How to convert .mpa audio to .mp4 format.
Converting MPEG-2 Audio Files directly to MPEG-4 Videos (.mpa to .mp4 conversion) is possible and quite straightforward. It relates to users attempting to encode MPA audio to MP4 video.
Try using a media editing software or (online) conversion tool, such as Adobe Premiere Pro or Tiny Audio Converter, which should allow users to import MPA audio and export it in MP4 format.
Multimedia encoding application from Adobe
A timeline-based video editing software from Adobe
Audio converter for Mac