Not sure if i have the right place to ask this question but I have a pioneer elite HD tv, about 4yrs old and when i had comcast cable tv i would get mico blocking on hd channels once in awhile, where the picture would go crazy little blocks ect and sometimes lose audio, now i have directv and same thing, is this due to weak signal from like abc, nbc, cbs ect or what, no one can find problem.

Yes, I believe it's from a weak signal or more likely atmospheric conditions. It happens to me sometimes on Comcast. It seem that certain channels are more susceptible to this. I know INHD and Nationiol Geographic HD seem to get it more often than others.

Might be sun spots but i'm not sure what the propagation is at this time.

It's due to over-compression by the cable/satellite company. It's a little different in MPEG2 than it is in MPEG4, but that's what it is. Low signal strength will not do this, it'll just shut down the receiver.

You can count on your provider to continue this practice, they all do. They use system-wide compression algorithms that compress all channels according to total bandwidth. When a bunch of channels all hit high bitrates at the same time, you get the breakup or dropout. Personally, I see it a little less on the MPEG4 channels, but it still happens. Generally it will happen at scene changes.

I notice this on the local HD channels only. It sucks! I notice this especially on fox and it annoys the living hell out of me since I am a huge fan of 24 and Prison Break. My Fox HD channel is actually really bad. It will break up anywhere between 10-20 times when watching these shows with the micro blocking. The other channels are crisp and clear though. Its only the local HD channels that to this, particularily Fox more than any other channel.

In a general sense CDan has summarized nicely. You don't want to dig any deeper and start talking about Discrete Cosine Transformation (DCT).

No, we don't!