[mythtv-users] Black blocks in video after CBS Buffalo (WIVB) adds first subchannel on new encoder

Barry Martin barry3martin at gmail.com
Mon Oct 23 12:58:21 UTC 2017

Hi Ian!

> in the Buffalo/Toronto area and record OTA you might be able to duplicate
> this issue by recording Colbert or CBS This Morning.
> After adding their first subchannel (which was already on another channel
> in the same city), I reached out to a WIVB station engineer to confirm what
> was happening. He said there was a subchannel ballet going on between the
> two stations, but yes, they had added the subchannel after getting a new
> encoder last week. That's around the same time I began noticing the
> problems. They are related to this 2016 thread: "Concert footage and video
> artifacts" (
> http://lists.mythtv.org/pipermail/mythtv-users/2016-November/389597.html)
> in which I described blocky video during fast transitions and got an
> education in compression artifacts and bandwidth.
> <snip>
> WIVB has only one subchannel and they're not trimming the bandwidth too
> much as a 2 hr show has gone from about 14gigs to 12. Other channels in the
> area have far more subchannels and I'm not seeing the black blocks on their
> programming. The station engineer says he's not seeing it with their
> off-the-air recordings but he'll keep looking. Is there anything I can
> tweak on my end? Given that channels with more subs don't have this issue
> could it be some setting/tweak on their new encoder? I know this is hard to
> diagnose but I'd appreciate any tips.

I think the problem might be you have Closed Captioning on(!), There are 
multiple options and if the TV is set to an option not being used 
normally nothing appears.  For some reason with CBS stations a large 
blackish box will overlay the bottom portion with one of the CC options; 
on other networks the box does not appear with the same setting.  The 
multiple black boxes you are seeing might be a form of the large black 
box issue.

So tap the CC button on your remote and hopefully your problem goes away!

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