A variety of unofficial players now exist, including MPlayer, and Real Alternative. However, Real Alternative does not decode the audio data by itself, but relies on the dynamically linked libraries (DLLs) from the official RealPlayer. Thus Real Alternative requires RealPlayer to be installed (or at least its DLLs) in order to function. Most other players are based on FFmpeg, which has its own audio codec library. The audio codecs in ffmpeg were written based on the publicly available information about the formats, and do not use the RealPlayer or Helix software. It is also possible to obtain codecs which allow Windows Media Player to play some versions of RealAudio.