What is RA? RealAudio Format Explained
RealNetworks' pioneering streaming audio format for low-bandwidth internet delivery.
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What is RA?
RA (RealAudio) is a proprietary streaming audio format developed by RealNetworks (then Progressive Networks) and first released in April 1995. It was one of the earliest formats designed to deliver audio in real time over low-bandwidth internet connections such as 28.8 kbps dial-up modems.
RealAudio files use the .ra extension and were played with RealPlayer. As a streaming format, the audio could begin playing while still downloading. Early versions used RealNetworks' proprietary PNA/PNM protocol, and the company later adopted the IETF-standardized Real Time Streaming Protocol (RTSP). Over the years RealAudio cycled through several proprietary codecs to balance quality against bandwidth.
How RealAudio Works
A RealAudio file begins with a RealMedia header that identifies the stream and codec, and the audio is packetized so it can be transmitted progressively.[3] Because it was designed for streaming, playback could begin while the file was still arriving, a notable capability when most users connected over 28.8 kbps dial-up modems.[1] Files used the .ra extension and were played in RealNetworks' RealPlayer.[2]
History and Protocols
RealNetworks, then called Progressive Networks, first released RealAudio in April 1995, making it one of the earliest practical internet streaming formats.[1] Early delivery relied on the company's proprietary PNA/PNM protocols, and RealNetworks later moved to the IETF-standardized Real Time Streaming Protocol (RTSP) for session control.[1]
Codecs and Legacy
Over its life RealAudio cycled through numerous proprietary codecs to trade quality against the very limited bandwidth of the era, from early low-bitrate speech codecs to later music-oriented ones.[3] Once dominant for web radio and on-demand audio, the format declined as broadband, MP3, and open streaming standards spread, and it is now largely historical.[2]
MKV Technical Specifications
RA vs Other Audio Formats
| Feature | RA | MP3 | RM |
|---|---|---|---|
| Compression | Lossy[1] | Lossy | Lossy |
| Developer | RealNetworks[2] | Fraunhofer / MPEG | RealNetworks |
| License | Proprietary[1] | Patented (now free) | Proprietary |
| Original use | Streaming audio[3] | Downloads & playback | Streaming media |
| Device support | Very limited | Universal | Very limited |
| Best for | Legacy RealMedia | General music | Legacy video/audio |
RA was built for early internet streaming but is now largely obsolete compared with the universally supported MP3.
Advantages & Disadvantages
Advantages
One of the first formats to make real-time internet audio practical.
Engineered to deliver listenable audio over slow dial-up connections.
Audio could start playing before the full file had downloaded.
Used codecs tuned to different bitrates and connection speeds.
Disadvantages
Tied to RealNetworks software and codecs rather than open standards.
Superseded by MP3, AAC, and modern streaming, with little current support.
Older low-bitrate RealAudio codecs sound poor by today's standards.
Common Use Cases
RA is associated with the early era of internet audio.
Internet radio (legacy) | FileFormer
Streaming live and on-demand audio over the 1990s and 2000s web.
Web-based audio clips | FileFormer
Embedding speech and music on early websites for dial-up users.
Archived recordings | FileFormer
Old news, lectures, and broadcasts preserved in RealAudio.
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Try Audio Converter FreeFrequently Asked Questions
What is an RA file?
It is a RealAudio file, a proprietary streaming audio format created by RealNetworks.
Who created RealAudio?
RealNetworks, then known as Progressive Networks, releasing it in April 1995.
How do I play RA files?
RealPlayer plays them natively; players like VLC can open some RealAudio files, though conversion to MP3 is often easiest.
Is RealAudio still used?
Rarely; it has been largely replaced by MP3, AAC, and modern streaming formats.
What is the difference between .ra and .rm?
.ra is audio-only RealAudio, while .rm (RealMedia) combines RealAudio with RealVideo.