3. Multimedia Networking - What do you really need?

As befits the consumer focus of CES, the key networking story is the battle of the multimedia networking strategies. The stakes are huge and so are many of the players. But from what I saw, there are multiple approaches, and no clear winners yet.

The consumer networking product guys (and their wireless chip suppliers) would like you to believe that all streaming will be done via "throughput enhanced" 802.11g wireless networks. The three major chipmakers (Atheros, Broadcom, and GlobespanVirata) have now laid their pumped-up 11g plans on the table and both Broadcom and GlobespanVirata were privately demoing their wares during the show. I viewed both demos and the results are described in the Enhanced 802.11g NeedToKnow.

But from what I saw in actual (or soon-to-be-actual) products at the show, many consumer product companies - including some real big players - aren't all drinking the wireless chipmakers' Kool-Aid.

Before I get into who was showing what, let me take a moment to try to put the networking requirements of streaming audio and video into perspective. The rules of thumb presented in the Gigabit Ethernet NeedToKnow are still generally applicable, even though more formats have appeared and the flavors of display devices - especially portable devices - have exploded since that article was written.

The table below is my take on an updated set of rules-of-thumb to keep in mind when separating multimedia networking hype from what you'll really need. The table is my attempt to simplify a very complicated and constantly changing topic. The numbers you see are not absolutes, but intended as guidelines only.

Standard	Application	Bit rate
MPEG 3, WMA	Audio	28 - 500kbps
MPEG 2	Standard TV (480i)	3 - 5Mbps
MPEG 2	DVD / HD (720p, 1080i)	6 - 25Mbps
MPEG 4, DivX	Portable video, "VHS-quality" TV	64kbps - 4Mbps
Table 1: Multimedia Formats and Bit rates

TIP: contains a great table describing the various ATSC formats.

You can see from the table that streaming audio is a non-issue in any networking scenario, given that its bandwidth requirements are minimal. The key driver in designs is video and that's where the magic of compression will eventually save the day - just as it has in audio.

One of the arms merchants in this battle is . These guys specialize in video-over-IP and their mantra is "the frames must go through!". They apply an amazing range of signal processing techniques to the transmisson end of a video stream so that a standard MPEG 2 or 4 stream is delivered at a steady 30 frames-per-second rate at the receiving end, no matter what (almost) happens to the effective bit rate in between.

VIXS' XCODE chips can deliver an HDTV grade signal with effective network throughput as low as 6 Mbps or a standard TV signal with a puny 1Mbps . Video at these rates will admittely be somewhat pixelated, but still very viewable.

VIXS also makes an 802.11a baseband processor (Matrix ) that uses two 802.11a channels for wireless video streaming. Note this use of multiple channels is completely standards compliant and doesn't employ channel bonding techniques as Atheros' Super-G does.

I'm admittedly low on the learning curve on this topic and trying to come up fast, but the main conclusions regarding multimedia networking that I drew from my look around the show are:

Products are being designed so that consumers will have a satisfactory multimedia experience over wide transmission medium throughput ranges. This is especially true for wireless distribution schemes, which they realize are highly susceptible to range and interference problems that seriously degrade throughput. 802.11a isn't dead - especially as a wireless video distribution medium IP-over-coax is also in the running

Let's take a look at some examples next.