Re: playing underruns

[Takashi Iwai <tiwai@suse.de>]

Hi,

check LAD site,
	http://www.linuxdj.com/audio/lad/resourceslatency.php3

you'll find some good information how to get low-latency.


Takashi

At Wed, 12 Feb 2003 17:56:19 -0500,
Chris Raphael wrote:
> 
> 
> Hello List,  
> 
>   This is my first post and I am new (a couple of weeks) to ALSA.
> 
> I am working on an application that plays audio output in response
> to audio input --- the relationship between input and output is 
> complicated and I will not describe it in any detail here --- I
> am building a musical accompaniment system.  I want the output to "respond"
> to the input with low latency so I cannot write the output samples
> very long before they are actually going to be played.  Currently
> I have a function that is called repeatedly (through a signal) and
> writes the samples about .05 secs before they will actually be played.  
> I monitor the delay, in samples, (I can't remember the name of the
> function (snd_delay_???) and see that the number of unplayed samples
> fluctuates but there does not seem to be an increasing or decreasing
> trend.  So I assume that I am writing at very close to the right
> rate and mostly the playback sounds fine.  But every so often,
> maybe once every 10 secs or so, I get a playback underrun.  I
> always check the system clock when my writing routine begins,
> so I know the underruns are almost always *not* due to my writing 
> routine getting a late callback.  By everything I can measure, the 
> samples are written on time.  Can anyone tell me what I need to do 
> to fix this problem? Perhaps it is not reasonable of me to hope to 
> write samples such a short time before they need to be played?
> 
> I would really appreciate any help I can get on this and will supply
> any relevant details.  I just didn't want to clutter up my question
> with lots of irrelevant info.
> 
> Thanks,
> 
> Christopher Raphael
> 
> 
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