Add loopback example.

examples/simple_loopback.c

+/*
+This example simply captures data from your default playback device until you press Enter. The output is saved to the file
+specified on the command line.
+
+The use loopback mode you just need to set the device type to ma_device_type_loopback and set the capture device config
+properties. The output buffer in the callback will be null whereas the input buffer will be valid.
+*/
+
+#define MINIAUDIO_IMPLEMENTATION
+#include "../miniaudio.h"
+
+#define DR_WAV_IMPLEMENTATION
+#include "../extras/dr_wav.h"
+
+#include <stdlib.h>
+#include <stdio.h>
+
+void data_callback(ma_device* pDevice, void* pOutput, const void* pInput, ma_uint32 frameCount)
+{
+    drwav* pWav = (drwav*)pDevice->pUserData;
+    ma_assert(pWav != NULL);
+
+    printf("Callback: %d\n", frameCount);
+    drwav_write_pcm_frames(pWav, frameCount, pInput);
+
+    (void)pOutput;
+}
+
+int main(int argc, char** argv)
+{
+    ma_result result;
+    drwav_data_format wavFormat;
+    drwav wav;
+    ma_device_config deviceConfig;
+    ma_device device;
+
+    /* Loopback mode is currently only supported on WASAPI. */
+    ma_backend backends[] = {
+        ma_backend_wasapi
+    };
+
+    if (argc < 2) {
+        printf("No input file.\n");
+        return -1;
+    }
+
+    wavFormat.container     = drwav_container_riff;
+    wavFormat.format        = DR_WAVE_FORMAT_IEEE_FLOAT;
+    wavFormat.channels      = 2;
+    wavFormat.sampleRate    = 44100;
+    wavFormat.bitsPerSample = 32;
+
+    if (drwav_init_file_write(&wav, argv[1], &wavFormat) == DRWAV_FALSE) {
+        printf("Failed to initialize output file.\n");
+        return -1;
+    }
+
+    deviceConfig = ma_device_config_init(ma_device_type_loopback);
+    deviceConfig.capture.pDeviceID = NULL; /* Use default device for this example. Set this to the ID of a _playback_ device if you want to capture from a specific device. */
+    deviceConfig.capture.format    = ma_format_f32;
+    deviceConfig.capture.channels  = wavFormat.channels;
+    deviceConfig.sampleRate        = wavFormat.sampleRate;
+    deviceConfig.dataCallback      = data_callback;
+    deviceConfig.pUserData         = &wav;
+
+    result = ma_device_init_ex(backends, sizeof(backends)/sizeof(backends[0]), NULL, &deviceConfig, &device);
+    if (result != MA_SUCCESS) {
+        printf("Failed to initialize loopback device.\n");
+        return -2;
+    }
+
+    result = ma_device_start(&device);
+    if (result != MA_SUCCESS) {
+        ma_device_uninit(&device);
+        printf("Failed to start device.\n");
+        return -3;
+    }
+
+    printf("Press Enter to stop recording...\n");
+    getchar();
+    
+    ma_device_uninit(&device);
+    drwav_uninit(&wav);
+
+    return 0;
+}

tests/ma_test_0.vcxproj

@@ -294,13 +294,14 @@
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">true</ExcludedFromBuild>
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Release|x64'">true</ExcludedFromBuild>
     </ClCompile>
+    <ClCompile Include="..\examples\simple_loopback.c" />
     <ClCompile Include="..\examples\simple_mixing.c">
-      <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">false</ExcludedFromBuild>
-      <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">false</ExcludedFromBuild>
-      <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Debug|ARM'">false</ExcludedFromBuild>
-      <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Release|ARM'">false</ExcludedFromBuild>
-      <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">false</ExcludedFromBuild>
-      <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Release|x64'">false</ExcludedFromBuild>
+      <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">true</ExcludedFromBuild>
+      <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">true</ExcludedFromBuild>
+      <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Debug|ARM'">true</ExcludedFromBuild>
+      <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Release|ARM'">true</ExcludedFromBuild>
+      <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">true</ExcludedFromBuild>
+      <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Release|x64'">true</ExcludedFromBuild>
     </ClCompile>
     <ClCompile Include="..\examples\simple_playback.c">
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">true</ExcludedFromBuild>

tests/ma_test_0.vcxproj.filters

@@ -60,6 +60,9 @@
     <ClCompile Include="..\examples\simple_mixing.c">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="..\examples\simple_loopback.c">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="..\miniaudio.h">