Datasat Digital Sound

[zoidberg]

Unless you have THX gear 0dB on the dial doesn't mean reference level, it's just the peak output of the amplifier.

[little-endian]

@zoidberg

Yes, that makes sense. I was just wondering what e.g. Denon, going from -80dB up to +18dB, defines as being 0dB then. Probably it's the relative input for the integrated DAC as this will be directly hooked up to the amp stages at full nominal power, since the "volume" control just triggers the changes the and the 0dB might consequently drive the DAC 1:1 according to the input data coming from S/PDIF or HDMI.

Anyway,

@all

Since I wanted to compare the Cinema DTS of "Armageddon" (which turned out to be rather disappointing because as far as I can tell at least, it's the same bloated mix, the Blu-ray and probably other sources offer, just in different codec "shapes"), I also checked the peak of the LFE channel which is calculated by the foobar plugin.

It reaches about -4.5dB, so a boost of +10dB obviously can't be correct for that release as this would result in severe clipping. The given facts that only movies starting from 1999 on are supposed to have a 10dB gain and that Armageddon flick being conveniently from 1998, both support that theory.

However, I'm facing the same effect as I have with Collateral - certain bass effects are actually weaker on the Cinema DTS result than on the track provided by the official Blu-ray release, for me most obviously when the vault-like air lock thing closes at 42:52 playback time (at 24 fps).

The LFE peaks on the Blu-ray somewhat supports this effect as it goes to the maximum and thus is at higher level than what results from the Cinema DTS sources.

Can anyone confirm that? Setup-wise I've normally configured a crossover at 80Hz and Audacity enabled but although it would apply to both sources anyway, just to really rule out any bass management effects, I've also tested that with everything set on "large" and no EQing whatsoever. Same phenomenon though.

[CSchmidlapp]

I'm also in the process of learning how to correctly decode and filter files from a DTS Cinema disc.
This thread is really fascinating and probably worth a sticky

There is alot of information to take in and I have to admit alot of it is beyond my understanding.
From what I can gather everyone is still in the process of experimenting and digging up information because of the lack of legit information on the subject for obvious reasons.

Just to highlight....

• DTS Cinema files are 16bit 44100kHz with a bitrate of 882 kbit/s
  

• Using the Foobar2000 method (with the latest apt-x100 plug-in) on default gives us a 5.0 file in which I low-pass filter the surround channels for the LFE. What frequency is the consensus? 80hz?
  

• Levels also have to be adjusted by a certain db, this is just the Surrounds and LFE? And to what adjustment to the levels depending on pre and post 1999 discs is also an ongoing experiment?
  

Sorry if i'm stating the obvious but I like round up posts after long discussions like this

For the record my disc is pre-1999.

[little-endian]

I'm also in the process of learning how to correctly decode and filter files from a DTS Cinema disc.

Yes, this definitely deserves more attention than it had so far ...

DTS Cinema files are 16bit 44100kHz with a bitrate of 882 kbit/s

Well, the DTS files themselves have a wordlength of 4 bit per sample as they apparently use some customized flavor of the - at that time - well established and tested ADPCM with sample prediction but no complex psychoacoustic model which MP1/2/3, AC3, AAC, Vorbis and others have.

Using the Foobar2000 method (with the latest apt-x100 plug-in) on default gives us a 5.0 file in which I low-pass filter the surround channels for the LFE.

For me so far, it always gave me 5.1 by default as it generates 6 LPCM channels with 44.1kHz/16 bit after generating the LFE out of the surround channels.

Here at latest, I already wonder whether this is really necessary as I always assumed that any consumer AVR nowadays would redirect the lower frequencies to the subwoofer(s) depending on the bass management anyway.

From today's technical point of view, I'd claim that the pure existence of a LFE channel is purely magnetic tape based legacy and not really required anymore as with LPCM, the SNR and dynamic range even at 16 bit is already huge and thus even enough headroom for any bass content (some then of course would maybe complain about the total mix being too quiet overall which can always be resolved my simply turning up the volume).

What frequency is the consensus? 80hz?

Yep.

Levels also have to be adjusted by a certain db, this is just the Surrounds and LFE?

Yes, the front and center channels remain unaltered. Some details are available in this document.

And to what adjustment to the levels depending on pre and post 1999 discs is also an ongoing experiment?

Although it effectively is now due to the lack of knowledge, it shouldn't be any experiment but pretty clear, at least to those who ran the Cinema DTS hardware stuff in the cinema and hopefully knew what they were doing. So there has to be some guideline in some drawers decribing how to set it up correctly.

Sorry if i'm stating the obvious but I like round up posts after long discussions like this

What was the musical claim in classic - "the power lies in repetition" or something? Might help to keep that thread alive.

[spoRv]

I think it's time to gather all the info we have about Cinema DTS in one place, so I started this thread:
https://fanrestore.com/thread-3132.html

I did my part, redacting the first document, "APT-X100: a low-delay, low bit-rate, sub-band adpcm audio coder for broadcasting" in PDF; now, some volunteers that would add more info are really welcome!