Resource Interface File Format.
The file format informally known as .wav and .avi. This is Microsoft's audio/video format, innovatively very similar in structure with Apple's AIFF format.
Technically, it's a rather simple format, one of the most basic binary file structures. It's based on chunks that have
- a 4-byte type identifier (known as a fourcc),
- 4-byte length field that tells how many bytes the data field has, and
- the data field itself.
The data fields can contain other RIFF chunks.
Here's an easy algorithm for ripping a .wav to raw data (assuming the file is PCM and the thing didn't add too much extra baggage to the file): Skip leading bytes until you find character sequence "data", read next four bytes and interpret as the size, then read that many bytes.