A method for forming a combined image frame of a combined video stream comprises: capturing image frames of first and second video streams; encoding image data of the image frames of the first and second video streams, wherein each image frame of the first and second video streams are respectively encoded into first and second encoded data comprising a plurality of rows wherein each row has a height of a single coding unit and a width equal to a width of the image frame and is encoded as one or more slices; and combining the first and second encoded data into combined encoded data by interleaving rows of the first and second encoded data. The combined encoded data representing the combined image frame of the combined video stream.