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Dolby Digital Plus is displayed as PCM in the soundbar when eARC is set to Auto
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Question:

Why does my soundbar display Dolby Digital (or Dolby Digital Plus) audio as PCM when the eARC setting is set to Auto on my Samsung TV?

 

Symptom:

  • When the eARC setting is set to Auto, Dolby Digital (or Dolby Digital Plus) audio is displayed as PCM on the soundbar.
  • When you turn off eARC, it is displayed as Dolby Digital (or Dolby Digital Plus) on the soundbar

 

Background/Cause:

This means that when the external source device and the soundbar support the Dolby MAT codec and are connected to a Samsung TV, the Samsung TV will transcode the Dolby Digital or Dolby Digital Plus audio through the Dolby MAT codec.

  • This is Dolby's certification required specification and Samsung TV works according to this certification specification.
  • This transcoding allows listeners to experience Dolby Atmos on PCM audio as well.
    • In other words, the soundbar receives Dolby MAT codec audio and (depending on the soundbar manufacturer) this is not marked as MAT, but as PCM instead.

What is Dolby Atmos?

Dolby Atmos is a surround sound tech developed by Dolby.

Dolby Atmos transports listeners into a spatial sound experience that provides a deeper sound, so listeners hear more and feel more.

Dolby Audio's three codecs which are used to deliver Dolby Atmos.

1. Dolby Digital Plus (includes Dolby Digital)

  • Dolby Digital Plus is the established standard for 5.1 channel surround sound on DVDs and HD broadcasts. This is a more capable digital audio codec based on the Dolby Digital (AC-3, 48Khz sampling rate) system that by having low bitrate provides suitability for online streaming. It also supports the metadata parameters currently employed by content producers. It is designed with the flexibility to support future metadata applications and features.
  • Major applications: Streaming from TV built in apps (like Netflix, Prime video, etc.) and Media devices (like Apple TV 4K, Amazon Fire TV, etc.)

2. Dolby TrueHD

  • Dolby TrueHD audio codec delivers Dolby Atmos in its highest resolution and quality 96Khz upsampling process. It makes it easier than ever for content creators and equipment manufacturers to deliver 100% lossless audio to the home theater. It delivers up to 16 channels of pristine audio at studio-master quality.
  • Major applications: Media devices (like BD player, Xbox one and PS4, etc.)

3. Dolby MAT

  • Certain source devices and soundbars are designed to encode and decode Dolby Atmos metadata into lossless pulse code modulation (PCM) audio. The devices are equipped with an integrated Dolby Atmos MAT encoder, allowing listeners to experience Dolby Atmos in PCM audio.
  • Major applications: Media devices (like X box X/S and Apple TV 4K, etc.)

 

Solution:

  • As explained in the background/cause, if Dolby Digital or Dolby Digital Plus audio is input under device connection conditions that support MAT encoding / decoding, please advise the customer that MAT transcoding takes place in the Samsung TV. In this case, please explain that MAT encoding audio may be displayed as PCM depending on the manufacturer of the soundbar. Through such MAT transcoding, listeners can also experience Dolby Atmos in PCM audio.
  • This is the certification specification requested by Dolby. Therefore, this operation cannot be manually changed, and if the customer wants it to be displayed as Dolby Digital or Dolby Digital Plus, they can turn off the eARC setting.
 
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