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RE: ASIO4ALL and sound card decoders?



Hi Alan

> Interesting article on the SDR-1000 in the current QST.  One thing which
> jumped out at me was the use of the ASIO4ALL utility to improve the sound
> card latency and other issues.  They are demanding maximum performance out
> of the sound card in the SD$-1000, but would the use of this utility
> benefit, significantly, other sound card programs?  I am thinking of
> telemetry programs, or higher data rate TNC emulations?  Bob?  Anybody?

ASIO is yet another API for talking to sound cards. For Windows, there is
already the native Windows Multimedia Extensions (MME) wave API and the
lower latency DirectSound API. Each API needs the application software to be
specifically written for it. Unfortunately it's not just a matter of
replacing the API calls: you often have to completely re-think how your app
works depending on the sound API in use as they often use significantly
different sound models at a higher level.

Its main two benefits of ASIO are that of being low latency (assuming it's
already sitting on a low latency platform) and of being cross-platform.
ASIO4ALL is pretty neat as it sits right on the kernel driver.

For real-time half duplex audio transceiver applications, such as the
SDR-1000, low latency is a real benefit, such as switching between transmit
and receive.

For full duplex satellite data applications using the PB style protocol, the
latancy issue is still there, but as long as it's not too large it is
probably less of an issue than for real time audio applications.

For simplex telemetry decoding, the latency is really not a problem at all.

If taken in isolation, for raw modulation and demodulation of data, there is
no real benefit to any of these approaches, high speed or low speed, as long
as they will support the sampling rates that your application needs.

For my DSP projects I have recently started to use the PortAudio API that
can sit on top of any of the above (MME, DirectSound, ASIO, *nix OSS), and
is cross-platform.

73, Howard G6LVB
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