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Audio Quality difference in Dolby Passthrough - Apple TV vs xbox?

superczar

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A little bit of background first. I have long been using an ATV (and subsequently ATV4K ) for all my streaming needs. Despite some minor limitations, the convenience aspect has been more than enough for me to use multiple units across the house.

Recently, Someone insisted that the AQ on streaming is noticeably better on the xbox (series S/X) . Even with a straight passthrough of the audio stream to the AVR.
Normally I wouldn‘t be inclined to believe this claim but said individual was insistent so I gave it a shot.

Both devices set to simply passthrough the audio to the AVR, I tested a couple of atmos encoded videos on netflix.
And what would I know, the xbox stream was noticeably more surround-ey (for the lack of a better word)
e.g. In a dialog that’s happening in a club (Altered Carbon Season 1 , episode 1 , around the 40:00 min mark) The ATV seemed to present the dialogues clearly while the xbox was doing a better job at recreating the background club music through the height speakers.

Intrigued by the results, I checked the audio information section on the AVR and noticed that the ATV stream shows a -31db offset (see screenshots)
So now on to the questions:

1) A straight forward digital passthrough should technically have resulted in the exact same audio ideally. Why would there be a difference ?
2) What is this -31db offset on the ATV . While there was a level difference between the two that I tried to match by my ears but it was certainly not a 31db difference

(ATV is connected directly to AVR while xbox is routed via eARC.. I am presuming that should not make a difference)
 

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Vincentponcet

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You see that ATV is not passthrough as the AVR does not show "DD+". ATV is actually decoding DD+ to 7.1 LPCM and pass atmos metadata in a container named MAT (Metadata-enhanced Audio Transmission), so it is LPCM+MAT (MAT 2.0 actually) which is sent by the ATV to your AVR, which is supposed to be the same as sending the DD+ bitstream, and the AVR doing the DD+ decoding.
The downside of ATV not supporting bitstream passthrough is you cannot read an atmos rip even with an app like infuse, it can only send LPCM, but cannot pass the MAT, so not atmos in this case.
 
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superczar

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Location
Pune, IN
You see that ATV is not passthrough as the AVR does not show "DD+". ATV is actually decoding DD+ to 7.1 LPCM and pass atmos metadata in a container named MAT (Metadata-enhanced Audio Transmission), so it is LPCM+MAT (MAT 2.0 actually) which is sent by the ATV to your AVR, which is supposed to be the same as sending the DD+ bitstream, and the AVR doing the DD+ decoding.
The downside of ATV not supporting bitstream passthrough is you cannot read an atmos rip even with an app like infuse, it can only send LPCM, but cannot pass the MAT, so not atmos in this case.
Thanks - am well aware of these limitations with local network playback but largely fine with it.
I try avoid rips whenever possible and While I do use Infuse once in a while (for some TV series that are not available to stream in my country), I can do without true atmos for such cases. (No prejudice BTW, I was a rather active usenet guy in my younger days :) )

However for regular streaming (e.g. netflix) , there should not have been any discernible difference .
And the audio with streaming apps via ATV and passthrough is pretty much the same as TV in-build app and/or other streaming devices.

What I am curious about is a) what exactly is the xbox doing differently
and b) what’s with the -31db offset with the ATV on the AVR
 
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