Can I turn off Dolby in iPhone/iOS

Can I turn off Dolby sound in iPhone/iOS? Not sure if it is hardware or operating system specific, but I have an iPhone 7+ and running iOS11.1.1 I want to turn off Dolby but can't seem to find a setting for that purpose in controls.

Why would I want to do this? So when I hook the iPhone to a pico or pocket projector I can get sound through the projector. In my case, the DBPower T20/T21 can't process Dolby audio so I get no sound when watching movies or certain TV shows from my phone (hooked up to the projector through the HDMI dongle). [Budget projectors usually don't want to pay the licensing fee and whatever additional electronics necessary for Dolby sound.] When I play a youtube video or a game or check email the projector's speakers work just fine. But no haps on Dolby audio signals from a movie. I know on Apple TV I can turn off Dolby, wondering about the phone?