BBC1/2 Pro Logic Terrestrial Digital sound

Discussion in 'Satellite TV, Sky TV & FreeSat' started by pwoody, Apr 17, 2002.

  1. pwoody

    pwoody
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    I e-mailed BBC Scotland in December about the fact that broadcasts where sounding out of phase on programs which had good sound ie.EASTENDERS / FILMS they replyed by saying they were experiancing problems with new equipment but were on the case with the maufacturers. Its now April & the sound is still crap on BBC1/2 most of the time. Has anyone else noticed that Terrestrial BBC sound is not okay when feeding it through an AV amp (I have since purchased a DENON 3802 & sound still crap)
     
  2. Stuart Brooks

    Stuart Brooks
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    Yes I noticed the problem at the same time as yourself, there are a couple of threads on uk.tech.broadcast. I notice a hollow tinniness / out of phase sound occasionally, (currently on BBC1), usually only on one of the BBC channels at at time. I'm listening on a Virtual Dolby set, it's even noticeable there. The effect disappears on switching to standard stereo, and doesn't occur at all on analogue.

    I've mailed BBC technical twice, they say said they were looking into it and forwarded my mails to a tech bod at Glasgow.

    It seems to me from the evidence that it may be when a channel gets less of the bandwidth and the MHEG compression is increased, that this distorts the phasing information used by Dolby Pro Logic. Even in the case when the broadcast is not Dolby, the supposedly "redundant" information discarded by MHEG compression results in phase distortions which are interpreted by the Dolby decoder as spurious encoded Surround information.

    I suspect the BBC will tough it out hoping not too many will complain, as the alternative for them is to upgrade the encoders to avoid this problem (if as they say the equipment is faulty) or to lose a channel from their MUX to accomodate a proper bitstream rate.

    BBC say they do not officially support DPL broadcasts. As it's quite hard to tell on Virtual (especially when out of phase) would you agree with this or have you heard proper Dolby programming on the BBC?

    It's a bit of a pain to have to manually set Virtual Dolby settings as well as aspect ratio when channel-hopping!:rolleyes:

    Stuart
     
  3. gringottsdirect

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    I find normal NICAM from my vcr or tv is better in Pro Logic through my AV amplifier than my Nokia co-axial digital connection or my Sony or Skyplus+ optical digital connection.
    That isn't the result I expected but after many episodes of for example, The Sopranos, Buffy The Vampire Slayer, Angel, Teachers, ER, Roswell High, West Wing, The X Files and so on, it is beyond doubt.
    I don't think the reverse phase aspect of some 3D-Phonic type virtual surround effects are any good. Some televisions have the absolute phase of their internal speakers incorrect too, might be worth taking the back off and checking, using the usual safety precautions of course. Try a pair of speakers connected to external speaker outputs if you can.
     
  4. Stuart Brooks

    Stuart Brooks
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    as there is no MHEG compression to muck about with the DPL

    My TV has proper Dolby Virtual Surround which on most channels and on NICAM sounds fine, even decoding the information from VCR recordings. The speaker phasing is fine. (I don't have speaker out connections). It's purely on BBC channels on DTT (and usually one channel at a time) that the weird effects arise. Sometimes when News24 simulcasts with BBC1 the effect is there with one channel and not the other.

    Stuart
     
  5. pwoody

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    I reckon the sound has pro logic info on BBC especially Films & funnily enough the sound on Eastender ain't bad but ITV Channel 4 etc are better now which is a real shame considering how much we pay for a TV license and have to watch BBC in analogue to avoid the annoying phase problems. Wonder if we should ask for compensation!!!!! :rolleyes:
     
  6. gringottsdirect

    gringottsdirect
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    For the first time I heard the weird out of phase effect. It was through my Nokia ITV Digital receiver.
    Following the World Superbikes from Japan, the trailer for BBC Sport Relief was tinny, hollow and out of phase. When the trailer ended the sound returned to normal.
    I've since heard this trailer about five times, sometimes out of phase, other times OK.
    It does sound horrible.
     

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