Techie question...

[avevale_intelligencer]

We have cable TV, which is ace and brill and all that except when it goes wrong, which is often. My question is this. When I am watching a cable channel, is the image supposed to be semi-pixelated into roughly three-quarter-inch squares? (I say semi, because there is detail inside the squares, but it's very noticeable, especially during fast camera moves in dark bits, that the screen has these gridlines, and I'm sure they shouldn't be there...

Comments

[zanda-myrande.livejournal.com]

It's mostly Sky-run channels (e.g. Sci-Fi, which I believe is run out of someone's back bedroom... ;) ) so it's likely the broadcaster. (They also skimp on things like making sure the programme's finished before running the continuity announcements, squeezing up the screen, et cetera...) I think they own everything right up to the box, so I probably shouldn't go messing with it (especially given my technical ineptitude), but when I get square with them again I'll ask about a replacement box just in case.

Many thanks for further enlightenment!

[deborah_c]

Interference will tend to produce blocks with entirely empty content, which generally turn up as bright green squares. If you're seeing those, you have a transmission problem. Excessive pixellation is generally an artifact caused by the bitrates being too low, and changing the box is very unlikely to help. Whinging at the provider may work, but I wouldn't hold your breath...

[pbristow.livejournal.com]

"Interference will tend to produce blocks with entirely empty content"

*Severe* interference will do that. Mild interference will cause occasional single-bit errors here and there, which, if they become frequent enough, will exceed the abilities of the error detection/correction, and have a similar effect to low bitrate. My understanding is that MPEG data is structured so that the most likely errors will tend to affect the least significant parts of the data (same as is done with audio CD encoding), so that up to a point, what you've got is still a rough approximation to the picture you should have been getting...*then* it all goes to hell.

Also, how the dead/suspicious blocks are rendered on screen is software dependant, so depends which box you're using.