If you choose the Apple/Universal or an ATV preset in Handbrake it should automatically create both a 5.1 and a stereo mix down if the 5.1 is available on the DVD.
[Pre-Edit: Wow, I got a little long-winded there. It's amazing how many words it can take to nail down an idea that's just like *that* in your mind. Here's the TL>DR version -- is it best to just always use the 5.1 source track from the DVD when it's available, or am I better off selecting the 2.0 source when I'm mixing down to 2.0 output file and/or playback equipment?]
Thanks, but maybe I wasn't totally clear in my question. Handbrake does make two tracks on the Apple TV preset -- one is just a straight passthrough of the source track with no compression (AC3 Passthru) and the other (AAC Mixdown) is compressed to AAC and converted to Dolby ProLogic II (by default, though you can select other mixdowns like Stereo, Mono, or Dolby Surround.) My question is about which track
from the DVD to use as a
source for these two tracks in the output file, particularly the mixdown.
Several of the DVDs I've come across so far have only either 2.0 or 5.1 audio, so with those ones there's no question. However, a few of them have both tracks available (as well as additional tracks for other languages, director's commentary, etc., but I'm not concerned with those), and for each track in the final output file, you can individually select which source it comes from. I don't think Handbrake has any sort of default behavior as far as preferring 5.1 or anything when it comes to selecting a source, it just chooses whichever one is labeled "Track 1," and uses that as the default source for both of the output tracks.
So one track that Handbrake makes is the AC3 Passthru. This is a bit-for-bit reproduction of the audio stream from the DVD. I understand that it (Apple TV) won't play this track unless it's connected to a home theater system. Does it have to be a 5.1 system? Is there even such a thing as a home theater system that's
not 5.1? I don't imagine there would be much sense in using the DVD's 2.0 track as a source for this whenever there's a 5.1 track available. I might as well use the 5.1 here and then I'll have it available if and when I get a better setup.
Or do I have that wrong, and it will only play through a home theater
if it's an actual 5.1 track, but otherwise would play the AC3 Passthru track just fine through my TV set if it comes from a 2.0 source? If that's the case I could use the 2.0 track and it would play the uncompressed audio through my TV insetad of the AAC mixdown. What kind of difference would you expect in quality, then, between this 2.0 passthru and the compressed AAC?
The other track that Handbrake makes is the AAC Mixdown. This is for playback on devices that don't support the AC3 Passthru, like my TV set, or basically anything else I have (VLC will play the 5.1 tracks on my computer, but it's only got a pair of desktop speakers attached...) This is what I'm mostly wondering about, because it applies to the movies I'll be watching on my TV right now, instead of movies I
might be watching on some possible home theater system in the future.
I've heard that 5.1 audio doesn't sound good (something about levels, and maybe being out of phase?, etc. I'm not up on all the technical details of it), when played back through 2.0 equipment. Now, I'm guessing this means like if I put the movie in my DVD player and chose the 5.1 track, and played it just through my TV speakers. That wouldn't sound good, and I'd be better off using the 2.0 mix. But it can't sound
too bad, though, because many (ok, some. A few? At least one of my) DVDs only
have a 5.1 track, and you don't even
get to select a 2.0 if you wanted it.
So, how does this apply to mixing down the audio? I can select the 5.1 track, and mix it down to Dolby ProLogic II. This I understand is a way of encoding surround sound info into just two channels of audio. Then, when you play it back on suitable equipment, it decodes the signal into its component parts and plays them back in surround sound. But this I don't quite understand -- I mean it makes sense if you're working in a medium that only has two channels available like a VHS or a cassette tape, but in a digital file it doesn't make much sense to me -- if you've got the surround sound home theater setup, wouldn't you just use the AC3 Passthru track anyway? And if you don't have the surround sound setup, does that encoding leave any artifacts that get in the way when playing back through 2.0 equipment? Is
that what people are talking about when they say it doesn't sound good? Would I be better off using the 2.0 source track, and just choosing the "Stereo" mixdown in handbrake?
Basically, I want to know which of these is best to use for playback on my TV set:
5.1 -> Dolby ProLogic II
2.0 -> Dolby ProLogic II (would this just be the same as 2.0 -> Stereo?)
2.0 -> Stereo
(there's also 5.1 -> Stereo, but that doesn't seem like it'd be good for anything.)