This is topic Optimizing the dolby error rate in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Josh Jones (Member # 447) on 08-25-2002, 02:01 AM:
What can be done to lower the dolby digital error rate? is the only thing you can do is adjust the video level, or is there more to it?Josh
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"Film is made of silver, video is made of rust"
'nuf said
Posted by Pete Naples (Member # 761) on 08-25-2002, 05:45 AM:
Lots of things Josh!Video level is crucial, also mechanical alignment of the reader (use a PC and DRAS10/WINDRAS, with calibrated alignment film). The alignment of a penthouse reader to the mech can affect the error rate, as does the smoothness of the film movement through the reader, so a bouncy reel or platter won't help, and wow/flutter won't help either.
Posted by Paul G. Thompson (Member # 655) on 08-25-2002, 01:42 PM:
Josh, look at the tension rollers in the CAT 700 and check to see how stable they are running. Any bounce is too much. Also, check and see if the center roller in your AW-3 pay-out heads have the holdback tension spring installed and working. Those should help to improve the error rate.Lot of people have removed those springs for one reason or another.
Pete Naples is right on target with his post.
Posted by Brad Miller (Member # 2) on 08-25-2002, 01:58 PM:
What's the specific goal here? Are you consistently getting high error readings and want to lower them overall, or is there one print that is giving you grief dropping in and out you want to try and get to play? The reader can be calibrated for a specific film, and there have been a couple of times in the past that I did just that to make it play. However do note that re-aligning it for that one film DID and WILL knock it off for all others to play back properly.When aligning I recommend you use an "average" loop from a Deluxe printed trailer. Just make sure you look at a bunch of different loops on the DRAS to find an "average one" of the variables. I've never been pleased after calibrating with actual Dolby loops. Also note that getting readings below 2 on a cat701 is almost impossible. The cat699 and 700 penthouses are easy to align such that 0-1 is a common reading.
Posted by Pete Naples (Member # 761) on 08-25-2002, 04:49 PM:
Brad, it's not almost impossible to get below '2' with a 701!I've got stacks of those in use up here and regularly see '0'.
Admittedly these are the newer type with the large diameter lens on the camera.
Also I've never touched the alignment of these, they are exactly as they came out of the box.
Posted by Brad Miller (Member # 2) on 08-25-2002, 04:50 PM:
I HAVE seen a 0 on a cat701 before, but it is very, very rare. Newer type?
Posted by Steve Kraus (Member # 476) on 08-25-2002, 05:07 PM:
I've seen 0's on my Kelmar (LED illumination) basement readers but that's with exceptionally good prints.
Posted by Richard Fowler (Member # 893) on 08-25-2002, 05:27 PM:
The card and lens have been upgraded in the 701 series early last year and we see 0 out of the box in addition to the BACP Digital penthouse.
Richard Fowler
TVP-Theatre & Video Products Inc. www.tvpmiami.com
Posted by Paul G. Thompson (Member # 655) on 08-25-2002, 06:10 PM:
Josh, as a rule of thumb, if the error rate does not exceed 5 and the system does not drop out, don't putz with it. It is happy.If the error rate creaps up over a period of time, it might be necessary to change the lamp in the 700. If you had an error rate of 1, I would guess that the lamp is in very good condition.
Posted by Josh Jones (Member # 447) on 08-26-2002, 12:21 AM:
I was just looking for generic troubleshooting should the need arrise to calibrate the reader. We've got a cat 700 at work and on "The emperor's new clothes, saw the error rate drop to 1 for a brief second, the best reading I've seen here. throughout that reel it was holding constant 2's.Brad, When you said you calibrated the system for a particular film, what exactly did you do to the unit to calibrate it.
Josh
It is indeed a sad day, the last day of summer. School begins Monday at 8:25 am <shudder>
Posted by Brad Miller (Member # 2) on 08-26-2002, 01:18 AM:
Just a regular alignment of the reader with a scope and DRAS. The only difference being to have the actual film that you want it calibrated to running.
Posted by Paul G. Thompson (Member # 655) on 08-26-2002, 03:12 AM:
Josh....just grab WFHS by the seat of its pants and shake the crap out of it, and show them how good you can be. Don't settle for hind tit. 
Posted by Christopher Seo (Member # 7) on 08-27-2002, 07:19 AM:
For those who have gotten error rates of 0, which SRD processor is being used... DA20, CP650, etc., or are they all equally good?
Posted by Steve Guttag (Member # 268) on 08-27-2002, 09:12 AM:
The processor _Shouldn't_ make a difference. I have had "0" on DA-10, DA-20, CP-500 and CP-650s. If any of those may be fudging things a bit, I'd say it is the CP-650.Steve
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"Old projectionists never die, they just changeover!"
Posted by Martin Dean (Member # 1416) on 08-27-2002, 09:44 AM:
If you are using an older penthouse reader, pre LED you may also want to check the bulb. As the bulb degrades the error rates will increase. Put a new bulb in and you usually find the error rate improves back to where it should be.Also if you are running a component engineering basement reader on a Westar or Century you may be having problems with vertical jitter. The problem appears as intermittent 'Fails' of the digital, a poorer error rat and can lead to they system timing out of digital on a regular basis. Endless time can be spent trying to track down the cause (which has may have no other visible effect), or you can do a small mod to help stabalise the top damper arm. This requires hooking a second spring from the top of the exisitng spring down onto the fixed part of the reverse scan assembly between the two tension arms. This will require drilling a small hole and inserting a small self-tapping screw to act as a fixing stud for the lower end of the spring. The spring used should be very similar to the one already fitted. If in doubt try a few springs and shorten them if more tension is required. If you go to tight there will be an effect on the analogue, as you will introduce some wow and flutter.
This mod vastly improves the stability of the digital and has no apparent affect on the analogue. I have carried out this mod on quite a few 'problem' machines and every time it has cured the problem. It can also improve wow and flutter effects on both digital and analogue.
Care should be taken if you want to do this mod as you will create swarf as you drill the hole. The very early version of this mod used a rubber band wrapped around the head as a temporary measure, but the spring is a more permamanet version.
The vertical jitted seems to be more prevalent on this type of sound head due to the lack of film that is wraped around the sound drum.
This mod is not official. We recieved all sorts of advice about changing sound drum bearings and the compression springs in the sound drum assembley, as well as adjsting the tension of the sound drum compression spring (this can make a small improvement). But the mod described above was apparently the ultimate cure.
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Martin Dean
martinidean@charter.net
Posted by Brad Miller (Member # 2) on 08-27-2002, 02:06 PM:
quote:
"The processor _Shouldn't_ make a difference. I have had "0" on DA-10, DA-20, CP-500 and CP-650s. If any of those may be fudging things a bit, I'd say it is the CP-650."
I am shocked you didn't know that the processor does or at least *can* make a difference, Steve. A couple of years back we tried this very test. We took a DA20 into an booth with a CP500 and ran a trailer twice in a row, once with the reader hooked into each unit. The CP500 ran 2 points higher than the DA20 did. Granted this wasn't *too* scientific of a test, as we did not get a pool of CP500s and DA20s to see if this was a repeatable fact, but it certainly proved that the processor CAN have something to do with the readings.
Posted by Steve Guttag (Member # 268) on 08-27-2002, 04:08 PM:
First off...I said shouldn't...second, where as the Dolby Digital sections of the DA-20 and CP-500 are identical (same cards), the difference can probably be attributed to the software revision running in each.Steve
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"Old projectionists never die, they just changeover!"
Posted by Brad Miller (Member # 2) on 08-27-2002, 04:40 PM:
It's ok Steve, I'm just teasing you. Anyway, now you have something to do research on. 
Posted by Darren Briggs (Member # 1071) on 08-27-2002, 05:51 PM:
Well its not uncommon for an average print to run at 1/2 on my Cinemeccanica basement readers with a DA-20.
Tested a BACP penthoude lately and that gave great results on most films which ran on it.
I think its down to the Tech who set the thing up. 2001 35mm prints ran at 0/1 all the way through so the print does make the most difference in my opinion, as this was one of 2 prints made inthe u.k.Darren
Posted by Manny Knowles (Member # 1171) on 08-27-2002, 09:14 PM:
I'm just installing brand new CP650s with 701 heads. The auditoria are still being fed from the CP45s. All we are doing at this stage is testing the connection (we are awaiting those crossovers I mentioned in another thread).Anyway, I'm getting a 3 for the error rate. Is this okay...for brand new gear?
Should a "fresh-out-of-the-box" 701 require adjustment/optimization?
~Manny.
"I know he can get the job...but can he DO the job!!??"
-- Mr. Waturi in Joe Versus The Volcano
Posted by Steve Guttag (Member # 268) on 08-27-2002, 10:09 PM:
Generally, the Cat. 701 is "ready" out of the box. The feature you are playing will have a great affect on the tracking quality.Just curious, which crossovers did you end up going with?
Steve
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"Old projectionists never die, they just changeover!"
Posted by Manny Knowles (Member # 1171) on 08-31-2002, 06:35 PM:
I went with the Smart crossovers.
Posted by Gordon McLeod (Member # 33) on 08-31-2002, 07:15 PM:
Good Smart decision I have been very happy with them
Posted by Steve Kraus (Member # 476) on 08-31-2002, 07:36 PM:
The other Steve said:
>where as the Dolby Digital sections of the DA-20 and CP-500 are identical (same
>cards), the difference can probably be attributed to the software revision running in each.Once you're in the digital domain differences should ascribe to the software but I wonder if perhaps individual characteristics of the Cat.670 card which is digitizing the video in the first place can also play a role. If both units were running the same software revision then it would be interesting to see the results of swapping the Cat.670's. This is pure conjecture of course.
Posted by Steve Guttag (Member # 268) on 09-01-2002, 02:18 AM:
Yeah, Gordon but you have been happy with all SMART products! Steve
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"Old projectionists never die, they just changeover!"