Streaming Media - August/September 2008 - (Page 56)

so many codecs, so little time whether the encoder dropped any frames to meet the target data rate. As you’ll see in each test, I rated all three codecs in each of these categories and then picked a winner. Let’s start with a brief overview of the H.264 codec, followed by a description of the codecs and encoding tools. H.264 Overview If you’ve produced H.264 files with different encoding tools, you know that the encoding parameters exposed by the various tools differ in both nature and extent. To a large degree, that’s because the H.264 standard doesn’t define a standard encoder; it defines a standard decoder, and codec vendors are free to employ any number of encoding techniques so long as the standard decoder can play the compressed file. Even when a codec vendor decides to implement a specific encoding technique, it may decide not to expose those controls to the user, either in its own encoding tools (like Apple with Compressor) or to licensees of the codec (like Sorenson with the Apple codec). Or the codec vendor may expose the options to its application developers but the licensee may decide not to expose them to its end users, preferring to make the encoding tool as simple as possible to use. Even the absence of specific controls (such as search pattern or entropy coding) doesn’t mean that these techniques are not being used since the codec or application vendor can tie them to higher-level controls such as a quality slider. This is why different encoding tools have very different interfaces, which makes it very challenging to understand exactly what’s going on under the hood. Though H.264 analysis tools like Inlet Semaphore provide some insight into the encoding techniques used by an encoding tool, to a great degree, each H.264 codec is a black box of techniques—you input a file, adjust the encoding parameters, and assess the quality of the result. Essentially, that’s what I did in this comparison. Figure 1. Encoding controls for the Apple codec are very basic. Figure 2. Here are the H.264 and other encoding controls for the Dicas codec as applied by Telestream Episode Pro. The Apple Codec The Apple codec is used in Apple Compressor, Grass Valley/Canopus ProCoder, and several versions of Sorenson Squeeze prior to the new release, Squeeze 5.0. The Apple codec is very simple to use; Apple exposes very few encoding parameters in any encoding tool (Figure 1). For example, where the other codecs let you select the profile (Baseline, Main, or High), Compressor includes a check box for Frame Reordering that encodes in the Main profile and can’t currently produce files conforming to the High profile. I produced all Apple-codec test files in both Squeeze and Compressor to identify which encoding tool produced the best results. Ultimately, I rated the SD and tutorial tests produced by Apple Compressor rather than Squeeze, because there was very little noticeable difference. I used the Squeeze files for the high-definition comparison because Compressor couldn’t hit the data rate target. Dicas The Dicas codec was developed by Dicas Digital Image Coding GmbH and is available in Telestream’s 56 STREAMING MEDIA August/September 2008 Figure 3. Encoding controls for Rhozet’s implementation of the MainConcept codec in Carbon Coder

Table of Contents Feed for the Digital Edition of Streaming Media - August/September 2008

Streaming Media - August/September 2008 Table of Contents No Doubt - Editor's Note Mo’ Videos, Mo’ Money: Solving the Problem of Network Cost Why Good Design Matters More Than Ever: Just. Press. Play. Technology and Business Trends by the Numbers High-Touch Encoding With Microsoft Expression Encoder 2 The State of the Content Delivery Market, 2008 Get a Life: New Tools Put Lifecasting Within Anyone’s Reach So Many Codecs, So Little Time: Comparing H.264 Files Using Codecs From Apple, Dicas, and MainConcept Writing an RFP for Maximum ROI: Things to Consider and Questions to Ask When Writing a Request for Proposal for a Corporate Webcasting System The Patent Wars Producing Screencams in Camtasia Studio Analyze That Using Video to Communicate Change for Business Success Intellectuals’ Property Rights

Streaming Media - August/September 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.