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Sound card programming for LINUX.

DISCUSSION Geoff Bagley 4 participants 4 messages Nov 23, 2007

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Geoff Bagley

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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

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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

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In reply to Geoff Bagley
Quoted 3 lines · Geoff Bagley

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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