[MEncoder-users] B Frames and mp4

Hi

There has been a lot of talk about Bframes (and one other type that
escapes me right now), how can I tell from a .mp4 file weather there are
B Frames being used, something like mplayer -v <file> ?

Alex
--
"I try to go for longer runs, but it's tough around here at the White House on the outdoor track. It's sad that I can't run longer. It's one of the saddest things about the presidency. "

- George W. Bush
interview with Runners World, Aug. 2002