If you think there's a codec missing on this list, you can always write your own codec module: FeOSMusic will load this module and use it to decode a certain file (you can configure the module which FeOSMusic should load for a certain extension in audiocodecs.cfg).
I also added support for filtering: FeOSMusic comes bundled with a lowpass filter by default. And yes, you can add your own filters too
If you're not willing to compile FeOSMusic, you can download binaries at (a link to the source can be found there too):
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