Occasionally I have come across cable TV reception where a large solid black square appears over half or more of the image. Just on one channel. And nothing naughty or controversial was being shown at the time; the last time I saw this happen was during an interview on Ellen. Changing to another channel and back didn’t help: the square was gone only momentarily upon return, but would reappear within seconds.
This hasn’t happened on my home reception, but at my gym and on a neighbor’s cable TV reception (my suspicious neighbor was sure she was being censored by someone).
Probably has something to do with close captioning, perhaps alternative language support or descriptive text. That usually shows up as a block of text on a black box in the middle of the screen.
But wouldn’t the text box for closed captioning be at the bottom of the screen, and only slightly larger than the text? The black boxes I saw covered more than half the whole
screen, and were more or less square.
In my case, the cable company and some channels were duking it out over money. The channels were rolling some text over the screen which presented their side of the issue, with the purpose of claiming support from viewers. The cable company, in turn, contrived to block that part of the screen with some black squares so you couldn’t see the channel’s message.
On my TV, the closed caption options are something like, C1,C2, T1,T2 through T5. Almost all of the stations don’t use the Text options, so nothing happens if I turn off CC by bumping it to T3. There’s one channel, though, that uses that T3, seemingly without inserting any text. I get a big black box. Last time it happened, I had to shut off the TV to make it quit.
Would the closed-captioning box appearing on the screen be a function of the channel, or of the television set? Remember, this box appears only on one of the cable channels when it happens.
In North America, closed captioning on analogue TV (NTSC), over the air and via cable is transmitted as data on unseen scan lines of the picture signal. So it’s channel-dependent.
I have absolutely no idea how it is done on digital transmissions–either ATSC (HD over the air) or digital cable/satellite.
Regular non-HD DVDs store their subtitles in a completely-different way than closed-captioning, essentially as picture overlays. Both text and simple graphics are handled as pictures, so non-alphabetic languages like Chinese aren’t a problem to handle. There can be up to 31 separate ‘streams’ of subtitle information as well, tagged with different languages.
I believe that non-HD DVDs can somehow store and reproduce NTSC closed-captioning, but I could be very wrong there.
What you are seeing is definitely the closed captioning in text mode. The fact that it turns on momentarily after switching back to the channel is the evidence. Just cycle through the various closed captioning options with your remote to turn off the empty black boxes (which will appear on some programs/channels but not others).