RealAudio files use a proprietary format designed specifically for playing audio-on-demand in real-time over the internet, introduced by Progressive Networks in 1995, consisting of a server application, and encoder, and a player which works within a Web browser. Normally, the RealAudio player delivers 16-bit sound, although an 8-bit option is available. Data rates range from 14.4 kBps (approximately the sound quality of a mono AM station) to dual ISDN Stereo at 16kHz, nearly CD-quality. See RTSP.