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

Ian Evans dheianevans at gmail.com
Mon Oct 23 14:43:52 UTC 2017

On Oct 23, 2017 8:59 AM, "Barry Martin" <barry3martin at gmail.com> wrote:

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.

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!

Sorry, it's got nothing to do with the closed captionings, which I don't
use. This is not one large black block but a randomly located sprinkling of
picture breakup across various areas of the screen. The blocks are quite
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