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Multimedia & VoIP Features

Introduction

For an updated view of powerline vs. 802.11n HD streaming performance see HD Streaming Smackdown: The Rematch.

I am fortunate enough to have designed the network layout for my recently-built home. (That story starts here.) As a result, I have Ethernet drops where I need them, including where my NAS and home entertainment gear sit. So I have plenty of steady, reliable bandwidth to ensure trouble-free streaming of even high-definition video.

But not everyone has Ethernet where they need or want it and either can't or are reluctant to bite the bullet and pull CAT5e/6 to solve the problem. Consumer networking companies know this, of course, and have been trying for years to convince us to buy a parade of "alternative" (to Ethernet) networking products instead of calling our friendly neighborhood electrician or network installer.

So I set out to see if I had anything in my pile o' reviewed products that could provide trouble-free streaming of high definition video over a not-too-difficult distance.

What does HD Need?

We first need to see what we need for bandwidth before we can choose an Ethernet alternative. For HD, you frequently hear 20 Mbps or thereabouts described as the required bandwidth. This gets us in the proper ballpark, but doesn't paint a complete picture.

Look at Figure 1 to get a better idea of what you really need to support HD streams. I used ReadError's NetMeter (free) to plot throughput profiles of a couple of 720p HD clips downloaded from Apple's HD Trailer website. (There is also Hoo Technologies' Net Meter if you like something with more plotting options and don't mind paying $20.)

720p HD bandwidth profiles

Figure 1: 720p HD bandwidth profiles

The vertical scaling on the plots isn't the same, but the maximum throughput number in the left-hand margin on each plot will help you interpret the results.

Even though Quicktime HD's H.264 encoding is pretty efficient, you can see that peak bandwidths still get up above 20 Mbps. And if you want to properly support fast-forward and reverse, you could see those peak numbers almost double.

By the way, I didn't use 1080p clips because the Netgear EVA8000 [reviewed] that I used for playback on my Panasonic TH-50PX75U Plasma wouldn't properly play Quicktime HD 1080p clips. (Netgear specs WMV up to 1080p, but doesn't say anything about H.264 or Quicktime HD.) I also found that the EVA8000 would stutter and grind to a halt on some 720p QTHD 720p trailers. So I first verified that all the clips used for testing played properly with an 100 Mbps Ethernet connection.

What can we use?

Given the throughput requirements of the 720p test clips, I decided to start with plenty of headroom and try 200 Mbps powerline and draft 11n wireless. Both of these Ethernet alternatives boldly advertise throughput numbers in the 100's of Mbps—actually 200Mbps and 300Mbps respectively—and are frequently touted as solutions for HD streaming. Of course, those are the maximum raw PHY rates before little things like protocols, error correction and security are included, which reduce throughput by at least 50% from the "maximum" numbers.

Figure 2 is taken from our Zyxel PLA-400 review and shows a summary of throughput tests in vie of my home's test locations. Location 3 is the one of interest, which is my living room. This spot is one floor above the office / lab, approximately 25 feet away (direct path). There is one wood floor, a sheetrock ceiling and no walls between the two locations. This isn't the most extreme test case that I could use. But I think that it may be typical of the distances and obstacles many Ethernet-less would-be HD streamers face.

Powerline networking test summary
Click to enlarge image

Figure 2: Powerline networking test summary

The chart also includes results for the Corinex AV200 powerline product [reviewed], which is based on DS2's 200 Mbps powerline technology. HomePlug AV and DS2's UPA (Universal Powerline Association) technology are roughly equivalent in performance, but not interoperable. The chart shows that either technology produced around 30 Mbps at the test location. This is a bit tighter than I would like it to be to handle streaming throughput peaks. But I decided to give it a shot anyway.

For draft 11n, I decided to use 5 GHz instead of 2.4, simply because the 2.4 GHz spectrum is just too crowded to use for reliable HD streaming. Even though 5 GHz has significantly smaller range than 2.4 GHz, my previous tests of draft 11n products showed that the signal strength in Location 3 (with the test AP in the lab / office / Location 1) was high enough to product sufficient throughput.

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