The Foobar decoder does outputs a true 5.1 stream, whereas the old winamp decoder would only allow you to decode a single channel at a time. In addition to that, the winamp filter did not decode the LFE and left it as part of the surround channels, as it was encoded. The Foobar decoder does use lowpass/highpass filtering to create the LFE channel and Surround channels, but but does not take into account that the hardware DTS decoders are set to attenuate the surround channels by 3dB. The result is that the surround channels are 3dB too hot which can lead to digital clipping in those channels during loud passages, and of course over emphasizes the surround channels in the mix. The solution is to simply declip and attenuate the surround channels after decoding.

When using the Winamp decoder, the Surround and LFE filtering must all be done in stages using software, while it’s mostly automated with Foobar, except for the 3dB gain eduction. The drawback is that the filtering used by the decoder is a bit of a black box. There’s no way to know the quality of the filtering being done, the cutoff being used or it’s steepness, or whether it follows the DTS white paper. It would probably be preferable to use higher quality software like iZotope Ozone to do the EQ filtering, but since the Winamp decoder has shown those audio problems, the method described seems to be the best possible solution.