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MillimeterMatrox CompressHD Test Drive: PC
Oct 26, 2009 12:00 PM, By Jan Ozer
Figure 1. Matrox CompressHD looks like a native Adobe Media Encoder codec, and it offers a simple encoding interface.
Working with CompressHD in Windows
CompressHD costs $495 and is based upon a chip from ASIC vendor Ambarella. In Adobe Premiere Pro, you access CompressHD through the traditional Export > Media function, choosing either Matrox MP4 or Matrox Blu-ray in the Format list. Matrox provides a number of useful presets, but it encodes only using a single-pass, constant-bit-rate (CBR) encoding technique. Once you choose a preset, your configuration options are limited to setting the video data rate, choosing the H.264 level and entropy encoding algorithm, and adjusting the GOP structure.
Compression novices who simply want to choose a preset and go will like this approach. On the other hand, experienced compressionists who want to glimpse under the hood may be frustrated by the inability to discern details such as which H.264 profile CompressHD uses with their various templates.
Figure 2. Can't set the audio data rate? What is up with that?
In addition, from where I sit, there's no reason to not let me adjust the audio data rate, but since you won't be using this encoder for streaming anyway, it really doesn't matter for this release. I'll note for the record that you can't extend GOP duration longer than 128 frames, though again, this is only critical in streaming configurations for which this tool isn't well suited.
Table 1. Matrox CompressHD performance comparisons on two HP workstations.
Test results
I tested CompressHD on two HP workstations; the first was a liquid-cooled, 3.2GHz dual-processor, quad-core Z800 (Intel Nehalem) workstation running 64-bit Vista. (Yeah, I know that liquid-cooled is irrelevant from a performance perspective, but I never get tired of mentioning it.) The other was a 2.83GHz dual-processor, quad-core xw6600 (Intel Xeon Q6850) workstation running 32-bit Windows XP.
Figure 3. At 3Mbps (for 640x360 upload to YouTube), CompressHD's quality was indistinguishable from that of Adobe Media Encoder (AME).
Working from multiple HD input formats, CompressHD decreased rendering time by up to 54 percent on the Z800 and up to 60 percent on the older xw6600. As mentioned, however, CompressHD was unable to meet the 500kbps target with my standard test file, which makes the encoding time in that test somewhat irrelevant, as did the comparatively poor quality. As my deadline drew near, I threw in a couple of encode-to-1080i-Blu-ray tests on the Z800, just to see if encoding at the higher resolution would affect the comparisons. It didn't on the Z800, and I suspect that it would have little impact on the slower HP workstation either.
In higher-bit-rate tests, such as producing at 640x360 at 3Mbps for uploading to YouTube, CompressHD's quality was indistinguishable from that of Adobe Media Encoder, as shown in Figure 3. As you would expect, at our 15Mbps target for Blu-ray, quality was also indistinguishable from that of Adobe. You can see the Encore project containing files from both AME and CompressHD in Figure 4.
Figure 4. The 720p files produced by CompressHD input into an Encore Blu-ray project with no problem.
On the Mac, CompressHD was a one-size-fits-all solution for H.264 encoding. In Windows, CompressHD is a fast, high-quality, and easy-to-use solution for high-data-rate encoding for Blu-ray and other full-quality HD outputs. Streaming producers seeking to accelerate their encoding, however, should look elsewhere.
Continue the discussion on “Crosstalk” the Millimeter Forum.