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NTL audio question

Discussion in 'Cable TV & Virgin Media TV' started by mikegrayy, Sep 18, 2005.

  1. mikegrayy

    mikegrayy
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    Hi
    just got ntl digital TV
    Engineer fitted a bypass so i can see the usual 4 channels without going through the digibox
    I have a JVC pro logic TV
    The PRO logic works fine on the passed through channels
    but when i select the digibox channel it will not work ?
    Why is this ?
     
  2. Starburst

    Starburst
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    The pass through channels are analogue so perhaps the TV is looking for NICAM (is NICAM used on analogue cable?) while digital channels from the STB do not use Nicam so may not automatically trigger the PL flag on the TV.

    The STB should be sending stereo and any surround info embedded in the broadcast should be intact so a PL amp will create the surround sound field, it may just not indicate as such.
     
  3. mikegrayy

    mikegrayy
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    Hi

    Thanks for that,
    you are on right track in that
    the OSD on the TV states thats its Nicam on the analogue channels
    when you change to the channel
    when i tune to the channel that the digi box is set to, the OSD
    reports nothing and i get no sound from the rear sound channel.

    Whats the difference between Nicam and stereo ?

    From my poor understanding of the pro-logic system the center and rear channels are "hidden" in the left and right channels
    therefore if NTL digital box recieves a stereo signal which is then sent to the tv, my pro-logic should work or have i missed something
     
  4. Starburst

    Starburst
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    NICAM is just a digital format used on analogue broadcasts to provide stereo audio (although I suppose it can carry a mono soundtrack as well) and it will only contain dolby surround information if the program being broadcast has the info embedded. So in effect there is really no practical difference between Nicam stereo and mpeg stereo audio (used by Digital Cable, DTT and Dsat), the main difference is that a Nicam TV will not indicate stereo even though it does exist.
    Dolby Prologic looks for the data embedded in the stereo soundtrack and then extracts the 4.1 audio if it exists, you really should be fine feeding the TV via scart (not RF) from the STB.

    Dolby Prologic2 takes this a step forward and can create a surround sound field even from mono audio but works better with stereo and surround sources.
     
  5. mikegrayy

    mikegrayy
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    thanks again
    but i still dont know why it dont work on my digibox
    i will try using a scart lead tommorrow and see if this fixes it
     
  6. Kevo

    Kevo
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    How are you watching yout NTL channels on your TV?
    You will only get stereo/surround if you use a SCART.
    RF modulated NTL channels will be in MONO, although 'pass thru' terrrestrial will be in NICAM. This sounds like what you are getting (or not getting!)
     

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