Add option to select audio source

Pass --audio-source=mic to capture the microphone instead of the device
audio output.

server/src/main/java/com/genymobile/scrcpy/AudioCapture.java

@@ -10,7 +10,6 @@ import android.media.AudioFormat;
 import android.media.AudioRecord;
 import android.media.AudioTimestamp;
 import android.media.MediaCodec;
-import android.media.MediaRecorder;
 import android.os.Build;
 import android.os.SystemClock;
 
@@ -18,7 +17,6 @@ import java.nio.ByteBuffer;
 
 public final class AudioCapture {
 
-    public static final int SOURCE = MediaRecorder.AudioSource.REMOTE_SUBMIX;
     public static final int SAMPLE_RATE = 48000;
     public static final int CHANNEL_CONFIG = AudioFormat.CHANNEL_IN_STEREO;
     public static final int CHANNELS = 2;
@@ -26,12 +24,18 @@ public final class AudioCapture {
     public static final int ENCODING = AudioFormat.ENCODING_PCM_16BIT;
     public static final int BYTES_PER_SAMPLE = 2;
 
+    private final int audioSource;
+
     private AudioRecord recorder;
 
     private final AudioTimestamp timestamp = new AudioTimestamp();
     private long previousPts = 0;
     private long nextPts = 0;
 
+    public AudioCapture(AudioSource audioSource) {
+        this.audioSource = audioSource.value();
+    }
+
     public static int millisToBytes(int millis) {
         return SAMPLE_RATE * CHANNELS * BYTES_PER_SAMPLE * millis / 1000;
     }
@@ -46,13 +50,13 @@ public final class AudioCapture {
 
     @TargetApi(Build.VERSION_CODES.M)
     @SuppressLint({"WrongConstant", "MissingPermission"})
-    private static AudioRecord createAudioRecord() {
+    private static AudioRecord createAudioRecord(int audioSource) {
         AudioRecord.Builder builder = new AudioRecord.Builder();
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
             // On older APIs, Workarounds.fillAppInfo() must be called beforehand
             builder.setContext(FakeContext.get());
         }
-        builder.setAudioSource(SOURCE);
+        builder.setAudioSource(audioSource);
         builder.setAudioFormat(createAudioFormat());
         int minBufferSize = AudioRecord.getMinBufferSize(SAMPLE_RATE, CHANNEL_CONFIG, ENCODING);
         // This buffer size does not impact latency
@@ -100,12 +104,12 @@ public final class AudioCapture {
 
     private void startRecording() {
         try {
-            recorder = createAudioRecord();
+            recorder = createAudioRecord(audioSource);
         } catch (NullPointerException e) {
             // Creating an AudioRecord using an AudioRecord.Builder does not work on Vivo phones:
             // - <https://github.com/Genymobile/scrcpy/issues/3805>
             // - <https://github.com/Genymobile/scrcpy/pull/3862>
-            recorder = Workarounds.createAudioRecord(SOURCE, SAMPLE_RATE, CHANNEL_CONFIG, CHANNELS, CHANNEL_MASK, ENCODING);
+            recorder = Workarounds.createAudioRecord(audioSource, SAMPLE_RATE, CHANNEL_CONFIG, CHANNELS, CHANNEL_MASK, ENCODING);
         }
         recorder.startRecording();
     }

server/src/main/java/com/genymobile/scrcpy/AudioSource.java

@@ -0,0 +1,30 @@
+package com.genymobile.scrcpy;
+
+import android.media.MediaRecorder;
+
+public enum AudioSource {
+    OUTPUT("output", MediaRecorder.AudioSource.REMOTE_SUBMIX),
+    MIC("mic", MediaRecorder.AudioSource.MIC);
+
+    private final String name;
+    private final int value;
+
+    AudioSource(String name, int value) {
+        this.name = name;
+        this.value = value;
+    }
+
+    int value() {
+        return value;
+    }
+
+    static AudioSource findByName(String name) {
+        for (AudioSource audioSource : AudioSource.values()) {
+            if (name.equals(audioSource.name)) {
+                return audioSource;
+            }
+        }
+
+        return null;
+    }
+}

server/src/main/java/com/genymobile/scrcpy/Options.java

@@ -14,6 +14,7 @@ public class Options {
     private int maxSize;
     private VideoCodec videoCodec = VideoCodec.H264;
     private AudioCodec audioCodec = AudioCodec.OPUS;
+    private AudioSource audioSource = AudioSource.OUTPUT;
     private int videoBitRate = 8000000;
     private int audioBitRate = 128000;
     private int maxFps;
@@ -72,6 +73,10 @@ public class Options {
         return audioCodec;
     }
 
+    public AudioSource getAudioSource() {
+        return audioSource;
+    }
+
     public int getVideoBitRate() {
         return videoBitRate;
     }
@@ -225,6 +230,13 @@ public class Options {
                     }
                     options.audioCodec = audioCodec;
                     break;
+                case "audio_source":
+                    AudioSource audioSource = AudioSource.findByName(value);
+                    if (audioSource == null) {
+                        throw new IllegalArgumentException("Audio source " + value + " not supported");
+                    }
+                    options.audioSource = audioSource;
+                    break;
                 case "max_size":
                     options.maxSize = Integer.parseInt(value) & ~7; // multiple of 8
                     break;

server/src/main/java/com/genymobile/scrcpy/Server.java

@@ -136,7 +136,7 @@ public final class Server {
 
             if (audio) {
                 AudioCodec audioCodec = options.getAudioCodec();
-                AudioCapture audioCapture = new AudioCapture();
+                AudioCapture audioCapture = new AudioCapture(options.getAudioSource());
                 Streamer audioStreamer = new Streamer(connection.getAudioFd(), audioCodec, options.getSendCodecMeta(),
                         options.getSendFrameMeta());
                 AsyncProcessor audioRecorder;