Notes about the RCF file extension:
To open this file type, a required software must be installed. Without it you only see a Windows message "The following file cannot be opened
" (Windows 7) or "How do you want to open this file?
" (Windows 10) if you double-click the file. There click on "More apps"
and choose a suitable software to view such files on your PC or from email attachments.
The RCF file type is primarily associated with 'Rhapsody' by RealNetworks. Rhapsody is powered by RealNetworks’ caching/streaming technology. This technology splits (or distills) audio files into two asymmetric pieces during the encoding process. The larger piece (called the Residual Audio Data, or RAD) contains 99% of the audio data and is streamed and cached (in encrypted form) to the subscriber’s hard drive during initial song playback. The remaining 1% of the file (called the Essential Audio, or EA) is streamed from RealNetworks’ servers and united (or rendered) with the larger file at playback, enabling subscribers to hear the sound. This process is nearly instantaneous and is invisible to the subscriber.
A proprietary file called RADFILE.RCF holds the cache. On first play songs appear to stream from the Internet; on second play during a session, from the cache.