Merge pull request #26698 from warped-rudi:mediandk2

AndroidMediaNdkVideoWriter pixel format enhancement #26698

* videoio(Android): Add source pixel formats RGBA and GRAY to AndroidMediaNdkVideoWriter

Let AndroidMediaNdkVideoWriter::write() deduce source pixel format from matrix type:

CV_8UC3 -> BGR   (as before)
CV_8UC4 -> RGBA  (use in conjunction with CvCameraViewFrame)
CV_8UC1 -> GRAY

* samples/android/video-recorder: Send images to VideoWriter in RGBA format

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x ] The PR is proposed to the proper branch
- [ ] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake

samples/android/video-recorder/src/org/opencv/samples/recorder/RecorderActivity.java

@@ -164,16 +164,15 @@ public class RecorderActivity extends CameraActivity implements CvCameraViewList
     {
         Log.d(TAG, "Camera frame arrived");
 
-        Mat rgbMat = inputFrame.rgba();
+        mVideoFrame = inputFrame.rgba();
 
-        Log.d(TAG, "Size: " + rgbMat.width() + "x" + rgbMat.height());
+        Log.d(TAG, "Size: " + mVideoFrame.width() + "x" + mVideoFrame.height());
 
         if (mVideoWriter != null && mVideoWriter.isOpened()) {
-            Imgproc.cvtColor(rgbMat, mVideoFrame, Imgproc.COLOR_RGBA2BGR);
             mVideoWriter.write(mVideoFrame);
         }
 
-        return rgbMat;
+        return mVideoFrame;
     }
 
     @Override