Using All as a Device Identifier

You can specify  all  (MCI_ALL_DEVICE_ID) as a device identifier for any command that does not return information. When you specify  all , MCI sends the command sequentially to all devices opened by the current application.

For example, the close4BA_J1  all  command closes all open devices and the playUDIOAK  all  command starts playing all devices opened by the application. Because MCI sequentially sends the commands to the MCI devices, there is an interval between when the first and last devices receive the command.

Using  all  is a convenient way to broadcast a command to all your devices, but you should not rely on it to synchronize devices; the timing between messages can vary.