Re: [LAU] Sound card for recording guitar

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To: <linux-audio-user@...>
Date: Friday, December 20, 2013 - 2:05 pm

Ralf Mardorf wrote:

The buffer size is the product of the period size (-p) and the number of
periods (-n). A larger buffer size increases latency, but reduces the
risk of underruns. A smaller period size _slightly_ increases CPU usage
because of the overhead needed for handling a period.

Therefore, when optimizing for low latency, one typcially uses two
periods and makes -p as small as possible.

With USB devices, the period boundaries (where interrupts are supposed
to happen) are not necessarily coincident with the USB frame boundaries
(where interrupts actually happen). This results in delays (jitter) of
up to 1 ms in the timing of period interrupts; with very small buffer
sizes, this increases the risk of underruns greatly. So if, e.g., the
machine is not able to handle "-p 64 -n 2" reliably, increasing the
number of periods to 3 results in lower latency (3*64=192) than
increasing the period size (2*128=256). (Using "-p 96 -n 2" would have
the same latency, but works only if that particular Jack version allows
period sizes that are not a power of two.)

Regards,
Clemens
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Messages in current thread:
[LAU] Sound card for recording guitar, Roberto Suárez Soto, (Thu Dec 19, 9:13 am)
Re: [LAU] Sound card for recording guitar, Jeremy Jongepier, (Thu Dec 19, 7:51 pm)
Re: [LAU] Sound card for recording guitar, Roberto Suárez Soto, (Fri Dec 20, 8:17 am)
Re: [LAU] Sound card for recording guitar, Ralf Mardorf, (Fri Dec 20, 10:18 am)
Re: [LAU] Sound card for recording guitar, david, (Fri Dec 20, 9:45 am)
Re: [LAU] Sound card for recording guitar, Ralf Mardorf, (Fri Dec 20, 10:19 am)
Re: [LAU] Sound card for recording guitar, Fons Adriaensen, (Fri Dec 20, 11:22 am)
Re: [LAU] Sound card for recording guitar, Ralf Mardorf, (Fri Dec 20, 11:48 am)
Re: [LAU] Sound card for recording guitar, Clemens Ladisch, (Fri Dec 20, 2:05 pm)
Re: [LAU] Sound card for recording guitar, Ralf Mardorf, (Fri Dec 20, 4:48 pm)
Re: [LAU] Sound card for recording guitar, Egor Sanin, (Fri Dec 20, 5:18 pm)
[LAU] _OT_: Sound card for recording guitar, Ralf Mardorf, (Fri Dec 20, 5:46 pm)
Re: [LAU] Sound card for recording guitar, Roberto Suárez Soto, (Fri Dec 20, 2:36 pm)
Re: [LAU] Sound card for recording guitar, Jeremy Jongepier, (Fri Dec 20, 11:50 am)
Re: [LAU] Sound card for recording guitar, Ralf Mardorf, (Fri Dec 20, 12:11 pm)
Re: [LAU] Sound card for recording guitar, Jeremy Jongepier, (Fri Dec 20, 12:35 pm)
Re: [LAU] Sound card for recording guitar, Ralf Mardorf, (Fri Dec 20, 12:48 pm)
Re: [LAU] Sound card for recording guitar, Jeremy Jongepier, (Fri Dec 20, 12:51 pm)
Re: [LAU] Sound card for recording guitar, Emiliano Grilli, (Thu Dec 19, 7:31 pm)
Re: [LAU] Sound card for recording guitar, Gianfranco Ceccolini, (Thu Dec 19, 1:15 pm)
Re: [LAU] Sound card for recording guitar, Will Godfrey, (Thu Dec 19, 5:04 pm)
Re: [LAU] Sound card for recording guitar, Steve Downes, (Thu Dec 19, 5:55 pm)