Windows Media Stereo Muxer is a command line tool to multiplex left and right file. Open a command line window (Start->Run, enter Cmd) and type WmxMux.exe -i1 "Oldtimers 1080p Left.wmv" -i2 "Oldtimers 1080p Right.wmv" -o "Output.wmv" (adjust the filenames). If WmvMux.exe and your video files are not located in the same directory, it is necessary to specify paths, e.g. "C:\Left.wmv". Input one (-i1) must be the left file, input two (-i2) the right file. Run WmvMux.exe without parameters to get a list of all available options.

WmvMux.exe -i<x> <file> [-l<x> <lang>] -o <file> [-p <file>] [-d <time>] [-t <time>] [-s] [-a] [-x]
-i<x> <file> Input Windows Media file name (x = input number)
-l<x> <lang> Language of corresponding input file (x = input number)
-o <file> Output Windows Media file name
-p <file> Preview file in JPEG format (160 x 120 pixels, max. 10kB)
-d <time> Maximum duration of the output file in 1/100 seconds
-t <time> Duration of 2D intro in 1/100 seconds (skipped by 3D players)
-s Move scripts in script stream to header
-a Add all streams of inputs x > 1, not video streams only
-x Ignore different length of input files

Stereoscopic Player displays a preview image for each video in the built-in video library. The preview image can be embedded in the Windows Media file, so that no additional metadata file is required. The following restrictions apply for preview images:
1. JPEG format
2. 160 x 120 pixels resolution
3. Maximum size of 10 kB (10240 Bytes)

To embed the preview image, use the -p <file> parameter, for example -p "Oldtimers.jpg".

By default, the output file will contain the audio track of the first (left) input file only. To keep all audio tracks, specify the -a parameter. Use this option only if your left input file doesn't contain an audio track but only the right one. Avoid to multiplex two audio tracks into the output file.

Windows Media Stereo Muxer will display an error message if the input files differ in length. If you edited and encoded left and right files properly, this should never happen. Nevertheless, parameter -x allows to ignore different lengths and -d limits the duration of the output file. For example -x -t 6000 will copy the first minute of input files differing in length to the output file. Use these options only if you know exactly what you are doing.

The license of this software is Freeware, you can free download and free use this audio utility software.