HDMI 1.3b

Testing specification released 26 March 2007.

Cable length

The HDMI specification does not define a maximum cable length. As with all cables, signal attenuation becomes too high at a certain length. Instead, HDMI specifies a minimum performance standard. Any cable meeting that specification is compliant. Different construction quality and materials will enable cables of different lengths. In addition, higher performance requirements must be met to support video formats with higher resolutions and/or frame rates than the standard HDTV formats.

The signal attenuation and intersymbol interference caused by the cables can be compensated by using Adaptive Equalization.

HDMI 1.3 defined two categories of cables: Category 1 (standard or HDTV) and Category 2 (high-speed or greater than HDTV) to reduce the confusion about which cables support which video formats. Using 28 AWG, a cable of about 5 metres (~16 ft) can be manufactured easily and inexpensively to Category 1 specifications. Higher-quality construction (24 AWG, tighter construction tolerances, etc.) can reach lengths of 12 to 15 metres (~39 to 49 ft). In addition, active cables (fiber optic or dual Cat-5 cables instead of standard copper) can be used to extend HDMI to 100 metres or more. Some companies also offer amplifiers, equalizers and repeaters that can string several standard (non-active) HDMI cables together.

HDMI and high-definition optical media players

Both introduced in 2006, Blu-ray Disc and HD DVD offer new high-fidelity audio features that require HDMI for best results. Dolby Digital Plus (DD+), Dolby TrueHD and DTS-HD Master Audio use bitrates exceeding TOSLINK's capacity. HDMI 1.3 can transport DD+, TrueHD, and DTS-HD bitstreams in compressed form. This capability would allow a preprocessor or audio/video receiver with the necessary decoder to decode the data itself, but has limited usefulness for HD DVD and Blu-ray.

HD DVD and Blu-ray permit "interactive audio", where the disc-content tells the player to mix multiple audio sources together, before final output. Consequently, most players will handle audio-decoding internally, and simply output LPCM audio all the time. Multichannel LPCM can be transported over an HDMI 1.1 (or higher) connection. As long as the audio/video receiver (or preprocessor) supports multi-channel LPCM audio over HDMI, and supports HDCP, the audio reproduction is equal in resolution to HDMI 1.3. However, many of the cheapest AV receivers do not support audio over HDMI and are often labeled as "HDMI passthrough" devices.

* = 36-bit support is mandatory for Deep Color compatible CE devices with 48-bit support being optional.

** = CEC has been in the HDMI specification since version 1.0 but has only begun to be used in CE products with HDMI version 1.3.

*** = Large number of additions and clarifications for CEC commands. One addition is CEC command allowing for volume control of an AV receiver.

**** = Playback of SACD may be possible for older revisions if the signal source (such as the Oppo 970) converts to LPCM. For those receivers that have only PCM DAC converters and not DSD, this means that no additional resolution loss occurs.

***** = Even for audio bitstream formats that a given HDMI revision can not transport, it may still be possible to decode the bitstream in the player and transmit the audio as LPCM. For HD DVD, this is always the case, for Blu-ray, this may be the case for newer profile 1.1 players (as these will feature audio decoders anyway), while older profile 1.0 players may or may not support non-mandatory audio codecs even if HDMI 1.3 is used.

NOTE: The Sony PlayStation 3 does not currently support the delivery of Dolby TrueHD or DTS-HD Master Audio bitstreams but can decode Dolby TrueHD and deliver it at up to 7.1 channel LPCM.