Technology

Sync or Swim in the Video Stream


Here are ways to beef up your home network to get the most from digital-video devices such as Apple TV

With more and more video becoming available on the Internet, the pressure is on to find better ways, such as Apple TV, to move that video stream from your computer to a large-screen TV display.

Nothing tests the speed of a home network like the massive data flows required for streaming video. In theory, all current wired and wireless technologies seem to offer plenty of speed to carry at least standard definition video, which, depending on compression, requires between 1.5 and 5 megabits per second. If only it were that simple.

Wired Ethernet offers speeds of up to a gigabit per second, though 100 megabit per second is more common. Wi-Fi wireless offers 11 to 54 Mb with the official 802.11a, b, and g standards and 200 Mb or more with the not-yet-ratified 802.11n version. Powerline networking, which uses the electrical wiring in your home, claims 200 Mb with either of two standards, DS2 or HomePlug AV.

Glitch Buffer

Don't believe any of these numbers. Networks are designed to achieve their average speed by carrying data in short, intense bursts. This does you no good with video, where the images have to arrive in a steady stream to provide a decent viewing experience. Since these networks don't have any particularly good way to give priority to video traffic, the only way to have a crack at its working well is to provide a lot more bandwidth than you seem to need, sometimes by a factor of 10 or more.

That's why Apple (AAPL) chose to rely primarily on syncing rather than streaming for Apple TV (see BusinessWeek.com, 3/21/07, "Apple TV's Blurry Future"). By copying, or syncing, content to Apple TV's hard drive and then playing it from there, the inevitable network interruptions will go unnoticed. While syncing, Apple TV can use its big hard drive to store enough content in a buffer that it can smooth over the glitches. But even for syncing, you are going to want a fast network to move those big files around.

The simplest, fastest, and most reliable solution is wired Ethernet. The problem is that very few homes have Ethernet cable installed, and although the wire itself is very cheap, the cost of pulling it through existing walls makes it very expensive to install.

Next-Gen Investment

Apple recommends the new 802.11n version of Wi-Fi. It's built into both Apple TV and the latest version of Apple's AirPort Extreme wireless access point. Whether 802.11n is really fast enough to deliver quality streaming video in your home depends on a huge number of variables—the distance, the number of walls the signal must pass through, and the materials used in construction being the most important. I had generally good results using Apple TV with both a Belkin N1 Wireless Router (about $100) and an AirPort Extreme ($179).

One problem with using 802.11n is that the standard won't receive final ratification from the Institute of Electrical & Electronic Engineers until early next year. However, it's likely that any changes to the draft standard could be handled by software updates. Intel (INTC) is confident enough about the current state of 802.11n that it will begin incorporating the standard into its chips for laptops later this spring. An 802.11n router, other than the pricey AirPort, costs $100—about $30 more than one using the current 802.11g standard. The extra money is probably worth it.

The sleeper technology for moving video around your home quickly is powerline networking, which uses adapters that plug into power outlets in your home and connect to computers or other devices using standard Ethernet cables. I got very good results using a pair of ZyXEL PLA-40 HomePlug AV adapters (about $160 for two). One important condition: This works only if the two outlets are on circuits that are connected somewhere, usually at the breaker box. It will work fine in most houses, but unless you have intimate knowledge of your home's electrical wiring, you won't know for sure until you try it.

Because Apple TV depends on copying for the most part, network speed isn't quite as important as it would be if you were streaming video from, say a Windows Media Center PC to an Xbox 360. For Apple TV, any of these technologies will work fine. For streaming, wireless should be O.K. provided the distance between the source and destination of the video isn't too great and doesn't involve nasty construction materials like wet plaster and metal lath. If wireless is problematic, powerline networking may well come to your rescue.

Wildstrom is Technology You columnist for BusinessWeek. You can contact him at techandyou@businessweek.com .

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