How to convert m4v and wmv videos to mp4 format using ffmpeg?

I am using ffmpeg to convert videos to mp4 in my PHPMotion project. I am not able to convert wmv and m4v video to mp4 format. I've pasted the command that I used to convert wmv and m4v:

ffmpeg -i 1.wmv -ab 128 -b 1200 test.mp4
ffmpeg -i 1.m4v -ab 128 -b 1200 test.mp4

When I use this codes, i got an error message:

Output #0, mp4, to 'test.mp4': Stream #0.0: Video: mpeg4, yuv420p, 640x360, q=2-31, 1 kb/s, 90k tbn, 24 tbc Stream #0.1: Audio: 0x0000, 44100 Hz, stereo, s16, 0 kb/s
Stream mapping: Stream #0.0 -> #0.0 Stream #0.1 -> #0.1
Unsupported codec for output stream #0.1

How can I solve this issue?