HD-DVD and Blu-ray discs might not be compatible, but they'll share more audio formats than previously announced because of a recent Blu-ray Disc Association (BDA) decision.
The BDA added Dolby Digital Plus and multichannel Meridian Lossless Packing (MLP) to Blu-ray's list of optional audio formats. Last year, the DVD Forum named Dolby Digital Plus as a mandatory audio format and multichannel MLP as an option.
For their respective standards, the BDA and DVD Forum have approved multiple mandatory audio formats that each player must support. At least one of those audio formats must be included on prerecorded discs, but the choice of formats is up to individual movie studios. Approved optional audio formats can also reside on the discs.
Whatever audio formats are encoded on a particular HD-DVD or Blu-ray disc, the disc's soundtrack will be compatible with the installed base of discrete 5.1-, 6.1- and 7.1-channel surround-sound receivers and preamp/processors. That's because the Blu-ray group previously adopted Dolby Digital 5.1 and DTS 5.1 as mandatory player formats, and the DVD Forum adopted Dolby Digital Plus and DTS ++ Lossy as mandatory formats. Dolby Digital Plus and DTS ++ Lossy are backward-compatible, respectively, with 5.1-channel Dolby Digital and DTS decoders.
Here's the full list of mandatory and optional audio codecs for both video formats (see TWICE, Oct. 11, 2004, for each codec's capabilities):
Blu-ray Mandatory Formats: DTS 5.1, Dolby Digital 5.1, and eight-channel (7.1-channel) 96/24 PCM.
Blu-ray Optional Formats: Dolby Digital Plus, multichannel MLP, uncompressed 5.1-channel 192kHz/24-bit PCM, DTS ++ Lossy, DTS ++ Lossless.
HD DVD Mandatory Formats: Dolby Digital Plus, two-channel MLP, and DTS ++ Lossy.
HD DVD Optional Formats: Multichannel MLP, DTS++ Lossy, DTS++ Lossless.