Add --audio-dup

Add an option to duplicate audio on the device, compatible with the new
audio playback capture (--audio-source=playback).

Fixes #3875 <https://github.com/Genymobile/scrcpy/issues/3875>
Fixes #4380 <https://github.com/Genymobile/scrcpy/issues/4380>
PR #5102 <https://github.com/Genymobile/scrcpy/pull/5102>

Co-authored-by: Simon Chan <1330321+yume-chan@users.noreply.github.com>

app/data/bash-completion/scrcpy

@@ -6,6 +6,7 @@ _scrcpy() {
         --audio-buffer=
         --audio-codec=
         --audio-codec-options=
+        --audio-dup
         --audio-encoder=
         --audio-source=
         --audio-output-buffer=

app/data/zsh-completion/_scrcpy

@@ -13,6 +13,7 @@ arguments=(
     '--audio-buffer=[Configure the audio buffering delay (in milliseconds)]'
     '--audio-codec=[Select the audio codec]:codec:(opus aac flac raw)'
     '--audio-codec-options=[Set a list of comma-separated key\:type=value options for the device audio encoder]'
+    '--audio-dup=[Duplicate audio]'
     '--audio-encoder=[Use a specific MediaCodec audio encoder]'
     '--audio-source=[Select the audio source]:source:(output mic playback)'
     '--audio-output-buffer=[Configure the size of the SDL audio output buffer (in milliseconds)]'

app/scrcpy.1

@@ -49,6 +49,12 @@ The list of possible codec options is available in the Android documentation:
 
 <https://d.android.com/reference/android/media/MediaFormat>
 
+.TP
+.B \-\-audio\-dup
+Duplicate audio (capture and keep playing on the device).
+
+This feature is only available with --audio-source=playback.
+
 .TP
 .BI "\-\-audio\-encoder " name
 Use a specific MediaCodec audio encoder (depending on the codec provided by \fB\-\-audio\-codec\fR).

app/src/cli.c

@@ -100,6 +100,7 @@ enum {
     OPT_NO_WINDOW,
     OPT_MOUSE_BIND,
     OPT_NO_MOUSE_HOVER,
+    OPT_AUDIO_DUP,
 };
 
 struct sc_option {
@@ -177,6 +178,13 @@ static const struct sc_option options[] = {
                 "Android documentation: "
                 "<https://d.android.com/reference/android/media/MediaFormat>",
     },
+    {
+        .longopt_id = OPT_AUDIO_DUP,
+        .longopt = "audio-dup",
+        .text = "Duplicate audio (capture and keep playing on the device).\n"
+                "This feature is only available with --audio-source=playback."
+
+    },
     {
         .longopt_id = OPT_AUDIO_ENCODER,
         .longopt = "audio-encoder",
@@ -2615,6 +2623,9 @@ parse_args_with_getopt(struct scrcpy_cli_args *args, int argc, char *argv[],
             case OPT_NO_WINDOW:
                 opts->window = false;
                 break;
+            case OPT_AUDIO_DUP:
+                opts->audio_dup = true;
+                break;
             default:
                 // getopt prints the error message on stderr
                 return false;
@@ -2891,6 +2902,18 @@ parse_args_with_getopt(struct scrcpy_cli_args *args, int argc, char *argv[],
         }
     }
 
+    if (opts->audio_dup) {
+        if (!opts->audio) {
+            LOGE("--audio-dup not supported if audio is disabled");
+            return false;
+        }
+
+        if (opts->audio_source != SC_AUDIO_SOURCE_PLAYBACK) {
+            LOGE("--audio-dup is specific to --audio-source=playback");
+            return false;
+        }
+    }
+
     if (opts->record_format && !opts->record_filename) {
         LOGE("Record format specified without recording");
         return false;

app/src/options.c

@@ -101,6 +101,7 @@ const struct scrcpy_options scrcpy_options_default = {
     .list = 0,
     .window = true,
     .mouse_hover = true,
+    .audio_dup = false,
 };
 
 enum sc_orientation

app/src/options.h

@@ -297,6 +297,7 @@ struct scrcpy_options {
     uint8_t list;
     bool window;
     bool mouse_hover;
+    bool audio_dup;
 };
 
 extern const struct scrcpy_options scrcpy_options_default;

app/src/scrcpy.c

@@ -394,6 +394,7 @@ scrcpy(struct scrcpy_options *options) {
         .display_id = options->display_id,
         .video = options->video,
         .audio = options->audio,
+        .audio_dup = options->audio_dup,
         .show_touches = options->show_touches,
         .stay_awake = options->stay_awake,
         .video_codec_options = options->video_codec_options,

app/src/server.c

@@ -292,6 +292,9 @@ execute_server(struct sc_server *server,
         ADD_PARAM("audio_source=%s",
                   sc_server_get_audio_source_name(params->audio_source));
     }
+    if (params->audio_dup) {
+        ADD_PARAM("audio_dup=true");
+    }
     if (params->max_size) {
         ADD_PARAM("max_size=%" PRIu16, params->max_size);
     }

app/src/server.h

@@ -50,6 +50,7 @@ struct sc_server_params {
     uint32_t display_id;
     bool video;
     bool audio;
+    bool audio_dup;
     bool show_touches;
     bool stay_awake;
     bool force_adb_forward;

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

@@ -26,6 +26,7 @@ public class Options {
     private AudioCodec audioCodec = AudioCodec.OPUS;
     private VideoSource videoSource = VideoSource.DISPLAY;
     private AudioSource audioSource = AudioSource.OUTPUT;
+    private boolean audioDup;
     private int videoBitRate = 8000000;
     private int audioBitRate = 128000;
     private int maxFps;
@@ -100,6 +101,10 @@ public class Options {
         return audioSource;
     }
 
+    public boolean getAudioDup() {
+        return audioDup;
+    }
+
     public int getVideoBitRate() {
         return videoBitRate;
     }
@@ -303,6 +308,9 @@ public class Options {
                     }
                     options.audioSource = audioSource;
                     break;
+                case "audio_dup":
+                    options.audioDup = Boolean.parseBoolean(value);
+                    break;
                 case "max_size":
                     options.maxSize = Integer.parseInt(value) & ~7; // multiple of 8
                     break;

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

@@ -167,7 +167,13 @@ public final class Server {
             if (audio) {
                 AudioCodec audioCodec = options.getAudioCodec();
                 AudioSource audioSource = options.getAudioSource();
-                AudioCapture audioCapture = audioSource.isDirect() ? new AudioDirectCapture(audioSource) : new AudioPlaybackCapture();
+                AudioCapture audioCapture;
+                if (audioSource.isDirect()) {
+                    audioCapture = new AudioDirectCapture(audioSource);
+                } else {
+                    audioCapture = new AudioPlaybackCapture(options.getAudioDup());
+                }
+
                 Streamer audioStreamer = new Streamer(connection.getAudioFd(), audioCodec, options.getSendCodecMeta(), options.getSendFrameMeta());
                 AsyncProcessor audioRecorder;
                 if (audioCodec == AudioCodec.RAW) {

server/src/main/java/com/genymobile/scrcpy/audio/AudioPlaybackCapture.java

@@ -18,9 +18,15 @@ import java.nio.ByteBuffer;
 
 public final class AudioPlaybackCapture implements AudioCapture {
 
+    private final boolean keepPlayingOnDevice;
+
     private AudioRecord recorder;
     private AudioRecordReader reader;
 
+    public AudioPlaybackCapture(boolean keepPlayingOnDevice) {
+        this.keepPlayingOnDevice = keepPlayingOnDevice;
+    }
+
     @SuppressLint("PrivateApi")
     private AudioRecord createAudioRecord() throws AudioCaptureException {
         // See <https://github.com/Genymobile/scrcpy/issues/4380>
@@ -60,7 +66,8 @@ public final class AudioPlaybackCapture implements AudioCapture {
             Method setFormat = audioMixBuilder.getClass().getMethod("setFormat", AudioFormat.class);
             setFormat.invoke(audioMixBuilder, AudioConfig.createAudioFormat());
 
-            int routeFlags = audioMixClass.getField("ROUTE_FLAG_LOOP_BACK").getInt(null);
+            String routeFlagName = keepPlayingOnDevice ? "ROUTE_FLAG_LOOP_BACK_RENDER" : "ROUTE_FLAG_LOOP_BACK";
+            int routeFlags = audioMixClass.getField(routeFlagName).getInt(null);
 
             // audioMixBuilder.setRouteFlags(routeFlag);
             Method setRouteFlags = audioMixBuilder.getClass().getMethod("setRouteFlags", int.class);