Dolby True HD - Blu-ray Disc

Blu-ray Disc

In the Blu-ray specification, Dolby TrueHD is an optional codec. Dolby TrueHD audiotracks may carry up to 24 bit audio in up to 8 discrete audio channels at 96 kHz or up to 6 channels (5.1 surround) at 192 kHz. The maximum encoded bitrate is 18 Mbit/s (the same as the uncompressed rate). Since TrueHD is an optional codec, a separate (primary) AC-3 audio track must be present on Blu-ray discs that contain a TrueHD track.

All Dolby TrueHD players are capable of downmixing the decoded Dolby TrueHD audiotrack to an arbitrary number of channels more suitable for player output. For example, all Dolby TrueHD-capable players can create a 2-channel (stereo-compatible) downmix from a 6-channel source audiotrack.

Dolby TrueHD sees its most popular usage as a high definition audio codec for Blu-ray Disc. While early Blu-ray Disc players did not support Dolby TrueHD, most current models support Dolby TrueHD, and an increasing percentage of movie releases feature a Dolby TrueHD audiotrack. However, by late 2009 and early 2010, Dolby TrueHD had been steadily losing the lossless audio market share to archrival DTS-HD Master Audio, but Dolby TrueHD has recently experienced a moderate resurgence on Blu-ray, particularly with the use of 7.1 Channel Surround Sound.