## MMPM/2 Device Driver Reference

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### DDCMDREGISTER Field - ulBufSize

ulBufSize (ULONG) Specifies VSD or PDD output buffer size in bytes that will be sent to the driver. The caller will fill in a default value. If the device driver does not override this value, it will be used to determine the buffer size.

Note: The device driver sets this field to indicate the buffer size that it would like to receive from the streaming subsystem. For MIDI, this field is usually set to 512. For DMA-based audio or other systems where the interrupt rate equals the buffer rate, this field should be set to about 1/ 30 the quantity of data consumed or produced per second. This field supplies the system with a minimal buffer size for wave audio. Because other system elements also negotiate to determine buffer size and for software motion video, the system might provide buffers smaller than the size requested.