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Dolby Digital problem

Discussion in 'AV Receivers & Amplifiers' started by mij, Feb 5, 2002.

  1. mij

    mij
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    Has anyone had a response regarding the the problem with certain DVD's losing the sound when used with certain receivers (Denon-Onkyo being just two)
    The whole matter seems to have been forgotten, I have the Denon AVR-1602, and apart from Denon acknowledging my e-mail, I have not heard a thing, seems they are all trying to blame each other (Dolby Labs, The amp maker, the DVD film maker)
    all the while leaving us in the dark, without a solution, do we need to change our amplifiers?
    I am very close to taking my amp back to the shop, but without any answer I am worried the replacement will have the same fault.

    Cheers mij
     
  2. Zone

    Zone
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    Seems as though Dolby are now saying it isn't the DVD that are at fault and offer this as some sort of intermediate solution, pretty poor really.

    Si
     
  3. bob007

    bob007
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    I should say so, paying all this money for equipment to listen to these new sound formats and reverting back to DPL.....DON'T THINK SO.
    I have had no problems with my Denon 3801, so could it be down to the decoders in certain models or a batch of decoders sent to various manufactures, lets hope they are on the case and not sitting at their desks thinking of new formats untill they have ironed out the problems of the current ones.........!!
     
  4. deang

    deang
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    I have been trying to get a satisfactory response out of Denon since early Jan. I've got a 1602 which exhibits the DD dropout on the Pearl Harbor DVD. I've been told it appears to be a Dolby induced problem and that the Denon chipset was approved by Dolby - indicating to me that Denon won't be accepting liability. I've also been told by Dolby it is also a problem with Jurrasic Park 3, and probably one other disc not yet released, but they won't say which one.

    From my 'customer' point of view I've spent over £2500 on a home cinema setup that wont play one of the biggest movies last year, plus at least 2 others. It's not good enough Denon. I don't care who's to blame, I want a solution.

    As an aside, my local hi-fi shop where I purchased it from have been excellent, and offered to replace it, so I could be looking at the Marantz SR5200 very soon!

    :mad:
     
  5. Stuart M. Robinson

    Stuart M. Robinson
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    Guys,

    These drop outs are caused by an updated version of Dolby Digital ‘fooling’ some decode chips – mainly Cirrus Logic Crystal – into muting their outputs.

    The problem stems from the Extended Bitstream Syntax (EBS) introduced in Dolby Digital encoder version 7, an extension put in place to carry the EX flag and Dolby Headphone information (among other things).

    In Dolby Digital streams with EBS, the TIMECOD2 14-bit instruction has five variables. DSUREXMOD (bits 13 and 12), DHEADPHONMOD (bits 11 and 10), ADCONVTYP (bit 9) XBSI2 (bits 8 to 1) and ENCINFO (bit 0). ENCINFO now carries information about the DVD author, the encoder used etc., and is another addition to the EBS.

    The ENCINFO data is encoded over several frames (Dolby Digital works by packing blocks of data into frames, each frame containing information about the bitstream, error correction data and the audio data itself), so the ENCINFO value can change by up to thirty-three times per second, as either the data is updated or appended.

    In the case of some decode chips, the Crystal CS49300 family specifically, each time any portion of the ENCINFO data changes, an audio configuration change message is generated. This would usually instruct the decoder to change mode only when the type of material changed – from a 2/0.0 trailer or menu to a 3/2.1 movie, for example – but in the Crystal the state change message is being generated up to thirty-three times per second, ie. with each new frame of data. Most decoders are designed to momentarily mute when the bitstream changes (you may hear a slight gap when going in and out of menus) so a constant barrage of state-change messages causes the decoder to mute continuously and erratically.

    All the malfunctioning discs were authored with Dolby Digital encoder v7 and at some point include the new EBS instructions.

    There are only two possible fixes.

    1) Dolby can revise (again) their bitstream syntax, changing the EBS data in some way, but this won’t address the problems caused by the discs already on the market.

    2) Manufacturers can update the code in their DSP engines, and Crystal have already released appropriate decoder revisions, but this isn’t going to help anyone with a malfunctioning receiver or processor unless you own something that is software upgradeable (Lexicon) or have a manufacturer willing to undertake a ‘repair’.


    Stuart M. Robinson
    SMR Group – http://www.smr-group.co.uk/
     

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