Not sure what Vegas Studio offers in settables. The quality levels you’re talking about are just made up — your DVD recorder is trying to relate the quality to the tape speed (thus quality) options on VHS tapes. But DVD quality is continuously variable, and based on several factors.
In general, the best rendering you can get is when your rendered DVD fills the disc, and when you render at 2-Pass Variable Bitrate. On Pro Vegas, you’d set these parameters by selecting a DVD preset that’s close to what you want (I’d probably choose “DVD Architect NTSC Widescreen”), then clicking on the “Custom” button. Here you can change the rendering mode and set up your bitrate options.
Bitrate is of course the analog to the “speed” of the VHS tape; slower bitrates will fit more video but the quality will be less. For any given project, you can figure out pretty optimal settings by using a bitrate calculator (there are dozens of these online.. you can find more about this searching the Vegas forum for “bitrate calculator” too). Here, you enter the length of your video, the type of audio being used (probably 2-channel AC-3 at 192kb/s or 5.1-channel AC-3 at 448kb/s), and the media (such as DVD5), and the calculator will suggest bitrate parameters to set in Vegas.
One other thing to consider… DVD has a maximum video bitrate. Professionally encoded DVDs store considerably more than an hour per disc, and also use DVD9 (8.5GB) discs. But you’ll often find that regular video is encoded in the 4-5Mb/s range, with action sequences and other fast motion boosted up to 7-8Mb/s. They have some other tricks to minimize MPEG-2 problems when encoding, too. For those without professional mastering gear, you’re going to encode it all at high bitrate if the video is short. Pretty much under 1 hour, you can encode it at any speed you like, and even CBR, since the benefit to VBR is smaller size.
The hard limits for audio and video together is 9.8Mb/s, which encodes an hour at 4.41GB… so this just fits on a DVD. In short, you can use the highest available video quality for an hour or less and not run out of room. The fact that you have a substantial bit of space left on that disc means you probably ran a lower encoding rate. Which can be a good idea, depending. Some early players were marginal on playback at full speed, and may fail completely on DVD-Rs with the same bitrate. So you usualy avoid too high, but for shorter videos, 8Mb/s or so is usually plenty.
-Dave