Not quite that easy!
I mean its easy enough to make Vegas do it BUT don't expect results like the Matrix. Problem is there just isn't that many frames to start with so it gets VERY jerky and / or blurred as Vegas tries to invent new frames.

The material needs to be shot at a higher frame rate or if you want a smooth speed ramp then you need a camera like the Varicam and even it's limited, still not as good as you can get with film cameras.

Don't let me put you off trying, just understand what you're trying has serious limitations and there's no magic bullet. Seems to be OK down to about 50% but to get a smooth ramp down to freeze is impossible if it's a long ramp.

A lot of the Matrix stuff was shot using multiple still cameras BTW.

. . . and don't be put off . . yes, you should record at high speed to get quality when slowing down .. . and yes the Bullet sequnce was recored using XCameras . . . if aint done any of that . . then Slap in a Velocity envel and have fun . . the management of your expectations we will all - inc farss - be availabe to listen to your "gripes" when - and it will - happen .. .

Grazie

How are they doing it in the NFL replays?

Don't know for certain, I know a lot of the sports stuff is shot with fast shutter speeds which helps, make normal viewing aweful in my opinion. I don't watch sports that much but I don't think they get a very smooth ramp down or up and secondly secondly they're not shooting DV although that shouldn't make that much difference.

It depends on just how smooth you want it to look, with overcranked cameras it looks perfect..

It goes something like this:

You need a minimum of 10fps or any motion starts to look like just a series of stills, very juddery. Now you've shot video at say 30 fps. As you ramp down at 1/3 speed you've only got 10 original frames so Vegas or any other system has to 'invent' new frames by a number of means, mostly some form of interpolation. But in the process resolution has to suffer big time, the more frames it's got to invent the worse it gets.

Of course speeding things up isn't a problem, you've got more frames than you need, I've sped stuff up 1000% and it still looks perfect.

I assume most of the modern sports slo-mo is done with special equipment that is taking more than 30 fps. This is certainly true of the super slo-mo they do of a pitched baseball where you can see the ball slowly rotating, and can make out the seams on the baseball.

I wish there was some way I could "overcrank" a video camera for little money, but I don't know of any cheap equipment.