Typically, a stream is established to read a series of moving images from the device. This continuous capture mode is called symmetric or real-time capture, and is performed at a constant frame rate and constant frame size. When established, a stream captures images continuously without assistance from the application code. However, video images can be captured one frame at a time when directed by the application. This type of capture mode is referred to as asymmetric capture because the time between successive frames is not constant. The frame rate is determined by how long the application delays between taking image snapshots. Asymmetric capture is performed with IOCtls only; the OS/2 multimedia streaming mechanism is not used.