Metal Shader for de-interlacing video frame

I am rendering interlaced video frames to the Metal texture (the video frame is a full-frame with both fields). Does anybody know how to write a Metal shader to de-interlace such an image? I am not sure if this is the right approach. I am capturing frames using BlackMagic SDK, and the input signal is 1080i50. According to documentation and what I received in the image buffer, the device should provide a de-interlaced image. Image buffer size is 1920x1080, and fps is 25. What is the right technique to suppress this "horizontal" interlacing effect I see in the final image? Do I have to split the frame into odd and even field, create two textures and then blend these two textures into a new one (using "an ? algorithm")? Thanks.