I was wondering why a studio would bother putting a 2.0 Dolby Stereo track on a DVD that already has a 5.1 track. If you only have a stereo sound system, then the 5.1 track will still play out of your speakers. If you have a 5.1 setup, Pro Logic will spread out the 2.0 track throughout all the speakers, but such would be pointless since the disc has 5.1 encoding. Is the presence of a stereo track there if you're a purist and want watch the movie in only stereo? Does anybody do that?

Well the disc sounds better in 2.0 if you have just a Tv and dvd player with no stero or surround sound system.

Don't forget those of us who travel and like to bring a few DVD's along for nights in the hotel. 5.1 doesn't do much on a laptop.

Although all DVD players will downconvert a 5.1 track to standard stereo if you do not have a surround sound system, generally the DVD player does a crude job of this, simply throwing out all of the bass and combining the other channels without any attempt to balance the volume levels. A track that has been specifically mixed for 2.0 by professional sound engineers will usually sound a lot better on stereo/ProLogic equipment than a 5.1 track that has been downmixed.

I see. Before I got a receiver I used to play DVDs with my stereo system handling the sound, but I could never tell the difference between the 5.1 and 2.0 tracks. Thanks. On a similar note, why are commentaries encoded in stereo? Wouldn't mono allow for more space for better picture/sound, or would the difference be marginal?

I think I am also right in saying that on older movies, say 70's and 80's movies that were originally recorded in Dolby Stereo, a lot of people usually like the option to have the 2.0 track, as it's closer to the way the movie would have originally sounded in theatres.

Choice.

It really depends on your DVD player. I have an old Pioneer DV-414 that downmixes 5.1 almost flawlessly into 2 channel. Combined with a good amp and speakers that can image well, you will have a very convincing setup. The 2.0 streams to me sound really compressed, I don't think much time is spent by the engineers getting a good sound since it's not of much concern.

Generally, the difference would be marginal. Some DVDs do encode the commentaries as 1.0 mono at a very low bit rate. I would think that if the commentary is in stereo it might be because the movie's soundtrack is playing in the background, and maybe the commentators stop to listen to it for some scenes?

I agree with this. If a movie has been redone in DD 5.1 I like the option of listening to the original audio. Its rare I actually like a DD 5.1 remix.