[Mp4-tech][systems][ISO-fileformat] timescale in mvhd and mdhd

[Girish Shenoy]

Hi All,
In the case where an iso format file has multiple tracks what would be 
the value of timescale field in mvhd?
The following possibilities cross my mind:
1. It has to be the LCM of the timescales in the mdhd box with the 
respective mdhd boxes maintaining their natural timescales.
2.  Use the LCM of timescales of all tracks to populate mvhd and all 
mdhd boxes (ie all the mdhd and mvhd in the file have the same value in 
timescale field; namely the LCM) and the decode/composition deltas for 
each track need to be multiplied with the factor obtained by dividing 
the LCM-Timescale with the track's natural timescale.
3. Mvhd timescale is not too relevant. The mdhd timescales need to 
necessarily match the natural timescales of the corresponding track. 
Timescale in mvhd does not matter.
Which one of the above (or otherwise) is the accepted way to populate 
mvhd and mdhd timescales?
Regards,
Girish