To change the synchronization mode of a sequencer device, use the MCI_SET command message with the MCI_SEQ_SET_MASTER and MCI_SEQ_SET_SLAVE flags. Two members in the MCI_SEQ_SET_PARMS structure, dwMaster and dwSlave, are used to specify the master and slave synchronization modes.
The master synchronization mode controls synchronization information sent by the sequencer to an output port. The slave synchronization mode controls where the sequencer gets its timing information to play a MIDI file. Following are the constants for the dwMaster member and their corresponding master synchronization modes.
| Constant | Synchronization mode |
|---|---|
| MCI_SEQ_MIDI | MIDI Synchronization. Send timing information to output port using MIDI timing clock messages. |
| MCI_SEQ_SMPTE | SMPTE Synchronization. Send timing information to output port using MIDI quarter-frame messages. |
| MCI_SEQ_NONE | No Synchronization. Send no timing information. |
Following are the constants for the dwSlave member and their corresponding slave synchronization modes.
| Constant | Synchronization mode |
|---|---|
| MCI_SEQ_FILE | File Synchronization. Get timing information from MIDI file. |
| MCI_SEQ_MIDI | MIDI Synchronization. Get timing information from input port using MIDI timing clock messages. |
| MCI_SEQ_SMPTE | SMPTE Synchronization. Get timing information from input port using MIDI quarter-frame messages. |
| MCI_SEQ_NONE | No Synchronization. Get timing information from MCI commands only and ignore timing information (such as tempo changes) that are in the MIDI file. |
Note Currently, for master synchronization, the MCI MIDI sequencer supports only the No Synchronization mode (MCI_SEQ_NONE). For slave synchronization, it supports only the File Synchronization mode (MCI_SEQ_FILE) and the No Synchronization mode (MCI_SEQ_NONE).