Blu-ray and HD-DVD include support for three new audio formats: Dolby Digital Plus, Dolby TrueHD, and DTS-HD. Blu-ray also allows uncompressed multichannel PCM tracks. DD+ and the basic version of DTS-HD ("DTS-HD High Resolution") are lossy compression algorithms similar to Dolby Digital and DTS, although not as compressed as those older formats. TrueHD is a lossless compression (using the same MLP compression technology as DVD-Audio), as is the lossless form of DTS-HD ("DTS-HD Master Audio"). Neither the BD30 nor the S300 can decode those three new formats, so all you can do us rely on the Dolby Digital or DTS core tracks in those cases. The BD30 does allow bitstream output of these formats over HDMI to a compatible receiver or processor, which the S300 does not. Multichannel PCM tracks on some Blu-rays can of course be played back via multichannel analog output or HDMI in both cases. (See my HDMI FAQ ...)