodec(baseMediaFormat, 8_000u)
 
     override fun updateMediaFormat(mediaFormat: MediaFormat, param: UInt) {
         mediaFormat.apply {

app/src/main/java/com/chiller3/bcr/format/AmrWbFormat.kt

@@ -5,8 +5,11 @@ package com.chiller3.bcr.format
 import android.media.MediaFormat
 import java.io.FileDescriptor
 
-data object AmrWbFormat : Format() {
+class AmrWbFormat : Format() {
     override val name: String = "AMR-WB"
+    override val mimeTypeContainer: String = MediaFormat.MIMETYPE_AUDIO_AMR_WB
+    override val mimeTypeAudio: String = mimeTypeContainer
+    override val passthrough: Boolean = false
     override val paramInfo: FormatParamInfo = RangedParamInfo(
         RangedParamType.Bitrate,
         6_600u..23_850u,
@@ -19,14 +22,8 @@ data object AmrWbFormat : Format() {
             23_850u,
         ),
     )
-    override val sampleRateInfo: SampleRateInfo = DiscreteSampleRateInfo(
-        uintArrayOf(16_000u),
-        16_000u,
-    )
-    override val mimeTypeContainer: String = MediaFormat.MIMETYPE_AUDIO_AMR_WB
-    override val mimeTypeAudio: String = mimeTypeContainer
-    override val passthrough: Boolean = false
-    override val supported: Boolean = true
+    override val sampleRateInfo: SampleRateInfo =
+        SampleRateInfo.fromCodec(baseMediaFormat, 16_000u)
 
     override fun updateMediaFormat(mediaFormat: MediaFormat, param: UInt) {
         mediaFormat.apply {

app/src/main/java/com/chiller3/bcr/format/FlacFormat.kt

@@ -5,24 +5,20 @@ package com.chiller3.bcr.format
 import android.media.MediaFormat
 import java.io.FileDescriptor
 
-object FlacFormat : Format() {
+class FlacFormat : Format() {
     override val name: String = "FLAC"
+    override val mimeTypeContainer: String = MediaFormat.MIMETYPE_AUDIO_FLAC
+    override val mimeTypeAudio: String = MediaFormat.MIMETYPE_AUDIO_FLAC
+    override val passthrough: Boolean = false
     override val paramInfo: FormatParamInfo = RangedParamInfo(
         RangedParamType.CompressionLevel,
         0u..8u,
         // Devices are fast enough nowadays to use the highest compression for realtime recording
         8u,
         uintArrayOf(0u, 5u, 8u),
     )
-    override val sampleRateInfo: SampleRateInfo = RangedSampleRateInfo(
-        1u..655_350u,
-        16_000u,
-        uintArrayOf(8_000u, 16_000u, 48_000u),
-    )
-    override val mimeTypeContainer: String = MediaFormat.MIMETYPE_AUDIO_FLAC
-    override val mimeTypeAudio: String = MediaFormat.MIMETYPE_AUDIO_FLAC
-    override val passthrough: Boolean = false
-    override val supported: Boolean = true
+    override val sampleRateInfo: SampleRateInfo =
+        SampleRateInfo.fromCodec(baseMediaFormat, 16_000u)
 
     override fun updateMediaFormat(mediaFormat: MediaFormat, param: UInt) {
         mediaFormat.apply {

app/src/main/java/com/chiller3/bcr/format/Format.kt

@@ -2,6 +2,7 @@ package com.chiller3.bcr.format
 
 import android.media.AudioFormat
 import android.media.MediaFormat
+import android.util.Log
 import com.chiller3.bcr.Preferences
 import com.chiller3.bcr.extension.frameSizeInBytesCompat
 import java.io.FileDescriptor
@@ -10,12 +11,6 @@ sealed class Format {
     /** User-facing name of the format. */
     abstract val name: String
 
-    /** Details about the format parameter range and default value. */
-    abstract val paramInfo: FormatParamInfo
-
-    /** Defaults about the supported sample rates. */
-    abstract val sampleRateInfo: SampleRateInfo
-
     /** The MIME type of the container storing the encoded audio stream. */
     abstract val mimeTypeContainer: String
 
@@ -29,8 +24,17 @@ sealed class Format {
     /** Whether the format takes the PCM samples as is without encoding. */
     abstract val passthrough: Boolean
 
-    /** Whether the format is supported on the current device. */
-    abstract val supported: Boolean
+    /** Details about the format parameter range and default value. */
+    abstract val paramInfo: FormatParamInfo
+
+    /** Defaults about the supported sample rates. */
+    abstract val sampleRateInfo: SampleRateInfo
+
+    /** Bare minimum [MediaFormat] containing only [MediaFormat.KEY_MIME]. */
+    protected val baseMediaFormat: MediaFormat
+        get() = MediaFormat().apply {
+            setString(MediaFormat.KEY_MIME, mimeTypeAudio)
+        }
 
     /**
      * Create a [MediaFormat] representing the encoded audio with parameters matching the specified
@@ -47,8 +51,7 @@ sealed class Format {
             paramInfo.validate(param)
         }
 
-        val format = MediaFormat().apply {
-            setString(MediaFormat.KEY_MIME, mimeTypeAudio)
+        val format = baseMediaFormat.apply {
             setInteger(MediaFormat.KEY_CHANNEL_COUNT, audioFormat.channelCount)
             setInteger(MediaFormat.KEY_SAMPLE_RATE, audioFormat.sampleRate)
             setInteger(KEY_X_FRAME_SIZE_IN_BYTES, audioFormat.frameSizeInBytesCompat)
@@ -90,17 +93,31 @@ sealed class Format {
     abstract fun getContainer(fd: FileDescriptor): Container
 
     companion object {
+        private val TAG = Format::class.java.simpleName
+
         const val KEY_X_FRAME_SIZE_IN_BYTES = "x-frame-size-in-bytes"
 
-        val all: Array<Format> = arrayOf(
-            OpusFormat,
-            AacFormat,
-            FlacFormat,
-            WaveFormat,
-            AmrWbFormat,
-            AmrNbFormat,
-        )
-        private val default: Format = all.first { it.supported }
+        val all: List<Format> by lazy {
+            val formats = mutableListOf<Format>()
+
+            for (constructor in arrayOf(
+                ::OpusFormat,
+                ::AacFormat,
+                ::FlacFormat,
+                { WaveFormat },
+                ::AmrWbFormat,
+                ::AmrNbFormat,
+            )) {
+                try {
+                    formats.add(constructor())
+                } catch (e: IllegalArgumentException) {
+                    Log.w(TAG, "Failed to initialize with $constructor", e)
+                }
+            }
+
+            formats
+        }
+        private val default: Format = all.first()
 
         /** Find output format by name. */
         fun getByName(name: String): Format? = all.find { it.name == name }
@@ -112,11 +129,8 @@ sealed class Format {
          * sample rate, if set, is set to the nearest valid value.
          */
         fun fromPreferences(prefs: Preferences): Triple<Format, UInt?, UInt?> {
-            // Use the saved format if it is valid and supported on the current device. Otherwise,
-            // fall back to the default.
-            val format = prefs.format
-                ?.let { if (it.supported) { it } else { null } }
-                ?: default
+            // Use the saved format if it is (still) valid.
+            val format = prefs.format ?: default
 
             // Convert the saved value to the nearest valid value (eg. in case the bitrate range is
             // changed in a future version).

app/src/main/java/com/chiller3/bcr/format/OpusFormat.kt

@@ -8,8 +8,18 @@ import android.os.Build
 import androidx.annotation.RequiresApi
 import java.io.FileDescriptor
 
-object OpusFormat : Format() {
+class OpusFormat : Format() {
+    init {
+        require(Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
+            "Only supported on Android 10 and newer"
+        }
+    }
+
     override val name: String = "OGG/Opus"
+    // https://datatracker.ietf.org/doc/html/rfc7845#section-9
+    override val mimeTypeContainer: String = "audio/ogg"
+    override val mimeTypeAudio: String = MediaFormat.MIMETYPE_AUDIO_OPUS
+    override val passthrough: Boolean = false
     override val paramInfo: FormatParamInfo = RangedParamInfo(
         RangedParamType.Bitrate,
         6_000u..510_000u,
@@ -24,16 +34,8 @@ object OpusFormat : Format() {
             48_000u,
         ),
     )
-    override val sampleRateInfo: SampleRateInfo = DiscreteSampleRateInfo(
-        // This what Android's C2 software encoder (C2SoftOpusEnc.cpp) supports.
-        uintArrayOf(8_000u, 12_000u, 16_000u, 24_000u, 48_000u),
-        16_000u,
-    )
-    // https://datatracker.ietf.org/doc/html/rfc7845#section-9
-    override val mimeTypeContainer: String = "audio/ogg"
-    override val mimeTypeAudio: String = MediaFormat.MIMETYPE_AUDIO_OPUS
-    override val passthrough: Boolean = false
-    override val supported: Boolean = Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q
+    override val sampleRateInfo: SampleRateInfo =
+        SampleRateInfo.fromCodec(baseMediaFormat, 16_000u)
 
     override fun updateMediaFormat(mediaFormat: MediaFormat, param: UInt) {
         mediaFormat.apply {