then do this..Now open avi-mux and load the movie (drag & drop) - good then press "generate data source from files" in the white box below you will see video and an audio...left click the audio,then in the box that appears to the right ( is the ms delay) click start and save as "synchronized - movie" Hope that helped!
Remember not to use any other processes while you are converting your files (this is what causes synchronization problems!)