Dummy Software Processor

What is it about ?

This is a simple software that I made, and that permits to process sound from an SB ISA sound card to another. Why SB ISA sound cards ? Just because I was just testing how to control the Sound Blaster cards directly with the DMA, IRQ and DSP signals. And, because we get very low latency with this (less than 30 msec for 44100 16 bits stereo), I wondered if I could be able to make a sound processor. And here it is. It works under DOS, with two Sound Blaster ISA cards.

Admire the screenshot in your right, that let see the processor in action. You can also follow this link to see a video.

For the moment, I implemented a noise gate, a stereo enlarger and a compressor-limiter. No frequency analysis for the moment.
I have to say that it MUST be two cards because they are full-duplex, but you cannot record and play both 16 bits at the same time on the same card. So, the only thing to do is to use two cards.

The hardware

Here is a nice shot of the hardware I'm using :

You can see the two SB ISA cards (a SB16 for recording and a SBAWE 64 Gold for playing). The CPU is under the goblet (water cooling to avoid noises from the CPU fan). It's a Pentium Pro @ 200MHz.

The software

All the software is made of Pascal (and a bit of inline assembler). Here are the files:

TSTSB16.PAS : The main file, with all the processing algorithm and display procedures.
SB16PLAY.PAS : The unit which is use to play a buffer to a soundcard. There are comments in the file, see them to understand how it works.
SB16REC.PAS : The unit which is use to record a buffer from a soundcard. There are also comments in the file, so you should read them too.

Does it really works ?

Well, yes it works. But, I don't know if it is because of my CPU cooling or because of the software, but sometimes the program quits abnormally, and I have to run it again (thanks to a .BAT file that does it for me, and faster). Also, in the TSTSB16.PAS file, you can see a $M directive at the beginning, and a value like 3601 just after. I don't know why, but every time I add code, I have to lessen this value, otherwise it makes horrible noise. If the value is too low, I get cracks in the sound. I still don't know why, but well, its just a test, not a professionnal program.

Contact me

You can write me something if you want, just by e-mailing this : mwyann [at] gmail [dot] com.