Originally posted by BVfan
Husker: I agree that CBS does not look as sharp now. I really can not pinpoint it to when UPN came on though. I thought the NFL looked better this fall that it does now, but that is rather subjective. I wonder if they also have some other subchannel(s) they are doing some data broadcasting on now that we don't see on our receivers.
KELO is broadcasting its HD channel at about 15 mbits/sec, and UPN at around 4 mbits/sec. That missing 4 mbits/sec results in quite a loss of picture quality, most notably on their NFL telecasts.
I'm not sure this shows how much compression (or band-width sharing) KELOHD is doing. I recorded NCIS on Tuesday and the files was about 6.8 GB. I recorded Alias from KSFYHD and it was about 8GB. Both were for 1 hour. My numbers aren't exact, but there was a definite difference.
KSFY is broadcasting in 720p (vs 1080i for KELO) at about 12.2 mbits/sec. If your files are the same size for both, you're recording the entire stream, including sub-channels and Null packets. 720p compresses a lot better than 1080i, unfortunately for CBS, so ABC's games don't suffer the artifacting and loss of quality that we're seeing on KELO.
I will also look at my PBSHD recording file sizes as they have subchannels. PBS has always looked very sharp, but they have no live sports to make a good comparision with.
PBSHD has the same issues as CBSHD - it's 1080i with subchannels, so PQ suffers, especially during fast motion scenes. Fortunately, most of the PBS HD content is slow-panning documentaries, so it still looks great. If you watch some of their Soundstage concerts, closeups of guitars playing and other motion scenes definitely are degraded. PSB does some statistical multiplexing, I believe, which helps smooth over the worst of the motion artifacting.