This is such a difficult question to answer, because there is no single right answer. Compression is not simply a matter of applying a formula and getting the best result possible - it is a combination of knowing your footage, the lighting, the speed of the action shots, the source material type (miniDV, etc) and whether or not you'll be using multiple audio streams, additional ROM material, subtitles (although small) and anything else. Quite apart from anything else, the person encoding needs to know these qualities and be able to run tests to find out which compression settings will work best.
Secondly, there are several types of DVD, each with different capacity - you don't say which you want to use. FOr example, a DVD-R single sided, single layer disc will hold 4.37Gb of data.. a double layer disc will hold, well, double. All of this affects the decision about what settings to use.
It is also not clear whether you want both sets of video on a single disc, or if you intend to use multiple discs of some kind. You might want to use a double DVD5 - i.e. two sided single layer disc (I doubt it, but it is an option).
Finally, you could use a variety of different types of encoding. A DVD will accept both MPEG1 and MPEG2 as material, and these have massively different qualities. Even if you choose MPEG2, you might then opt for half D1 as a type... essentially using MPEG2 algorithms and stripping out half the horizontal resolution (which has a lesser impact on visual quality) resulting in smaller file sizes.
It goes on and on....
So - after all that, if you simply don't mind what the final product looks like, and are using a DVD-R of 4.37Gb capacity, and encoding audio to AC3 at 192kbps (assuming stereo audio only), not using any ROM data or adding additional graphics or subtitles, and only working with one of your videos not both (so total time is indeed 179 minutes, and you are not using video backgrounds to any menus... you should aim for 3Mbps as the bit rate on your disc. If you use a double layer DVD-R you can go up to 5.8Mbps.
Have a look for an online bitrate calculator - you'll find plenty.
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lafcpug mod