With the Hitachi 9550, the sendVideo command takes two parameters. The first is the command string to send to the player. See the Hitachi 9550 manual for details on the content of that string. The second parameter is optional. If present, it is the character to wait for from the player to indicate that the player is ready for the next command. If the second parameter is left off, the first character of the command is used, with it's top-most bit set
(this is the normal acknowledgement character for most commands).