You can cast your Android device's screen to one or more Android devices using my Duplila app.

Duplila allows you to project your display content and audio onto another Android device, similar to adding a second display, through WiFi or a USB cable.

It ams to provide good performance and low latency, but for low-end devices, it also allows to configure resolution and other parameters.

Duplila works with various devices running Android OS, including tablets, TVs, or even smartwatches.

In this post, I'll show how to connect one or more target devices and how to cast your screen & audio output onto the connected devices.

You can find Duplila on Google Play.

How to connect

Duplila uses the ADB protocol to cast the screen between Android devices.

You'll use Duplila with 2 or more devices. One device will be host. The other devices that you connect are the targets.

You only need to install Duplila to one device - the host device.

The target devices will need to enable Developer options and USB/Wireless debugging. The procedure for this can vary between different devices. If you're not sure how to enable Developer options and USB/Wireless debugging, check out the official docs for more information.

Connect Through USB

After enabling Developer options and USB debugging do the following

• Plug in the USB cable. When using OTG adapter, the adapter should be plugged into host device. With USB C, you might need to play with "Controlled by" USB settings, if connection doesn't work.
• Confirm the pop-up dialog on the host asking for USB connection permission
• Confirm the pop-up dialog on the target asking for ADB authorization

On some devices, you might first need to enable OTG connection in Android settings manually. Otherwise, USB host mode won't work, and no device is detected after plugging in the cable.

Connect Through WiFi

When connecting for the first time, you'll need to pair your target device. This needs to be done only once. After this, you'll be able to connect your target device wirelessly.

To pair your target device, first go to Developer options -> Wireless debugging -> Pair device with pairing code in Android settings on your target.

Then on your host, inside Duplila app, tap on the "+" PLUS icon in the top toolbar.

In the connection dialog that appears, tap on "Pair new device...".

Fill in the IP address, port, and pairing code that you see on your target.

Now return to Connect Wirelessly dialog on the host in Duplila app, and use the IP address and port shown on target in Wireless debugging on top. Note that the connection port and pairing port differ.

Then tap on CONNECT.

Wireless Connection on Port 5555

You can connect your target that was previously connected through USB also through WiFi by tapping the WiFi icon to the right of the device item in Duplila.

This can also be useful when you pair and connect to the target with the method shown in the previous section. Your port number stays fixed, whereas with the previous method, the system generated a random number each time you try to establish new connection.

How to Cast Screen to Single Target Device

I assume that you were able to connect to your target Android device. It should appear inside Duplila in the device list on the initial screen as show below.

Switch to the "Project" tab. Then tap on the target that you want to project your host screen onto. You should be asked for Media projection permission. Duplila obviously needs the permission to project the screen.

Once you give permission, the host's screen content should appear on the target device that you've selected.

Duplila will try to use most of the target's screen and keep aspect ratio. But because there are so many device types out there, and the screens and resolutions can differ significantly, Duplila also offers multiple ways to adjust how the screen is projected manually.

If you only need slight adjustment, use the controls shown after the projection started.

For larger adjustments (e.g. you want to project a phone screen that is portrait onto a TV's screen that is landscape) go to preferences, by clicking the gear icon in top toolbar, and change the resolution settings. Note that there's a difference between landscape and portrait mode resolution, even though the numbers seem to be the same.

Casting Screen to Multiple Targets Simultaneously

You can project screen and audio to multiple target devices simultaneously.

For this to work again switch to the Project tab inside Duplila. Then tap and hold one of the target devices shown in the device list inside Duplila app. Checkboxes should appear next to the targets in the list. Select your targets and tap on START in top right of the toolbar.

Enabling & Controlling Sound Settings

Duplila allows you to configure various parameters related to screen casting.

You can select a resolution that would give you the best experience, considering the display properties & performance of your host and target devices.

You can also enable/disable sound and choose audio encoding format.

For this you only need to tap on the gear icon in top toolbar and scroll down to the Projection settings section.

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