Mix Voice to Video without losing video quality I have recorded video from Canon HFR 36 camera and recorded voice separately to computer using a clip on mic. (The video camera does not have mic input) Now I want a simple software to remove original audio from the video and add the recorded voice. When I make the edited file, the video quality should not be decreased dramatically.  

I am using windows 8 Operating system. My video files are in MTS format (AVCHD). I recorded audio using windows voice recorder so that voice files are in wma format.
You can use tsMuxer to simply switch out the audio in the MTS without re-encoding the video or audio. MTS is just a container format, it's the "housing" for the video and audio streams. Though your audio has to have the exact same length to be in sync with the video and the audio format has to be supported by the M(2)TS file format.