When the camera scans while watching sports my hd lcd tv.the pixals seem to sparkle and dance.why?

Question

it seems to affect lines vertical and horizontel.when the camera is still the picture is fine.

Answer 1

could be your cable signal strength

Answer 2

The short answer is, it has to do with the digital encoders that the program originator and other TV stations and cable / satellite companies are using.  A digital encoder is a device that prepares the video and audio for transmission to a TV receiver.

The longer answer is, there are only so many bits available to encode a digital picture.  If the program supplier is also squeezing in more channels (i.e. an SD signal, an HD signal, perhaps the broadcaster is adding sub channels or the cable/satellite system is re-encoding) then there are even fewer bits to devote to any one picture.

Encoders deal with this by periodically sending a complete picture and then only "updates" of what changed from frame to frame.  If the camera pans a crowd, the updates can't keep up, especially if the encoder is trying to leave more stuff out because it's making room for other channels.  There is a technology out called "dynamic encoding" that will allow the encoder to "steal" bits from the other channels when one channel demands more updates.  However dynamic encoding is not widespread at the moment.

Disclaimer: I oversimplified this for public consumption.  Techies, please don't go on the attack.