So I guess that most (almost all) movies do not stream DD+ or Atmos with 7 discrete channels. I would like to use the two back surround speakers using Dolby PLiix. Unfortunately my receiver can’t process PCM 7.1 (with only 5 discrete channels) using Dolby PLiix and Apple TV does not just pass through DD+ or Atmos. If I force Apple TV to recode to Dolby 5.1 and process Dolby PLiix do I lose sound quality?
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DD+ 7.1 and PLiix
- Thread starter RachelleK
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Dolby Digital Plus (DD+) has better sound quality than Dolby Digital (DD) unless the original audio is really bad and in that case, it won't make any difference which is technically better.
The Apple TV 4K internally decodes DD+ to multichannel PCM and sends it out to the receiver. Somewhere in the audio chain, the DD+ needs to be converted to PCM and, if things are working properly, there should make no difference if the decoding takes place in the ATV or receiver.
The ATV 4k internally decodes the DD+ audio to multichannel PCM and adds the Atmos metadata to the PCM audio output. At the Apple TV's Dolby MAT 2.0 output will be no different than the Dolby Atmos audio from any other streaming device.
DD+ is capable of supporting 5.1 and 7.1 audio.
The Apple TV 4K internally decodes DD+ to multichannel PCM and sends it out to the receiver. Somewhere in the audio chain, the DD+ needs to be converted to PCM and, if things are working properly, there should make no difference if the decoding takes place in the ATV or receiver.
The ATV 4k internally decodes the DD+ audio to multichannel PCM and adds the Atmos metadata to the PCM audio output. At the Apple TV's Dolby MAT 2.0 output will be no different than the Dolby Atmos audio from any other streaming device.
DD+ is capable of supporting 5.1 and 7.1 audio.
Apple TV 4K - Technical Specifications
View the tech specs for Apple TV 4K and the Siri Remote — including size, weight, capacity, ports, and more.
www.apple.com
But hardly anyone streams movies in DD+ 7.1 with 7 channels, correct?DD+ is capable of supporting 5.1 and 7.1 audio.
Apple TV 4K - Technical Specifications
View the tech specs for Apple TV 4K and the Siri Remote — including size, weight, capacity, ports, and more.www.apple.com
Some do, some don't.
You can force the ATV to output DD but this only serves to degrade the sound in my opinion.
But even with Atmos they are only using 5 discrete channels and then adding the Atmos data?
Yes, the "extra" rear surrounds that you'd normally get in 7.1 are now rendered as Atmos objects.
Thanks. Guess I need to read more about Atmos. I thought they had a DD+ base and then added objects.
No, it is more complicated than that. Up to 16 objects are mastered. Then they are encoded into 5.1 channels, for backward compatibility. In Atmos-capable decoder, these channels are then dismantled back to the objects.
How exactly does it work in the TrueHD lossless codec, is still proprietary information.
Very informative link!
On a side note, this article also contains the most definitive quote from Dolby themselves for why streaming services like Apple do not provide lossless Atmos, ie. TrueHD; "It [Dolby TrueHD] is used exclusively for Blu-ray disc delivery."
On a side note, this article also contains the most definitive quote from Dolby themselves for why streaming services like Apple do not provide lossless Atmos, ie. TrueHD; "It [Dolby TrueHD] is used exclusively for Blu-ray disc delivery."
One of the reasons - apparently - it is not possible to guarantee fixed bitrate with a lossless codec.
Streaming services love fixed bitrate. The lower, the merrier.
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