Re: Audio application

Actually, Virgil, the winmm.dll exports all the low-level sound card functions you need in the simpler (for Swiftforth) DLL function calls. You do not need to resort to DirectX unless you want to. I think Winmm is a little better because it is pre-installed on the older operating systems (Win95, for example).

The procedure is to allocate a couple of buffers to hold the data from the sound card (double buffering), open a sound "file" in the format you specify, and the system will automatically put the sound data in one of the buffers and give you a callback whenever the buffer is full. The system will automatically go to the other buffer and start filling it so you don't have any data loss as long as you process a full buffer before the other one fills. An identical procedure is used to send sound data you've processed back to the speaker(s), if you want to hear what you've done.

All sound formats are streams of integers of some sort, so an integer FFT would seem to make sense. I would suspect the integer FFT would be faster than floating point even on a Pentium, but don't know this for sure. Same for the digital filters.

I have some resources and sample code at home and will try to post them on Monday.

Regards,
Glenn Dixon
WA7PBD

>>> stamps_at_brokersys.com 01/11/01 05:56PM >>>
SFTalk Group..
I am desireous to utilize the Sound Card in a application for my hobby (Amateur Radio). I want to process the audio from a receiver with a FFT algorithm and use SwiftForth to view the real-time audio spectrum. In addition, I want to be able to click on an area of interest and set adjustable digital filters. For a little background, take a look at the following: http://www.arrl.org/tis/info/pdf/9402qex2.pdf . This explains the algorithms needed. My question to the group is has anyone interfaced to the sound card, or developed spectagraph software using SwiftForth ? What about real-time FFT ? It looks like the API for the sound card is DirectX from Microsoft. That is all I can find for now. Any comments on the subject appreciated.
Virgil
Received on Fri Jan 12 2001 - 09:08:23 PST