HDMI audio output : "expert mode"

1.  I'm not sure which navigation guide you're configuring (TV, Audio/Video Receiver, Roku, Contour, etc).
2.  When you say "channel," do you mean TV channel or a speaker channel?

The keywords in your post are "passed through" and "best available."

Stereo:  2-channel audio (left and right speakers)

Auto Detect:  Most soundtracks are encoded with either Dolby Digital or DTS.  For whichever component you're configuring, it can decode up to 5.1 channels in either format.

Expert Mode:  It's an elusive term but it means special logic.  It could mean 2 things:  high-end processing or not high-end processing.

If your media source (Blu-ray, game console, streaming) is encoded with more than 5.1 channels (6.1, 7.1, 9.1, 11.1) and your Audio/Video Receiver can decode that format, your component will not alter or process the audio signal but instead allow it to "pass through" to your receiver.  Your receiver will then decode and steer the audio signals to the proper surround speakers.

If your media source is encoded with more than 5.1 channels but your TV or cables can't process the format, your components will negotiate the "best available" format.

As far as the explanation for Expert Mode..."best available Dolby sound will be passed through"...I don't know why it singles out Dolby.  I'd assume it would pass through all formats, including DTS and THX.  It's an odd explanation.  Expert Mode should read as "Passthrough" or "A/V Receiver" or maybe just "Best Available."

Since I'm In a cox forum I figured it would be easy to figure out which menu I'm in. Obviously it is the contour menu, why would I ask about the tv menu on a cox forum??? Settings, device settings, audio.

I've never heard of "Expert Mode" so it may not have been the menu on a cable box.  The only reference to Expert Mode on the Cox website is for a Kyocera Tomo mobile phone.  If you're using the speakers on your TV, the audio settings on your TV can affect your audio.  Your type of cable(s) can affect your audio.  Lots of things affect audio, so it's not always obvious.

Excluding power and the CATV coax, what cable(s) are connected to your cable box...HDMI, RCA, Optical?  If you're using a combo of cables, the audio portion of your HDMI stream will be disabled.  If it's disabled, Expert Mode is selecting a format compatible with the cable and TV...maybe even Mono.

If you only have HDMI connected, you should only see the following audio settings:
  - Surround Sound (AC-3)
  - Stereo (PCM)

Since you're seeing Auto Detect and Expert Mode, these may be audio settings for RCA and/or Optical.

If you don't have other cables connected, you may have a glitch in your Contour software.  Unplug your Contour for about 5 minutes to reload it.

If a reload doesn't correct it, you may have a defective port on your box.  Meaning, although there is no RCA or Optical cable connected, the port is stuck to an "on" mode.

What cable box do you have?  What is your setup?

Hate to fill you in but yes, it is in the settings of the contour box under audio. It's obviously new. Can take a photo for the non-believers.

I have no doubt you're seeing the Expert Mode.  I'm just figuring why you're seeing the Expert Mode.

Again...what's the make and model of your box.  Also...what cable(s) are connected.