I have a 45 minute mpeg1 clip that I demuxed using Tmpeg

If I remux it using Tmpeg, it takes about 5-6 minutes but when I use
Bbmpeg, it takes over an hour.

Why does it take so long using Bbmpeg? Are there special settings
within Bbmpeg that speed the muxing process up?

I using a Thunderbird 1.2 Gig with 512 megs of Ram.