Film-Tech Forum ARCHIVE: Questions about some digital glitches...

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Posted by Mark Lensenmayer (Member # 134) on 07-24-2013, 09:17 PM:

I attended a screening of RED 2 at the local Starplex and there were a couple of problems I've never seen before.

1) During the scene where Helen Mirren is pretending to be a crazy Queen of England, the screen went blank for a few seconds and the movie appeared to jump forward. I can't say how far as I don't know the movie, but it was most likely more than a few seconds. It looked similar to what happens when a blu-ray player hits some bad data and jumps to the next good section.

2) Later in the screening, the movie stuttered for a few seconds...sounded like the old Max Headroom effect.

I'm guessing that these were server related problems, but I've never encountered them before.

The surrounds during this movie were totally silent. I would be very surprised if a modern action movie would have no surround activity at all, so I'd appreciate hearing from someone running the movie about this.

Starplex seems to be like most of the theatres around here in not removing the Real-D screen during 2D movies. That really takes a toll on the image.

Posted by Justin Hamaker (Member # 2165) on 07-24-2013, 10:00 PM:

I've heard of glitchy things like this happening when a server starts to overheat. Could be related to a cpu fan or a tower fan not working properly.

Posted by Brad Miller (Member # 2) on 07-24-2013, 11:25 PM:

That is definitely a server failure. Starplex chose GDC.

The surround issue is probably not server related and they need to get a sound tech out there.

Posted by Gavin Lewarne (Member # 5397) on 07-25-2013, 02:44 AM:

perhaps it was playing from some sort of screener Blu-ray ? if not set up properly you would lose surround channels and it may explain the visual glitches as well

Posted by Marcel Birgelen (Member # 6801) on 07-25-2013, 01:11 PM:

I've seen similar things with DCPs too, on different servers. The corrupted data theory is an interesting one, because:

1) Ingested content is checked for corruption against the provided check-sums. Although corruption can also occur after ingestion, either at RAID or filesystem level.
2) The content is encrypted with AES in CBC mode, if it gets corrupted, the data should not make sense at all after decryption, at least not for the corrupted blocks.

Posted by Monte L Fullmer (Member # 2797) on 07-26-2013, 03:19 AM:

And speaking of GDC's (and seen those on-screen glitches where it was a server issue,esp with GDC's): Know of a drive-in in the neighboring area that installed digital (Barco 32B with the basic GDC unit - so far all is well).

Owner didn't know anything about digital and the installer prob didn't show them what to do on how to ingest, assemble playlists, operate, etc.

Owner had a computer tech friend who "dove in head first" in figuring out how to work this server.

He was telling me all about what went on those first two weeks in getting things up where I asked him what server did the owner purchased, for I thought the owner was going to use the Doremi ShoVault unit...and I have experience with Doremi's.

But, he mentioned GDC - a unit with three drives. I asked him if he knew that the OS was on one of the drives and to watch out for that for this can have some potential problems.

He then asked me: "what's an OS?"

[Eek!]

I then asked him his how his computer business is doing ...

-Monte

Posted by Carsten Kurz (Member # 5396) on 07-26-2013, 03:50 AM:

I think GDC is the only server that offers playback directly of the distribution harddrives. I know some operators who use that feature regularly, although clearly it should only be used in the rare event there is/was no time for a full ingest. Playing from distribution drives of course may cause such glitches.

- Carsten

Posted by Antti Nayha (Member # 4980) on 07-26-2013, 07:52 AM:

Dolby servers also allow playback directly from a CRU distribution drive, or in the case of the DSS220, a drive connected with eSATA. Not possible through USB or Ethernet, though. Of course, I agree with Carsten that it's bad practice. Also, with the Dolby it's not possible to build shows if you do it like this - you can only play single clips with no automation.

Once I've seen a DSS200 (with 4.4 software) stutter with the playback from RAID, while another DCP was being ingested from a CRU drive at the same time. Stopping the ingestion fixed it immediately. Seems like a rare bug, though, since simultaneous ingestion & playback is fairly common practice and I've only ever ran across this problem once.

Posted by Jim Cassedy (Member # 4115) on 07-26-2013, 12:40 PM:

The only time I've had problems like this (video/audio stuttering) is when I've had to
play back a show directly from the shipping drive, without ingesting.

I do a lot of advance preview & press screenings and sometimes I don't get the hard
drives far far enough in advance to ingest. I've had pressers where the drives are
hand carried by the studio PR person, who sometimes show up at the last minute.
So I have no choice except to play it right off the removable disk drive.

I'm using a Dolby server. Most of the time the screenings go OK.- -
But whenever I HAVE had a problem (including a complete system lock-up) it's
ALWYAS been when playing directly off of a removable drive.

Posted by Dennis Benjamin (Member # 1137) on 07-26-2013, 12:50 PM:

I know exactly what happened:

They were moving content around on the network while the show was running.

If they were paying attention, they would have seen the error:

"Frames dropped during playback" (or something to that effect).

They had a G.D.C. server and they were moving a trailer, a feature, or an ad (some type of CPL) around while the show was playing. It happens every time.

Posted by Marco Giustini (Member # 4544) on 07-26-2013, 03:11 PM:

Or one HDD failed during playback. Even a RAID will freeze for a second if an HDD is showing issues.
Only the other day an HDD in a Dolby Server failed, causing the show to pause for a few seconds. When the show restarted, the server began a rebuilding process on the bad HDD - which was showing 189 bad sectors. The rebuild completed succesfully, then the HDD was replaced the next day.