HD Audio
There have been many attempts to create a higher resolution audio format than what was available on CD. Super Audio CD (SACD) and DVD Audio (DVD-A) were both attempts that failed rather miserably because of there not being enough software (music / movies) available.
With the advent of BluRay disc, a format that holds up to 100Gig of data, it is now possible to include an HD sound option with the HD picture.
Both Dolby and DTS have developed HD (High Definition) sound formats to include onto these discs.
Dolby Digital Plus
Dolby Digital Plus is the next-generation audio format that delivers "better-than-DVD" sound in high-definition packaged media because it requires less compression and provides more channels (up to 7.1 discreet). Dolby Digital Plus also provides new coding efficiencies for future broadcasting and streaming of multichannel audio, which means that it can be broadcast via normal satellite TV like we currently have.
Dolby TruHD
Dolby® TrueHD is Dolby’s latest lossless technology, the ultimate audio experience for high-definition disc-based media. Dolby TrueHD on Blu-ray DiscTM allows viewers to hear exactly what was captured during the recording and mastering process, bringing a palpable and involving audio presence to the home theater experience. This format has a higher resolution than ever before possible on any previous format. For the first time there is real lifelike sound from a consumer format with dynamics (the differences between the loudest and softest pasts of a soundtrack) comparable with what we hear in real life! Together with DTS HD MASTER Audio, this is possibly the best sound quality currently available to the consumer.
HD High Resolution
Designed for projects with disc space constraints, DTS-HD High Resolution Audio delivers a high definition reproduction of the original studio master.
This near perfect reproduction has a constant bit-rate that can range from 2.0 Mbps to 6.0 Mbps. Like DTS- HD Master Audio, DTS-HD High Resolution Audio can provide up to 7.1 discrete channels via HDMI 1.3 or analog connections. The audio resolution can support up to 96 kHz / 24 bit and includes backward compatibility with DTS Digital Surround Core. This is ideal for consumers with legacy equipment. Higher sampling frequencies, greater bit depth and additional channels also contribute to higher-peak bit rates.
HD Master Audio
DTS HD Master Audio provides lossless audio that matches, bit-to-bit, the original studio master soundtrack, and is fully backward compatible with all DTS decoders.
HD MASTER audio is very possibly the best sound quality currently available.