To quickly give an overview of my workflow, I'll start with that. Operating on CS4 for everything. When I have my project edited, I then use Media Encoder to export my projects out as Mpeg2/dvd, and Dolby Digital audio, for use in Encore.
Now for my question. Every once in a while, I have a wedding video that exceeds 2 hours (15-20 minutes over). First, is it possible for me to get that onto a DVD/single layer, and secondly, how do I do this? I hate having to use a dual layer disc for 15-20 minutes of video over 2 hours. I also hate having to cut my project down, missing what may be important to my client. Any and all help would be a beautiful thing.
You can put as much video as you want on a DVD, being aware that the lower data rate will reduce quality. With talking head videos, 3 hours can look fine...all depends on the footage. I routinely make dance recital DVDs of 150-165 minutes, never a complaint. Have never made a dual-layer project myself (cost of media, incompatibility woes).
There are many "data rate calculator" apps online, just search, otherwise a formula I got from Adobe is 560/minutes=data rate. For instance 560/135=4.148 and then I round down a bit for safety. A setting of 4.0 should be safe, while 4.1 might cut it close. Will you use animated menus that might take additional space?
Definitely use 2-pass VBR for better quality encoding.
About the Dolby encoding, unless you paid for the SurCode upgrade, your audio export options from CS4 Media Encoder would not include Dolby. Standard practice is to encode "PCM" audio which is a .wav file, and then Encore will transcode to Dolby. If you have Dolby available in your AME, then by all means go for it. The CS6 version of AME now includes the Dolby stereo encoder, which outputs an .ac3 file.