在 Android 中使用 WebRTC 自定义视频源格式可以通过实现 VideoCapturer 接口来实现。以下是一个示例代码：

首先，创建一个实现 VideoCapturer 接口的自定义视频源类，例如 CustomVideoCapturer：

import android.content.Context;
import android.graphics.ImageFormat;
import android.hardware.Camera;
import android.os.SystemClock;

import org.webrtc.CameraEnumerationAndroid;
import org.webrtc.Logging;
import org.webrtc.SurfaceTextureHelper;
import org.webrtc.VideoCapturer;
import org.webrtc.VideoFrame;
import org.webrtc.VideoFrame.Buffer;
import org.webrtc.VideoSink;

import java.nio.ByteBuffer;

public class CustomVideoCapturer implements VideoCapturer {

    private static final String TAG = "CustomVideoCapturer";
    private static final int FRAME_RATE = 30;
    private static final int IMAGE_WIDTH = 640;
    private static final int IMAGE_HEIGHT = 480;

    private SurfaceTextureHelper surfaceTextureHelper;
    private VideoSink videoSink;
    private Camera camera;
    private int cameraId;
    private boolean running;
    private boolean capturingFrames;

    public CustomVideoCapturer(Context context, VideoSink videoSink) {
        this.videoSink = videoSink;
        this.cameraId = CameraEnumerationAndroid.getDeviceIndex(CameraEnumerationAndroid.getNameOfFrontFacingDevice());
    }

    @Override
    public void initialize(SurfaceTextureHelper surfaceTextureHelper, Context context, CapturerObserver capturerObserver) {
        this.surfaceTextureHelper = surfaceTextureHelper;
    }

    @Override
    public void startCapture(int width, int height, int framerate) {
        if (running) return;
        running = true;

        camera = Camera.open(cameraId);
        Camera.Parameters parameters = camera.getParameters();
        parameters.setPreviewSize(IMAGE_WIDTH, IMAGE_HEIGHT);
        parameters.setPreviewFormat(ImageFormat.NV21);
        camera.setParameters(parameters);

        camera.setPreviewCallbackWithBuffer(new Camera.PreviewCallback() {
            @Override
            public void onPreviewFrame(byte[] data, Camera camera) {
                if (capturingFrames) {
                    Buffer buffer = new VideoFrame.Buffer(data, IMAGE_WIDTH, IMAGE_HEIGHT, ImageFormat.NV21);
                    VideoFrame frame = new VideoFrame(buffer, 0, SystemClock.elapsedRealtimeNanos());
                    videoSink.onFrame(frame);
                    frame.release();
                }
                camera.addCallbackBuffer(data);
            }
        });

        int bufferSize = IMAGE_WIDTH * IMAGE_HEIGHT * ImageFormat.getBitsPerPixel(ImageFormat.NV21) / 8;
        byte[] buffer = new byte[bufferSize];
        camera.addCallbackBuffer(buffer);

        camera.startPreview();
        capturingFrames = true;
    }

    @Override
    public void stopCapture() {
        if (!running) return;
        running = false;

        capturingFrames = false;
        camera.stopPreview();
        camera.setPreviewCallbackWithBuffer(null);
        camera.release();
    }

    @Override
    public void changeCaptureFormat(int width, int height, int framerate) {
        // Not supported
    }

    @Override
    public void dispose() {
        stopCapture();
    }

    @Override
    public boolean isScreencast() {
        return false;
    }
}

然后，在使用 WebRTC 的地方，使用自定义视频源类来进行视频捕获：

import org.webrtc.EglBase;
import org.webrtc.PeerConnectionFactory;
import org.webrtc.SurfaceViewRenderer;
import org.webrtc.VideoCapturer;
import org.webrtc.VideoSink;
import org.webrtc.VideoSource;

public class MainActivity extends AppCompatActivity {

    private PeerConnectionFactory factory;
    private VideoSource videoSource;
    private VideoCapturer videoCapturer;

    private SurfaceViewRenderer surfaceViewRenderer;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        surfaceViewRenderer = findViewById(R.id.surface_view_renderer);
        EglBase.Context eglBaseContext = EglBase.create().getEglBaseContext();
        surfaceViewRenderer.init(eglBaseContext, null);

        factory = new PeerConnectionFactory.Builder().createPeerConnectionFactory();

        videoCapturer = new CustomVideoCapturer(this, new VideoSink() {
            @Override
            public void onFrame(VideoFrame videoFrame) {
                // 处理视频帧
                surfaceViewRenderer.renderFrame(videoFrame);
            }
        });

        videoSource = factory.createVideoSource(videoCapturer.isScreencast());
        videoCapturer.initialize(null, this, videoSource.getCapturerObserver());
        videoCapturer.startCapture(640, 480, 30);

        surfaceViewRenderer.setMirror(true);
        videoSource.adaptOutputFormat(640, 480, 30);
        videoSource.add