"Problems" compressing 5+ hours onto a single DVD5?

[niccador]

Good evening to all.
I tried looking through the forums for a reasonable answer to this question before I posted, but found none. If I gave up too early, please forgive me, and feel free to point me in the right direction.

My problem is this:
I need (read: absolutely have to) fit 5-6 hours of video onto a single DVD5. (5 is the hard requirement, 5:15 if possible for some wiggle room, 6 would be nice but is probably unreachable for this project.)
Naturally, I'm trying to maintain the best possible quality at the same time. (What a shock, huh?)

The video source is 720x480, 12Mbit CBR MPEG-2, 384K LCPM Stereo.
The nature of the video in this case is a video game walkthrough. So, while there are some full-motion scenes, the bulk of the video consists of primarily static screens with subtle movements and text dialogue.

The initial target encoding was 352x480, 2500Kbit avg VBR (2-pass, 3000-3500max), 192K AC3 Stereo.
The majority of static screens initially lead me to believe that it would be rather simple to maintain quality at these settings....which was sort of correct.

Using TMPGEnc Xpress 3.0's standard NTSC DVD template (with the above settings, and 10-bit precision, highest motion detection), the quality was....reasonable...but the overall file size was too large....

Using the XDVD template (again with the same settings as above), the quality was still reasonable. There was naturally a noticable loss of sharpness over the original source, but outside of that, the effects of the compression were negligible -- at least on my TV, to my eyes...but then I may need glasses...heh.
The benefit of the XDVD template settings, was that the resulting filesize would definitely allow for 6 hours on a single DVD 5.

When compiling the test DVD with TMPGEnc DVD Author Pro 2, it reported errors with the GOP (expected), which were ignored at first. However, errors were experienced upon playback, namely when trying to fast forward through scenes, or skipping chapters -- which would sometimes skip tracks instead. (I have not yet ruled out the possibility that these errors were due to my Philips DVD player, and not actually the disc...but still proceeded under the assumption that this non-standard format was to blame. Err on the side of caution, and all that.)

Based on another forum post found here, I ran the XDVD MPG files through Womble mpeg-vcr's GOP Fixer, and compiled a new test DVD.
The new DVD produced no errors during compiling, and seemed to function properly on the Philips.
The downside though, is that the altering of the XDVD files seemed to have a noticably negative effect on the quality, as well as increasing the overall size by an average of 20%, bringing my total runtime to a little over 4 hours.

So I'm kind of stuck at square one still...

Is there anyone who can offer any suggestions on the ideal compression for this video?
Or anyone who would perhaps like to help directly by playing around with and encoding some sample clips?
(If you're interested in downloading sample portions of the original source files to work with, please PM me.)

[guns1inger]

Honestly, 1 - 2 hours will look OK at full-D1. 2 - 4 hours will look OK at half-D1. More than 4 hours you need to consider VCD resolution. DVD5 is simply not designed to hold that much data with any real image quality. At VCD resolution you can fit up to 7 hours (or more if you really squeeze it).

5:15 with 192 kbps audio requires a video bitrate of no more than 1742 kbps, which is substantially lower than your 2500 kbps target. At this bitrate, you can't expect even half-D1 to look too good.

[AlanHK]

The initial target encoding was 352x480, 2500Kbit avg VBR (2-pass, 3000-3500max), 192K AC3 Stereo.

You can reduce the audio bitrate a bit. Demux and reencode audio to 128k. If it's just speech, you can go right down to 64 or 48 and have AM radio quality.

I fit 6 x 55 min TV episodes on a DVD 5 using HCEnc with a bitrate of 1640.
Works for me. (Cue flames by "It looks like crap" videophiles.)

[guns1inger]

(Cue flames by "It looks like crap" videophiles.)

Been there, done that

HCEnc does handle low bitrates very well, and is a good choice for this type of work. Faster than Tmpgenc as well.

[redwudz]

What guns1inger said. You might want to drop down to VCD MPEG-1 format if you need playback on a stand alone DVD player. MPEG-2 won't likely look very good at 1700Kbps, no matter what you do.

Otherwise, think about H.264 or similar.