First 30 frames used to identify the fps

[sunil]

I played a video in the following speeds and the correct fps was displayed only after few seconds
- 30 fps - after 1 sec
- 15 fps - after 2 sec
- 5 fps   - after 6 sec
From this i understood, DXtory takes the first 30 frames and then decides the fps. Is this true??

[Millian]

Would a method like that be reliable?