Initial commit

.gitignore

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+*.iml
+.gradle
+/local.properties
+/.idea/
+.DS_Store
+/build
+/dist
+/captures
+.externalNativeBuild
+.cxx

BUILD.md

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+# Build
+
+## Debug
+
+This project is an Android application with some shell scripts to execute on the
+computer. Therefore, just use `gradle` as usual:
+
+```
+./gradlew assembleDebug
+```
+
+(or build from _Android Studio_)
+
+To run it:
+
+```bash
+./run
+./run <serial>  # if several devices are connected
+```
+
+_Since building is very fast, `./run` also executes `./gradlew assembleDebug` to
+always run an up-to-date version._
+
+
+## Release
+
+To build and install a release, you need to generate a signed APK.
+
+For that purpose, first generate a _keystore_:
+
+```bash
+# generate sndcpy.keystore file
+keytool -genkey -v -keystore sndcpy.keystore -alias sndcpy \
+        -keyalg RSA -keysize 2048 -validity 30000
+```
+
+Then, add these lines (and adapt) in `~/.gradle/gradle.properties`:
+
+```bash
+SNDCPY_STORE_FILE=/path/to/your/sndcpy.keystore
+SNDCPY_STORE_PASSWORD=the_keystore_password
+SNDCPY_KEY_ALIAS=sndcpy
+SNDCPY_KEY_PASSWORD=the_key_password
+```
+
+Then, execute `./release.sh`. It will generate a release in `dist/`.

LICENSE

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+MIT License
+
+Copyright (c) 2020 Romain Vimont
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# sndcpy
+
+This tool forwards audio from an Android 10 device to the computer. It does not
+require any _root_ access. It works on _GNU/Linux_, _Windows_ and _macOS_.
+
+The purpose is to enable [audio forwarding][issue14] while mirroring with
+[scrcpy]. However, it can be used independently.
+
+[issue14]: https://github.com/Genymobile/scrcpy/issues/14
+[scrcpy]: https://github.com/Genymobile/scrcpy
+
+
+## Requirements
+
+ - The Android device requires at least Android 10.
+ - [VLC] must be installed on the computer.
+
+[vlc]: https://www.videolan.org/
+
+
+## Get the app
+
+Download the latest release:
+
+ - [`sndcpy-v1.0.zip`][release]  
+   _SHA256: TODO_
+ - [`sndcpy-with-adb-windows-v1.0.zip`][release-adb]  
+   _SHA256: TODO_
+
+_On Windows, for simplicity, take the second archive, which also contains
+`adb`._
+
+[release]: https://github.com/rom1v/sndcpy/releases/download/v1.0/sndcpy-v1.0.zip
+[release-adb]: https://github.com/rom1v/sndcpy/releases/download/v1.0/sndcpy-with-adb-windows-v1.0.zip
+
+Alternatively, you could [build the app][BUILD].
+
+[BUILD]: BUILD.md
+
+## Run the app
+
+Plug an Android 10 device with USB debugging enabled, and execute:
+
+```bash
+./sndcpy
+```
+
+If several devices are connected (listed by `adb devices`):
+
+```bash
+./sndcpy <serial>  # replace <serial> by the device serial
+```
+
+_(omit `./` on Windows)_
+
+It will install the app on the device, and request permission to start audio
+capture:
+
+![screenshot](assets/request.png)
+
+Once you clicked on _START NOW_, press _Enter_ in the console to start playing
+on the computer. Press `Ctrl`+`c` in the terminal to stop (except on Windows,
+just disconnect the device or stop capture from the device notifications).
+
+VLC may print this error message once:
+
+```
+main stream error: connection error: Connection refused
+```
+
+It is "expected", just ignore it.
+
+The sound continues to be played on the device. The volume can be adjusted
+independently on the device and on the computer.
+
+## Uninstall
+
+To uninstall the app from the device:
+
+```bash
+adb uninstall com.rom1v.sndcpy
+```
+
+## Apps restrictions
+
+`sndcpy` may only forward audio from apps which do not [prevent audio
+capture][allow]. The rules are detailed in [§capture policy][rules]:
+
+> - By default, apps that target versions up to and including to Android 9.0 do
+>   not permit playback capture. To enable it, include
+>   `android:allowAudioPlaybackCapture="true"` in the app's `manifest.xml` file.
+> - By default, apps that target Android 10 (API level 29) or higher allow their
+>   audio to be captured. To disable playback capture, include
+>   `android:allowAudioPlaybackCapture="false"` in the app's `manifest.xml`
+>   file.
+
+So some apps might need to be updated to support audio capture.
+
+[allow]: https://developer.android.com/guide/topics/media/playback-capture#allowing_playback_capture
+[rules]: https://developer.android.com/guide/topics/media/playback-capture#capture_policy
+
+## Audio delay
+
+This is just a proof-of-concept, so it's far from perfect.
+
+For example, jitter may cause VLC to automatically increase its buffering,
+causing an unacceptable delay:
+
+```
+main input error: ES_OUT_SET_(GROUP_)PCR  is called too late (pts_delay increased to 377 ms)
+```
+
+In that case, just restart it.
+
+## Blog post
+
+ - [Audio forwarding on Android 10][blogpost]
+
+[blogpost]: https://blog.rom1v.com/2020/06/audio-forwarding-on-android-10/

app/.gitignore

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+/build

app/build.gradle

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+apply plugin: 'com.android.application'
+
+android {
+    compileSdkVersion 29
+    buildToolsVersion "29.0.3"
+
+    defaultConfig {
+        applicationId "com.rom1v.sndcpy"
+        minSdkVersion 29
+        targetSdkVersion 29
+        versionCode 1
+        versionName "1.0"
+
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
+    }
+
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
+        }
+    }
+}
+
+if (project.hasProperty("SNDCPY_STORE_FILE")) {
+    android.signingConfigs {
+        release {
+            // to be defined in ~/.gradle/gradle.properties
+            storeFile file(RELEASE_STORE_FILE)
+            storePassword RELEASE_STORE_PASSWORD
+            keyAlias RELEASE_KEY_ALIAS
+            keyPassword RELEASE_KEY_PASSWORD
+        }
+    }
+    android.buildTypes.release.signingConfig = android.signingConfigs.release
+}

app/proguard-rules.pro

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+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# proguardFiles setting in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Uncomment this to preserve the line number information for
+# debugging stack traces.
+#-keepattributes SourceFile,LineNumberTable
+
+# If you keep the line number information, uncomment this to
+# hide the original source file name.
+#-renamesourcefileattribute SourceFile

app/src/main/AndroidManifest.xml

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+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.rom1v.sndcpy">
+
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
+    <uses-permission android:name="android.permission.RECORD_AUDIO" />
+
+    <application
+        android:allowBackup="false"
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:roundIcon="@mipmap/ic_launcher_round">
+        <activity
+            android:name="com.rom1v.sndcpy.MainActivity"
+            android:theme="@style/Theme.Transparent"
+            android:showWhenLocked="true"
+            android:turnScreenOn="true">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+
+        <service
+            android:name="com.rom1v.sndcpy.RecordService"
+            android:enabled="true"
+            android:exported="false"
+            android:foregroundServiceType="mediaProjection" />
+    </application>
+</manifest>

app/src/main/java/com/rom1v/sndcpy/MainActivity.java

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+package com.rom1v.sndcpy;
+
+import android.Manifest;
+import android.app.Activity;
+import android.content.Intent;
+import android.content.pm.PackageManager;
+import android.media.projection.MediaProjectionManager;
+import android.os.Bundle;
+
+public class MainActivity extends Activity {
+
+    private static final int REQUEST_CODE_PERMISSION_AUDIO = 1;
+    private static final int REQUEST_CODE_START_CAPTURE = 2;
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        if (checkSelfPermission(Manifest.permission.RECORD_AUDIO) != PackageManager.PERMISSION_GRANTED) {
+            String[] permissions = {Manifest.permission.RECORD_AUDIO};
+            requestPermissions(permissions, REQUEST_CODE_PERMISSION_AUDIO);
+        }
+
+        MediaProjectionManager mediaProjectionManager = (MediaProjectionManager) getSystemService(MEDIA_PROJECTION_SERVICE);
+        Intent intent = mediaProjectionManager.createScreenCaptureIntent();
+        startActivityForResult(intent, REQUEST_CODE_START_CAPTURE);
+    }
+
+    @Override
+    public void onActivityResult(int requestCode, int resultCode, Intent data) {
+        if (requestCode == REQUEST_CODE_START_CAPTURE && resultCode == Activity.RESULT_OK) {
+            RecordService.start(this, data);
+        }
+        finish();
+    }
+}