HDMI: Dolby, DTS, Formats

Are Dolby Digital, DTS, and other high resolution audio formats supported by HDMI?

Are Dolby Digital, DTS, and other high resolution audio formats supported by HDMI? Are these the only audio formats that are supported by HDMI? Do I need a specific version of HDMI? These are all very good questions that need to be answered. First let's look at the various HDMI versions and specifications.

First lets talk about what HDMI is. HDMI are the initials that stand for High-Definition Multimedia Interface. HDMI is the newest digital interface standard, supported by the industry, to be used when connecting components of consumer electronics, like high definition television or home theater systems. HDMI allows personal computer manufacturers and audio/visual consumer electronics to bring to the market products that are rich in features and innovative.

HDMI is a signal that is all-digital and not compressed. All the predecessors of HDMI were analog interfaces. Using an analog interface means that a clean digital signal is converted into a “not as precise” analog, and sent out to the T.V, where the signal is translated back again into digital signal to show the screen display. Each time that the signal is converted, the digital signal weakens and loses strength and integrity. This causes some distortion of the quality of the picture. With HDMI the source digital signal is preserved, and there is no conversion of the signal to create the richest, sharpest picture quality available.

HDMI was designed from the very first version to carry 8-channels of 192kHz, 24-bit uncompressed audio, which is more than all the current consumer media formats. Plus HDMI can transmit any currently available compressed audio format. These formats include Dolby, like Dolby Digital EX 7.1, Dolby Digital Plus 7.1, and Dolby TruHD, and DTS, like DTS-ES 6.1, and DTS-HD Master Audio. These compressed formats are the only multi-channel or high-resolution audio formats that can be carried across the older S/PDIF or AES/EBU interfaces. HDMI 1.3 adds extra support for new lossless digital surround audio formats Dolby TrueHD and DTS-HD Master Audio. Plus most existing HDMI sources can output any compressed stream, and the newer HDMI sources can output uncompressed 6-channel, 96kHz audio from a DVD-Audio disk. There are A/V receivers on the market that can accept and process the 6- or 8-channel audio from HDMI.

Two competitive high definition optical disc formats were released in 2006, HD DVD and Blu-ray Disc. These two formats support higher fidelity audio than the old DVD format. These audio formats include DTS-HD Master Audio, Dolby Digital Plus, and Dolby TrueHD. Not all of these formats are mandatory by the BD and HD DVD formats. High definition players may provide a number of different ways to transmit this audio. Currently, the best fidelity is available when the player is set to output LPCM over HDMI when using one of these higher fidelity formats. This requires a preprocessor or audio/video receiver capable of handling multi-channel LPCM over HDMI. While this has been supported by the HDMI spec since version 1.0, not all devices that support HDMI 1.1 support this feature. In the future, it is likely that most devices claiming at least version HDMI 1.1 as a feature will support at least 5.1 LPCM over HDMI.

HDMI version 1.3 will allow for sending TrueHD and DTS-HD over a bitstream rather than LPCM. This would allow a preprocessor or audio/video receiver that has the necessary decoder to decode the data. It is not clear how this will be useful, as all the current players are decoding the audio stream because this is required for interactive audio. The players would either have to skip mixing of interactive audio, or encode the mixed audio to one of these other formats before sending it over HDMI. HDMI 1.3 will support the output of DTS-HD Master Audio and Dolby TrueHD streams for outside decoding by Audio Video A/V Receivers. These are lossless audio codec formats that are used on high definition DVD's and BluRay discs.

The answer to the question is that, yes HDMI will support Dolby Digital, DTS, and other high resolution audio formats. HDMI version 1.3 specifications have included specifications for very high bit rate lossless compressed streams like DTS and Dolby Digital.