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TrueHD "core" vs. other DD track
Posted: Sun May 02, 2010 4:51 pm
by WCVanHorne
Here is a typical MakeMKV screen. What I find a little confusing is the presentation and/or terminology used for the main DD stream and the TrueHD steam. AFIAK TrueHD is not a core+residual encoding scheme like DTS-HD. In other words the DD and TrueHD are standalone tracks, thus it doesn't make a heck of a lot of sense to me presenting it as a sub-selection to TrueHD. I am further confused by the ability to select DD as a separate stream just above. When extracted these two are exactly the same. There may be a perfectly good reason to present it this way but I couldn't find a reference when searching. Perhaps someone could enlighten me. Thanks!
Re: TrueHD "core" vs. other DD track
Posted: Sun May 02, 2010 6:48 pm
by NomadCF
While it is true it doesn't have a core stream, it does have a inter-weaved AC3 stream.
CORRECTION:
I should have said:
While it is true it doesn't have a core stream, it can have a inter-weaved AC3 stream.
Re: TrueHD "core" vs. other DD track
Posted: Sun May 02, 2010 9:06 pm
by WCVanHorne
What though is the purpose of, or what advantage is there to, presenting the AC3 track as two selections that do the same thing? I'm pretty sure the bluray doesn't have two identical copies in the full stream.
Re: TrueHD "core" vs. other DD track
Posted: Sun May 02, 2010 9:40 pm
by NomadCF
I'm not understanding your question, but heres what I can tell you from your picture.
1. Your 1st check-boxed Audio Stream is either a DTS for AC3 standalone stream.
2. Your bluray as A TrueHD Track which has a inter-weaved.
3. All TrueHD streams always have an identical ac3 stream (around 640 kbps), on the disc. weather this is part of the TrueHD is up to the authors of the disc. This is to allow for backwards compatibility with older receivers.
Correction on my last post, I Said
NomadCF wrote:While it is true it doesn't have a core stream, it does have a inter-weaved AC3 stream.
I should have said:
While it is true it doesn't have a core stream, it
can have a inter-weaved AC3 stream.
Re: TrueHD "core" vs. other DD track
Posted: Mon May 03, 2010 12:30 am
by WCVanHorne
NomadCF wrote:I'm not understanding your question, but heres what I can tell you from your picture.
1. Your 1st check-boxed Audio Stream is either a DTS for AC3 standalone stream.
2. Your bluray as A TrueHD Track which has a inter-weaved.
3. All TrueHD streams always have an identical ac3 stream (around 640 kbps), on the disc. weather this is part of the TrueHD is up to the authors of the disc. This is to allow for backwards compatibility with older receivers.
If I am understanding you correctly you are saying that the authors put two, identical, DD-AC3 tracks on the disc. This doesn't make a heck of a lot of sense to me. The first, stand alone, stream takes care of backwards compatibility. The second, interweaving, of the same DD-AC3 track into the TrueHD stream seems to be a complete waste. I could understand if they were different bit rates or mixes or some other difference; but when I rip them them are exactly the same.
In other words, why would one have an interwoven AC3 track when an older receiver (which couldn't understand the TrueHD track or the interwoven AC3 in the first place) would just use the standalone AC3 track for backwards compatibility?
Re: TrueHD "core" vs. other DD track
Posted: Mon May 03, 2010 2:18 am
by NomadCF
That is because, of course there is a Blu-ray requirement that there be a legacy AC3 track in the same language as the main audio of the movie. On every English-language movie with TrueHD there will be at least one English language AC3 track, and in most cases there will be two: a separate AC3 track that you can select from the Blu-ray menu or by pressing the audio button; AND a hidden AC3 track that is interleaved with the TrueHD track so that it basically appears as one TrueHD/AC3 track to the player. The player must play the TrueHD track if there's an HDMI connection to a compatible receiver, or it can decode to multichannel analogue; if not, it must play the interleaved AC3 track if there is an optical/coaxial connection.
Re: TrueHD "core" vs. other DD track
Posted: Tue May 04, 2010 2:50 am
by WCVanHorne
NomadCF wrote:That is because, of course there is a Blu-ray requirement that there be a legacy AC3 track in the same language as the main audio of the movie. On every English-language movie with TrueHD there will be at least one English language AC3 track,
Yup, knew that bit.
and in most cases there will be two: a separate AC3 track that you can select from the Blu-ray menu or by pressing the audio button; AND a hidden AC3 track that is interleaved with the TrueHD track so that it basically appears as one TrueHD/AC3 track to the player. The player must play the TrueHD track if there's an HDMI connection to a compatible receiver, or it can decode to multichannel analogue; if not, it must play the interleaved AC3 track if there is an optical/coaxial connection.
It's this that doesn't quite make sense as part of the standard, and I do realize that it is purely academic at this point. Surely the players should have been made smart enough to fall back to sending the legacy AC3 stream over optical/coax if they could not negotiate an TrueHD connection over HDMI. Anyhow, as I say, it's basically moot. Although IMHO I just think it's unnecessary bloat. This is exactly why I love ripping out the junk out of the stream with makemkv or similar!
Re: TrueHD "core" vs. other DD track
Posted: Tue May 04, 2010 3:15 am
by NomadCF
Remember it's always easier to to be backwards compatible then it future compatible, that being said looking at the TrueHD & AC3 "issue" at hand. I look at it like this. It's almost guaranteed any receiver out there can decode a AC3 or DTS stream (these are both DVD standards). But it's just the opposite about a TrueHD, meaning most receivers out there don't know anything about a TrueHD stream or the fact it might have a AC3 component to it. So they wouldn't be able to "extract" it and use it.
** Side note: DTS is part DVD standard and has been since before the spec set finalized.
Well I think thats more then enough ranting from me here
