How to correct aspect ratio
FFMpeg has an option to modify the aspect ratio of a video file without actually modifying the video, see http://www.ffmpeg.org/ffmpeg-all.html#Video-Options

For example, in your case, the desired aspect ratio is 720 / 480 = 1.5 (3:2) (which is NOT 4:3, it should be 540 in that case)

So your command line may look like:

ffmpeg -i input_file.avi -c copy -aspect 1.5 output_file.avi


This copies both audio and video streams unchanged to the output file, and specify into the file's metadata that the aspect ratio is 1.5 as a hint for video players.