Acronym for Sony Digital Interface Format. A professional digital audio interface utilizing BNC-type connectors, one for each audio channel, and a separate BNC-type connector for word clock synchronization, common to each channel. All interconnection is done using unbalanced 75-ohm coaxial cable of the exact same length (to preserve synchronization), and is not intended for long distances.

The SDIF format is a sequence of frames, similar to chunks in the IFF/AIFF/RIFF formats, but not strictly compatible. Every frame’s length is a multiple of 8 bytes. Every SDIF file or stream must begin with a small opening frame. The body of the file or stream is a contiguous sequence of time-tagged frames, sorted in ascending temporal order, with multiple types of frames allowed in a single file or stream.

The most recent version of this format, SDIF-3, is the standard multi-channel hardware connection employed in DSD recording systems.