Chromatic Producer I

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Trying to wrap my head around Arc, ARC, Dolby Digital, Dolby Digital Plus and Atmos

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I have or had every intention of purchasing the Arc and was really excited.

Now that it has been released I have about what it can and can not do with my current setup. It will be replacing my Beam that's connected to my Sony Bravia Android TV that purchase in 2018 though I believe it's a 2017 model.

So it has ARC but not eARC. What does this mean for me. I've been finding conflicting information.

My main concern is will I be able to get Atmos. I've read post that say yes and others that say no.

After spending lots of time googling info for my TV I have found that it supports Dolby Digital and Dolby Digital Plus (and honestly I don't know what it's outputting to my Beam). However no where do I see Atmos support or decoding for it. Will this mean no Atmos for me with the Arc or will the Atmos signals somehow be carried through the Dolby Digital Plus?

Please help... I may need to rethink my purchase. Normally I would speakers for my TV, not the other way around.

Just FYI, I also have a pair of Sonos One's and a Sub Gen 2.

Thanks in advance for any feedback.

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AirgetlamAnswer

First, split the concept of codec and transmission methods in your mind, they’re two different things. Optical is the transmission method, Dolby Digital is the codec. Now, take it one step further, with Atmos being the content on top of both of those concepts.

Working backwards from the top, Atmos, by definition, has a multitude of speaker streams in it. This data is manifested in two different codecs, TrueHD, which carries all streams in an uncompressed manner, and Dolby Digital Plus, which carries a smaller number of discrete channels and may be in a lossy state.

So, the carrier method of each of these is determined by available bandwidth. TrueHD, carrying the ‘ultimate’ expression of Atmos, requires so much bandwidth that it can only run across an eARC connection. Dolby Digital Plus can carry the ‘normal’ version of Atmos, and needs the bandwidth of ARC via HDMI, there’s just too much data to be carried across optical as it was designed.

My personal opinion is that using a sound bar for Atmos, such as the Sonos Arc is unlikely to provide any significant audio difference between the two methods of transmission. If you have your own dedicated home theater with 20 + professionally installed and placed speakers, I would think eARC is the better way to go. But for the Arc, I suspect that regular Atmos across the Dolby Digital Plus transmission on HDMI ARC will be amazing.

Bruce

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A

Anonymous

Apple TV can be set to output either Dolby digital 5.1 OR Multichannel pcm, the latter must be selected if you’re to get Atmos. Google it.

A

Anonymous

Ask Apple, it’s ridiculous, but it’s true

jgatie

Apple TV can be set to output either Dolby digital 5.1 OR Multichannel pcm, the latter must be selected if you’re to get Atmos. Google it.

Actually, in the settings of my Apple TV 4K, audio can be set to “Change Format On/Off - Dolby Digital 5.1 (when On)” and “Immersive Audio - Atmos On/Off”. Nothing about Multi-Channel PCM. I have Change Format set to Off and Atmos set to On, and I get DD+ w/ Atmos just fine from Netflix, Disney+, and Amazon Prime Video.

Have you tried this on your Apple TV?

A

Anonymous

Yes long term owner and av receiver owner. I know the setting you’re referring to. I really feel like you’re shooting the messenger here. Whatever you’re experiencing now, the Sonos arc will not so this. Do a bit of research and you will see that if Apple TV is set to Change format (off) it’s outputting pcm.

jgatie

From: https://developer.dolby.com/blog/dolby-audio-support-on-apple-tv/

It is important to keep in mind that while the Apple TV supports Dolby Digital Plus, this does not mean the Apple TV is necessarily sending a Dolby Digital Plus bitstream over its HDMI® output. After it decodes the Dolby audio, the Apple TV sends the audio to your receiver via HDMI; how it sends the audio depends on the Apple TV settings as well as the capabilities of your HDMI-connected device.

Notice the bolded. Seems like “it’s either LPCM or DD 5.1” isn’t so cut and dried.

G

GenAckbar73

Lyricist III

I want to chime in and give you my two cents:

1.

It was widely reported in the past (when the new Apple TV 4K was released) that the Apple TV 4K (only the 4K model!) plays Dolby Atmos in a “special” format (DOLBY MAT = “Dolby Metadata-enhanced Audio Transmission”). It looks like the reason for that is, that they want to mix the System Sounds and Siri voice over into the sound mix. By doing that, they have to decode the DD+ w Atmos Singal and put it back together with the System Sounds as a “DOLBY MAT” signal witch is a LPCM signal with Atmos information packed in it. This DOLBY MAT signal cannot be transmitted over regular HMDI ARC but only over eARC.

2.

When “reviewers” are reporting, that they managed to get Atmos from Apple TV over a regular ARC connection out of their TV, the reason is probably their TV. Some TVs are apparently able to convert an DOLBY MAT w/Atmos signal into DD+ w/Atmos and send it via regular ARC to a soundbar.

3.

Regarding the observations of @jgatie: Could it be that a recent software update for the Apple TV 4K changed anything in that regard (always converting into DOLBY MAT)?

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