Declan,
Getting the best out of the DVD Studio Pro has become a problem.
Forget about HD when using DVDSP (except when you are content with an HD-DVD image file as end result that will only play on a

)
So SD it is. Make sure that in DVDSP you have chosen the right DVD settings BEFORE you create a new project (see picture)
You have two options in adding the video content to your project:
- Import the video asset in its current format/codec
- Use Compressor to convert your video asset to the right MPEG2 format required fro your DVD disc
In your case you have a H264 original. This file needs conversion before it can be put on a SD disc. When you use option 1, upon import, DVDSP will place a yellow or red dot next to the asset indicating it needs conversion. Upon DVD build DVDSP will use default settings to do the conversion for you.
Note it the conversion is too complicated to DVDSP it will not let you import the video asset. This may happen when your original is NTSC (30 frames) and your DVD is set as PAL (25 frames).
In case you want control over the conversion -> use Compressor. Compressor can bite practically any comversion-bullet.
Choose the right Compressor preset and/or make one yourselves.
Your one (1) H264 file will result in two (2) target files. One for containing video only, the other audio only. Import both files in DVDSP. A green bullet will appear.
Now the Build process will be extremely fast as your video/audio does not require any further encoding.
Groetjes
Coen