Changing Video Encoding
I first mentioned the open source application, Handbrake, in the Tip of the Night for November 23, 2015, as a means to add captioned text to a video. Handbrake can also be used to change the codec for multiple video files.
When you click on the Source button on the toolbar, you'll see you have the option to process an entire folder of video files.
Handbrake allows you to convert to the common H.264; H.265; MPEG-2; and MPEG-4 codecs.
The MPEG-2 codec will encode a video in less time than the other options, but will also generate a larger file.