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For about the last month I've bee using the contour app on my iPad mini 4 in a room without a TV. When I used it this morning the audio is being decoded incorrectly. During the national morning news I get a low mix on the dialog/center channel making the selected volume too load during stereo or surround music bumps. Also during commercials many seem to have the voice over completely assigned to the center channel affectively muting it all together, other then the sound effects and background music. Just to check it wasn't a temporary problem I check the OTA signal and also tuned it with my cox feed on a TV and everything sounds normal in both situations. I downloaded the Contour app to my iPhone 6 running iOS 11.3.1 and had the same problem. I have, just this morning, updated the iOS on my iPad to 11.4 but with the same problem on the iPhone running the earlier iOS I think this may be a problem on the Cox streaming feed.
I found this, but the site look spammy. Basically instructions talking about a soft mute that only mutes 3rd party apps, not main apps like Netflix or Ringer.
Double tap the home button
I also found this