Film-Tech Forum ARCHIVE: Cable HD vs Over The Air HD

This is topic Cable HD vs Over The Air HD in forum The Afterlife at Film-Tech Forum ARCHIVE.

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Posted by Joe Redifer (Member # 3) on 10-23-2004, 06:40 PM:

Is there a difference? I was talking to a guy at our local CBS station briefly and and I was telling him that I notice artifacts at times in his HD signal. He asked me if I was wathing it over the air or on satellite/cable, and then went on to say that he doesn't notice as much artifacting over the air.

That leads me to believe that there must be a difference. Is the bitrate for cable HD lower? I can't imagine cable being able to handle 19mbps per customer especially when they stream regular TV and internet over the same line. Does cable HD = ass quality or something? Or have I been misled?

Posted by Daryl C. W. O'Shea (Member # 1303) on 10-23-2004, 07:10 PM:

Most cable and satellite systems that I'm familiar with use adjustable constant (based on what's being broadcast) or variable bitrate streams.

19mbps is not required, unless it's on demand programming, and then that's only 19mbps from the local neighborhood cache. If it's regular programming then it's basically the equivallent of a network broadcast, so it'd be 19mbps per channel.

As for cable bandwidth, my cable modem can hit 8mbps and it only consumes a small amount of the total cable bandwidth. Although I can't recall exactly what percentage it consumes compared to the percentage consumed per television channel.

That said, the last time I was debugging processor chips inside satellite receivers (hey, you've got to do something to keep occupied in electronics lab), my local providers satellite HD streams consumed about 12mbps compared to the regular channels 5 to 8mbps.

Posted by Joe Redifer (Member # 3) on 10-23-2004, 10:39 PM:

But everypone loves to bag on cable "the more people in your neighborhood who are online at the same time, the slower it gets and the more you get raped from the cable company". Wouldn't a whole bunch o' peeps in the same neighborhood watching different HD shows at the same time lower the overall bandwidth if the above quote were true? What if all of those people at the same time started downloading porn at 8 mbits per second on their cable line while also watching HDTV? And also the same cable line was routed into 4 rooms of each house and each room had a different HDTV channel on and different porn downloading? Why can't cable modem be allowed 19mbps?

Posted by Daryl C. W. O'Shea (Member # 1303) on 10-23-2004, 11:11 PM:

The cable internet service band and the digital cable-on-demand band are exclusive of each other and aren't necessarily sized even similarily.

On-demand programming is supposed to be handled by local neighborhood caches to segment system load. It's up to your provider to provision adequately for the number of customers on any network segment, not unlike an ISP has to do.

quote:
ouldn't a whole bunch o' peeps in the same neighborhood watching different HD shows at the same time lower the overall bandwidth if the above quote were true?

Only if they're all watching on-demand programming, which would limit the bandwidth usage to the local network segment. If there wasn't enough bandwidth to handle this load I'd imagine they'd either limit start times of popular on-demand programming, limit selction of un-popular programming, or send a lower bitrate version across the network to the local cache if possible.

Internet usage would have no effect on television load since it doesn't share the same bandwidth.

Posted by David Stambaugh (Member # 1102) on 10-24-2004, 12:02 AM:

Comcast claims no difference between their cable HD bitrate and over-the-air. I can't tell any difference comparing them either. They look the same to me, at least on my set.

Side note: Comcast is experimenting with digital-on-demand here and I can find all kinds of interesting stuff for free on my Sony RPTV's built-in ATSC tuner. Like, oh, say, adult movies. [Big Grin]

Posted by Joe Redifer (Member # 3) on 10-24-2004, 12:17 AM:

Are you saying you're getting other people's demanded programs via your ATSC tuner?