New to this: Duplicate Titles and TrueHD

[Stevie-O]

I have a rather large (a few hundred) collection of Blu-Ray discs, and I wish to use MakeMKV to serve two purposes: (1) to capture as much of the meaningful data as possible for archival purposes, (2) to create MKV files that can be transcoded for the myriad devices I have (iPod, low-end laptop, high-end laptop, WD-TV, to name a few.)

My first few tests seemed to work, but before I spend the time really going through all my discs, I have some questions about some odd things I've run into. I've tried searching around (both on these forums and elsewhere on the Internet), but in all cases, I either failed to find anything, or I found multiple sources with contradictory information.

For reference, I'm working from the Blu-Ray of the 1989 Batman (by Tim Burton), since it seems like a relatively simple starting point.

* Multiple/duplicate titles

The disc has two candidates for the primary title -- 00004 and 00014. Both are the same size and length. Furthermore, both have the same segment map (a single segment, #4). However, the languages available are very different: 00004 has English, French, German, Italian, Spanish, and Portuguese (audio), as well as an even larger list of subtitles, while 00014 is just English and Japanese.

Question 1: What's going on here? Why are these separated?

* Different audio types

This is something I have thus far been completely unable to figure out; I see lots of contradictory answers.
The "main" title (00004) has several audio tracks, as follows:

Code: Select all

[ ] DD Surround 5.1 English (call it A)
[ ] TrueHD Surround 5.1 English (call it B)
--- [ ] DD Surround 5.1 English (call it C) <- "underneath" TrueHD 

When I first scan the disk, MakeMKV automatically checks (A) and (C) but unchecks (B).
I can, however, check A, B, and C independently.

Question 2: What is the difference between (A) and (C)?
Is it simply two separate copies of the data, or is it two pointers to the same physical data?
If I leave both checked, will MakeMKV output a file with a duplicate audio stream?

Question 3: Why does MakeMKV leave (B) unchecked by default?

Question 4: What happens if I check only A and B? What about if I check B and uncheck A and C?

[ndjamena]

1. English and European language titles are for Region B, English and Japanese language titles are for Region A

2. C would be the TrueHD core, TrueHD was not mandatory for early Blu Ray players so they added an AC3 core for compatibility reasons. A TrueHD core is unnecessary for playback and can be discarded, DTS-HD cores however are a vital component of the HD audio track. A would be a separate AC3 track... it's kind of redundant considering the TrueHD track has an AC3 core anyway but they too were reacting to the fact that TrueHD compatibility wasn't guaranteed.

3. B is unchecked by default because it's HD sound and in the past there's been a lot of players that are incapable of playing them. Even now support for them is sketchy and player dependant. If you know you're going to be playing them on a system that can decode TrueHD and DTS-HD properly you can go into the preferences, enable expert mode and change the default selection rule in the advanced settings.

4. A: you get two versions of the audio, one in AC3 one in TrueHD. B: you only get the TrueHD track. WDTV should pass through TrueHD to a capable receiver, a laptop with a proper codec or player should be able to play it directly, but you'll need to re-encode the audio for iPod into AAC or ALAC. (and since it's Batman, you'll need to re-encode the video for iPod too.)

[Stevie-O]

1. English and European language titles are for Region B, English and Japanese language titles are for Region A

Okay, that make a little bit of sense. So what, they made a whole bunch of identical discs and simply stamped some as region A and the rest as region B?

I say 'identical' because the HDMV script doesn't seem to check the region code.

2. C would be the TrueHD core, TrueHD was not mandatory for early Blu Ray players so they added an AC3 core for compatibility reasons. A TrueHD core is unnecessary for playback and can be discarded, DTS-HD cores however are a vital component of the HD audio track. A would be a separate AC3 track... it's kind of redundant considering the TrueHD track has an AC3 core anyway but they too were reacting to the fact that TrueHD compatibility wasn't guaranteed.

I'm not sure exactly what the word "core" means in the context of "TrueHD core". It is my understanding that a different "HD audio" standard, DTS-HD, works by starting with a regular non-HD stream that can be decoded independently (the "core"), then adds a second, dependent stream that is only useful when decoded alongside the former . A non-DTS-HD-capable receiver will simply decode the non-HD stream, while a DTS-HD-capable receiver will decode both together. This is extremely similar to how FM radio stations deliver stereo output; they have a "core" monaural (L+R) signal at one frequency, and a secondary stereo signal (L-R) at a different frequency. A mono FM receiver only decodes the first frequency. A stereo FM receiver decodes both frequencies and combines the two to recover the original L and R channels. Based on what you said, the TrueHD stream is independent, so the TrueHD is, in fact, its own core.

I'm trying to come up with a scenario that this structure is designed to solve, and I can't come up with any that make sense.

• First, it's my understanding that if the user doesn't have an amp that supports TrueHD, they need to be fed a different stream.
• It my further understanding that the TrueHD "stream" is actually a superstream comprised of two independent streams, the real TrueHD stream and an AC3 stream.
• I'm guessing that a Blu-Ray player that knows about TrueHD will lock onto the superstream automatically, by default.

So far the existence of the separate AC3 stream is quite clear -- if the player has no support for TrueHD, it *must* use the top-level AC3 stream, because it wouldn't know how to split the AC3 out the TrueHD superstream.
What I still don't get is the existence of the AC3 stream inside the TrueHD superstream. Under what circumstances would a player access that embedded AC3 stream, instead of using the top-level AC3 stream? While not all players support TrueHD, all of them *do* support AC3.

[ndjamena]

A Blu Ray player that doesn't support TrueHD decoding still has to be capable of processing the thing, that's what the AC3 core is for.

What you're looking at is two different attempts to solve the same problem (ie non-universal support for TrueHD). The first was mandated by the Blu Ray Association, which dictated that a TrueHD track MUST by definition contain a separate AC3 track for compatibility reasons. The second was made by the authors of the disc, who decided to add a separate AC3 track for players that couldn't decode TrueHD.

Batman was an early release, I think you'll find that kind of thought process has mostly ceased to exist in newer releases, although both VC1 and TrueHD are becoming less common now.

-edit- the first AC3 track may just be the audio from the old, un-remastered DVD version, but if the player plays IT by default that becomes a rather unlikely scenario.

http://www.blu-ray.com/movies/Batman-Blu-ray/1296/

[ndjamena]

OK, I just ripped both AC3 tracks from my Batman disc again, converted them to PCM and did a waveform analysis on two of the channels and as far as I can tell both AC3 tracks are exactly the same.

They're both the same mix, the Blu Ray player plays the first AC3 by default... It's a redundant stream, an over-reaction to TrueHD compatibility issues... Welcome to the world of Blu Ray/DVD ripping!

[Stevie-O]

OK, I just ripped both AC3 tracks from my Batman disc again, converted them to PCM and did a spectral analysis on two of the channels and as far as I can tell both AC3 tracks are exactly the same.

They're both the same mix, the Blu Ray player plays the first AC3 by default... It's a redundant stream, an over-reaction to TrueHD compatibility issues... Welcome to the world of Blu Ray/DVD ripping!

Ah. They didn't really know what they were doing and they wanted to make sure they'd covered all of their bases. As a software engineer, I don't find that at all surprising (can't even fault 'em, really.)

Anyway, thank you for the detailed explanations! I have loaded several more discs into MakeMKV since my original post, and I can confirm that most of the more recent titles did not have the weirdness going on.