Add mono audio input to PortAudio shim

The way the PortAudio callback works it is possible to reuse the buffer
used for sharing output audio data between Julia and the C-library.

The output data can be pushed from the shared buffer to the PortAudio's
output buffer, after which the same location in the buffer can be used
for storing the data read from the input buffer.

This does assume equal lengths for the in- and output buffers.

deps/src/shim.c

@@ -4,18 +4,16 @@
 #include <unistd.h>
 
 static int paCallback(const void *inputBuffer, void *outputBuffer,
-                          unsigned long framesPerBuffer,
-                          const PaStreamCallbackTimeInfo* timeInfo,
-                          PaStreamCallbackFlags statusFlags,
-                          void *userData);
+                      unsigned long framesPerBuffer,
+                      const PaStreamCallbackTimeInfo* timeInfo,
+                      PaStreamCallbackFlags statusFlags,
+                      void *userData);
 
 static PaStream *AudioStream;
 static int JuliaPipeReadFD = 0;
 static int JuliaPipeWriteFD = 0;
 static sem_t CSemaphore;
-static void *OutData = NULL;
-static unsigned long OutFrames = 0;
-
+static void *Buffer = NULL;
 
 int make_pipe(void)
 {
@@ -27,11 +25,9 @@ int make_pipe(void)
     return JuliaPipeReadFD;
 }
 
-
-void wake_callback_thread(void *outData, unsigned int outFrames)
+void synchronize_buffer(void *buffer)
 {
-    OutData = outData;
-    OutFrames = outFrames;
+    Buffer = buffer;
     sem_post(&CSemaphore);
 }
 
@@ -39,13 +35,12 @@ PaError open_stream(unsigned int sampleRate, unsigned int bufSize)
 {
     PaError err;
 
-
     err = Pa_OpenDefaultStream(&AudioStream,
-            0,          /* no input channels */
+            1,          /* single input channel */
             1,          /* mono output */
             paFloat32,  /* 32 bit floating point output */
             sampleRate,
-            bufSize,        /* frames per buffer, i.e. the number of sample frames
+            bufSize,    /* frames per buffer, i.e. the number of sample frames
                            that PortAudio will request from the callback. Many
                            apps may want to use paFramesPerBufferUnspecified,
                            which tells PortAudio to pick the best, possibly
@@ -66,7 +61,6 @@ PaError open_stream(unsigned int sampleRate, unsigned int bufSize)
     return paNoError;
 }
 
-
 //PaError stop_sin(void)
 //{
 //    PaError err;
@@ -84,17 +78,16 @@ PaError open_stream(unsigned int sampleRate, unsigned int bufSize)
 //    return paNoError;
 //}
 
-
 /*
  * This routine will be called by the PortAudio engine when audio is needed.
  * It may called at interrupt level on some machines so don't do anything that
  * could mess up the system like calling malloc() or free().
  */
 static int paCallback(const void *inputBuffer, void *outputBuffer,
-                           unsigned long framesPerBuffer,
-                           const PaStreamCallbackTimeInfo* timeInfo,
-                           PaStreamCallbackFlags statusFlags,
-                           void *userData)
+                      unsigned long framesPerBuffer,
+                      const PaStreamCallbackTimeInfo* timeInfo,
+                      PaStreamCallbackFlags statusFlags,
+                      void *userData)
 {
     unsigned int i;
     unsigned char fd_data = 0;
@@ -102,9 +95,9 @@ static int paCallback(const void *inputBuffer, void *outputBuffer,
     sem_wait(&CSemaphore);
     for(i=0; i<framesPerBuffer; i++)
     {
-        ((float *)outputBuffer)[i] = ((float *)OutData)[i];
+        ((float *)outputBuffer)[i] = ((float *)Buffer)[i];
+        ((float *)Buffer)[i] = ((float *)inputBuffer)[i];
     }
-    // TODO: copy the input data somewhere
     write(JuliaPipeWriteFD, &fd_data, 1);
     return 0;
 }

src/portaudio.jl

@@ -36,13 +36,10 @@ end
 
 ############ Internal Functions ############
 
-function wake_callback_thread(out_array)
-    ccall((:wake_callback_thread, libportaudio_shim), Void,
-          (Ptr{Void}, Cuint),
-          out_array, size(out_array, 1))
+function synchronize_buffer(buffer)
+    ccall((:synchronize_buffer, libportaudio_shim), Void, (Ptr{Void},), buffer)
 end
 
-
 function init_portaudio()
     info("Initializing PortAudio. Expect errors as we scan devices")
     err = ccall((:Pa_Initialize, "libportaudio"), PaError, ())
@@ -83,17 +80,17 @@ end
 
 function portaudio_task(jl_filedesc::Integer, stream::PortAudioStream)
     info("Audio Task Launched")
-    in_array = zeros(AudioSample, stream.info.buf_size)
+    buffer = zeros(AudioSample, stream.info.buf_size)
     desc_bytes = Cchar[0]
     jl_stream = fdio(jl_filedesc)
     jl_rawfd = RawFD(jl_filedesc)
     try
         while true
             # assume the root mixer is always active
-            out_array::AudioBuf, _::Bool = render(stream.mixer, in_array,
-                                                  stream.info)
+            buffer::AudioBuf, _::Bool = render(stream.mixer, buffer, stream.info)
+
             # wake the C code so it knows we've given it some more data
-            wake_callback_thread(out_array)
+            synchronize_buffer(buffer)
             # wait for new data to be available from the sound card (and for it
             # to have processed our last frame of data). At some point we
             # should do something with the data we get from the callback