Streaming Media - June/July 2008 - (Page 60) moment back in 2006 but is now decidedly pedestrian. Perhaps even more interesting was the fact that at these encoding parameters, both versions of the H.264 file were almost always easier to decode than either the FLV or WMV files. Overall, the quality difference between the two H.264 files was less than I expected, but so was the difference in required decompression horsepower— which, in any event, was less than that Figure 2. The tricked-out Main Profile is on the left; the Baseline Profile is on the right. Unless you’re in the witness prorequired for VP6 and Windows Media. At tection program, the Main Profile produces a better result. or below 640x480 resolution, I’d recommend using the Main Profile and optimizing any quality-related parameters available in your This is a pretty grim and conservative range, ignoring encoder, which I discuss below. The only exception all the quad- and eight-core systems sold over the last would be if you were targeting very old systems, but even 12–18 months. then, you’d probably be better off producing at a lower During playback of the same 1-minute section of the file, resolution with the Main Profile. I recorded the high and low figures for processor utilization as presented by Windows Task Manager and Apple’s Activity Monitor. For good measure, in addition to testing the High-Resolution Results H.264 files, I tested Windows Media 9 Main Profile and FLV High-resolution results differed from SD in several critical (VP6) files encoded to the same general specifications. ways. First, at 4Mbps, I saw no quality difference On low-end systems, the difference between the two between the two files, and at 1.5Mbps, I saw only a slight H.264 files was real but not profound and moved into the quality improvement using a tricked-out Main Profile as irrelevant range when I got to the Precision 390, which was opposed to Baseline (Figure 3). It’s possible that encoding the most powerful computer on the planet for one shining at lower rates may have increased the differential, but cracking the h.264 codec 60 STREAMING MEDIA June/July 2008
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