webrtc/examples/androidapp/res/layout/activity_call.xml

<?xml version="1.0" encoding="utf-8"?>

<merge xmlns:android="http://schemas.android.com/apk/res/android">

    <org.webrtc.SurfaceViewRenderer
        android:id="@+id/fullscreen_video_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <org.webrtc.SurfaceViewRenderer
        android:id="@+id/pip_video_view"
        android:layout_height="144dp"
        android:layout_width="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="16dp"/>

    <FrameLayout
        android:id="@+id/call_fragment_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
    <FrameLayout
        android:id="@+id/hud_fragment_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</merge>