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.

Dolby Digital film format, developed for encoding audio tracks for films. It supports up to 6 audio channels: left, right, front, rear, upper and lower. Because of this, it allows you to store “3-dimensional” audio tracks. It’s widely used both in movie theaters and by the users themselves for storing audio tracks in film libraries at home.