Tutorial: Using Windows Media Registry Keys

Force Video Scaling
Force Video Scaling tells the codec to reduce the resolution at which the video is internally encoded under bandwidth stress, so the image loses detail instead of developing pronounced artifacts. The Aggressive mode emphasizes softness over artifacts more than the Conservative mode, and can lose a lot of detail with hard shots. Set the Force Video value to 1 for conservative; 2 for aggressive; 0 for off.

Motion Search Level
Motion Search Level controls whether and how color is included with motion search. Most previous codecs have done motion search purely in the luma (black and white) channel, just assuming that the chroma (color) channels follow along. With the new codec, you can activate a separate chroma search, which can yield big improvements in quality and efficiency with highly colorful content, like motion graphics.

For the absolute best quality, a value of 2 delivers, but encoding can be much slower than the default luma-only mode. For decent speed and improved quality, a value of -1 delivers a lot of the value of chroma search, but with better performance. If there isn’t enough horsepower for -1, the -2 (integer chroma) can offer much of the quality boost with a more modest performance hit.

Motion Search Range
Motion Search Range controls the size of the area the codec will search for an element of a frame that may have moved from a different frame. A larger search window will help find faster motion, but has a big (negative) impact on performance—CPU requirements roughly double at each level.

For live encoding, your best bet is to pick the highest value at which you can encode without dropping frames. For on-demand, or for when you’ve got CPU power to burn for live webcasting, the Macroblock-Adaptive mode is generally the best, because it will dynamically select the most efficient mode dynamically.

Perceptual Option
The Perceptual Option applies methods that emphasize making the image look right to the human eye over strict mathematical accuracy; use a value of 1 for conservative and a value of 2 for aggressive. At bit rates where the content could otherwise start showing artifacts, perceptual mode can help quite a bit. It isn’t a silver bullet, however, and the aggressive mode in particular can make the image look overly processed or synthesized.

Video Type
The Video Type parameter is only applicable when doing interlaced encoding with WMV9-AP. The value of 0 uses a basic automatic detection mode, which is fast but not optimal. For typical real-world interlaced content, where an interlaced stream can have blocks or even whole frames that are progressive, a value of 4 (auto progressive/interlace frame/interlace field detection) produces the most reliably high quality. But it’s very slow, and only really helps with mixed mode content (with mixed interlaced and progressive frames). For faster encoding, a value of 2 (interlace field) should be used.

More information about the new Windows Media codecs, including registry keys, can be found here.