16 Sep
2015
16 Sep
'15
11:46 a.m.
Hi list,
I'm writing some signal processing algorithm for real time processing
that has to run on a 8 kHz sampling frequency embedded device.
My code is in C and I wrote a simple jack client for testing my algorithms.
For now, I'm using a sample frequency of 44.1 kHz but I want to test the
behaviour of my code at 8 kHz.
With my sound card, is impossible to set jack to run at 8 kHz.
It is possible in some way, to fake the 8 kHz sampling frequency (for
example using plugins?).
I've seen the Steve Harris Decimator, but it is not designed to run in
real time. I've tried to put in jack-rack a low-pass (antialias) filter
followed by the SH Decimator, but the result is (as expected) a 44.1 kHz
signal with reduced bandwith and some "aliasing" (I don't think that
what I get is alias -by definition- but some other artifacts).
What can I do to test my algorithm at 8 kHz in realtime using jack?
Thank you all :)
--
a.
17 Sep
17 Sep
5:08 p.m.
[Alessio Degani]
With my sound card, is impossible to set jack to run
at 8 kHz.
[...]
What can I do to test my algorithm at 8 kHz in
realtime using jack?
Jack does not support multirate processing, so you'll have to do the
down- and upsampling in your client. For a C application I'd look at
libsamplerate first.
Cheers, Tim
6:01 p.m.
On Thu, 17 Sep 2015 17:08:22 +0200 (CEST)
Tim Goetze <tim(a)quitte.de> wrote:
[Alessio Degani]
Or simpler : use the 'dummy' backend for jackd at 8kHz, and connect
your soundcard using zita-a2j/j2a.
-a.
With my sound card, is impossible to set jack to
run at 8 kHz.
[...]
What can I do to test my algorithm at 8 kHz in
realtime using jack?
Jack does not support multirate processing, so you'll have to do the
down- and upsampling in your client. For a C application I'd look at
libsamplerate first.
24 Sep
24 Sep
9:26 p.m.
[Alexandre DENIS]
On Thu, 17 Sep 2015 17:08:22 +0200 (CEST)
Tim Goetze <tim(a)quitte.de> wrote:
Very nice if it works! I wasn't aware the zita jack backend allows
for that much of a difference in sample rate, but I probably should
have expected it to given Fons' dedication to excellence.
Cheers, Tim
Jack does not support multirate processing, so
you'll have to do the
down- and upsampling in your client. For a C application I'd look at
libsamplerate first.
Or simpler : use the 'dummy' backend for jackd at 8kHz, and connect
your soundcard using zita-a2j/j2a. 
27 Sep
27 Sep
11:50 p.m.
On Thu, Sep 24, 2015 at 09:26:41PM +0200, Tim Goetze wrote:
Well... with the current release (0.6.0) a2j works but j2a doesn't
seem to handle this. But I know why, and it's being fixed. Expect
0.6.1 soon.
Ciao,
--
FA
A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)
Or simpler :
use the 'dummy' backend for jackd at 8kHz, and connect
your soundcard using zita-a2j/j2a.
Very nice if it works! I wasn't aware the zita jack backend allows
for that much of a difference in sample rate, but I probably should
have expected it to given Fons' dedication to excellence.
17 Sep
17 Sep
6:52 p.m.
On 17/09/2015 17:08, Tim Goetze wrote:
[Alessio Degani]
Thank you for your reply.
I try to avoid to use libraries because the code must be easily portable
to a microcontroller.
At the moment I've writed my own downsampling algorithm with a simple
low-pass (mean) + decimation. But I'ts only a workaround for the moment :)
What can I do to test my algorithm at 8 kHz in
realtime using jack?
Jack does not support multirate processing, so you'll have
to do the
down- and upsampling in your client. For a C application I'd look at
libsamplerate first. Cheers, Tim
--
a.
3348
days inactive
3359
days old
linux-audio-user@lists.linuxaudio.org
5 comments
4 participants
participants (4)
-
Alessio Degani -
Alexandre DENIS -
Fons Adriaensen -
Tim Goetze