A video data extension system includes a transmitter and a receiver for transmitting and receiving encoded serial data. Transmitter is configured to receive one SDI 3G video stream at 2.97 Gb/s, two HD-SDI video streams at 1.485 Gb/s, two SD-SDI at 270 Mb/s, or one HD-SDI at 1.485 Gb/s and one SD-SDI at 270 Mb/s. Received data is segmented into packets to form an extended video stream for transmission at 3.75 Gb/s. To each packet, idle and header are provided. Data such as RS422 data may be included in the extended video stream. Where the received data includes data from two HD streams, received data are segmented into two groups of data packets for arranging into extended video stream in an alternate manner. Upon receiving the extended video stream, receiver uses idles to align data and header information to separate the HD streams.