The reason for this is that such files have IndexTableSegments which when parsed
cover EditUnit ranges like this:

 [0,1)
 [249,250)
 [249,377)
 [0,249)

where each interval is [IndexStartPosition,IndexStartPosition+IndexDuration).
This would be reduced to a sparse index like:

 [0,1), [249,250)

instead of the full range:

 [0,249), [249,377)

See TimeCode_HD.mxf, UMID =
060a2b340101010101010410130000000004001aa0e59175025b2a5600da4101.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>