Occasionally you'll see blocks in the screen that are left over from the previous frame from the video. That's pixalization. I also get audio squelching when that happens too.
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Any other examples to look for?
Look for image jumps. That occurs when frames are missing or dropped preceding the jump.
Look for fast moving areas of the image that are very blocky and contorted. If you can slow motion any playback it will become 10 times more obvious. The compressions assumes you are watching in real-time.
Yup. I get that too. When I call customer support about these problems, they they tell me to reboot my DVR which takes about 15 minutes to cycle. The problems stop for a while but slowly return again.