Sound card programming for LINUX.

Sound card programming for LINUX.

[Geoff Bagley]

I would be interested to hear from any other ham who is experienced in 
writing low-level code for
any of the sound-cards commonly found in a PC.

Most of the stuff I have seen is for a Microsoft environment, which I  
no longer  have.

I now run Debian GNU/LINUX 4.0,   and would be interested in writing an  
IQ demodulator for SDR.

Can the erratic timing of a multi-task system be overcome,  perhaps by  
altering "nice" numbers ?

This is an area of programming where my experience is poor.  I have in 
the past used a Motorola DSP
card, but that was in my M$  days more than six years ago.

73

Geoff
G3FHL

Re: Sound card programming for LINUX.

[Thomas Sailer]

> Can the erratic timing of a multi-task system be overcome,  perhaps by  
> altering "nice" numbers ?

If you just want to write a demodulator (which doesn't need low latency,
just no missing samples), you don't need to play with any scheduler, it
will just work (if you have enough memory, and don't send your machine
into swap death).

Just avoid ALSA's OSS compatibility layer, it is broken for DSP stuff.
Use ALSA directly.

If you need low latency, you can use the POSIX 4 API (i.e.
sched_setscheduler and friends).

73,
Tom
HB9JNX / AE4WA

Re: Sound card programming for LINUX.

[Nate Bargmann]

* Geoff Bagley <geoff.bagley@btinternet.com> [2007 Nov 23 05:15 -0600]:

> This is an area of programming where my experience is poor.  I have in the 
> past used a Motorola DSP
> card, but that was in my M$  days more than six years ago.

Hi Geoff.

Welcome to Linux in general and Debian specifically.

Right now the digi modes program that seems to be receiving the most
active development is Fldigi by W1HKJ, http://www.w1hkj.com and with a
support mailing list at Yahoo Groups under LinuxHam.  It's a GPL
program and seems to employ some high performance concepts.  I'm sure
Dave and his team would be quite willing to share their knowledge of
sound card programming.

73, de Nate >>

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Re: Sound card programming for LINUX.

[Frank Brickle]

On Nov 23, 2007 6:03 AM, Geoff Bagley <geoff.bagley@btinternet.com> wrote:

> I now run Debian GNU/LINUX 4.0,   and would be interested in writing an
> IQ demodulator for SDR.

You might be interested by DttSP:

http://groups.yahoo.com/group/dttsp-linux
http://www.dttsp.org

73
Frank
AB2KT