android13/packages/services/Car/car-evs-helper-lib

car-evs-helper-lib

This directory contains two modules that are used by other apps to process CarEvsBufferDescriptor and render its contents to the display with EGL.

• car-evs-helper-lib: This library contains CarEvsGLSurfaceView and CarEvsBufferRenderer classes.
• libcarevsglrenderer_jni: This is a JNI library CarEvsBufferRenderer uses to render the contents of CarEvsBufferDescriptor with EGL.

How to use

Please follow below instructions to delegate a CarEvsBufferDescriptor rendering to this library. A reference implementation is also available at packages/services/Car/tests/CarEvsCameraPreviewApp.

1. Make the application refer to car-evs-helper-lib and libcarevsglrenderer_jni libraries by adding below lines to Android.bp.

static_libs: ["car-evs-helper-lib"],
jni_libs: ["libcarevsglrenderer_jni"],

2. Implement CarEvsGLSurfaceView.Callback interface. For example,

/**
 * This method is called by the renderer to fetch a new frame to draw.
 */
@Override
public CarEvsBufferDescriptor getNewFrame() {
    synchronized(mLock) {
        // Return a buffer to render.
        return mBufferToRender;
    }
}
/**
 * This method is called by the renderer when it is done with a passed
 * CarEvsBufferDescriptor object.
 */
@Override
public void returnBuffer(CarEvsBufferDescriptor buffer) {
    // Return a buffer to CarEvsService.
    try {
        mEvsManager.returnFrameBuffer(buffer);
    } catch (Exception e) {
        ...
    }
    ...
}

3. Create CarEvsGLSurfaceView with the application context, CarEvsGLSurfaceView.Callback object, and, optionally, a desired in-plane rotation angle.

private CarEvsGLSurfaceView mView;
@Override
protected void onCreate(Bundle savedInstanceState) {
    ...
    mView = CarEvsGLSurfaceView(getAppliation(), this, /* angleInDegree= */ 0);
    ...
}

4. Start a video stream and update wheneven new frame buffer arrives. For example,

private final CarEvsManager.CarEvsStreamCallback mStreamHandler =
    new CarEvsManager.CarEvsStreamCallback() {
    ...
    @Override
    public void onNewFrame(CarEvsBufferDescriptor buffer) {
      synchronized(mLock) {
        mBufferToRender = buffer;
      }
    }
}