5.1 Audio from Stereo Sources

Deep tech question. I have an XG1v4 DVR. When I play content from third party apps like YouTube and Spotify, which only do stereo, the XG1v4 output is 5.1. When set to Expert mode, I get 5.1 PCM. When set to Auto Detect, the output is DD+ 5.1.

So, what is Xfinity doing that takes a 2.0 source and sends it as 5.1? Is there someone in tech support there who might be able to explain this?

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XfinityAmandaB

Official Employee

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2.8K Messages

19 hours ago

BIslander, That is a great question. I am not a technician, but I was able to find that some boxes can wrap the two audio channels (Left, Right) in a 5.1 Dolby Digital signal.

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BIslander

Problem Solver

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558 Messages

17 hours ago

@XfinityAmandaB Thanks for the reply.

Yes, expanding stereo to 5.1 is a feature of many sound systems. I guess the question is how Xfinity is doing the expansion. Is it using a tool like ProLogic or Dolby Surround? Is it duplicating the LR channels to the surrounds? Or, is it sending the stereo signal in a 5.1 wrapper where the other channels are silent?

Also, is there a way on the X1 to send stereo in stereo? I can change the audio output to PCM, but doing that means genuine 5.1 and Atmos content is downmixed to stereo. So, that's no good.

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XfinityMartyR

Official Employee

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2.8K Messages

BIslander

I found out that Xfinity is enhancing audio experiences by utilizing Dolby Digital surround sound technology, which takes a 2.0 audio source and processes it into a 5.1 surround sound format. This involves delivering sound through five discrete channels (left, center, right, and two surround channels) plus a subwoofer channel for low-frequency effects. This advanced audio coding allows for a more immersive and realistic sound experience, similar to what is found in movie theaters, thereby improving the overall quality of television viewing for customers.

The X1 system supports both Dolby Digital and Dolby Pro Logic surround sound formats. Dolby Digital 5.1 surround sound includes five discrete channels plus a subwoofer, while Dolby Pro Logic features four channels: front left, center, front right, and a mono surround channel. You should be able to switch between these audio modes depending on your setup and preferences.

On the Xfinity X1, you can set the audio output to stereo, which will downmix genuine 5.1 and Dolby Atmos content to stereo. To do this, navigate to **Settings > Device Settings > Audio > HDMI Audio Output** and select **Stereo**. However, this means that you will not receive the full surround sound experience from 5.1 or Atmos content, as it will be downmixed to stereo output instead.

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16 hours ago

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BIslander

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558 Messages

5 hours ago

@XfinityMartyR Thanks. I'm quite familiar with DD 5 1, ProLogic, and DD+, which you you didn't mention. ProLogic is a 2.0 output with the extra channels folded into the signal for extraction by the home audio processor. It is used when the source content is multichannel. But, with apps like Spotify and YouTube, the source content is only 2.0 to begin with, so how would ProLogic be used?

Let's drill down a little more. I asked which type of expansion to 5.1 the X1 is doing and your reply says i should be able to switch between DD 5.1 and PL depending on my set up and preferences. I don't see a way to do that on my XG1v4 boxes or to even identify which format the X1 is applying. As noted in my first post, Expert mode sends 5.1 PCM while Auto Detect sends 5.1 DD+. So, my initial question remains, how is X1 expanding a 2.0 source into a 5.1 output.

As for a setting to send the original stereo, my post and your reply both note that the current setting for that means actual multichannel content will be downmixed to 2.0, making that setting a non-starter.

Thanks again.

(edited)

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BIslander

5.1 Audio from Stereo Sources

XfinityAmandaB

BIslander

XfinityMartyR

BIslander

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