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

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

melvimbe

To add to what Bruce said above, another factor to consider is the source content. Because TrueHD requires higher bandwidth, it is never used with streaming sources. You’ll only get TrueHD from bluray disks. Streaming sources are going to be in dolby digital plus to get your atmos format data. In other words, if you only use streaming sources, then you don’t really need to be concerned about getting an eARC capably TV, your ARC capable TV is all you really need.

Danny

R

Ravica3Author

Chromatic Producer I

Thanks both of you. That gives me some relief.

@Airgetlam you should teach this stuff. First time explained where I understood it. Appreciate you taking the time to do so.

@melvimbe that's good to know as the vast majority of my content is streamed.

What got me so worried is that more recent Sony Android TV's recently received an update and it specifically stated support for Atmos was included in the updated and my set was not on the list for that update.

I feel better placing a order now.

Thanks a million

B

Beagle

Enthusiast I

I’ll be ordering my Arc through Sonos so I have 100 days to make sure it’s what I want, it’s not cheap, I do have a Playbase 5.1 system so it’s not as if I really need one! It’s doubtful I’ll be returning it though, my Sonos speakers have always exceeded our expectations.

melvimbe

What got me so worried is that more recent Sony Android TV's recently received an update and it specifically stated support for Atmos was included in the updated and my set was not on the list for that update.

That could mean that your TV doesn’t support the Atmos format in it’s internal smart apps...the android part of your TV, while it does support Atmos when it comes in through an HDMI input.

Danny

R

Ravica3Author

Chromatic Producer I

What got me so worried is that more recent Sony Android TV's recently received an update and it specifically stated support for Atmos was included in the updated and my set was not on the list for that update.

That could mean that your TV doesn’t support the Atmos format in it’s internal smart apps...the android part of your TV, while it does support Atmos when it comes in through an HDMI input.

Good point. Makes sense. Guess time will tell. I'm coming from a Beam so either way it's still an upgrade.

R

Ravica3Author

Chromatic Producer I

I’ll be ordering my Arc through Sonos so I have 100 days to make sure it’s what I want, it’s not cheap, ....

You make an excellent point. Was wondering if I should order direct. Have over 3 months to try it has won me over.

A

Anonymous

To add to what Bruce said above, another factor to consider is the source content. Because TrueHD requires higher bandwidth, it is never used with streaming sources. You’ll only get TrueHD from bluray disks. Streaming sources are going to be in dolby digital plus to get your atmos format data. In other words, if you only use streaming sources, then you don’t really need to be concerned about getting an eARC capably TV, your ARC capable TV is all you really need.

Unless you’ve an Apple TV for your streaming sources! If that’s the case and you’ve no earc, no Atmos!

jgatie

Unless you’ve an Apple TV for your streaming sources! If that’s the case and you’ve no earc, no Atmos!

Not entirely true. Apple TV only streams Apple content as Multi-Channel LPCM w/ Atmos. Any other streaming app, Netflix, Amazon Prime Video, Disney+, etc., are streamed as DD+ w/ Atmos and are fully compatible with ARC. I tested this myself last night.

A

Anonymous

Not sure I get your point, but I’ll say it again, if you’re using a Sonos Arc with an Apple TV box with a tv that only has arc, and want Atmos, it’s a no no.

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