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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

It’s irrelevant if Disney+, Amazon, Netflix are using DD+ for Atmos as there’s only two output options on Apple TV that will be sent to your Sonos arc, Dolby Digital 5.1, and Multichannel PCM, the first Which will not carry Atmos obviously, and the latter which is not supported by Sonos arc

jgatie

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.

My point is, once again, that is not entirely true. Only the Apple sources won’t work with ARC. All the other streaming services will give you Atmos over ARC when streamed on Apple TV 4K. I experimented with it last night. I played an Apple TV+ source (See with Jason Momoa) and my AVR said Multi-Channel 7.2.1. Then I went to the Disney+ app and played Black Panther. My AVR said “DD+ Atmos”. Narcos: Mexico on Netflix? “DD+ Atmos”. Jack Ryan on Amazon Prime VIdeo? “DD+ Atmos”.

So as I said, saying you cannot get Atmos from an Apple TV without eARC is not entirely true, for I watched 3 sources from an Apple TV 4K and got ARC compatible Atmos just fine. And as one who isn’t going to purchase any Apple content, just use the other services, the Apple TV 4K suits me just fine.

jgatie

It’s irrelevant if Disney+, Amazon, Netflix are using DD+ for Atmos as there’s only two output options on Apple TV that will be sent to your Sonos arc, Dolby Digital 5.1, and Multichannel PCM, the first Which will not carry Atmos obviously, and the latter which is not supported by Sonos arc

Again, not true. See above. I actually tested it.

A

Anonymous

So your av receiver has taken the multichannel pcm that has come from the Apple TV and extracted the relevant codec (DD+ Atmos) as expected. Try this with a Sonos Arc, which will downconvert the multichannel pcm to stereo. It won’t work.

jgatie

So your av receiver has taken the multichannel pcm that has come from the Apple TV and extracted the relevant codec (DD+ Atmos) as expected. Try this with a Sonos Arc, which will downconvert the multichannel pcm to stereo. It won’t work.

Nope. If that were the case, my AVR would have said “Input = Multi-Channel 7.2.1” and “Output = DD+ Atmos”. The input was “DD+ Atmos”. Also, Multi-Channel LPCM isn’t a wrapper for DD+ to be extracted from. It’s the rawest form of Multi-Channel audio there is, there is no “extracting” anything from it.

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Anonymous

Ok perhaps I used the wrong terminology. Still, this makes no sense. Apple TV is outputting multichannel pcm, so I’ve no idea how it’s inputting dd+ to your receiver (over arc). Check again, if what you’re saying is true, then I suspect, regardless of what info your receiver is displaying, you’re only getting 2 channels outputting sound, then perhaps you’ve it upmixing via Dolby surround etc.

jgatie

Ok perhaps I used the wrong terminology. Still, this makes no sense. Apple TV is outputting multichannel pcm, so I’ve no idea how it’s inputting dd+ to your receiver (over arc). Check again, if what you’re saying is true, then I suspect, regardless of what info your receiver is displaying, you’re only getting 2 channels outputting sound, then perhaps you’ve it upmixing via Dolby surround etc.

So my receiver is lying? It’s telling me I’m getting DD+ w/ Atmos when I’m only getting stereo? That’s what you are going with?

Can you really not fathom it may be you who has it wrong? Sorry, but my hands-on experiment trumps your specious speculation: Apple TV 4K will output the audio format as is. In the case of Apple sources, it is Multi-Channel LPCM. In the case of apps that stream DD+ w/ Atmos, it is DD+ w/ Atmos.

And by the way, why are you arguing? This is something that should make you happy, seeing how Atmos partially works for ARC connections to Apple TV. Instead you are making up nonsense (DD+ “extracted” from LPCM???) to justify your criticism?

A

Anonymous

Keep your knickers on!

First of all I’m argueing (discussing) because I wouldn’t like anyone to buy the arc with any false expectations from misleading/mistaken information

i didn’t make up anything, I used the wrong terminology, my mistake, partly because you were talking about Apple TV outputting multi channel pcm yet your receiver showing dd+ being input, that threw me.

The various 3rd party apps on the Apple TV using DD+ Atmos are being re-encoded by the Apple TV, which is outputting multichannel PCM, I trust we can agree on that… so, if Sonos Arc does not support multichannel pcm, anything, ANYTHING coming from the Apple TV will be downconverted to stereo.

Being an AV receiver it will handle multichannel pcm and somehow (I don’t know) is giving you your DD+ Atmos.

This will not happen with the Sonos arc, I wish it would, but it won’t/can’t!! Meet here back in a few weeks when there’s conclusive testing instead of back and forth, as I will not yield in this, as it’s technical impossible!

melvimbe

The various 3rd party apps on the Apple TV using DD+ Atmos are being re-encoded by the Apple TV, which is outputting multichannel PCM, I trust we can agree on that… so, if Sonos Arc does not support multichannel pcm, anything, ANYTHING coming from the Apple TV will be downconverted to stereo.

Why are you claiming agreement on something that @jgatie has clearly disagreed with and personally tested to be false?

Why would an Apple TV take a DD+ signal from the netflix service and then re-encode it to a different, less likely to be supported format? It makes sense for them to record their own content in a format they feel is superior, but there is nothing to gain by doing that with content already in DD+.

Being an AV receiver it will handle multichannel pcm and somehow (I don’t know) is giving you your DD+ Atmos.

This will not happen with the Sonos arc, I wish it would, but it won’t/can’t!! Meet here back in a few weeks when there’s conclusive testing instead of back and forth, as I will not yield in this, as it’s technical impossible!

Do you have a link to tech docs on the Apple TV to support your claim?

Danny

jgatie

Keep your knickers on!

First of all I’m argueing (discussing) because I wouldn’t like anyone to buy the arc with any false expectations from misleading/mistaken information

i didn’t make up anything, I used the wrong terminology, my mistake, partly because you were talking about Apple TV outputting multi channel pcm yet your receiver showing dd+ being input, that threw me.

The various 3rd party apps on the Apple TV using DD+ Atmos are being re-encoded by the Apple TV, which is outputting multichannel PCM, I trust we can agree on that… so, if Sonos Arc does not support multichannel pcm, anything, ANYTHING coming from the Apple TV will be downconverted to stereo.

No, we cannot agree on that. My actual experiments say otherwise. Any source that is originally DD+ w/ Atmos is output as DD+ w/ Atmos. Which makes perfect sense. Why would the Apple TV change the audio stream if it doesn’t have to?

Being an AV receiver it will handle multichannel pcm and somehow (I don’t know) is giving you your DD+ Atmos.

This will not happen with the Sonos arc, I wish it would, but it won’t/can’t!! Meet here back in a few weeks when there’s conclusive testing instead of back and forth, as I will not yield in this, as it’s technical impossible!

I don’t need to wait. I’ve already seen the results.

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