Dolby Surround / ProLogic 6 Channel

[Traveller]

In DVDFab versions after 9.0.3.8 the Audio options in Advanced Settings for Dolby Surround / ProLogic (and Dolby ProLogic II) have changed from 6 channel (Bit Rates 448 and above) to 2 channel (up to 160 kbps) processing.

I have found that the Dolby Surround / ProLogic setting (up to 9.0.3.8) has less lip-sync issues than 5.1 Multichannel option when played back through a Home Theatre system

Why has DVDFab changed the Dolby options from 6 channel (probably Dolby) to 2 channel (something) processing and are there any plans to reintroduce Dolby 6 channel?

[MrVideo]

This is going to be a WAG.

I suspect it was done to correct a technical issue. Dolby Surround/ProLogic is not 6-channel audio. Never has, never will. It is only two physical stereo channels with an out-of-phase mono rear channel. The Dolby Surround/ProLogic "decoder" strips out the rear channel and feeds it to the rear channel speakers. It also "decodes" center channel audio and feeds that to the center speaker and what remains of the two channels is fed to the left and right speakers.

All other multi-channel Dolby encodings are done via the Dolby AC3 specification.

Since I've never had a version that old, it would surprise me if it ever did have 6-channel audio in anything but Dolby Digital or DTS. That is because it is impossible to do phase encoded audio (which is what Dolby Surround is) with 6 channels.

[Traveller]

Thanks, but it seems to be a bit more complicated!

Using the Dolby Surround / Prologic setting @ 448 Kbps (or higher) in 9.0.3.8 produces what appears to be 6 channel sound (analysis of the file indicates 6 Channel @ 448 Kbps). When played thru a Home Theatre system good quality audio is split across all channels (may or may not be Dolby....I'm only quoting the setting title?).

Using the Dolby Surround / Prologic setting at 160 Kbps (the maximum in the list) in 9.0.4.7 produces what appears to be poor quality stereo sound with some inaudible low level static thru the surround channels (analysis of the file indicates 2 channel audio @ 160Kbps).

All I'm seeking is to have the same audio processing under the Dolby Surround / ProLogic setting in future DVDFab versions as was in 9.0.3.8 and earlier versions with the higher bit rates available.

I don't really know what actual audio processing was in 9.0.3.8 under the Dolby Surround / ProLogic setting but it is far superior to the later versions and has less lip sync issues than the Multichannel 5.1 option.

Perhaps DVDFab can explain the difference between the two versions.