Film-Tech Forum ARCHIVE: Different levels between digital formats?

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Posted by Brad Miller (Member # 2) on 06-27-2003, 03:59 AM:

From the FITA forum...

quote:
Somebody must have told whoever encoded the DTS track that the film was titled Charlie's Angels: Full Fader, because it's loud. Possibly loud enough to damage speakers if you've got a crappy sound system that has no headroom. The Dolby Digital track was at a normal level.

I have always found that SRD, DTS, and SDDS have happily maintained the same level. So much in fact that I can switch between the three randomly during reels and no one can tell. If this is indeed true and there wasn't something screwy with Daryl's system he was using during this screening, then this will pretty much defeat the purpose of installing 2 or 3 digital formats for fallback purposes, as well as for any digital reversion to SR. Has anyone else seen this?

Posted by Daryl C. W. O'Shea (Member # 1303) on 06-27-2003, 04:11 AM:

I thought it was weird too. I was under the impression that the digital tracks were all encoded from the same source, so that they would all be the same.

I'm sure it wasn't just my throbbing headache, the (attatched) trailers were normal in both DTS and Dolby Digital but the feature was insane in DTS. Not as bad as xXx was, but half way there.

Posted by Michael Schaffer (Member # 1204) on 06-27-2003, 04:16 AM:

Do you have the dts test disc to check the output levels? I am sure you do.
I agree with Brad - the films should be and usually are at the same level for all formats.
What is the FITA forum?

Posted by Brad Miller (Member # 2) on 06-27-2003, 04:25 AM:

Feature Info and Trailer Attachments forum

One of the local prints has a bad reel. I'll do a test next week or two with that reel before it is sent back and verify for certain if there is an issue between any of the 3 formats.

Posted by Jack Ondracek (Member # 1466) on 06-27-2003, 04:38 AM:

We have 2 prints. One had 2 bad reels (being replaced)... yet another case where it looks like someone threw a handful of dirt at the film. DTS in the indoor house is absolutely insane. We ran it at 6, but I wouldn't be surprised if it wound up at 5.5-ish by the time we get an audience in there.

2 Fast was the same... 2 Loud.

Posted by Daryl C. W. O'Shea (Member # 1303) on 06-27-2003, 10:43 AM:

The A and B chain is fine. Actually it was checked last week and was dead on.

Without knowing that the system is fine (which it is), I would still know that everything but the actual feature, including the attatched trailers, play at normal levels in both DTS and Dolby Digital.

Not to mention that every print played up until just before I screened Charlie's Angels didn't have this problem.

Posted by Mark J. Marshall (Member # 1409) on 06-27-2003, 12:44 PM:

Last night, I ran it in our THX house in SDDS @ reference level because the managers wanted to hear it that way.

It sounded great from the lobby with the doors shut.

Posted by Matt Hale (Member # 1518) on 06-27-2003, 02:03 PM:

Variation in the level between the various soundtrack formats can depend a great deal on what point in the post-production process the soundtrack was sent out for encoding. Normal procedure around here is to sum the multitrack stem master into a 5.1 print master on a DA88 tape. All soundtracks are derived from that printmaster digitally at the lab.
However I have seen occasions where the soundtracks are derived directly from the stem masters. In these situations the track summing and encoding is done in one pass - usually with an analogue connection because it much easier (read: cheaper) to sum analogue signals than digital ones.

The issue you run into as soon as you start converting from digital to analogue and back again is that there is no hard standard for matching levels. In a digital signal, there is no headroom above 0dB because you run out of bits to describe the waveform, whereas in the analogue world there is typically 14-20dB of headroom above 0 before overload. It is therefore standard practice in film to calibrate 0dB Vu to -20dB digital. In other areas (music, radio, etc...) 0dB Vu is calibrated to -18 or -14 or even -12 dB digital. This is further complicated by the fact that 0dB on a vU meter is not the same as 0dB on a ppm meter, its more like +4. Confused yet? The bottom line is that its incredibly easy for things to get out of wack when moving between analogue and digital, and this is probably the source of the level variations. If the stems are recorded on analogue dubbers then you have to be very, very careful about calibrating the different equipment when you are encoding the digital tracks.

Posted by Manny Knowles (Member # 1171) on 06-27-2003, 02:32 PM:

One of our prints of CHARLIE'S ANGELS is playing fine in DTS at the normal level which, for that particular room, is between 6 and 7. It's loud but not a whole lot louder than analog.

I just set this theatre up with DTS for the release of MATRIX RELOADED so it's a very recent installation and setup.

Coincidentally, as I was investigating the DTS showing, I got a call from one of the other theatres that is showing it in SRD and they complain that Reel-6 keeps hopping in and out of digital...How about that!?

Posted by David Stambaugh (Member # 1102) on 06-27-2003, 05:58 PM:

I just sat through about 45 minutes of Full Throttle, which was all I could stand. Besides the movie sucking, the sound was excruciatingly loud. The trailers all played in digital and they were "normal", not too loud at all. The feature however was WAY louder. I believe it was playing in SDDS, but it could have been SR-D. Highly unlikely it was DTS because it fell back to analog at lab splices. They almost always run in SDDS in that house if the print has it.

Posted by Ron Lacheur (Member # 1126) on 06-27-2003, 06:29 PM:

Just saw it in Dolby Digital. Feature was really loud. Trailers were tolerable but during the 'Gigli' trailer, Affleck's voice was effecting the horns, making an odd sound when he spoke.

Posted by Daryl C. W. O'Shea (Member # 1303) on 06-27-2003, 11:41 PM:

I watched a good part of this again this afternoon, in Dolby Digital. Now that my massive headache has reduced itself to being only huge, I found that the Dolby Digital track was indeed also loud, but I'm still sure that it isn't as loud as the DTS track.

Posted by Jack Ondracek (Member # 1466) on 06-28-2003, 03:29 AM:

We wound up settling at 5.5. Our experience is pretty much as is Daryl's... everything else is fine at 7.

Now that I read through all this, the trade screening was also painfully loud (though they did turn it down when we asked). THAT screening was in SDDS.

It would be interesting to know if the problem is one of actual average levels being overly high, or if they've got some limiting in there that's kicking the average up past normal.