examples: Add portaudio sine wave example

PortAudio already has a FB header, this adds an example
usage to play a sine wave from a buffer.

Author: thekhalifa

examples/Makefile

@@ -46,7 +46,8 @@ NETWORK		:= $(subst .bas,,$(wildcard network/*.bas network/*/*.bas \
 			network/*/*/*.bas))
 #OPTIMIZE	:= $(subst .bas,,$(wildcard OptimizePureAbstractTypes/*.bas))
 #REGEX		:= $(subst .bas,,$(wildcard regex/*/*.bas))
-SOUND		:= $(subst .bas,,$(wildcard sound/*/*.bas))
+SOUND		:= $(subst .bas,,$(wildcard sound/*.bas)) \
+			$(subst .bas,,$(wildcard sound/*/*.bas))
 THREADS		:= $(subst .bas,,$(wildcard threads/*.bas)) \
 			threads/timer-lib/libtimer$(DLLEXT) threads/timer-lib/test
 UNICODE		:= $(subst .bas,,$(wildcard unicode/*.bas))

examples/sound/portaudio-sine.bas

@@ -0,0 +1,82 @@
+''
+'' PortAudio Sine wave example
+''
+'' Requires libportaudio2
+
+#include "portaudio.bi"
+
+Const Pi as Double = 3.14159265358979323846
+Const SampleRate as Integer = 44100
+Const SineSamples as Integer = SampleRate / 10
+
+Type PlayPayload
+    frequency As Single
+End Type
+
+Function PlayCallback (InputBuff as Const Any Ptr, OutputBuff as Any Ptr, _
+                    FrameCount as CUlong, TimeInfo as Const PaStreamCallbackTimeInfo Ptr, _
+                    StatusFlags as PaStreamCallbackFlags, UserData as Any ptr) as Long
+
+    Dim as Long Ptr outBuff = OutputBuff
+    Dim as PlayPayload Ptr payload = UserData
+    Dim as Single frequency = payload->frequency
+    For i as Integer = 0 To FrameCount - 1
+        outBuff[i] = CLng(&h7FFFFFFF * 0.5 * Sin(2 * Pi * frequency * i / SampleRate))
+    Next
+    Function = paContinue
+End Function
+
+Sub Play(Frequency as Single, Duration as Single)
+    Dim as PaError pe
+    Dim as PaStream Ptr stream
+
+    Dim as PlayPayload payload
+    payload.frequency = Frequency
+
+    pe = Pa_OpenDefaultStream(@stream, 0, 1, paInt32, SampleRate, SineSamples, @PlayCallback, @payload)
+    If pe <> paNoError Then
+        Print "Error: "; Pa_GetErrorText(pe)
+        End 1
+    End If
+
+    Print "Playing "; Frequency; "Hz for "; Duration; "ms"
+    pe = Pa_StartStream(stream)
+    If pe <> paNoError Then
+        Print "Error: "; Pa_GetErrorText(pe)
+        End 1
+    End If
+
+    'Sleep 2
+    Pa_Sleep(Duration)
+
+    pe = Pa_StopStream(stream)
+    If pe <> paNoError Then
+        Print "Error: "; Pa_GetErrorText(pe)
+        End 1
+    End If
+
+    pe = Pa_CloseStream(stream)
+    If pe <> paNoError Then
+        Print "Error: "; Pa_GetErrorText(pe)
+        End 1
+    End If
+End Sub
+
+Dim as PaError pe
+Print "Initialize PortAudio ("; *Pa_GetVersionText(); ")"
+
+pe = Pa_Initialize()
+If pe <> paNoError Then
+    Print "Error: "; Pa_GetErrorText(pe)
+    End 1
+End If
+
+'' Play from A4 (440Hz) for 44ms until A2 (220Hz) for 22ms
+For i as Integer = 440 to 220 Step -10
+    Play(i, i / 10)
+Next
+
+Print "Shutdown PortAudio"
+Pa_Terminate()
+
+End 0