Video and audio stream can be multiplexed when the video stream's length is equal to the audio stream.
The input video can be any MPEG video elementary stream. The input audio can be any MPEG1 layer2 audio stream.
Press Multiplex button, or select Multiplex menu in the Tool menu. A dialog will be displayed. Type the file name or using the browser to select the input video file (*.mpv), input audiofile (*.mpa) and output MPEG file (*.mpg), press OK, the status bar will display the multiplexing progress.