Master/Slave Relationship

A master/slave relationship is a specification of a chain of command for controlling a synchronized event. The relationship is 1:N, where one object (the synchronization master) controls the behavior of one or more subordinate objects (the slaves). The relationship is established using the SpiEnableSync function, where one data stream is designated the master and one or more data streams are designated as slaves. Real-time information, transmitted from the master to all slaves by the Sync/Stream Manager, gives each of the slaves the current time in the time base of the MMTIME standard (1/3 msec units). This time information (sync pulse) allows each slave stream handler to adjust the activity of that stream so that synchronization can be maintained.

Certain rules govern master/slave synchronization relationships:

• A data stream can be a slave in only one synchronization relationship.

• Stream handlers must be able to enslave multiple data streams (if multiple data streams are supported) according to different sync masters. For example, each active stream under that handler's control might have a different master.

• A stream cannot become the master of two separate groups of slaves (any additional streams become slaves in the existing master/slave group).

• The sync group (master and all slaves) can be started, stopped, and seeked as a group by using the "slaves" flag on each of the following SPI functions:

  • SpiStartStream
    
  • SpiStopStream
    
  • SpiSeekStream
  
  Any slave in a sync relationship may be arbitrarily started or stopped without affecting the activity of the master or any other slave. The master can be stopped independently of any slave streams in the same sync group and the option is available for all of the slave to be stopped at the same time that the master stream is stopped.
  
  Group synchronized stream time will always be the master stream time. This includes slave streams that have been stopped and re-started.
  
  Stream seeking is done on a per stream basis. For example, a seek in a master stream does not seek in any slave streams that may be in the same sync group.

  It is possible for a slave to fail to maintain synchronization. This condition, called sync overrun, happens when a stream handler has not processed the last sync pulse received from the Sync/Stream Manager and another sync pulse is received. The application can optionally request (by way of the SpiEnableEvent function) to be notified of any sync overruns. The stream is not stopped but the application could request a stop once it receives a sync overrun event.

  ---

  [Back: Synchronization Features]
  [Next: Sync Pulse Generation]