feat(poc/audio): add Android mobile audio spike

Closes the mobile half of the PoC plan §2 audio exit criterion left open by poc/audio-capture-playback-spike. The desktop and mobile halves together fully retire the audio PoC. Stack: Kotlin (MainActivity) → JNI → Rust cdylib → cpal 0.16 → Oboe (AAudio / OpenSL ES) → Android audio HAL Layout: rust crate (src/lib.rs) — JNI_OnLoad, initContext, playSine440, record1sToFile; panic-catching at JNI boundary; android_logger → logcat android/ (Gradle 8.7, — minSdk 24, compileSdk 34, AGP 8.5.2. AGP 8.5.2, Kotlin 1.9.24) cargoBuildRust task wraps cargo-ndk -P 26 -t <abi> for all four ABIs; wired into preBuild so AGP picks up the produced .so files. Verified on 2026-05-13 on a physical Motorola Moto G Stylus 5G (2023), Android 14 SDK 34 arm64-v8a: - Playback: 500 ms 440 Hz mono sine, 22,050 frames emitted at 44.1 kHz through cpal/Oboe/AAudio/device speaker. - Capture: 1 s from default input, 42,624 frames written to /data/data/app.chanora.poc.audio/files/chanora_poc_capture.wav. File pulled via 'adb exec-out run-as ... cat' and confirmed by file(1) as 'RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, mono 44100 Hz'. Header bytes cross-checked against the reported frame count. Notes: - cpal links libaaudio (introduced API 26), so cargo-ndk targets API 26 via -P 26 while the Android module's minSdk stays at 24 (DEC-004). API 24/25 devices would fall back to OpenSL ES at runtime; not exercised here. - JNI panic safety: every JNI entry point wraps its body in std::panic::catch_unwind and a tracing panic hook routes panic messages to logcat under tag 'ChanoraAudioPoC'. Without this, cpal panicking inside an extern "system" function would abort the process. - The emulator AVD chanora-poc-api34 and its system image were installed during Phase 0 but emulator verification was skipped once the physical-device run succeeded. Real-device evidence is stronger. Surfaced finding: DEC-011.1 mobile half promoted from Deferred to Accepted for Android in the same docs commit; iOS remains explicitly Deferred (requires macOS + Xcode hardware). Authority: PoC plan §2, DEC-011, DEC-011.1. Not product code; not promoted into chanora_audio.
2026-05-14 18:24:53 +08:00
parent eca93a141e
commit ec21a880d2
15 changed files with 2278 additions and 0 deletions
@@ -0,0 +1,124 @@
+plugins {
+    id("com.android.application")
+    id("org.jetbrains.kotlin.android")
+}
+
+android {
+    namespace = "app.chanora.poc.audio"
+    compileSdk = 34
+
+    defaultConfig {
+        applicationId = "app.chanora.poc.audio"
+        minSdk = 24      // matches DEC-004
+        targetSdk = 34
+        versionCode = 1
+        versionName = "0.1.0-poc"
+
+        ndk {
+            // Keep all four common ABIs so the same APK works on both
+            // the x86_64 emulator and a physical arm64 device.
+            abiFilters += listOf("x86_64", "arm64-v8a", "armeabi-v7a", "x86")
+        }
+    }
+
+    sourceSets {
+        getByName("main") {
+            // cargo-ndk drops .so files here.
+            jniLibs.srcDirs("src/main/jniLibs")
+        }
+    }
+
+    buildTypes {
+        getByName("debug") {
+            isMinifyEnabled = false
+        }
+        getByName("release") {
+            isMinifyEnabled = false
+        }
+    }
+
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+    kotlinOptions {
+        jvmTarget = "17"
+    }
+    packaging {
+        // Avoid duplicate-resource conflicts from native libs if any
+        // future deps bring them in.
+        resources.excludes += setOf("META-INF/AL2.0", "META-INF/LGPL2.1")
+    }
+}
+
+dependencies {
+    implementation("androidx.core:core-ktx:1.13.1")
+    implementation("androidx.appcompat:appcompat:1.7.0")
+}
+
+// ---------------------------------------------------------------------
+// Rust cdylib build via cargo-ndk.
+//
+// Each ABI maps to a Rust target triple; cargo-ndk handles linker
+// selection. The task copies the produced .so into the per-ABI
+// jniLibs directory expected by Android Gradle Plugin.
+// ---------------------------------------------------------------------
+
+val rustCrateDir = rootProject.projectDir.parentFile  // ../  -> the spike root
+val rustTargetDir = file("$rustCrateDir/target")
+val jniLibsDir = file("$projectDir/src/main/jniLibs")
+
+val cargoBuildRust = tasks.register("cargoBuildRust") {
+    group = "build"
+    description = "Builds the Rust cdylib for all enabled Android ABIs via cargo ndk."
+
+    val abis = listOf(
+        Triple("x86_64",       "x86_64-linux-android",      "x86_64"),
+        Triple("arm64-v8a",    "aarch64-linux-android",     "arm64-v8a"),
+        Triple("armeabi-v7a",  "armv7-linux-androideabi",   "armeabi-v7a"),
+        Triple("x86",          "i686-linux-android",        "x86")
+    )
+
+    doLast {
+        // Resolve cargo: try CARGO_HOME/bin first, then PATH, then the
+        // rustup shim location.
+        val cargoBinDir = System.getenv("CARGO_HOME")?.let { "$it/bin" }
+            ?: "${System.getProperty("user.home")}/.cargo/bin"
+        val cargo = listOf("$cargoBinDir/cargo", "/usr/local/bin/cargo", "/usr/bin/cargo")
+            .firstOrNull { file(it).exists() }
+            ?: error("cargo not found; install via rustup")
+        val cargoNdkBin = listOf("$cargoBinDir/cargo-ndk", "/usr/local/bin/cargo-ndk")
+            .firstOrNull { file(it).exists() }
+        check(cargoNdkBin != null) { "cargo-ndk not installed (cargo install cargo-ndk)" }
+
+        val ndkHome = System.getenv("ANDROID_NDK_HOME")
+            ?: System.getenv("NDK_HOME")
+            ?: "/opt/android-sdk/ndk/26.3.11579264"
+        check(file(ndkHome).exists()) { "NDK not found at $ndkHome" }
+
+        // cargo-ndk is a cargo subcommand; invoke via `cargo ndk ...`.
+        // We must ensure cargo's PATH lookup can find cargo-ndk too.
+        // `-p 26` selects API 26 for the NDK toolchain so cpal can
+        // link against libaaudio (introduced in API 26). minSdk in
+        // the Android module stays at 24 — the device just won't
+        // execute the AAudio code path below API 26; cpal/Oboe falls
+        // back to OpenSL ES there.
+        val abiArgs = abis.flatMap { listOf("-t", it.first) }
+        val cargoCmd = listOf(cargo, "ndk", "-P", "26") + abiArgs +
+            listOf("-o", jniLibsDir.absolutePath, "build", "--release",
+                   "--manifest-path", "$rustCrateDir/Cargo.toml")
+
+        println("[cargoBuildRust] running: ${cargoCmd.joinToString(" ")}")
+
+        exec {
+            commandLine(cargoCmd)
+            environment("ANDROID_NDK_HOME", ndkHome)
+            environment("PATH", "$cargoBinDir:${System.getenv("PATH")}")
+        }
+    }
+}
+
+// Make Android's preBuild depend on the Rust build so AGP picks up the .so files.
+tasks.matching { it.name == "preBuild" }.configureEach {
+    dependsOn(cargoBuildRust)
+}
@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <!-- Required for capture. Cpal's Oboe input stream needs this. -->
+    <uses-permission android:name="android.permission.RECORD_AUDIO" />
+
+    <application
+        android:label="Chanora Audio PoC"
+        android:allowBackup="false"
+        android:supportsRtl="true"
+        android:theme="@android:style/Theme.Material.Light">
+        <activity
+            android:name=".MainActivity"
+            android:exported="true">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+    </application>
+</manifest>
@@ -0,0 +1,134 @@
+package app.chanora.poc.audio
+
+import android.Manifest
+import android.app.Activity
+import android.content.pm.PackageManager
+import android.os.Bundle
+import android.util.Log
+import android.view.View
+import android.widget.Button
+import android.widget.LinearLayout
+import android.widget.TextView
+import androidx.core.app.ActivityCompat
+import androidx.core.content.ContextCompat
+import java.io.File
+import kotlin.concurrent.thread
+
+/**
+ * Chanora PoC — Android mobile audio spike.
+ *
+ * Two buttons:
+ *   1) Play 500 ms 440 Hz sine wave through the default output device.
+ *   2) Record 1 s from the default input device to app-private storage.
+ *
+ * Both call into the Rust cdylib via JNI. Status is logged to logcat
+ * under the tag "ChanoraAudioPoC" (Rust) and "ChanoraPoCActivity"
+ * (Kotlin). The UI also displays the result string.
+ */
+class MainActivity : Activity() {
+
+    private companion object {
+        const val TAG = "ChanoraPoCActivity"
+        const val REQ_RECORD = 1001
+    }
+
+    private lateinit var status: TextView
+    private lateinit var recordBtn: Button
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+
+        // Hand the Application Context to the Rust side BEFORE any
+        // audio call, so cpal's Oboe backend can find Android audio
+        // services via ndk_context.
+        NativeAudio.initContext(applicationContext)
+
+        val root = LinearLayout(this).apply {
+            orientation = LinearLayout.VERTICAL
+            setPadding(48, 48, 48, 48)
+        }
+
+        val title = TextView(this).apply {
+            text = "Chanora Audio PoC (Android)"
+            textSize = 20f
+        }
+
+        status = TextView(this).apply {
+            text = "ready"
+            textSize = 14f
+            setPadding(0, 24, 0, 24)
+        }
+
+        val playBtn = Button(this).apply {
+            text = "Play 500 ms sine"
+            setOnClickListener { onPlay() }
+        }
+
+        recordBtn = Button(this).apply {
+            text = "Record 1 s to file"
+            setOnClickListener { onRecord() }
+        }
+
+        root.addView(title)
+        root.addView(status)
+        root.addView(playBtn)
+        root.addView(recordBtn)
+        setContentView(root)
+    }
+
+    private fun setStatus(s: String) {
+        Log.i(TAG, s)
+        runOnUiThread { status.text = s }
+    }
+
+    private fun onPlay() {
+        setStatus("playing…")
+        thread(name = "chanora-poc-play") {
+            val frames = NativeAudio.playSine440(500L)
+            if (frames < 0) {
+                setStatus("PLAY ERROR (see logcat)")
+            } else {
+                setStatus("PLAY OK frames=$frames")
+            }
+        }
+    }
+
+    private fun onRecord() {
+        if (ContextCompat.checkSelfPermission(this, Manifest.permission.RECORD_AUDIO)
+                != PackageManager.PERMISSION_GRANTED) {
+            ActivityCompat.requestPermissions(this, arrayOf(Manifest.permission.RECORD_AUDIO), REQ_RECORD)
+            setStatus("requesting RECORD_AUDIO…")
+            return
+        }
+        doRecord()
+    }
+
+    private fun doRecord() {
+        setStatus("recording 1 s…")
+        thread(name = "chanora-poc-record") {
+            val path = File(filesDir, "chanora_poc_capture.wav").absolutePath
+            val frames = NativeAudio.record1sToFile(path, 1000L)
+            if (frames < 0) {
+                setStatus("RECORD ERROR (see logcat)")
+            } else {
+                val sz = File(path).length()
+                setStatus("RECORD OK frames=$frames bytes=$sz path=$path")
+            }
+        }
+    }
+
+    override fun onRequestPermissionsResult(
+        requestCode: Int,
+        permissions: Array<out String>,
+        grantResults: IntArray
+    ) {
+        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
+        if (requestCode == REQ_RECORD) {
+            if (grantResults.firstOrNull() == PackageManager.PERMISSION_GRANTED) {
+                doRecord()
+            } else {
+                setStatus("RECORD_AUDIO permission denied")
+            }
+        }
+    }
+}
@@ -0,0 +1,22 @@
+package app.chanora.poc.audio
+
+import android.content.Context
+
+object NativeAudio {
+    init {
+        System.loadLibrary("audio_capture_playback_android_spike")
+    }
+
+    /**
+     * Must be called once after `System.loadLibrary` with the
+     * application Context. Initialises the Rust-side `ndk_context`
+     * that cpal/Oboe relies on to locate Android audio services.
+     */
+    external fun initContext(context: Context)
+
+    /** Returns the number of frames emitted, or -1 on error. */
+    external fun playSine440(durationMs: Long): Long
+
+    /** Returns the number of frames captured, or -1 on error. */
+    external fun record1sToFile(path: String, durationMs: Long): Long
+}
@@ -0,0 +1,5 @@
+// Root build file — versions only; module config lives in app/build.gradle.kts.
+plugins {
+    id("com.android.application") version "8.5.2" apply false
+    id("org.jetbrains.kotlin.android") version "1.9.24" apply false
+}
@@ -0,0 +1,4 @@
+org.gradle.jvmargs=-Xmx2g -Dfile.encoding=UTF-8
+android.useAndroidX=true
+kotlin.code.style=official
+android.nonTransitiveRClass=true
@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.7-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
@@ -0,0 +1,249 @@
+#!/bin/sh
+
+#
+# Copyright © 2015-2021 the original authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/HEAD/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+# This is normally unused
+# shellcheck disable=SC2034
+APP_BASE_NAME=${0##*/}
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd "${APP_HOME:-./}" > /dev/null && pwd -P ) || exit
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='-Dfile.encoding=UTF-8 "-Xmx64m" "-Xms64m"'
+
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"
@@ -0,0 +1,18 @@
+// Settings: declare the single :app module.
+pluginManagement {
+    repositories {
+        gradlePluginPortal()
+        google()
+        mavenCentral()
+    }
+}
+dependencyResolutionManagement {
+    repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
+    repositories {
+        google()
+        mavenCentral()
+    }
+}
+
+rootProject.name = "chanora-audio-poc"
+include(":app")