Multi-Channel Synchronization

We are building a very specialized multimedia "player" and we are trying to use SMIL to schedule it. 

Our "player" has multiple output "channels" for media presentations. Each "channel" has its own 
independent output window. So our "channel" entity sounds like a SMIL "viewport".

We need the ability to synchronize the play of media files across multiple "viewports".   

For example, the play of video3.mpg on viewport #1 should be synchronized with the play of video5.mpg
on viewport #2. 

Some sections of a presentation maybe be synchronized and other sections may be completely 
independent. 

Is there a SMIL 2.0 recommendation that addresses this requirement? 

Also, we hoped to use independent SMIL documents to schedule each viewport when media synchronization
is not required. We would use one SMIL document when synchronization across viewports is required. 

Is there a SMIL 2.0 recommendation that addresses this requirement?