Add simple_mixing example.

examples/simple_mixing.c

+/*
+Usage:   simple_mixing [input file 0] [input file 1] ... [input file n]
+Example: simple_mixing file1.wav file2.flac
+*/
+
+#define DR_FLAC_IMPLEMENTATION
+#include "../extras/dr_flac.h"  // Enables FLAC decoding.
+#define DR_MP3_IMPLEMENTATION
+#include "../extras/dr_mp3.h"   // Enables MP3 decoding.
+#define DR_WAV_IMPLEMENTATION
+#include "../extras/dr_wav.h"   // Enables WAV decoding.
+
+#define MINIAUDIO_IMPLEMENTATION
+#include "../miniaudio.h"
+
+#include <stdio.h>
+
+/*
+For simplicity, this example requires the device use floating point samples.
+*/
+#define SAMPLE_FORMAT   ma_format_f32
+#define CHANNEL_COUNT   2
+#define SAMPLE_RATE     48000
+
+ma_uint32   g_decoderCount;
+ma_decoder* g_pDecoders;
+ma_bool32*  g_pDecodersAtEnd;
+
+ma_event g_stopEvent; /* <-- Signaled by the audio thread, waited on by the main thread. */
+
+ma_bool32 are_all_decoders_at_end()
+{
+    for (ma_uint32 iDecoder = 0; iDecoder < g_decoderCount; ++iDecoder) {
+        if (g_pDecodersAtEnd[iDecoder] == MA_FALSE) {
+            return MA_FALSE;
+        }
+    }
+
+    return MA_TRUE;
+}
+
+ma_uint32 read_and_mix_pcm_frames_f32(ma_decoder* pDecoder, float* pOutputF32, ma_uint32 frameCount)
+{
+    /*
+    The way mixing works is that we just read into a temporary buffer, then take the contents of that buffer and mix it with the
+    contents of the output buffer by simply adding the sample together. You could also clip the samples to -1..+1, but I'm not
+    doing that in this example.
+    */
+    float temp[4096];
+    ma_uint32 tempCapInFrames = ma_countof(temp) / CHANNEL_COUNT;
+    ma_uint32 totalFramesRead = 0;
+
+    while (totalFramesRead < frameCount) {
+        ma_uint32 framesReadThisIteration;
+        ma_uint32 totalFramesRemaining = frameCount - totalFramesRead;
+        ma_uint32 framesToReadThisIteration = tempCapInFrames;
+        if (framesToReadThisIteration > totalFramesRemaining) {
+            framesToReadThisIteration = totalFramesRemaining;
+        }
+
+        framesReadThisIteration = (ma_uint32)ma_decoder_read_pcm_frames(pDecoder, temp, framesToReadThisIteration);
+        if (framesReadThisIteration == 0) {
+            break;
+        }
+
+        /* Mix the frames together. */
+        for (ma_uint32 iSample = 0; iSample < framesReadThisIteration*CHANNEL_COUNT; ++iSample) {
+            pOutputF32[totalFramesRead*CHANNEL_COUNT + iSample] += temp[iSample];
+        }
+
+        totalFramesRead += framesReadThisIteration;
+
+        if (framesReadThisIteration < framesToReadThisIteration) {
+            break;  /* Reached EOF. */
+        }
+    }
+    
+    return totalFramesRead;
+}
+
+void data_callback(ma_device* pDevice, void* pOutput, const void* pInput, ma_uint32 frameCount)
+{
+    float* pOutputF32 = (float*)pOutput;
+
+    ma_assert(pDevice->playback.format == SAMPLE_FORMAT);   /* <-- Important for this example. */
+
+    for (ma_uint32 iDecoder = 0; iDecoder < g_decoderCount; ++iDecoder) {
+        if (!g_pDecodersAtEnd[iDecoder]) {
+            ma_uint32 framesRead = read_and_mix_pcm_frames_f32(&g_pDecoders[iDecoder], pOutputF32, frameCount);
+            if (framesRead < frameCount) {
+                g_pDecodersAtEnd[iDecoder] = MA_TRUE;
+            }
+        }
+    }
+
+    /*
+    If at the end all of our decoders are at the end we need to stop. We cannot stop the device in the callback. Instead we need to
+    signal an event to indicate that it's stopped. The main thread will be waiting on the event, after which it will stop the event.
+    */
+    if (are_all_decoders_at_end()) {
+        ma_event_signal(&g_stopEvent);
+    }
+
+    (void)pInput;
+}
+
+int main(int argc, char** argv)
+{
+    ma_result result;
+    ma_decoder_config decoderConfig;
+
+    if (argc < 2) {
+        printf("No input files.\n");
+        return -1;
+    }
+
+    g_decoderCount   = argc-1;
+    g_pDecoders      = (ma_decoder*)malloc(sizeof(*g_pDecoders)      * g_decoderCount);
+    g_pDecodersAtEnd = (ma_bool32*) malloc(sizeof(*g_pDecodersAtEnd) * g_decoderCount);
+
+    /* In this example, all decoders need to have the same output format. */
+    decoderConfig = ma_decoder_config_init(SAMPLE_FORMAT, CHANNEL_COUNT, SAMPLE_RATE);
+    for (ma_uint32 iDecoder = 0; iDecoder < g_decoderCount; ++iDecoder) {
+        result = ma_decoder_init_file(argv[1+iDecoder], &decoderConfig, &g_pDecoders[iDecoder]);
+        if (result != MA_SUCCESS) {
+            for (ma_uint32 iDecoder2 = 0; iDecoder2 < iDecoder; ++iDecoder2) {
+                ma_decoder_uninit(&g_pDecoders[iDecoder2]);
+            }
+            free(g_pDecoders);
+            free(g_pDecodersAtEnd);
+
+            printf("Failed to load %s.\n", argv[1+iDecoder]);
+            return -3;
+        }
+        g_pDecodersAtEnd[iDecoder] = MA_FALSE;
+    }
+
+    /* Create only a single device. The decoders will be mixed together in the callback. In this example the data format needs to be the same as the decoders. */
+    ma_device_config config = ma_device_config_init(ma_device_type_playback);
+    config.playback.format   = SAMPLE_FORMAT;
+    config.playback.channels = CHANNEL_COUNT;
+    config.sampleRate        = SAMPLE_RATE;
+    config.dataCallback      = data_callback;
+    config.pUserData         = NULL;
+
+    ma_device device;
+    if (ma_device_init(NULL, &config, &device) != MA_SUCCESS) {
+        for (ma_uint32 iDecoder = 0; iDecoder < g_decoderCount; ++iDecoder) {
+            ma_decoder_uninit(&g_pDecoders[iDecoder]);
+        }
+        free(g_pDecoders);
+        free(g_pDecodersAtEnd);
+
+        printf("Failed to open playback device.\n");
+        return -3;
+    }
+
+    /*
+    We can't stop in the audio thread so we instead need to use an event. We wait on this thread in the main thread, and signal it in the audio thread. This
+    needs to be done before starting the device. We need a context to initialize the event, which we can get from the device. Alternatively you can initialize
+    a context separately, but we don't need to do that for this example.
+    */
+    ma_event_init(device.pContext, &g_stopEvent);
+
+    /* Now we start playback and wait for the audio thread to tell us to stop. */
+    if (ma_device_start(&device) != MA_SUCCESS) {
+        ma_device_uninit(&device);
+        for (ma_uint32 iDecoder = 0; iDecoder < g_decoderCount; ++iDecoder) {
+            ma_decoder_uninit(&g_pDecoders[iDecoder]);
+        }
+        free(g_pDecoders);
+        free(g_pDecodersAtEnd);
+
+        printf("Failed to start playback device.\n");
+        return -4;
+    }
+
+    printf("Waiting for playback to complete...\n");
+    ma_event_wait(&g_stopEvent);
+    
+    /* Getting here means the audio thread has signaled that the device should be stopped. */
+    ma_device_uninit(&device);
+    
+    for (ma_uint32 iDecoder = 0; iDecoder < g_decoderCount; ++iDecoder) {
+        ma_decoder_uninit(&g_pDecoders[iDecoder]);
+    }
+    free(g_pDecoders);
+    free(g_pDecodersAtEnd);
+
+    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_mixing.c" />
     <ClCompile Include="..\examples\simple_playback.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="..\research\tests\ma_resampler_test_0.c">
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">true</ExcludedFromBuild>

tests/ma_test_0.vcxproj.filters

@@ -57,6 +57,9 @@
     <ClCompile Include="..\examples\advanced_config.c">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="..\examples\simple_mixing.c">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="..\miniaudio.h">