MP4 Publishing does not have Audio in Blender v2.79.6 Video editing for MP4 does not work with audio anymore with v2.79.6. I got only an mp4 without an audio.
It seems it is working after I test it first with MP3 format. I'm using a WAV file for the video. initially it did not work. But after testing with MP3 input to MP3 output, WAV input to MP3 Output work on the mp4. so its fine now.