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Terrible PQ on NBCHD OTA

Discussion in 'Local Reception' started by SPACEMAKER, Sep 12, 2010.

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  1. SPACEMAKER

    SPACEMAKER Freethinker

    3,183
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    Dec 11, 2007
    Mason, MI
    I have noticed lately that my local OTA NBCHD PQ is friggin' awful.

    I am in the Lansing MI market and get NBC, Fox, CBS, ABC and PBS OTA as well. All 95%+ signal strength and all except NBC look fantastic.

    So I am wondering if this is a national issue or a local affiliate issue.
     
  2. CCarncross

    CCarncross Hall Of Fame

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    Jul 19, 2005
    Jackson
    I am also in the Lansing DMA, but I have noticed other DMA's where NBC gets very pixellated with any fast motion, and I am referring to OTA as well so it might be a national NBC issue.
     
  3. Jim5506

    Jim5506 Hall Of Fame

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    Jun 7, 2004
    Does your NBC station have any sub-channels?

    If so, they may be squeezing the bandwidth for the HD channel to make room for the other(s), this causes macro blocking with major screen movement, especially with a 1080i broadcast.
     
  4. SPACEMAKER

    SPACEMAKER Freethinker

    3,183
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    Dec 11, 2007
    Mason, MI
    There is 1 sub-channel. However PBS (3 sub-channels) ABC (1 sub-channel) and FOX (1sub-channel) do not have this issue.

    I watched part a of the UM-Notre Dame game last Saturday and the macro-blocking and PQ was terrible.
     
  5. bidger

    bidger Hall Of Fame

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    Nov 19, 2005
    Thank you!

    This sub-channel thing comes up any time someone mentions how awful NBC-HD is, especially for Sports. The local ABC has two sub-channels, but I see none of the issues there that I do with NBC, which has one sub-channel. It has nothing to do with it.
     
  6. Jim5506

    Jim5506 Hall Of Fame

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    Jun 7, 2004
    ABC and FOX are 720p, NBC is 1080i. A good 1080i picture requires nearly the whole 6 mhz spectrum allocated per channel, whereas 720p only requires about 85% of that bandwidth.

    There is also a type of encoder that uses balancing to determine which channel "needs" the greater share of bandwidth on the fly while 2 or 3 or more channels are simultaneously broadcast.

    Perhaps, your NBC station not only is robbing bandwidth from the 1080i stream but also has a cheap encoder.

    You might look at Rabbitears.info and find your NBC station and see how the station allocates its bandwidth.
     
  7. bidger

    bidger Hall Of Fame

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    Nov 19, 2005
    Then why do I not see the anomalies on my local PBS, which is 1080i with 4 sub-channels, 2 video and 2 audio-only?
     

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