March 10, 2011
By Jan Ozer Contributing Editor
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For the rest of the Spring 2011 (Sourcebook) issue of Streaming Media magazine please click here

Choosing a Streaming Encoding Tool

The ideal streaming encoding tool should provide great quality, blazing performance, a discrete set of critical encoding parameters, and a range of other time-saving automation and input/output options. We all know the names—Adobe Media Encoder, Compressor, Squeeze, Episode (in its many flavors), and Expression Encoder—so how do they stack up against this ideal? Glad you asked, because that’s what we’re going to explore.

Encoding Organization

Specifically, I’ll analyze desktop programs that cost less than $1,000 or so, leaving higher-end enterprise tools such as Rhozet Carbon Coder and Telestream Episode Engine for another day. I’ll take a codec-by-codec look at each encoding tool (H.264, VP6, and WMV), focusing on quality and performance, and I’ll present the results separately for both Mac and Windows computers.

Since these tools offer a variety of automation and I/O features, I’ll present these as well, but in a single group because three of the programs—Adobe Media Encoder, Sorenson Squeeze, and Telestream Episode Pro—are available on both Mac and Windows platforms with an identical feature set.

For quality tests, I changed both test file and test parameters from those I’ve used in the past. The new test file comprises clips from stock footage company Artbeats and from independent producer Connie Simmons of SimmonsArt, from her award-winning PBS series Landscapes Through Time With David Dunlop. My old test clips comprised DV, HDV, and AVCDH footage often shot under less than ideal conditions. I wanted to step up the quality of my starting point, and I’d like to thank both Artbeats and Ms. Simmons for supplying their high-quality clips. Since some of the source clips lacked audio, I filled in the blanks with a track from the always-handy SmartSound collection.

In previous years, I tested SD and HD files at very aggressive parameters. While this definitely revealed qualitative differences in the encoding tools, the differences may not have been relevant to most readers. For example, last year’s HD test used 720p video encoded at 800Kbps, while YouTube distributes its 720p video at 2Mbps, a data rate 2.5 times higher. Sure, this created plenty of quality differences, but would producers encoding at normal rates see the same results?

So this year I encoded using the same basic parameters as CNN, 640x360 resolution, 29.97 fps at 735Kbps video and 64Kbps mono audio, using constrained variable bitrate encoding with peak bitrate set to 2x target, or 1470Kbps. I used these parameters for all of the quality and performance tests, encoding to the codec-specific parameters discussed in each section. While the qualitative differences weren’t as dramatic, hopefully they are more relevant to the day-to-day encoding performed by most streaming media professionals.

To complete the procedural picture, I fed each encoding tool a file that was prescaled to 640x360 progressive format, so all the encoder had to do was encode. I could have input the original HD test file, but that would have involved many more variables, including scaling and deinterlacing quality, which was more than I could bite off for this article.