First of all, you have to understand how encoding works. It’s not just based on how long your movie is. You could actually fit more than 2 hours on a normal DVD disk but you would have to use so much compression that the quality would be terrible. There is a trade off when it comes to compression, quality and size. In general, less compression yields better quality video but takes up more room. The more you compress a video, the smaller the file gets but after a certain point, you will notice a drop in quality. The trick is finding the right combination.
If you want to fit that 1 hr 45 min project on a disk, set the encoder in PP to use 4mb VBR 2 pass and change the audio setting to use the Main Concept MPEG Audio instead of the PCM Audio. This should give you the best results with all things considered and your video should fit. Keep in mind that when you use VRB 2-pass encoding, it will take twice as long to burn a disk because PP is actually going through the AVI file from your timeline twice. The first time it’s learning about the difference between each video frame while taking notes to itself so that the second time it knows what bitrate it should use for that frame. In other words it’s optimizing the compression rate needed for that frame while giving you the best quality too. When you use CBR, there is no optimizing. It will use the mbps setting that you set for the entire clip. That end file will always be larger than the same clip encoded using a VBR setting.
When using VRB encoding, one thing that could be an issue is how fast the action was on your video. It can be harder to fit lets say a 1 hr 45 min NASCAR race on a DVD versus something slower like a wedding. When the encoder sees so much changing in between each frame (with the cars going by so fast) it will be forced to use higher bitrates because it’s trying to maintain the best mbps it was told to, which takes up more room in the end on your disk.
The best quality comes from anything over 6 mbps. 7 is even better and I believe that 8 mbps is that max that a DVD player can read. That includes video and audio added together. You can go as low as 4 but you will start to see some blocking or artifacting in fast moving action.
This stuff can get kind of confusing but if you do a search on the Inet regarding "video compression", you should find some articles that will better explain how all this works.
Good luck.
RAM