Encoded mpeg1 files appear as different sizes in QT & wmp

This is baffling to me, but I’m sure there is an obvious explanation:
I have a client that is creating a CD-rom that will include video I am providing in mpeg1 files. My original video is 720x480 dv that I exported from an Avid XpressDV as uncompressed avi files.
I have been doing tests using TMPGenc+ to encode as mpeg1 in a variety of sizes. I have several questions:

  1. When I play the mpeg files using Quicktime or Windows Media Player, the size (resolution) is slightly different than the size I created.

For example, in TMPGenc I make a 320x208 file.
Quicktime (according to its “movie properties”) says it is 288x208.
Windows Media Player says it is 284x288.
When my client opens it in Java, it says it is the original correct size (320x208)
And when I check the original avi file, it says it is the original size, too.

This discrepancy is true in any size file I use.

  1. This a TMPGenc question: When I drag in my source avi file, it tells me in the Advanced tab that the source is “4:3 525 line (ntsc, 704x480),” but the source avi is actually 720x480. As a test I’ve changed the source aspect ratio in the drop down box to “4:3 525 line NTSC.” That results in minor black borders on the width sides of the frame when played in Quicktime.

So the 704x480 looks better (because it fills the window), but why is this true?

  1. And one more question: There are three different frame sizes (resolutions) my client may be using. His initial sizes, when played with Quicktime, resulted in “letterboxing” to show the full frame of video. So I then created new samples sized close to the same ratio as 720x480, coming up with 320x208, 640x424 and 240x160. (everything divisible by 8) These all played without the letterboxing.

But, using my algebra again, I see that 720x480 isn’t the same ratio as 4:3.

Sorry for the long post, but as you can see I need help before I get too far along.
Thanks!