You can use pretty much any authoring program that accepts MPEG-2 files for a source to author Gigapocket files, but if you want 4 hours on a single DVD-R, there will be some additional steps involved.
You didn't mention which mode you captured in, so I'm going to assume HQ mode since you're wanting to make a DVD from it. I do all my captures in HQ mode, and it uses between 3GB and 3.5GB per hour. Since a DVD-R can only hold 4.37GB, that means you'll either have to split it between multiple discs or re-encode before authoring. If you use a good MPEG-2 encoder, you should be able to get better compression without sacrificing any quality, and a lot better compression without losing much quality.
You can also resize the video to either Half D1 (352x480/576) or SIF (352x240/288) resolution. With fewer pixels to encode, the file size will be much smaller. Reducing the resolution will, of course, reduce image quality, but I author all my captures at Half D1 and I'm very happy with the results.
You should also look at converting the audio to AC3. It's much smaller than either the MPA format that Gigapocket captures in, or wave format. Also MPA isn't DVD compliant for NTSC, although it will probably play fine in most standalones and is still smaller than wave format. Before making an AC3 file I'd recommend converting it to a wave and using some sort of denoising filter, because Gigapocket's audio seems to have a lot of noise.
I know it probably sounds like a lot more time and work than it's worth, but once you get past the initial learning stage it's really not that hard or time consuming if you use the right tools. Here's my basic workflow:
1. DVD2AVI to make a file AviSynth can read and demux
2. VirtualDubMod to determine edit points (to remove commercials and trim the beginning and end)
3. AviSynth to edit, filter, and frameserve
4. VirtualDubMod again to Demux the audio as a wave file and visually inspect the video filters
DVD2AVI, VirtualDubMod, and AviSynth are all free. CCE SP is pretty expensive (over $1000), but you could also use TMPGEnc Plus, which is much cheaper ($48 if I remember correctly), but it takes a lot longer to encode. Wavelab is around $400-$500 (not sure - I bought mine used), but you can get BeSweet for free to denoise the audio. Soft Encode isn't available any more, so you would have to find a used copy. You can encode AC3 with BeSweet, but this feature is really just for testing purposes, and a lot of people seem to have problems with it. Other than that, the only AC3 encoders I've seen have been much more expensive (or bundled with expensive software). DVD-Lab is $99 (free 30 day trial), and you can also get a version of TMPGEnc called TMPGEnc DVD Source creator for another $29. If you're going to use TMPGEnc, you could also get it bundled with their authoring program, TMPGEnc DVD Author, for $99. I've seen RecordNow Max for $39 as a download or $49 for an actual CD. Of course you could use other programs like Nero to burn, and there's a free program called Burnatonce that a lot of people seem to like.
Starting with an MPEG-2 file that needs edited to remove extra material at the beginning and end and also commercials, it takes me about 1-1.5 hours for the entire process (I author miniDVD and get 1 tv episode to a CD), but it probably took about 100 hours to figure out AviSynth and CCE so I could get the results I wanted (and I'm still learning).
