RealAudio is a proprietary audio format developed by RealNetworks?. It consists of a number of audio codecs, from low-bitrate to high-fidelity formats. Today it also contains a lossless codec, but it needs to be downloaded as a free upgrade. RealAudio is primarily a streaming audio format. It is developed for use when the audio is being played while still being downloaded. As such it is used by a number of Internet Radio stations and even the BBC. RealAudio files originally had the extension .ra (for Real Audio). In 1997 RealNetworks? introduced a video format called RealVideo. The combination of the audio and video formats was called RealMedia and used the file extension .rm. Files with the extension .rv are video files (with or without audio), while .rmvb stands for VBR video files. Other formats are .ram (Real Audio Metadata) and .smil (Synchronized Multimedia Integration Language). These two are text files containing a link to the audio stream.