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When I press a key, there is a delay before I hear any sound (Latency)
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Q: When I play notes on my MIDI controller keyboard there is a delay between hitting the note and when I hear it.  What is causing this delay?

A: This delay, known as latency, is directly dependent on your sound card, the type of driver it uses, and the size of the audio buffer set for the sound card.


Windows
Most on-board sound cards only support MME drivers, a very old driver standard that has been around since the first Windows versions.  It is the slowest of all audio drivers and suffers from high latency, and may not perform well when configured with low latency settings.  Professional audio cards and applications utilize WDM or ASIO* drivers.  WDM drivers will perform much better than MME drivers; and ASIO* drivers are the industry standard because they offer the best performance with the lowest latency.

* Note: Some users are able to improve performance with the built-in sound card with ASIO4ALL.  For assistance with ASIO4ALL, please refer to their forum.

As previous mentioned, latency is dependent on the size of the audio buffer (often the number of samples; i.e. 256, 512, or 1024 samples) set for your sound card.  Smaller buffer sizes equate to lower latency times, however, smaller buffer sizes also increase the processing demand put on your CPU.  The buffer size is generally set in the audio preferences of the application you are running.  Some professional audio cards, including most M-Audio sound cards, have a control panel where the latency or buffer size can be adjusted.  Please refer to the documentation for your audio application and/or sound card to determine how to adjust the buffer size.


Mac OS X
OS X utilizes Apple's own low latency Core Audio driver format.  As previous mentioned, latency is dependent on the size of the audio buffer (often the number of samples; i.e. 256, 512, or 1024 samples) set for your sound card.  Smaller buffer sizes will give you lower latency times, but will also increase the processing demand put on the CPU.  The buffer size is generally set in the audio preferences for the application you are running.  Please refer to the documentation for your audio application to determine how to adjust the buffer size.


What is the right buffer size?
The actual latency times and performance at a given buffer size depend on a variety of factors including CPU speed, the sound card's drivers, and the software you are using.  A buffer setting of 512 samples is a good place to start.  If you still perceive a delay when playing, try lowering the buffer size to 256 samples.  If you hear pops or clicks when you play, your system is not able to process the audio fast enough and you should increase the buffer size.