Film-Tech Forum ARCHIVE: Strange Sound Issue

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Posted by Justin Hamaker (Member # 2165) on 02-27-2018, 11:31 PM:

Sunday we had a strange sound problem on a showing of Black Panther. It may have been related to an advertising package, but I have not conformed this.

Issue occurred during our first showing of Black Panther on Sunday. Movie had already been playing in this auditorium for 10 days with no issues. No changes to trailers or movie version. The only thing that changed was the advertising package, but the everything played fine Friday and Saturday.

During the ads the sound went completely out. Not problem was identified with breakers being off/tripped, or anything similar. Following the ad package the sound came back, but went out again toward the end of the trailers. The movie started with the sound normal, but following the prologue started to get a muffled, foreign language sound from the sub - did not sound like the same dialog coming from the R/C/L channels. After rebooting the server the show played normal.

I removed the ad package and have not had the problem reoccur, but I can not say for certain the ad package was the problem to begin with.

GDC SX2001 server, Dolby CP750 processor. 7.1 version of movie.

Any thoughts on what might have caused this? If it was not recurring should I just chalk it up to a random glitch?

I removed the ad package and every

Posted by Marcel Birgelen (Member # 6801) on 02-28-2018, 12:31 AM:

To me this feels more like a server glitch and maybe something that should be reported to GDC.

quote: Justin Hamaker
The movie started with the sound normal, but following the prologue started to get a muffled, foreign language sound from the sub - did not sound like the same dialog coming from the R/C/L channels. After rebooting the server the show played normal.

Did you check the Black Panther DCP if there's any foreign language CPL there, for example Spanish? And do you have the keys loaded?

Did any other content in your playlist contain a foreign language CPL?

Posted by Carsten Kurz (Member # 5396) on 02-28-2018, 08:00 AM:

There have been reports of the CP750 mixing channels. In theory, the same could happen on the GDC. You could try to load the audio mxf from trailers or add packs into DCP-o-matic or Audacity, and see wether there is something on the tracks normally not played (HI/VI-N, or anything above that). Unfortunately, this won't work for a (usually encrypted) main feature.
Other than that, I guess things like that just happen occasionally.

- Carsten

Posted by Justin Hamaker (Member # 2165) on 02-28-2018, 01:43 PM:

quote: Marcel Birgelen
Did you check the Black Panther DCP if there's any foreign language CPL there, for example Spanish? And do you have the keys loaded?

We only use the English 5.1/7.1 versions of movies. Even if we receive an alternate language version, we never use it, and never load keys for it. In some cases we'll use an OC version for sensory sensitive shows, but that is not the case with Black Panther.

I should add that I don't know own for certain it was a foreign language track. All I know was it did not match the speech patterns coming from the stage channels. It's possible it was the VIN track.

Posted by Marcel Birgelen (Member # 6801) on 02-28-2018, 04:59 PM:

quote: Carsten Kurz
There have been reports of the CP750 mixing channels.

quote: Justin Hamaker
I should add that I don't know own for certain it was a foreign language track. All I know was it did not match the speech patterns coming from the stage channels. It's possible it was the VIN track.

The CP750 messing up channel assignments every now and then is a known problem, though I'm not sure how this can be reliably reproduced.

So it could also be a CP750 problem.

It would be interesting to see if you could reproduce the problem by simply including the suspected ad package again.

Posted by Jason Raftery (Member # 6291) on 02-28-2018, 08:09 PM:

Was the server power cycled earlier Sunday morning, by chance? I've experienced quite a number of audio misrouting incidents with GDCs and almost all of them were on the first show following a server (and projector, if a model with an IMB) power cycle. On a number of these, the VI track ended up being output on one of the first three AES channel pairs in error (most commonly ending up going to the subwoofer or a surround channel).

This doesn't sound like a CP750 issue to me if rebooting only the server resolved the problem. It would probably be a good idea to send a server log package to GDC, but most of the server/IMB audio misrouting cases I've experienced left no trace in the logs.