Is there a way to convert .mp4 videos to .m4a format.
Converting MPEG-4 Videos directly to MPEG-4 Audio Files (.mp4 to .m4a conversion) is certainly possible and should be quite straightforward. In fact, if your MP4 file only contains audio, you won't have to convert it. Simply rename its suffix to M4A.
In case your MP4 contains video data, use one of several media editing programs or (online) conversion tools, such as Helium Music Manager or MediaMonkey which allow users to import MP4 videos and export them in M4A format.
A set of audio and ripping utilities for Windows