buffer time

buffer time

[Joël Krähemann]

What's the correct buffer time to use with alsa?

since I have following in ags.sf.net

buffer size: 940
alsa iterations: 47 per second

Since I don't have segmentation of tact in my application BPM is the
only scale I got really slow output.
Further can't run anymore with realtime priorities. I would prefer using
940 because its near a good throughput rate. Years ago I calculated it
the exact value would be something 93.whatever

Please help

best regards
Joël



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Re: buffer time

[Joël Krähemann]

Am Montag, den 18.08.2014, 22:34 +0200 schrieb Joël Krähemann:
> What's the correct buffer time to use with alsa?
> 
> since I have following in ags.sf.net
> 
> buffer size: 940
> alsa iterations: 47 per second
> 
> Since I don't have segmentation of tact in my application BPM is the
> only scale I got really slow output.
> Further can't run anymore with realtime priorities. I would prefer using
> 940 because its near a good throughput rate. Years ago I calculated it
> the exact value would be something 93.whatever
> 
> Please help
> 
> best regards
> Joël
> 
> 
> 
Sorry there went something wrong it should be 943.dontknow




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Re: buffer time

[Clemens Ladisch]

Joël Krähemann wrote:
> What's the correct buffer time to use with alsa?

That depends.

For playback, a shorter buffer reduces latency.
A larger buffer reduces the chances of an over/underrun.


Regards,
Clemens
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Re: buffer time

[Mike Looijmans]

On 08/18/2014 10:34 PM, Joël Krähemann wrote:
> What's the correct buffer time to use with alsa?

Playback or capture?

Anyway, Linux performs at its very worst when faced with typical 
audio/video work, because it tends to postpone things and execute them 
in a single big chunk. This is good for throughput, as it can re-order 
everything so that less harddisk head seeks are required, but it causes 
an application that, say, writes out data at a constant but quite low 
rate, to experience latencies of well over 2 seconds on an otherwise 
idle system.

Because of that, my answer to such a question it usually: All the memory 
that you can spare.
In case of ALSA, that means get the biggest you can possibly get, 
because the DMA buffer is usually pre-allocated when the driver probed, 
so it's going to waste if you don't use it.
-- 
Mike Looijmans
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Re: buffer time

[Joël Krähemann]

Am Montag, den 18.08.2014, 22:34 +0200 schrieb Joël Krähemann:
> What's the correct buffer time to use with alsa?
> 
> since I have following in ags.sf.net
> 
> buffer size: 940
> alsa iterations: 47 per second
> 
> Since I don't have segmentation of tact in my application BPM is the
> only scale I got really slow output.
> Further can't run anymore with realtime priorities. I would prefer using
> 940 because its near a good throughput rate. Years ago I calculated it
> the exact value would be something 93.whatever
> 
> Please help
> 
> best regards
> Joël
> 
> 
> 

I've just found

https://perf.wiki.kernel.org/index.php/Tutorial#multiplexing_and_scaling_events

thank you
Joël Krähemann


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