ASIO buffer size help

lucasvickers

Sorry if this is answered elsewhere but I have not come across it in the documents yet, and I searched the forum but did not find what I am looking for.

what's the advantage / disadvantage of bigger / smaller buffers for the ASIO, or any driver?

bigger buffer = delay but less chance of crackle?

Thanks!
Lucas

miguel

exactly, also the smaller buffers cause higher CPU load

lucasvickers

are there any docs on this subject?

dj_stick

not kX related… but it means the CPU has to work harder to keep the buffers full

miguel

I guess the smaller the buffers the more often they need to be refilled

lucasvickers

yeah I noticed that --- if I had a small buffer then whenever i opened a webpage or something the sound would crackle.

i am curious what each buffer correlates to. thats really what i dont get

thanks for the help everyone

miguel

You might notice less cracling if you set priority to background services in the system's properties. With this setting you should be able to cause high enough system load to lock the screen refresh but audio will keep playing in time.

lucasvickers

good call

thanks

Soeren_B

Audio processing is done in buffers in your audio programs (and also inside VST effects).
The buffer size is a number of samples, and depending on the sample rate it represents the latency (the same number of samples at a _higher_ sample rate results in a _lower_ latency, but also a higher CPU load, since it has to process more samples within a given time).

Why buffers?
Usually the programs initializes a lot of stuff before you process the buffer, and keep as little code as possible inside the buffer process loop. Stuff ouside the loop could/should be "heavy" computation, such as calculating coefficients for a sweeping filter etc., while the buffer loop would contain only the simple multiplication and addition operations required to do the actual filtering. By doing this we save _a_lot_ of CPU time, which we can use for processing even more buffer loops.
When the buffer loop is complete, the program probably also has to set some variables and perform some copy/mix operations. The buffer is then handed over to the next process in the chain.
All this is done for each process you add to your sound(s). Each plugin you add will add yet another buffer loop to the pool.

When you decrease the buffer size you _increase_ the number of "outside loop" operations, and thus you increase the load on the CPU. When you computer gets too busy it may not complete the buffer loop in time to deliver its samples to the mixing bus, which, in turn, has to deliver to the driver/soundcard. The result will be unpleasant cackling noise or what's worse (crash?).

/Soeren

lucasvickers

Thank you everyone for the detailed information,
it has been very insightful.

I am still curious, however, what each buffer is used for (there exists about 6 I believe on the KX buffer setup menu - I am at work so I can not see).

again thanks for your time

Lucas

dj_stick

very detailed soeren… and lucasvickers, i think that each buffer may be for a seperate channel

Doomsayer

It tells you if you place your cursor over them.