I'll make this quick and easy... have a 16:9 project that I want to encode to an mp4... when I export it from FCP as "current settings" (DV NTSC anamorphic) then bring it into compressor, it never encodes to that aspect ratio! Instead it squishes it which looks rediculous. I went into some of the settings in compressor and made something anamorphic or 16:9 on a second attempt and it still was squished. what gives? I want it to be widescreen on the web!
Your source is 720x480 anamorphic. For web, you'll need 853x480 with square pixels. That conversion makes it look correct on computer monitor.
Duplicate one of the MPEG-4 settings and modify it. Go to Geometry tab. Set frame size to custom. Set Contrain to Display Aspect to 16:9. Set Pixel Aspect to Square. Move back up and set height to 480. You'll end up with 853x480 size in the setting. Apply this to your source and go.