There are a number of open source software that are available to instructors without any cost or low cost.
Video recording software: Open Broadcaster is free at https://obsproject.com/
Video and audio processing software: FFmeg is free at https://ffmpeg.org
White board software: Airsketch app is free at https://itunes.apple.com/us/app/air-sketch-free-wireless-smart/id376796733?mt=8. Instructors may want to get the paid version at low cost. This app allows instructors to write on an iPad or a mobile device, and share the screen to a desktop computer which is recorded using a video recording software such as Open Broadcaster. Instructors may use some whiteboard extensions for Chrome, for example ziteboard, if a touch screen computer is available and write directly on the screen and record the videos.