Rotate webcam as well as screen (portrait mode)

You might be able to do this as described here. Install and modprobe the v4l2loopback module (you may need to compile it) to create a new video device, then copy the webcam video stream to it via ffmpeg:

ffmpeg -f v4l2 -i /dev/video0 -vf transpose=1 -f v4l2 /dev/video1

1) Install utilities:

$ sudo apt-get update
$ sudo apt-get install v4l-utils
$ sudo apt-get install v4l2loopback-utils

2) Download v4l2loopback

3) Uncompress 'v4l2loopback-master' folder

4) Compile v4l2loopback module:

$ make

5) Install:

$ sudo make install

6) Enable device:

$ sudo modprobe v4l2loopback exclusive_caps=1

7) Check if device is enabled:

$ v4l2-ctl --list-devices

Dummy video device (0x0000) (platform:v4l2loopback-000):
  /dev/video1

USB2.0 UVC 2M WebCam: USB2.0 UV (usb-0000:00:1a.0-1.2):
  /dev/video0

8) Copy the webcam video stream to it via ffmpeg:

$ ffmpeg -f v4l2 -i /dev/video0 -vf "transpose=1,format=yuv420p" -f v4l2 /dev/video1

You can see for more details about paramters:

https://ffmpeg.org

https://www.ostechnix.com/20-ffmpeg-commands-beginners/

https://github.com/qTox/qTox/wiki/Video