Gremlins In My TV Broadcast Signal

November 5, 2007 11:32 AM

DIRECTV/Fox Broadcasting Error

I'm getting tiny weird checkerboard pattern errors flicking up on my screen for one or two frames at a time, all in different seemingly random locations every few seconds during every Fox broadcast (Simpsons, NFL, etc - not Fox News). I have an LCD TV & DIRECTV's new (non-Tivo) DVR. Does anyone have any idea about what's going on? It's not really a problem, since they're so small & they disappear in a heartbeat, but it's just quirky & I'm curious about it.

posted by jonson to Technology (8 answers total)

It's usually caused by poor signal quality, either from the satellite to your dish or in the cable between your dish and your receiver.
posted by grumpy at 11:44 AM on November 5, 2007

Best answer: More from Cisco Press:
"MPEG-2 coded material is extremely sensitive to errors and lost information because of the way in which MPEG-2 puts certain vital information into a single packet. If this packet is lost or corrupted, there can be a significant impact on the decoder, causing it to drop frames or to produce very noticeable blocking artifacts. If you think of an MPEG-2 stream as a list of instructions to the decoder, you can understand why the corruption of a single instruction can play havoc with the decoded picture."
posted by grumpy at 11:46 AM on November 5, 2007

I don't know about cable but it can and does happen with satellite, too, it's an imperfect signal
posted by matteo at 11:47 AM on November 5, 2007

yeah, exactly as grumpy says. with satellite it's mostly a sign of decoder problems, I don't know about cable
posted by matteo at 11:48 AM on November 5, 2007

As other said, it's a common mpeg failure phenomenon. Check your signal quality. Have you had this configuration long? If not, you probably want to address it sooner rather than later - that degradation is annoying now, but when you get a bad cloud cover or storm or whatever and you lose -all- signal because you started out poor, well, then you'll be unhappy.

I've also seen this happen with older splitter devices. My darling girlfriend's 2-8 device was getting flaky on a few transceivers before she moved and left it behind. You might have a failing component, or a cable with some damage.
posted by phearlez at 11:51 AM on November 5, 2007 [1 favorite]

I saw these little black lines on my new LCD tv yesterday watching football on Fox (via Verizon FIOS) and freaked -- thought one of the kids screwed up the screen or maybe we had some bad pixels, but then calmed down after changing the channel and seeing it was just on Fox. Still, annoying.

So, I don't think it had anything to do with your setup, or with DirectTV -- I'm pretty sure it was coming from the Fox broadcast.
posted by Ike_Arumba at 4:10 PM on November 5, 2007

In other words, the link from DirecTV to you was fine. It was the link from Fox to DirecTV (and possibly other carriers) that was bad, and you have no control over that. If it was a bad Fox feed, I assure you that DirecTV was on the case, as they are very good at monitoring their incoming signals.

I checked DBStalk just now and there was no mention of a general problem, but I didn't look very hard.

Unless it continues, and affects other channels, I wouldn't worry about it.

FYI, one of the advantages of MPEG4 (starting to roll out in DBS applications) is that it has a deblocking filter so that you don't see that checkboard effect. It just gets a little blurry instead, which is far less annoying and you probably wouldn't even notice it.
posted by intermod at 7:14 PM on November 5, 2007

intermod, which MPEG4 - Part 2 or 10?
posted by Gyan at 2:57 AM on November 6, 2007