I've been using this calculator for a long time: http://dvd-hq.info/bitrate_calculator.php
And it's extremely useful but my problem is that it tells me what my i, B and P frames should be for the GOP structure but in Sony Vegas Movie Studio 15 Platinum I can not find the option to select my P frame amount. Is there a way or is that automatic upon setting the other two kinds? I'm in the MainConcept MPEG-2 widescreen DVD Architect NTSC template.
What the calculator says:
FOR NTSC
FOR PAL
Your cool calculator just uses a less common way of reporting the same information. The numbers 18-2 in Vegas mean one I-frame every 18 frames, two consecutive b-frames, with every internal third frame implied as a p-frame, thus IBBPBBPBBPBBPBBPBB-I...
Vegas allows us to interrupt the sequence with new I-frames at cuts, fx keyframes, chapter points, etc. for frame-accurate indexing.
The Vegas defaults are correct and should not be changed to avoid playback stutter. However, NTSC encoded at 15- or 18- frame GOP should never show a difference.
Great question. Your interest in knowing what's going on under the hood is admirable, and should be recognized as such by most of the forum posters here.