Bitstream Dolby TrueHD over HDMI

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Hi-bit Audio Application to Hi-def DVD Formats

In September 23, 2004, Dolby Laboratories announced that the DVD Forum decided to include Dolby Digital Plus and MLP Lossless, the core audio technology behind multichannel DVD-Audio, as mandatory audio standards for HD DVD. Later, Dolby TrueHD was also selected as mandatory audio format for HD DVD. However, both Dolby formats were selected as optional audio formats for Blu-ray players. DTS-HD was declared as optional for the players of both Hi-def DVD formats.

According to Silicon Image, the HDMI transport is able to handle 24Mbps of audio speed, suitable for any of the proposed audio formats from either disc format, including DTS HD Master Audio. However, the version 1.3 HDMI specification would enable the players to output those audio formats over HDMI for them to be decoded externally, by a future A/V receiver capable to do so, for example, if one prefers so the protocols and specifications were finalized and available in June 2006.Dolby is working closely with Silicon Image to ensure transmission of Dolby Digital Plus and TrueHD signals on HDMI v. 1.3.

As an alternative, HD players with internal hi-bit-rate decoders are expected to also have 6.1 or 7.1 analog outputs that could support the hi-bit-rate and be connected to receivers with 6.1 or 7.1 channel analog inputs.

Hi Def DVD, Using HDMI for Audio

In September 2005, Dolby announced that A/V receivers capable of processing PCM over their HDMI 1.1 inputs should also be able to have sufficient bandwidth to accept the HD video and the PCM multi-channel audio decoded by the Hi-def DVD player.

Any HDMI suited A/V receiver should be capable to input the PCM and reproduce the higher bandwidth of the soundtracks. Initially, it was believed that those HDMI 1.1 suited A/V receivers would have to use analog cables from the multi-channel audio connectors (as with DVD-Audio), and wait until specification version 1.3 of HDMI be completed (and eventually change to a 1.3 compliant A/V receiver).

According to Dolby, there should be no need to replace a receiver suited with HDMI 1.1 to get the benefit of the higher-bit audio formats. However, when using the latest HDMI version 1.3 from player to receiver, the decoding would not have to happen in the player, the connection would stream the native mandatory and optional audio formats to the HDMI 1.3 suited A/V receiver, which would perform the decoding job.

Reportedly, DTS intends to suit players as well as receivers with their decoders, Dolby was quoted as concentrating initially on players.

Hi-definition DVD disc players are expected to support Internet-streamed audio content (such as director's comments) while playing the movie, and they have to internally mix the various audio components (soundtrack, Internet, PCM sounds, etc) before converting the final audio mix to individual PCM channels to be output over the HDMI connection.

The newer hi-bit formats, Dolby Digital Plus lossy, Dolby TrueHD lossless, and DTS HD lossless (previously named DTS++ lossless, and now extended to Master Audio 24 Mbps), are much faster than the supported speed of typical digital coaxial connections (S/PDIF) used for the current legacy Dolby Digital and DTS multichannel audio formats, however, those legacy connections would still transport the down-converted legacy versions (derived from the hi-bit) produced by Hi-def DVD players.