dcadec is a free DTS Coherent Acoustics decoder with support for HD extensions.

Supported features:
Decoding of standard DTS core streams with up to 5.1 channels
Decoding of DTS-ES streams with discrete back channel
Decoding of High Resolution streams with up to 7.1 channels and extended bitrate
Decoding of 96/24 core streams
Lossless decoding of Master Audio streams with up to 7.1 channels, 192 kHz
Downmixing to stereo and 5.1 using embedded coefficients

Features not implemented:
Decoding of DTS Express streams
Applying dynamic range compression and dialog normalization