[alsa-devel] arecord | aplay expected delay

van der Linden ejvanderlinden at hetnet.nl
Tue Mar 18 19:08:26 CET 2008

The purpose is to connect a headset and to provide side-tone from the 
microphone to the headset.

The idea is to first create a short "software" loop and then to add filter 
With these algorithms I like to experiment.

However the side-tone delay must be short. Before I start making real audio 
filter algorithms, I want to know the bear minimum delay.

What can be expected using the Linux OS?

----- Original Message ----- 
From: "Rene Herman" <rene.herman at keyaccess.nl>
To: "van der Linden" <ejvanderlinden at hetnet.nl>
Cc: <alsa-devel at alsa-project.org>
Sent: Sunday, March 16, 2008 10:36 PM
Subject: Re: [alsa-devel] arecord | aplay expected delay

> On 16-03-08 11:05, van der Linden wrote:
>> I'm running arecord and aplay under uCLinux on a Blackfin DSP.
>> In this way I loopback my audio.
>> Does anyone know what delay I can expect between audio input and audio 
>> output?
> Not me, but you just want to loop without doing anything to it? An 
> analogue input? Every card I know can just loop it's own inputs out again. 
> That is, In -> Out, while you have In -> ADC -> bus -> cpu/memory -> 
> bus -> DAC -> Out.
>> I measure at my test board 50ms. I want to have about 1ms!
> You'd need a pretty fast system I suppose. Why does your card not loop 
> directly itself? You can still record it as well...
> Rene 

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