Datasat Digital Sound

[schorman]

The cinema version of DTS-ES was not a separate format like the 6 and 8 channel variants were. DTS-ES was encoded into the standard 5 channel DTS APT-X100 format. It would have required an external decoder unit to decode the Center Back channel from the standard stereo surrounds, just like a matrixed 6.1 DTS-ES or Dolby Digital EX for home formats. This of course means that the surround channels encode 4 channels into two, three surround channels plus the LFE.

When working with DTS-ES cinema titles, the ideal would be to simply encode the finished audio as 5.1 with a matrixed center back channel, meaning either a matrixed 6.1 DTS-ES (or DTSHD-MA) or DDEX. Your AVR will decode the back center channel just like the cinema processor would.

[borisanddoris]

That may be a good thing, actually.  The two issues I ran into with decoding the DTS cinema discs were that the winamp decoder introduces audible artifacts in the Right and Right Surround channels.  The foobar decoder does not have this issue, and is therefore preferable.  However, the foobar decoder automatically separates the LFE and surround channels, but unfortunately the levels for those channels do not seem to be accurate.  For instance, DTS documents suggest that the surround channels should be attenuated by 3dB and the LFE track needs some amount of gain applied (The amount is dependent on when the film was released, and I'm not sure it's been established exactly how much should be applied).  The foobar decoder does not attenuate or apply gain to any of the channels, it just separates them by applying low and high pass filters.  As far as the crossover, I'll just say I'm not sure it's accurate to the DTS specs provided in their white paper.

Anyway, the newer decoder may allow us to avoid the audible glitches of the winamp decoder and still decode the LFE and surround channels in software, thus avoiding the potentially inaccurate low and high pass filtering being done by the older decoder.  As far as I'm aware, there's not a big need to use the decoder for real-time playback, so while it's nice to have the LFE and surround channels split, I'd rather do that in software for better results.

See this document here: http://www.film-tech.com/warehouse/manua...STPROD.pdf

"Subject: SMPTE RP200 changes DTS subwoofer level (REVISED) August 1999

At a SMPTE meeting held in late 1998, all three digital sound companies agreed to comply with the recommended practice for subwoofer level, SMPTE RP200. The subwoofer level has changed to enable the use of one master recording when transferring to all three digital sound processes and to provide playback consistency in theaters. As of January 1, 1999, the recorded subwoofer level on 6-track masters has been lowered to the SMPTE recommended level of 10dB in-band gain (as compared to the screen channels).

To comply with this new standard, all DTS films released in North America after January 1, 1999 have been transferred into the DTS digital process with subwoofer at 10dB in- band gain. The SMPTE RP200 logo is clearly visible on the discs of these films.

Because the recorded subwoofer level has been lowered, the DTS theater subwoofer playback should be increased. Increasing the DTS subwoofer level compensates for the new lowered recording level, resulting in the same playback as before the change.

To maintain the integrity of the cinema sound equipment, DTS discs of pre 1999 films should be played only after the subwoofer playback level has been restored to the previous 88 dBC level."

If my understanding is correct, subs should be set to 91dB for films released 1999 and onward, and 88dB for those released prior to this.  

BandD

[spoRv]

I'm pretty sure this was discussed before, can't remember if here or on OT.

The fact is: which level does the FooBar plugin produce?!?

[dvdmike]

I would like to chime in and say that I have talked to one theater person I know and he said that the Datasat audio is encrypted and it isn't the same as the cinema DTS .aue file system so getting the audio and decrypting it are two totally different and difficult beasts at the moment.

Good to know, thanks for the info Jetrell. Did he say if they changed the file formatting too or just the encryption type?

Great thread. Thanks guys.

'Dunkirk' is getting a 70mm and 35mm release, would this just be limited to the Dolby Digital mix then?
There is an ATMOS mix, but I gather no way to marry the two.

The 35mm would almost have to be DD, my Interstellar 35mm showing was and there is not much in the way of other choices. Not sure about the 70mm since Datasat said Hateful Eight was the last shipped disc. Someone could of taken that over I guess or maybe Datasat does one offs.

Maybe we should ask on the projector forum.

On a side note, has anyone ever figured out what sound system 70mm IMAX venues use? I've seen The Force Awakens and Rogue One at the IMAX dome in San Jose, (R1 had an extended Dunkirk trailer) but all the info graphics at the museum only cryptically refer to the soundtrack being on a CD.

Here you go:

http://in70mm.com/newsletter/1997/50/ima.../index.htm

It's all DTS CD

[deleted user]

I talked to the programmer of the foobar plugin, Maxim, via email. He's friendly and very helpful and was so kind to make the LFE filtering optional, you can now set it in Preferences->Tools->Advanced->Tools>apt-x100 or similar. The reason I asked him was because I thought the LFE filtering was possibly introducing clipping in the decoded file (since a waveform has both + and -, subtracting something can result in clipping to the opposite direction), but it might have the positive side effect that now it can all be manually filtered if we find out the best process to do so.

Edit: Noticed my old post in this thread. I actually mistakenly thought it was decoding to 5 channels only in that new (now old) version in the older comment but it seems like that was just a display error in foobar2000, but now it actually can do it right I think.

[little-endian]

I got in contact with the plugin developer as well, originally because I had encountered a bug when doing a batch conversion in an already outdated version (0.1.1) which I ended up using somehow instead of 0.1.8 that time.

There seem to be more bugs which can be hopefully fixed:

From various sources, I've got two slightly different variants of the Jurassic Park Cinema DTS files (well, for the first disc at least), one in file form, the other as an ISO. Only difference is a header in the AUD ones (R1T5.AUD, R2T5.AUD, etc.) which aren't in the ones one gets out of the image file (S1003T6.R1, S1003T6.R2, etc.):

00000000  4A 75 72 61 73 73 69 63 20 50 61 72 6B 00 00 00  Jurassic Park...
00000016  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000032  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000048  00 00 00 00 00 00 00 00 00 00 00 00 45 4E 47 4C  ............ENGL
00000064  49 53 48 00 4A 4F 45 00 49 53 00 00 00 00 01 00  ISH.JOE.IS......
00000080  EB 03 05 00 00 00 00 00 00 00 00 00              ë...........

So with the headerless/tagless variant, version 0.1.10 at least for me produces awful highpitched "scrambling noises" (while foobar stating a weird bitrate of 1058 kbps instead of the nominally correct 882 kbps), whereas 0.1.8 and 0.1.1 play them fine, but only if named "AUD". If "AUE", only the first two minutes are played correctly, followed by stuttering throughout the rest of the file.

Furthermore, as far as I've got it, besides the LFE-level confusion, the topic about the surround channels is still open as well, as it is not clear whether the PCM output of the plugin has the surround channels lowered by 3dB or not.

Since the bug report shows that the developer of that decoder (which is already marvelous to have) isn't entirely familiar with all aspects of the Cinema DTS format either (no surprise without any official support), we'd need to find some "Insider" (also a good and underrated movie by the way) with first-handed information.

[zoidberg]

If you're listening to these tracks at anything close to the reference level then ±3dB is a pretty big deal

[little-endian]

As TomArrow graciously pointed out for me, apparently I fell into the "RTFM"-trap as the feature of retrieving the channel decoding setup from the filename for files without headers is decribed in the latest readme.txt of the plugin version 0.1.10, oops.

Interesting though that there are then two versions of Jurassic Park floating around - with headers and without.

@zoidberg: I'm not sure if your posting is meant to be ironic as while a difference of 3dB for sure is significant enough so it should be properly considered, it will hardly make a huge difference (surround channels of 90s mixes tend to be very quiet and held back for my taste anyway), so I'm not sure how to interprete your statement. Maybe you could kindly elaborate on that one, thanks.

[zoidberg]

I was being serious, SPL is measured on a logarithmic scale as you already know. The point I was implying was that if you are listening to these tracks at the intended levels then the difference should be noticeable. At lower levels not so much.

I'm surprised you find 90s mixes 'held back' in the surrounds little-endian, in my experience they are among some of the best for effects steering. Those sound designers/mixers got a new toy and boy did they play with it (yes I am aware 6-track existed way before but very few films got the treatment per year).

[little-endian]

@zoidberg

Ah, I see. Thanks for the elaboration. I am still not sure, whether the scaling on regular consumer grade AV-receivers try to indicate 0dB as such reference point (which would be prone to inaccuracy due to the varying efficiency factor of the driven speakers alone), but with most mixes there days, at least in my room, that would be way too loud. Often, -10dB is already quite "heavy". I have to admit that I'm still struggling with the room acoustics (bass traps, absorbers, diffusors, etc.) and also that my levelling is still pretty "half assed" in terms of only being correct to the extent of what Denon's audyssey implementation recommends (no professional dB© measuring yet, either). So I guess, having surround channels 3dB too low or too high as of today is my slightest problem.

However, for the sake of academics alone, the decoding result should be correctly done according to the specs, of course.

As for the mixes, while not necessarily only referring to those from the 90s, many (again: for my taste) tend to be extemely "front heavy" where I wonder what the fuss is about 7.1 if 5.1 is rarely really fully used. For example, often enough, things cleary move out of the picture behind the viewer but nonetheless are still hearable out of the front channels. A for me very good example how it should be done, was recently the Korean movie "Parasite" - what is behind also comes out of the surround channels, consequently depending on the perspective.