Waveform looping is the repeated output of a set of data buffers. Clients mark the beginning and ending buffers of a loop by setting flags in the WAVEHDR buffer header, which is part of each buffer passed with a WODM_WRITE message. Clients also specify the number of loop iterations. User-mode drivers repeatedly output the contents of the buffers defining the loop, until the client sends either a WODM_BREAKLOOP or a WODM_RESET message, or until the iteration count has been reached.