Dolby Atmos in Dolby TrueHD
Dolby expanded the Dolby TrueHD format employed in Blu-ray Disc media to allow the format to support Dolby Atmos content. Prior to Dolby Atmos, Dolby TrueHD provided lossless support exclusively for channel-based audio, such as 5.1 and 7.1. We have added a fourth substream to Dolby TrueHD to support Dolby Atmos playback. This substream represents a losslessly encoded, fully object-based mix.
Dolby Atmos signals encoded in Dolby TrueHD are transmitted from a Blu-ray player to your sound bar with Dolby Atmos through an HDMI connection. The sound bar receives the Dolby TrueHD soundtrack and its associated object-based audio and positional metadata, and then decodes, processes, and renders the sound to the specific speaker configuration in the device.
Dolby Atmos audio can be encoded with Dolby TrueHD at multiple sampling rates (including 48 kHz and 96 kHz) and bit depths (16-bit and 24-bit). Dolby Atmos enabled sound bar products will also support legacy Dolby TrueHD bitstreams at multiple sampling rates (including 48, 96, and 192 kHz) and bit depths (16-, 20-, and 24-bit) to provide full backward compatibility with legacy Blu-ray Disc media and Dolby TrueHD music files.
Dolby Atmos in Dolby Digital Plus
Dolby Digital Plus has been updated to include a new decoder capable of processing content encoded for Dolby Atmos. This module employs new bitstream metadata to extract Dolby Atmos object-based audio and then outputs this information for further processing by the object audio renderer, which adapts and scales the Dolby Atmos mix for the onboard speaker system in the sound bar. The sampling rate for Dolby Atmos content is 48 kHz, the same sample rate as for Dolby Digital Plus content.
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Dolby Digital Plus is employed for over-the-air (OTA) and cable broadcast delivery and is the preferred audio codec for multichannel OTT or streaming media content.
Full compatibility
Both audio decoders are designed to be fully backward compatible with legacy channel-based Dolby Digital Plus and Dolby TrueHD soundtracks.
Dolby Atmos in Dolby MAT
A Dolby MAT encoder resides in a Blu-ray player to pack the variable bit-rate Dolby TrueHD bitstreams for transmission over the fixed bit-rate HDMI. A Dolby MAT decoder is concurrently employed in the Dolby TrueHD decoder in the sound bar to unpack the Dolby TrueHD bitstreams. With the introduction of Dolby Atmos, we have expanded the Dolby MAT technology to support encoding and decoding of Dolby Atmos metadata incorporated in lossless pulse-code modulation (PCM) audio.
A key benefit of Dolby MAT 2.0 is that Dolby Atmos object-based audio can be live encoded and transmitted from a source device with limited latency and processing complexity. Among the likely sources are broadcast set-top boxes and game consoles. The Dolby MAT 2.0 decoder in the Dolby Atmos enabled sound bar outputs the object-based audio and its metadata for further processing inside the device. The Dolby MAT 2.0 container is scalable and leverages the full potential of the HDMI audio pipeline.