Dolby TrueHD is a lossless audio codec developed by Dolby Laboratories. It supports up to 14 seperate channels of 24 bit audio at 96khz at bitrates of up to 18Mbit/s overall. It has support for extensive metadata including diagog normalisation and dynamic range control. HD DVD hardware is required to support the codec while its support is optional for Blu-ray Disc hardware. All HD DVD hardware must be able to decode Dolby TrueHD to at least 2CH uncompressed audio.
Since its support is not mandatory for Blu-ray Disc hardware, some Blu-ray players are incapable of decoding the audio. However, the High-Definition Multimedia Interface (HDMI) 1.3 specification added support for the codec, meaning that streams that haven't been decoded can be transferred to an external receiver providing that it supports HDMI (1.3+). Doly TrueHD's general competitor is DTS-HD Master Audio.
While Dolby TrueHD can technically output up to 14 channels, it is limited to 8 by both HD DVD and Blu-ray Disc technology.
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