Add example for the vocoder node.

research/_extras/nodes/ma_vocoder_node/ma_vocoder_node_example.c

+/*
+Demonstrates how to apply an effect to a duplex stream using the node graph system.
+
+This example applies a vocoder effect to the input stream before outputting it. A custom node
+called `ma_vocoder_node` is used to achieve the effect which can be found in the extras folder in
+the miniaudio repository. The vocoder node uses https://github.com/blastbay/voclib to achieve the
+effect.
+*/
+#define MINIAUDIO_IMPLEMENTATION
+#include "../../../../miniaudio.h"
+#include "../../../miniaudio_engine.h"
+#include "ma_vocoder_node.c"
+
+#include <stdio.h>
+
+#define DEVICE_FORMAT      ma_format_f32;   /* Must always be f32 for this example because the node graph system only works with this. */
+#define DEVICE_CHANNELS    1                /* For this example, always set to 1. */
+
+static ma_waveform         g_sourceData;    /* The underlying data source of the excite node. */
+static ma_audio_buffer_ref g_exciteData;    /* The underlying data source of the source node. */
+static ma_data_source_node g_sourceNode;    /* A data source node containing the source data we'll be sending through to the vocoder. This will be routed into the first bus of the vocoder node. */
+static ma_data_source_node g_exciteNode;    /* A data source node containing the excite data we'll be sending through to the vocoder. This will be routed into the second bus of the vocoder node. */
+static ma_vocoder_node     g_vocoderNode;   /* The vocoder node. */
+static ma_node_graph       g_nodeGraph;
+
+void data_callback(ma_device* pDevice, void* pOutput, const void* pInput, ma_uint32 frameCount)
+{
+    MA_ASSERT(pDevice->capture.format == pDevice->playback.format);
+    MA_ASSERT(pDevice->capture.channels == pDevice->playback.channels);
+
+    /*
+    The node graph system is a pulling style of API. At the lowest level of the chain will be a 
+    node acting as a data source for the purpose of delivering the initial audio data. In our case,
+    the data source is our `pInput` buffer. We need to update the underlying data source so that it
+    read data from `pInput`.
+    */
+    ma_audio_buffer_ref_set_data(&g_exciteData, pInput, frameCount);
+
+    /* With the source buffer configured we can now read directly from the node graph. */
+    ma_node_graph_read_pcm_frames(&g_nodeGraph, pOutput, frameCount, NULL);
+}
+
+int main(int argc, char** argv)
+{
+    ma_result result;
+    ma_device_config deviceConfig;
+    ma_device device;
+    ma_node_graph_config nodeGraphConfig;
+    ma_vocoder_node_config vocoderNodeConfig;
+    ma_data_source_node_config sourceNodeConfig;
+    ma_data_source_node_config exciteNodeConfig;
+    ma_waveform_config waveformConfig;
+
+    deviceConfig = ma_device_config_init(ma_device_type_duplex);
+    deviceConfig.capture.pDeviceID  = NULL;
+    deviceConfig.capture.format     = DEVICE_FORMAT;
+    deviceConfig.capture.channels   = DEVICE_CHANNELS;
+    deviceConfig.capture.shareMode  = ma_share_mode_shared;
+    deviceConfig.playback.pDeviceID = NULL;
+    deviceConfig.playback.format    = DEVICE_FORMAT;
+    deviceConfig.playback.channels  = DEVICE_CHANNELS;
+    deviceConfig.dataCallback       = data_callback;
+    result = ma_device_init(NULL, &deviceConfig, &device);
+    if (result != MA_SUCCESS) {
+        return result;
+    }
+
+
+    /* Now we can setup our node graph. */
+    nodeGraphConfig = ma_node_graph_config_init(device.capture.channels);
+
+    result = ma_node_graph_init(&nodeGraphConfig, NULL, &g_nodeGraph);
+    if (result != MA_SUCCESS) {
+        printf("Failed to initialize node graph.");
+        goto done0;
+    }
+
+
+    /* Vocoder. Attached straight to the endpoint. */
+    vocoderNodeConfig = ma_vocoder_node_config_init(device.capture.channels, device.sampleRate);
+
+    result = ma_vocoder_node_init(&g_nodeGraph, &vocoderNodeConfig, NULL, &g_vocoderNode);
+    if (result != MA_SUCCESS) {
+        printf("Failed to initialize vocoder node.");
+        goto done1;
+    }
+
+    ma_node_attach_output_bus(&g_vocoderNode, 0, ma_node_graph_get_endpoint(&g_nodeGraph), 0);
+
+    /* Amplify the volume of the vocoder output because in my testing it is a bit quiet. */
+    ma_node_set_output_bus_volume(&g_vocoderNode, 0, 4);
+
+
+    /* Source/carrier. Attached to input bus 0 of the vocoder node. */
+    waveformConfig = ma_waveform_config_init(device.capture.format, device.capture.channels, device.sampleRate, ma_waveform_type_sawtooth, 1.0, 50);
+
+    result = ma_waveform_init(&waveformConfig, &g_sourceData);
+    if (result != MA_SUCCESS) {
+        printf("Failed to initialize waveform for excite node.");
+        goto done3;
+    }
+
+    sourceNodeConfig = ma_data_source_node_config_init(&g_sourceData, MA_FALSE);
+
+    result = ma_data_source_node_init(&g_nodeGraph, &sourceNodeConfig, NULL, &g_sourceNode);
+    if (result != MA_SUCCESS) {
+        printf("Failed to initialize excite node.");
+        goto done3;
+    }
+
+    ma_node_attach_output_bus(&g_sourceNode, 0, &g_vocoderNode, 0);
+
+
+    /* Excite/modulator. Attached to input bus 1 of the vocoder node. */
+    result = ma_audio_buffer_ref_init(device.capture.format, device.capture.channels, NULL, 0, &g_exciteData);
+    if (result != MA_SUCCESS) {
+        printf("Failed to initialize audio buffer for source.");
+        goto done2;
+    }
+
+    exciteNodeConfig = ma_data_source_node_config_init(&g_exciteData, MA_FALSE);
+
+    result = ma_data_source_node_init(&g_nodeGraph, &exciteNodeConfig, NULL, &g_exciteNode);
+    if (result != MA_SUCCESS) {
+        printf("Failed to initialize source node.");
+        goto done2;
+    }
+
+    ma_node_attach_output_bus(&g_exciteNode, 0, &g_vocoderNode, 1);
+
+
+    ma_device_start(&device);
+
+    printf("Press Enter to quit...\n");
+    getchar();
+
+    /* It's important that we stop the device first or else we'll uninitialize the graph from under the device. */
+    ma_device_stop(&device);
+
+/*done4:*/ ma_data_source_node_uninit(&g_exciteNode, NULL);
+done3: ma_data_source_node_uninit(&g_sourceNode, NULL);
+done2: ma_vocoder_node_uninit(&g_vocoderNode, NULL);
+done1: ma_node_graph_uninit(&g_nodeGraph, NULL);
+done0: ma_device_uninit(&device);
+
+    (void)argc;
+    (void)argv;
+    return 0;
+}