[MP4-tech] Systems: ES_Descriptor to ES (VOP) ?

[Alexei Ioudovski]

Hello,
I came across an mp4 file with Separate Configuration/Elementary Stream
meaning that the VOP data starts at byte 28 (the first vop_start_code), and
a corresponding VOL is at the end of the file somewhere inside the esds
atom.
What exactly is the mechanism in Systems that associates the VOL data
(inside the ES_Descriptor or somewhere else?) with that particular set of
VOPs at the beginning of the file? Note that there are only two elementary
streams: video and audio. 
In other words, where is the indication that VOL data should be applied to
the VOP starting from byte 28?
Thank you,
Alexei Ioudovski
Vega Imaging Technologies Inc.