Visitor

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33 Messages

09/06/2026 9:24 PM

4k audio

Why is the audio on the 4K channels coming through as two channel PCM when the audio on the non-4K channel for the same program is showing as Dolby digital?

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Problem Solver

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694 Messages

12 hours ago

In my testing, the 2 channel issue only happens when the original source material is 2.0.  I observed it on MLB Extra Innings baseball games that are 2.0.  Also saw it on old programs.   Seems like the Xi6 is converting everything to 5.1 PCM regardless of what's in the channels.

I'm looking at the Indiana game in 4K right now.  In Auto, I get Atmos/PCM. In Expert, my Xi6 outputs it as 5.1 PCM in a Dolby MAT envelope.  When i switch to the regular Fox HD channel, it's DD+ 5.1 in Expert.

(edited)

Visitor

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33 Messages

As of yesterday morning, I confirmed for the Xfinity folks that using Expert, my 4k channels were still 2.0 only, using the channel 1354 loop. I’ll check again tomorrow and report back. 

I’ll see if I can find an old program that  should be output in 2.0 and see what it shows as well. 

(edited)

Problem Solver

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694 Messages

11 hours ago

@user_x1npns  Have they explained anything ... or just asked you to report things? 

They, of course, have access to an Xi6 and can see what it does.  And there must be technical specs.

(edited)

Visitor

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33 Messages

Just to report things. Basically everything I had already reported. 

Visitor

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33 Messages

3 hours ago

Following is a photo of a list of the current audio inputs by type of channel. Sorry it’s an analog list! 😂

Official Employee

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1.1K Messages

No worries, @user_x1npns. This should come in handy if needed, the engineering team is investigating this further. They set the expectation that we should receive an update in about 3-4 days, we'll monitor the ticket closely for any new updates. 👍

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Visitor

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33 Messages

3 hours ago

I think this is self explanatory.

Problem Solver

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694 Messages

2 hours ago

Thanks @user_x1npns

@XfinityJustinM  Please add these comments to the engineering team report.

That list matches what my Xi6 outputs, too.  I would add that on Auto, everything is Dolby MAT, not standard MultiCh In 5.1 PCM.  Music Choice and old programs like Andy Giffith on MeTV arrive from the Xi6 as 5.1, but only have sound in the L/R channels.  You can get sound to other speakers using MultiCh Stereo but not regular upmixers like Dolby Surround since the arriving source is flagged as already being 5.1.

On Expert, we differ slightly on 4K sources.   My Xi6 outputs standard 5.1 PCM, not MAT, but the only sound is in the L/R channels, essentially acting like 2.0 which can't be upmixed.  Also, I get a DD+ 2.0 input on MeTV, which plays all those old TV shows.  It acts the same as Music Choice.

@XfinityJustinM My receiver is a Denon X3800H in a 5.1.4 Atmos layout.  @user_x1npns say

s he has an Atmos capable Yamaha AVR configured in 5.1 without height speakers.

Problem Solver

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694 Messages

16 minutes ago

Sundance is a channel that sends DD+ 5.1.  It upmixes stereo source content itself so that there's sound in the center and surround channels.  MeTV does DD+ 2.0 and the AVR has to upmix, which it can do correctly in Expert.  But, in Auto, the Xi6 converts the original track to Dolby MAT 5.1 PCM without upmixing and you get a 5.1 transmission with the only sound in the L/R channels. 

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