MTP or (Media Transfer Protocol) is a set of custom extensions to the Picture Transfer Protocol (PTP) devised by Microsoft, to allow the protocol to be used for devices other than digital cameras, for example digital audio players such as MP3 players, and other portable media devices, for example portable video players.
Media Transfer Protocol (commonly referred to as MTP) is part of the "Windows Media" framework and thus closely related to Windows Media Player. Windows Vista has built-in support for MTP. Support for Media Transfer Protocol in Windows XP requires the installation of Windows Media Player 10 or higher. Apple and Linux systems do not support it natively but have software packages to support it.
The USB Implementers Forum device working group is presently working on standardizing MTP as a fully fledged Universal Serial Bus (USB) device class. When that process is complete, MTP will be a USB device class peer to USB mass storage device class, USB Video Class, and so on.