& Media Mill News: Preset Revamp

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Preset Revamp

I've just finished revamping all of the Quicktime 7 download presets. While working on testing for the upcoming WMV presets, I couldn't help but notice that the WMV9 looked a whole lot better than the Quicktime7 (h264) that we were generating. Well, perhaps not a whole lot better, but better nonetheless.

After poking around a bit, I came to a few conclusions. First, a lot of the perceived quality advantage of WMV9 is just because they're oversharpening the decoded results on playback. There isn't actually more detail, the edges are just more vibrant. Next, I realized that WMV9 is not using a fixed keyframe cadence (at least, as best as I can tell). I had previously had our QT7 presets set to keyframe every 30 frames. I've now switched that to automatic.

Finally, I don't think that WMV9 actually maintains a fixed bitrate, even with the CBR setting. I think it's more like semi-fixed - it won't exceed the cap, but may shift bits around a bit. In order to replicate that effect, I've switched the download presets from using a hardcoded bitrate to using a spatial quality setting. I had previously been wary of this, as it can result in files that are of an unexpected size, but in my testing, I think the new presets will deliver file sizes about on par with the old settings, while providing higher quality results.

Why you may ask, does it provide such better results? By using a spatial quality setting (temporal stays at 50%), the compressor is able to shift bits around, giving a few more bits to a complex scene and giving less bits to a less complex scene. This means the video is much less likely to "fall apart" and start showing big macroblocks.

The streaming settings remain unchanged, as I still believe that a constant bitrate is a high priority for good streaming.

Please, let me know if you think the new presets are good, bad, or still lacking.