The 129 page document, recently published but dated September 2001, details the transmission of both digital audio and video from DVD-Audio and DVD-Video players through an IEEE 1394 (Institute of Electrical and Electronics Engineers Inc.) bus to peripheral equipment, such as receivers, processors and even digital televisions. The data must comply with the MPEG Transport Stream (MPEG-TS) specifications or the Audio and Music Data Transmission Protocol (A&M Protocol).

The DVD Forum guidelines are divided into two halves to best accommodate the differences between DVD-Video and DVD-Audio content. Using MPEG-TS, both video and audio data can be transmitted, which is particularly suited to DVD-Video material where compressed audio content is often used. The A&M Protocol is optimised for high-quality digital audio such as that from DVD-Audio; linear PCM data will be transmitted according to type – either DVD-MBLA or DVD-SMBLA – via the A&M Protocol that will allow up to six channels with a maximum sample rate of 192kHz to be sent from source to processor.

MPEG-TS and the A&M Protocol can be used simultaneously by a player; for the purposes of DVD-Audio, any video content can be carried via partial MPEG-TS (with the applied DVD-Video audio limitations) whereas any ‘high-resolution’ audio content can be transmitted via the A&M Protocol.

However, under the DVD Forum guidelines, the source component retains the responsibility of primary audio decoding for DVD-Audio material. Within the player, Meridian Lossless Packing is decoded before either being passed to the A&M Protocol converter (in the case of ‘high-resolution’ audio) or the MPEG-TS multiplex, in the case of Dolby Digital or DTS and out via the IEEE 1394 interface. It would appear therefore, that processors capable of receiving and decoding a DVD-Audio stream, will not necessarily require Meridian Lossless Packing decoders, but instead an A&M Protocol converter, since the transmission format is linear PCM.

Any copy protection present (according to format) will be carried via the IEEE 1394 interface.

A digital interface between all types of DVD player and processors, receivers and digital televisions will undoubtedly be a turning point for both software and hardware manufacturers, but most importantly for the purposes of DVD-Audio, should dispense with the need to use six analogue interconnect cables between source and receiving equipment. The advantages are clear; bass management and time alignment can be performed within the digital domain by high-end hardware whose digital to analogue converters and analogue stages are superior to those in the player. The move will also give DVD-Audio a significant advantage over the competing Super Audio CD (SACD) format, for which no digital interface is currently planned.

Download the complete DVD Forum document here.