Add --camera-facing

Add an option to select the camera by its lens facing (front, back or
external).

PR #4213 <https://github.com/Genymobile/scrcpy/pull/4213>

Co-authored-by: Romain Vimont <rom@rom1v.com>
Signed-off-by: Romain Vimont <rom@rom1v.com>

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

@@ -6,6 +6,7 @@ import android.annotation.SuppressLint;
 import android.annotation.TargetApi;
 import android.hardware.camera2.CameraAccessException;
 import android.hardware.camera2.CameraCaptureSession;
+import android.hardware.camera2.CameraCharacteristics;
 import android.hardware.camera2.CameraDevice;
 import android.hardware.camera2.CameraManager;
 import android.hardware.camera2.CaptureFailure;
@@ -28,6 +29,7 @@ import java.util.concurrent.atomic.AtomicBoolean;
 public class CameraCapture extends SurfaceCapture {
 
     private final String explicitCameraId;
+    private final CameraFacing cameraFacing;
     private final Size explicitSize;
 
     private HandlerThread cameraThread;
@@ -37,8 +39,9 @@ public class CameraCapture extends SurfaceCapture {
 
     private final AtomicBoolean disconnected = new AtomicBoolean();
 
-    public CameraCapture(String explicitCameraId, Size explicitSize) {
+    public CameraCapture(String explicitCameraId, CameraFacing cameraFacing, Size explicitSize) {
         this.explicitCameraId = explicitCameraId;
+        this.cameraFacing = cameraFacing;
         this.explicitSize = explicitSize;
     }
 
@@ -50,7 +53,7 @@ public class CameraCapture extends SurfaceCapture {
         cameraExecutor = new HandlerExecutor(cameraHandler);
 
         try {
-            String cameraId = selectCamera(explicitCameraId);
+            String cameraId = selectCamera(explicitCameraId, cameraFacing);
             if (cameraId == null) {
                 throw new IOException("No matching camera found");
             }
@@ -62,7 +65,7 @@ public class CameraCapture extends SurfaceCapture {
         }
     }
 
-    private static String selectCamera(String explicitCameraId) throws CameraAccessException {
+    private static String selectCamera(String explicitCameraId, CameraFacing cameraFacing) throws CameraAccessException {
         if (explicitCameraId != null) {
             return explicitCameraId;
         }
@@ -70,8 +73,22 @@ public class CameraCapture extends SurfaceCapture {
         CameraManager cameraManager = ServiceManager.getCameraManager();
 
         String[] cameraIds = cameraManager.getCameraIdList();
-        // Use the first one
-        return cameraIds.length > 0 ? cameraIds[0] : null;
+        if (cameraFacing == null) {
+            // Use the first one
+            return cameraIds.length > 0 ? cameraIds[0] : null;
+        }
+
+        for (String cameraId : cameraIds) {
+            CameraCharacteristics characteristics = cameraManager.getCameraCharacteristics(cameraId);
+
+            int facing = characteristics.get(CameraCharacteristics.LENS_FACING);
+            if (cameraFacing.value() == facing) {
+                return cameraId;
+            }
+        }
+
+        // Not found
+        return null;
     }
 
     @Override

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

@@ -0,0 +1,33 @@
+package com.genymobile.scrcpy;
+
+import android.annotation.SuppressLint;
+import android.hardware.camera2.CameraCharacteristics;
+
+public enum CameraFacing {
+    FRONT("front", CameraCharacteristics.LENS_FACING_FRONT),
+    BACK("back", CameraCharacteristics.LENS_FACING_BACK),
+    @SuppressLint("InlinedApi") // introduced in API 23
+    EXTERNAL("external", CameraCharacteristics.LENS_FACING_EXTERNAL);
+
+    private final String name;
+    private final int value;
+
+    CameraFacing(String name, int value) {
+        this.name = name;
+        this.value = value;
+    }
+
+    int value() {
+        return value;
+    }
+
+    static CameraFacing findByName(String name) {
+        for (CameraFacing facing : CameraFacing.values()) {
+            if (name.equals(facing.name)) {
+                return facing;
+            }
+        }
+
+        return null;
+    }
+}

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

@@ -26,6 +26,7 @@ public class Options {
     private int displayId;
     private String cameraId;
     private Size cameraSize;
+    private CameraFacing cameraFacing;
     private boolean showTouches;
     private boolean stayAwake;
     private List<CodecOption> videoCodecOptions;
@@ -126,6 +127,10 @@ public class Options {
         return cameraSize;
     }
 
+    public CameraFacing getCameraFacing() {
+        return cameraFacing;
+    }
+
     public boolean getShowTouches() {
         return showTouches;
     }
@@ -360,6 +365,15 @@ public class Options {
                         options.cameraSize = parseSize(value);
                     }
                     break;
+                case "camera_facing":
+                    if (!value.isEmpty()) {
+                        CameraFacing facing = CameraFacing.findByName(value);
+                        if (facing == null) {
+                            throw new IllegalArgumentException("Camera facing " + value + " not supported");
+                        }
+                        options.cameraFacing = facing;
+                    }
+                    break;
                 case "send_device_meta":
                     options.sendDeviceMeta = Boolean.parseBoolean(value);
                     break;

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

@@ -137,7 +137,7 @@ public final class Server {
                 if (options.getVideoSource() == VideoSource.DISPLAY) {
                     surfaceCapture = new ScreenCapture(device);
                 } else {
-                    surfaceCapture = new CameraCapture(options.getCameraId(), options.getCameraSize());
+                    surfaceCapture = new CameraCapture(options.getCameraId(), options.getCameraFacing(), options.getCameraSize());
                 }
                 SurfaceEncoder surfaceEncoder = new SurfaceEncoder(surfaceCapture, videoStreamer, options.getVideoBitRate(), options.getMaxFps(),
                         options.getVideoCodecOptions(), options.getVideoEncoder(), options.getDownsizeOnError());