In addition to supporting Miracast-type wireless display mirroring, Windows Phone 8.1 also lets you mirror—or “cast”—your handset’s display over USB. This setup requires a Windows 7 or newer PC and comes with significant limitations. But it works with all Windows Phone handsets, even those that aren’t powerful enough to support wireless display streaming.
Here’s what you need to know about USB-based screen mirroring with Windows Phone.
It can’t be used for protected media. You cannot stream DRM-protected content over USB, so Xbox Video, Netflix and services like that will not work.
It’s video-only. Unlike Miracast, which projects both video and audio, USB-based stream is video-only. Audio will continue to play through your phone’s speaker.
What you should use it for. Given the limitations, USB-based screen mirroring isn’t as versatile as is Miracast. I’ve found it works well into two primary situations: you need to demonstrate Windows Phone to an audience, or you wish to show off Windows Phone-based photos on a display that is connected to a PC.
You need a Windows PC and a special application. Before you get started, you will need to download and install the Project My Screen desktop application for Windows 7 or newer.
This is how you connect. Yes, you can use the same Project My Screen settings app you use with Miracast, but here’s a simpler approach. Just connect your phone to your PC and then run the Project My Screen application on the PC. When you do, a notification will appear on your phone’s display, letting you connect instantly.
It runs in full-screen mode by default. The Project My Screen application takes over the screen on your PC by default, which is usually what you want. But you can see that it also displays a pretend phone body around the project phone display. (And this rotates if you rotate the phone, too.) This may not be desirable, so see below.
Change to “true” full-screen mode. If you want the external display to work as it does with Miracast—i.e. without that pretend phone body and in a true full-screen mode that actually fills the display, tap two shortcut keys in sequence: B (which toggles that background image) and E (which puts the display in “expanded” full screen. Voila!
Learn the keyboard shortcuts. Those two shortcut keys are just a few of the many shortcut keys supported by the Project My Screen application. Here’s a complete list.
ESC. Switch to windowed mode
B. Toggle the display of the background image
E. Toggle expanded screen mode
F (or ALT + ENTER). Toggle full screen mode
R. Display the frame rate
LEFT ARROW. Force device orientation to landscape left
RIGHT ARROW. Force device orientation to landscape right
UP ARROW or DOWN ARROW. Force device orientation to portrait up
SPACE. Reset device orientation and automatically match the phone’s actual orientation