This is a proprietary format (with a paid license) developed by Matthew T. Ashland. Sound is stored without any loss, but the format isn’t too common because of license restrictions and because the official codecs works only on the Windows platform.

RA is an audio format developed by RealNetworks to use in its RealPlayer for streaming audio which means that it can be played while downloading. It uses several audio codecs, they range from the ones for delivering high-fidelity sound to those for recording low bitrate audio data. Although, the format was pretty popular and was used by many radio station to stream online, now it is technically inferior to other newer formats.