# Terrible PQ on NBCHD OTA



## SPACEMAKER (Dec 11, 2007)

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.


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## CCarncross (Jul 19, 2005)

SPACEMAKER said:


> 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.


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.


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## Jim5506 (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.


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## SPACEMAKER (Dec 11, 2007)

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.


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## bidger (Nov 19, 2005)

Jim5506 said:


> Does your NBC station have any sub-channels?





SPACEMAKER said:


> 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.


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.


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## Jim5506 (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.


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## bidger (Nov 19, 2005)

Jim5506 said:


> 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.


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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