ASI (Asynchronous Serial Interface) - is a streaming data format which often carries an MPEG Transport Stream (MPEG-TS). It is electrically identical to an SDI signal and is always 270Mbit/s. There are two transmission formats commonly used by the ASI interface, the 188 byte format and the 204 byte format. The 188 byte format is the more common ASI transport stream. When optional Reed-Solomon error correction data is included the packet can stretch an extra 16 bytes to 204 bytes total.