ALSA / Soundcard latency

ALSA / Soundcard latency

[Feilmeier Daniel (Ask De)]

Hello,

My company is a supplier of car manufacturers. We develop and produce digital audio amplifiers.



We would like to build our test setup for echo order cancelation

routines for our audio amplifiers with a

real- time Linux and ALSA.



We have very strong requirements regarding the maximum latency from

audio input via line in to audio output. We would like to achieve a

maximum latency < 1ms. The alsaloop example mentions a latency of 1 ms

which is on our test setup with the latest rt kernel from This Mächler

not working due to broken pipe errors. Is 1 ms feasible with a standard PC ?

Currently we still don´t know what the lowest possible latency using

ALSA is. We tried different soundcards and found out that they have an

internal FIFO, which seems to be one of the limiting factors. The min.

latency we can achieve is currently 5,6 ms, but this is still to high.

Is there any possibility to switch this FIFO off via ALSA ? Is it possible at

all to achieve such low latency values ?



Kind regards,


___________________________________________________________________________________

Feilmeier Daniel

R&D Software Electronics

Tel.:  +49-9962-2003-629
Fax.:  +49-9962-2003-79
E-Mail: FeilmeierD@askgroup.de<mailto:FeilmeierD@askgroup.de>


ASK Industries GmbH
Hauptstrasse 73
D-94559 Niederwinkling

HRG Straubing  HRB 10703
Geschaeftsfuehrer: Ruggero Marchetti   Franz Maier   Juergen Pledl
___________________________________________________________________________________

Re: ALSA / Soundcard latency

[Clemens Ladisch]

Feilmeier Daniel (Ask De) wrote:
> We have very strong requirements regarding the maximum latency from
> audio input via line in to audio output. We would like to achieve a
> maximum latency < 1ms. The alsaloop example mentions a latency of 1 ms
> which is on our test setup

What hardware?  USB and FireWire have long packet queues.

> We tried different soundcards and found out that they have an
> internal FIFO, which seems to be one of the limiting factors.

What are the numbers?

What settings did you use for alsaloop?


Regards,
Clemens