Originally Posted by hiker
"improved" compression scheme without affecting video quality.
Why am I skeptical? And I wonder if it works with TiVo, we already know SDV does not.
I am pretty sure what they are talking about is gear that transrates multiple MPEG2 streams in realtime. That is, let's say you have 12 SD channels in a 6 Mhz package, based on the case that you have to constantly allocate for each SD channel the peak data rate that signal could consume. Well, turns out, most of the time, the data streams are well below the peak rate, so capacity is sitting around idle.
What you can do today dynamically allocate capacity to each channel, and when you have overlapping peaks, then the hardware at the hub transcodes the MPEG2 streams to a lower bit rate for the peaking streams, effectively "shaving" capacity per stream so they all fit in the capacity available. So for example, you could fit 18 SD streams in a 6 mhz channel instead of 12.
The savings are even bigger for HD because the peak to average ratio is higher than for SD. You should only need to reduce the quality for a second or few seconds in realtime when you get overlapping peaks.
Generally, you can't really tell this is going on. The impact on quality is slight and fleeting, but it saves quite a bit of capacity. Of course, you could overuse it and get a bigger hit to quality, but the MSO's tend not to do this.
This doesn't affect the endpoints, as they just display the "shaped" stream. No CPE changes required.
SDV on the other hand, screws everything that is not a two way box. Though just for the channels that are supported using SDV. So let's say they add 20 new HD channels using SDV (effectively turning them into on-demand streams). If you had a Tivo, you could still access all the other HD channels that are simulcast, but you would not be able to view the 20 new HD channels. If you had the comcast STB, then you could still see all of them, even if it was a new cablecard equipped STB, because DSG and other techniques.
Basically if you can't do on-demand, which Tivo's and MCE media centers can't, you won't be able to see programming that is sent via SDV exclusive transport. Channel changing takes longer for SDV channels, just like starting up an ondemand stream. In general it's not too bad.
Time-warner has deployed SDV pretty extensively and has had good luck with it. Comcast isn't really a technology leader per se among the MSO's, but given how well it's worked on other operators, I think when it shows up here it'll work pretty well - most of the bugs have been ironed out by now.