The last time I pitted powerline vs. wireless technology to see if either could handle the demands of HD video streaming was over two years ago. 802.11n wireless was still in "draft" form and powerline networking was still locked in a battle between incompatible HomePlug and UPA technologies.
As I write this in late summer 2010, 802.11n has been finalized for almost a year and HomePlug AV seems to have emerged as the leading technology for powerline networking.
Can either 802.11n or HomePlug AV keep up with this action?
My recent roundup of HomePlug AV adapter kits found them more alike than different and almost all capable of delivering steady throughput in the mid-to-high 40 Mbps range. But while these results are significantly improved from past tests, HomePlug AV still doesn't have the rock-solid throughput that a wired Ethernet connection provides. So the only way to really know if either wireless or powerline can provide trouble-free HD streaming is to use both with actual HD streams.
What does HD Need?
As noted in the Video Streaming Need To Know, and in the previous Smackdown, it's essential that you understand the bandwidth demands of the content that you'll be trying to stream. The best way to do this is to play the content from your networked source using an Ethernet connection while running a bandwidth metering program.
I've used both ReadError's NetMeter (free) and Hoo Technologies' Net Meter ($20), but prefer the latter because of its better plotting options and ability to clear the plot without killing and restarting the program.
You might frequently hear 20 Mbps or thereabouts described as the required bandwidth for HD streaming. This gets us in the proper ballpark, but doesn't paint a complete picture.
I used Apple's QuickTime Pro 7 to download 720p and 1080p movie trailers to use as test material. Figure 1 shows the properties of the 720p version of the Megamind trailer 3 used for testing. Note that the data rate is stated as 5.52 mbits/sec. So that should be a piece of cake for even an 802.11g wireless connection, right?
Figure 1: Megamind 720p trailer 3 properties
Now look at the actual bandwidth profile taken with Hoo Tech's NetMeter in Figure 2. Although the Avg Down throughput shown as 5.4 Mbps matches nicely with the file data rate properties, you can see a maximum of 19.1 Mbps, with frequent excursions above 10 Mbps. So the Quicktime properties Data Rate is obviously the average data rate, which doesn't help in determining what you need for flawless playback.
Figure 2: Megamind 720p trailer 3 bandwidth profile
Looking at the 1080p version of the same trailer, Figure 3 shows almost a 2x boost in average data rate to 9.4 Mbps.
Figure 3: Megamind 1080p trailer 3 properties
Figure 4 shows the bandwidth profile, with an average down rate of 9.1 Mbps closely matching the 9.4 Mbps Quicktime average data rate. As we'd expect, the profile looks very similar in shape to the 720p profile. But the peak rate has almost doubled from 19.1 to 31.8 Mbps!
Figure 4: Megamind 1080p trailer 3 bandwidth profile
So 1080p can still be doable with powerline networking or 802.11n wireless with a strong signal. But bandwidth headroom is significantly reduced.