Dolby Digital 2.0 vs. DPL 2.0 or "Dolby Surround"

[Icaras]

I am trying to find out if there is any distinguishable difference between Dolby Digital 2.0 and Dolby Pro Logic in 2 channels, other than it being stereo.

The reason why is that I have some TV shows on DVD that were originally encoded to play in Dolby Digital 2.0, and those same movies and TV shows that are stereo sources to begin with do not display the DD logo in the iTunes store, which to me means, just Dolby Pro Logic, matrixed in just your basic 2 channel stereo source.

Maybe I'm just confusing the hell out of myself over nothing, but could anyone tell me if the DD 2.0 on the DVDs would actually be of a higher quality than the 2.0 material found on Apple's iTunes store? Thats what I'm really trying to find out.

[cleric]

Depends what the source is for the stereo encodes. I assume they are encoded in to aac which is a better compression algorithm than ac3, but the ac3 may have been sourced higher.

[eddyg]

Without knowing the bitrate you can't say which is better. AAC (which the dolby surround stream is using) at the same bitrate as AC3 (DD) will give better fidelity due to having better compression.

Personally I think the following are comparable in quality:

AC-3, rate=48000Hz, bitrate=224000 (2.0 ch)
AAC, rate=48000Hz, bitrate=160000 (2.0 ch)

Don't worry about stereo sources, but do choose for DD 5.1 sources over matrixed dolby surround sources, that is noticeable.

Cheers, Ed.

[Icaras]

Don't worry about stereo sources, but do choose for DD 5.1 sources over matrixed dolby surround sources, that is noticeable.

Cheers, Ed.

Yes, this I do know very well and clear. But thank you both for clearing up some of the differences between AAC vs. AC3.