Review: LSI Tarari Encoder Accelerator LCPX-6140

Which leads us to the next question: Who’s in and who’s out?

Compatible Programs
According to LSI’s product brief, the "LSI Tarari Encoder Accelerator provides seamless acceleration for any WMV and VC-1 encoding applications based on the Microsoft Windows Media Format SDK—without the need for any special scripting or digital glue." Obviously, this means that there are programs that won’t be accelerated. I checked the status of the most commonly used Windows encoding programs with the LSI representative.

Most of the prominent encoding tools work today or will work very soon. In addition, note that if you’re encoding using scripts that call Microsoft’s Professional, Enterprise, or even the older SDK 11 for WMV, the Tarari board will accelerate your rendering.

The Adobe situation stems from the company using a MainConcept API rather than a Microsoft API for the Adobe Media Encoder. Barring any changes, it may not be possible to make the Tarari accelerators compatible with the Adobe Media Encoder. On the other hand, LSI has been compatible with previous versions of Sorenson Squeeze, and the company promised the necessary fixes very soon. Still, if you’re buying the software to use it with Sorenson Squeeze, you should first verify that LSI has completed the necessary work.

With coprocessor cards such as Tarari, your results will vary based on the encoding program you’re using, input and output resolution, and the encoding setting you’re using (1-pass or 2-pass encoding). When comparing your results to baseline, computer-only encoding, the speed and the number of cores in the test computer will also affect the results. To try to illustrate this, I ran different tests on the programs that I had available.

Let’s start with Canopus ProCoder, a relentlessly efficient encoding program on multicore systems such as my test bed HP xw8400. Here, I encoded five 1-minute SD files to 640x480 resolution at a data rate of 500Kbps (468 video/32 audio) and three 720p files to 1280x720p resolution at a combined data rate of 928Kbps (800 video/128 audio). I produced all files using 2-pass encoding since that’s my general practice.

With the Tarari accelerator, it took 11:21 (min:sec) to produce the files; without the card, it took 45:46. On a percentage basis, this means that Tarari reduced encoding time by 75%. I compared the quality of the files produced with and without the card and found them visually identical, though the final size varied slightly. Something was different, though it wasn’t noticeable.

I then rendered a single HD file to the same parameters in Rhozet Carbon Coder, using single-pass rather than 2-pass encoding. Encoding without the card took a glacial 20:30, while encoding with the card took 2:41—a time savings of more than 87%. I then reran the tests using 2-pass encoding to see if Tarari accelerated the first analysis pass. With and without the card, the analysis pass took about 2:20.

This illustrates why single-pass encoding should produce higher-percentage speed increases than 2-pass. Essentially, the first pass is a "fixed cost" that remains the same whether the Tarari card is used or not, bringing down the percentage of time savings. However, the actual minutes saved will be about the same, which is probably the more important metric.

Microsoft Encoding Tools
Let’s move on to the Microsoft encoding tools: the venerable Windows Media Encoder and the more current Expression Encoder 2. I considered running identical tests to those used for ProCoder, but I was concerned that this might compromise the broad applicability of my findings. So in each encoder, I rendered three HD source files (two 1080i and one 720p) to 720p presets.

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