added audio example

src/test/sound/Readme.md

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+This is a modified example of sound generation taken from www.waltzballs.org/other/prog.html#audio
+
+

src/test/sound/beep.Mod

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+MODULE beep;
+IMPORT Files := OakFiles, rm:=oocRealMath, Unix;
+
+CONST (*pi2=6.28318;*)
+pi2 = 6.2831802368164062;
+rate=44.1E3;
+lf=20.0;
+seconds=2.0;
+
+VAR t,a,b,freq,xkm1,ykm1,est,gf:REAL; 
+    i,e:LONGINT;
+    ai:INTEGER;
+    outvar: Files.File;
+    outfile: Files.Rider;
+    first: BOOLEAN;
+
+PROCEDURE highpass(t,fhp,xk:REAL;VAR yk:REAL);
+BEGIN
+IF first THEN 
+   est:=rm.exp(-pi2*fhp*t);
+   gf:=(1+est)/(1-est);first:=FALSE; 
+END(*IF*);
+
+yk:=(xk-xkm1)/2;
+xkm1:=xk; 
+xk:=yk;
+yk:=est*ykm1+(1-est)*xk;
+ykm1:=yk;
+yk:=gf*yk;
+END highpass;
+
+BEGIN
+t:=1.0/rate; xkm1:=0.0; ykm1:=0.0; first:=TRUE;
+
+outvar:=Files.New("beepfile");
+IF outvar # NIL THEN
+   Files.Set(outfile, outvar, 0);
+ELSE
+   HALT(1)
+END;
+
+e:=ENTIER(rate*seconds);freq:=1000;
+
+FOR i:=1 TO e DO
+   a:=3000*rm.sin(pi2*freq*i/rate);
+(*   highpass(t,lf,a,b);*)
+(*   ai:=SHORT(ENTIER(b));*)
+   ai:=SHORT(ENTIER(a));
+   IF i>ENTIER(rate*10/lf)THEN
+      Files.WriteInt(outfile, ai);;
+   END;
+END;
+
+Files.Register(outvar);
+i:=Unix.System("oggenc -r -C 1 beepfile");
+i:=Unix.System("ogg123 beepfile.ogg");
+END beep.
+

src/test/sound/makefile

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+
+VOC = /opt/voc/bin/voc
+
+all:
+	$(VOC) -M beep.Mod
+
+clean:
+	rm *.o
+	rm *.c