posted 24 September 2001 03:36            

1polefilters.kym

Someone was asking about the Sound tester for determining whether they handle stereo or only Left/Right channels. This is included in the attached Sound file as "L/R Tester". Just drop your Sound prototype in question in place of the "Device Under Test" Sound and then run it. The VCS will show you which channels it pays attention to. This is not totally fool-proof, but works well enough for most of the sounds.

Also included is a sound named "LRMS Encoding". This is intended for headphone listeners and relieves the pressure differential in your ears when sounds are hard panned left and right. It uses a psychoacoustic delay and a clever cross mixing between left and right channels to both relieve the pressure differential and maintain the sound field spatialization.

LRMS Encoding is unique among cross mixers in that it completely avoids the comb-filtering effects on monaural tracks, and most stereo tracks -- since the majority of the sound is near the field center. Comb filtering artifacts appear most strongly only when there is sound hard panned to one side and silence in the other side. This is a rare event in most recordings.

Only one delay line is needed for the LRMS encoding because we delay the Side = (Right - Left) and then reconstruct Left and Right channels from the Middle and modified Side information.

- DM