.wmv Video File Format
According to the Wikipedia page on the subject, "Windows Media Video (WMV) is a compressed video file format for several proprietary codecs developed by Microsoft. The original codec, known as WMV, was originally designed for Internet streaming applications, as a competitor to RealVideo. The other codecs, such as WMV Screen and WMV Image, cater for specialized content. Through standardization from the Society of Motion Picture and Television Engineers (SMPTE), WMV has gained adoption for physical-delivery formats such as HD DVD and Blu-ray Disc."
WMV files use both progressive encoding and streaming technology. Progressive encoding requires viewers to download a video file in its entirety before being able to view any of its content. Streaming technology enables viewers to watch portions of video footage without downloading the entire file, a nice feature that allows viewers to review footage after only a few seconds.
WMV files also use temporal compression, which reduces the amount of data stored within a sequence of frames by employing key frame technology. Rather than storing every pixel in each frame, temporal compression stores a key frame, the only the information which is changing between key frames. Quality of the footage can be significantly lower than progressive encoding formats as a result of temporal compression being used. Temporal compression also has the drawback of not allowing future editing of the file.
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