Open Sound Control - Design

Design

OSC messages consist of an Address pattern, a Type tag string, Arguments and an optional time tag. Address patterns form a hierarchical name space, reminiscent of a Unix filesystem path, or a URL. Type tag strings are a compact string representation of the argument types. Arguments are represented in binary form with 4-byte alignment. The core types supported are

• 32-bit two's complement signed integers
• 32-bit IEEE floating point numbers
• Null-terminated arrays of 8 bit encoded data (C-style strings)
• arbitrary sized blob (e.g. audio data, or a video frame)

Applications commonly employ extensions to this core set. Recently some of these extensions such as a compact Boolean type were integrated into the required core types of OSC 1.1.

The advantages of OSC over MIDI are primarily speed and throughput; internet connectivity; data type resolution; and the comparative ease of specifying a symbolic path, as opposed to specifying all connections as 7-bit numbers with 7-bit or 14-bit data types.