Like with MIDI File Format's Time Signature MetaEvent, the Denominator is expressed as a power of 2. Again, this is similiar to the same field in MIDI File Format's Time Signature MetaEvent. The Bar Marker message indicates the start of a musical measure. Zero and negative numbers up to -8,190 indicate count off measures. A value of zero would indicate no count off.
Positive values indicate measures of the piece.
This would be used by a device wishing to mark the passage of measures without keeping track of the actual measure number. Here's the general template for the message. Depending upon the Type, the message may have additional bytes placed where is. The following values for Event Types are defined, and here's what each does. For example, a piece of video and a piece of music that are supposed to go together may be created at different times, and likely have different absolute time code positions.