Multichannel PCM on eARC but Dolby Digital on ARC

Pretty much the title. I only realized recently when i disabled earc and shows started playing in dolby atmos.

Using a samsung q930c connected to my lg oled c2 via earc port.

ATV4k 3rd Gen

What audio setting do you have in Infuse? If it is Dolby digital plus file with Atmos, then it should play Dolby digital plus out of your tv. Otherwise It will be PCM with no Atmos. Apple TV can only play Atmos with Dolby digital plus files

Sorry but how would it switch to dolby if i wasnt playing a dolby digital file. Thought that was clear. This is a earc issue since appletv plays dolby just fine on earc

Just to be clear you’re talking about ARC versus eARC?

Yup. On arc, dolby digital shows up on the soundbar. On eArc it only shows multichannel pcm. On disney+ or apple tv it shows dolby digital/atmos on both arc and earc

What type of audio does the file have that is being played in Infuse?

Normal ARC will support up to 5.1 channels of lossy audio (or 2.0 channels of PCM). I believe Apple TV understands this, which is why it may be switching to Dolby Digital for you in this case. A little known fact is the Apple TV has the ability to re-encode all audio to Dolby Digital, which can help get multichannel audio in cases like this where only ARC is available. EG Playing a 5.1 DTS track in Infuse could result in your device receiving a 5.1 Dolby Digital stream, which was re-encoded by the Apple TV.

If you are using E-ARC, then you should have the ability to pass multichannel PCM from the Apple TV.

Atmos output is only available when playing E-AC3 files (Apple TV limitation), so if you are playing something else then it’s likely you will see normal PCM instead of Atmos.

Hi, thanks for the reply. Yup the files are eac3, i tested with brooklyn nine nine, scott pilgrim vs the universe and a couple others. No matter what, earc only shows multichannel pcm on infuse while working perfectly fine on arc.

Multichannel pcm is what it should show as that is what the AppleTV passes out (pcm is uncompressed audio). Arc doesn’t have the bandwidth so you get a re-encoded compressed/lossy Dolby digital. You want PCM.

But you don’t want pcm for eac3 (dd+) otherwise you are losing the Atmos metadata.

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The AppleTV should pass that through using its Dolby MAT implementation. If it doesn’t through eARC then it’s because the soundbar sucks.

So how do you explain it working just fine on tv plus, amazon and disney plus but not infuse? Earc works fine on all those.

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That makes me think the original file wasn’t eac3. Can you post mediainfo of one of the eac3 files that is passing pcm instead?

Isnt e-Arc a tv protocol and not a media file protocol?

Sorry, wrong acronym. Edited above

No worries, will do once im home from work

Oh right do i find the mediainfo in plex or infuse?

Neither, that’s a separate program that gives details about a media file.

here ya go sorry about the delay.


The AppleTV internally decodes all audio to multichannel PCM and outputs that. Along with atmos metadata when relevant. However only eARC has enough bandwidth for multichannel PCM.

If you disable eARC (why?) and use ARC, then the AppleTV detects this and internally re-encodes everything to 5.1 Dolby Digital, so it can be sent over ARC.

I think there are also situations where your LG TV can take the multichannel PCM and convert it to Dolby Digital or Dolby Digital Plus and output that over ARC.

Makes absolutely no sense to me at all. this is an issue with infuse and earc. i disabled earc so i can enjoy the dolby digital shows fully, multichannel isnt bad, its just not better than dolby.