Technical question for those receiving Turner Classic Movies

Discussion in 'Archived Threads 2001-2004' started by Michael Reuben, Mar 23, 2002.

  1. Michael Reuben

    Michael Reuben Studio Mogul

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    OK, here's fair warning: If you're not familiar with how dialnorm works on Dolby Digital soundtracks, you might as well skip this thread, 'cause it won't interest you. [​IMG]
    I recently upgraded to digital cable and now have access to a wonderful array of alternate programming, including OAR-friendly services like Sundance, IFC and TCM. But I'm having a technical problem with TCM, and I'm trying to determine whether it's TCM's problem or that of the cable service (corporate cousin Time Warner Cable).
    TWC's digital cable service sends a Dolby Digital soundtrack for every channel except the major networks. The most common format is, not surprisingly, DD 2.0 -- which is appropriate for many of the mono sources shown on TCM.
    But I can barely hear it, even with the volume on my Lexicon turned to the max. I finally checked the technical readout on the TCM signal and was astonished to find a dialnorm setting of -31db. Yes, that minus thirty-one. Those of you familiar with previous dialnorm discussions in Software know that the default setting on the Dolby encoder is -4db, and that's what most DVDs use. Minus 31db is a much greater reduction in volume than anything I've never encountered before, even on DVDs from Columbia TriStar DVDs, which are known for their aggressive use of dialnorm. It has to be a mistake. There's no reason on earth for such a setting.
    I would much appreciate it if anyone here who receives TCM with a DD signal could check the dialnorm setting and let me know what it is. When I start pursuing this, it's going to be a battle just to find a customer service person who even understands what DD is, let alone dialnorm. So before I start, I'd like to try to identify whether this is a TCM problem or a Time Warner Cable issue. Thanks in advance!
    M.
     
  2. Robert Cranwell

    Robert Cranwell Stunt Coordinator

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    Michael, there could be 2 parts to this. First TCM is fine on my system in NJ so lets stick with TWC in your sytem. The signal off the satellite has a correction factor that is adjusted at each cable Head-End, the video to audio delta should be between 12dbmv to 17dbmv. At each stage in the Head-End be it commercial insertion or emergency alert sytem, the audio and video needs to be checked and rebalanced. At the 64Qam stage there is another adjustment for audio to enable mono,stero,and SAP onto the particular channel.

    If anything is missed or overlooked it goes out onto the sytem as compressed Qam and for the technician aslong as the Qam modulation error rate and bit error rate fall into place on the constellation pattern everything is fine, unless someone like yourself points out the flaw.

    We always say our best status monitoring is our customers and if they get the proper feedback to us through customer service we can keep everthing running as flaw free as posssible.

    Rob
     
  3. Michael Reuben

    Michael Reuben Studio Mogul

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    Thanks, Rob. At what point in the process does the Dolby Digital encoder enter the signal path? The dialnorm setting is strictly a function of the Dolby encoder, and it won't have any impact on the signal until the signal passes through a DD decoder.

    M.
     
  4. Wayne Bundrick

    Wayne Bundrick Cinematographer

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    I think there's a slight bit of confusion here. A dialnorm setting of -31 means dialog is at -31 dBFS and no reduction in volume is needed. The default on Dolby Digital encoders is -27, which indicates a reduction of 4 dB is needed to bring the dialog down to -31 dBFS. I believe A/V receivers subtract the dialnorm value from -31 and display the result, since that is how much they are reducing the volume and that's the useful information you want to see.

    I think that if you're seeing an indication of "-31", that means the dialnorm value is 0, which specifies dialog is at 0 dBFS (absolutely no headroom for peaks, has the dynamic range of a Ricky Martin CD -- no, it's worse than that, more like a TV commercial for a Ricky Martin CD) and is asking for a volume reduction of 31 dB. That's why TCM is too quiet.

    The reason I explained all of this is so that you can use the proper numbers when you speak to the one smart person at the cable company who will know what you're talking about. A dialnorm value of zero is wrong, and if one isn't measuring the dialog and doesn't know what it should be then it should be set at -31 or even left at the default -27.
     
  5. Robert Cranwell

    Robert Cranwell Stunt Coordinator

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    Michael, to enighten what Wayne said about commercials, when a A/V delta balance is done you need a monitor to see if you are on the actual program or a commercial. All balancing except for premiums and PPVs is done without a commercial being displayed.

    The encoding process is the very last before it 1: becomes a compressed QAM carrier 2: goes to a combiner with the analog channels 3: is sent to a laser basket to be injected out on fiber to a node in the system.

    I really beleive someone is missing a A/V balancing portion in the Head-End somewhere. If it was analog channel you could use a meter to measure the A/V signal stregth of the carrier and point out how far apart the delta is,therefore causing the audio to be lower than the adjacent channels.

    Rob
     
  6. Michael Reuben

    Michael Reuben Studio Mogul

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  7. Robert Cranwell

    Robert Cranwell Stunt Coordinator

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    Michael, the encoding process is an analog to digital on there end. As I posted earlier in the A/V balance at the HE is probalby off there. I can't see the DD dialnorm being off that much " it will post an alert if the level is below factory norm" but your inputs have to be within that window of 12dbmv to 17dbmv delta of the video to work properly on the result user of end being you.
    To see whats is what off the satellite and what encoding process is uplinked and downlinked try www.lyngsat.com
    Go to the amercias and you see satellites first,than you have to look for the info at each transponder. There are links there back to each affiliate also.
    Rob
     

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