How to convert .mp4 videos to .rmvb format.
Converting MPEG-4 Videos directly to RealMedia Variable Bit Rate Files (.mp4 to .rmvb conversion) might be possible, even though your options are limited.
Try using video editing programs or (online) conversion tools, such as Any Video Converter or VIP Video Converter, which should allow users to import MP4 videos and export them in RMVB format.
Video converting software