$sudo apt-get install linux-headers-$(uname -r)
$git clone https://github.com/umlaeute/v4l2loopback.git
$sudo apt install make
$sudo apt install libelf-dev
$sudo apt install gcc
$cd v4l2loopback
$make clean
$make
$sudo make install
$sudo depmod -a
$sudo modprobe v4l2loopback
$lsmod | grep v4l2loopback
 v4l2loopback           40960  0
 videodev              184320  4 videobuf2_core,videobuf2_v4l2,v4l2loopback,uvcvideo
$sudo apt install ffmpeg
$ffmpeg -loop 1 -re -i 1.png -f v4l2 -vcodec rawvideo -pix_fmt yuv420p -vf transpose=4 /dev/video1
$~/Android/Sdk/emulator/emulator -camera-front webcam1 -no-snapshot -avd Nexus_S_API_27_x86_64