Windows Media Video (WMV) is a file type which can contain video in one of several video compression formats developed by Microsoft. The original video compression format used in the file, also known as WMV, was originally designed for Internet streaming applications, as a competitor to Real Video. The other compression formats, such as WMV Screen and WMV Image, cater for specialized content. Through standardization from the Society of Motion Picture and Television Engineers (SMPTE), WMV9 has gained adoption for physical-delivery formats such as HD DVD and Blu-ray Disc. Though sometimes used interchangeably, note the distinction between Windows Media, the file type, and Windows Media Video, the video compression format. Windows Media the file type is a container (in the Advanced Systems Format) which can contain video in one of several different video compression format, only one of which is the Windows Media Video video compression format, alongside audio in an audio coding format.
MPEG-4 Part 14 or MP4 is a digital multimedia format most commonly used to store video and audio, but can also be used to store other data such as subtitles and still images. Like most modern container formats, it allows streaming over the Internet. The only official filename extension for MPEG-4 Part 14 files is .mp4, but many have other extensions, most commonly .m4a and .m4p. M4A (audio only) is often compressed using AAC encoding (lossy), but can also be in Apple Lossless format. M4P is a protected format which employs DRM technology to restrict copying. MPEG-4 Part 14 (formally ISO/IEC 14496-14:2003) is a standard specified as a part of MPEG-4. Some devices advertised as "MP4 Players" are simply MP3 Players that also play AMV video or some other video format, and do not necessarily play the MPEG-4 Part 14 format.