Just wanted to give a shout out to TMPGenc Video Mastering Works 6 for HD to SD conversion. Never had much success with Vegas downconverting. TMPGenc does a much better job with built in Lanzcos 3 scaling. I'm working on project with a number of DVDs where I have to fit up to 2 hours per DVD and the videos are looking great even though my VBR is as low as 4.5 to 8 on some of them.

My basic workflow:

The source footage is 4k but I'm editing in a 1080p Vegas 13 project so I can pan/zoom.

I create the final master file using the XAVCs 1080p Intra codec. (This looks great and the color levels do not get messed up like some other codecs coming out of Vegas when using in other programs). It's also a smart codec so if I have to make some changes I can without having to waiting hours for a new render.

Bring files into TMPGenc. Start with the standard MPEG DVD preset and make sure all the settings are on best quality. I find that 2 pass VBR works best and I set it as high as possible depending on length of source material. (I ran some tests in CBR but a red logo was pixelating until I switched to 2-pass VBR).

The program can export Ac-3 but personally I prefer to export a wav file and then use Vegas for the AC3 conversion. This allows me flexibility in case I want to audio tune etc. I export with peaks normalized at -12 db.

This program also has a batch tool so I can set up multiple projects to render while I'm away.

Hope this helps some who still has DVD requests and wants the best quality possible.