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

3 years ago
20 May 2020
26 replies
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Ravica3
Chromatic Producer I
124 replies

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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Best answer by Airgetlam 20 May 2020, 15:45

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Airgetlam
38951 replies
3 years ago
20 May 2020
Answer

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.

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