RM (Real Media) is a multimedia format developed by RealNetworks. It features a .rm filename extension and is typically multiplexed with RealAudio and RealVideo when streaming content online. The stream is usually in constant bitrate (CBR), although a file container for variable bitrate (VBR) is now available, called Real Media Variable Bitrate (RMVB).
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WMV (Windows Media Video) is a collection of video codecs with their respective coding formats introduced by Microsoft on its Windows Media framework. Initially, it was designed to compete with RM format on online streaming apps. It stores compressed videos and is even used to deliver content on Blu-ray/DVDs.
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