pcmaudio: set amplitude to biased zero at end

pcmtest2: small updates to the demo program

examples/pcmtest2.pas

@@ -1,32 +1,21 @@
-{$H1536}
+{$H2560}
 program pcmtest2;
 uses pcmaudio;
 
 var filename:string;
     buf:SndBufPtr;
-    f:file;
-    size:integer;
-    i:integer;
-    c:char;
     sampleRate:integer;
     err:integer;
     done:boolean;
-begin
+    c:char;
-	if ParamCount > 0 then
-		filename := ParamStr(1)
-	else
-	begin
-		write('Filename> ');
-		readln(filename);
-	end;
 
-	err := 1;
+function readAudioFile(fname:string):SndBufPtr;
-	if ParamCount > 1 then
+var i,size:integer;
-		val(ParamStr(2), sampleRate, err);
+    c:char;
-	if err > 0 then
+    buf:SndBufPtr;
-		sampleRate := 16000;
+    f:file;
-
+begin
-	open(f, filename, ModeReadOnly);
+	open(f, fname, ModeReadOnly);
 	size := FileSize(f);
 	new(buf, size);
 
@@ -41,17 +30,42 @@ begin
 
 	close(f);
 
+	readAudioFile := buf;
+end;
+
+begin
+	if ParamCount > 0 then
+		filename := ParamStr(1)
+	else
+	begin
+		write('Filename> ');
+		readln(filename);
+	end;
+
+	err := 1;
+	if ParamCount > 1 then
+		val(ParamStr(2), sampleRate, err);
+	if err > 0 then
+		sampleRate := 32000;
+
+	buf := readAudioFile(filename);
+
 	SampleQStart(buf, sampleRate);
 
-	write('Press Q to stop> ');
+	write('Press ESC to stop> ');
 	done := false;
 	while not done do
 	begin
 		read(c);
-		if upcase(c) = 'Q' then
+		if c = #27 then
-			done := true
+		begin
+			done := true; writeln(';');
+		end
 		else
-			writeln('Queue size: ', SampleQSize);
+		if c = '?' then
+		begin
+			writeln; writeln('Queue: ', SampleQSize);
+		end;
 	end;
 
 	SampleQStop;

lib/pcmaudio.s

@@ -232,6 +232,12 @@ SMPLQ_I_END:
 	STOREI
 	DROP
 
+	; set amplitude out to zero (biased)
+	LOADC AUDIO_BASE+2
+	LOADCP 32768
+	STOREI
+	DROP
+
 SMPLQ_I_XT:
 	LOADC IRQC_REG		; re-enable interrupts
 	LOADC IRQC_EN