Add watermark to encoded video in grafiak

Question

I have created a sample using grafika code where I am creating the video from camera feeds. In grafika sample there is a method to drawExtra while passing data to muxer which add dots in vidoe. I want to add water mark in place of this at left top corner.

Please suggest.

if (mFileSaveInProgress && showCam) {

         Log.e(TAG, "drawFrame  saving to new video");
          mEncoderSurface.makeCurrent();
          GLES20.glViewport(0, 0,720, 1280);
          mFullFrameBlit.drawFrame(mTextureId, mTmpMatrix);
        drawExtra(mFrameNum, viewWidth, viewHeight);
          mCircEncoder.frameAvailableSoon();
       mEncoderSurface.setPresentationTime(mvideoTexture.getTimestamp());
          mEncoderSurface.swapBuffers();

}