Initial mixer using audio params

Author: cwoffenden

test/webaudio/audioworklet_params_mixing.c

@@ -0,0 +1,147 @@
+#include <assert.h>
+#include <string.h>
+#include <stdio.h>
+
+#include <emscripten/em_js.h>
+#include <emscripten/webaudio.h>
+
+// Tests processing two stereo audio inputs being mixed to a single stereo audio
+// output in process() (by adding the inputs together).
+
+// This needs to be big enough for the stereo output, 2x inputs and the worker stack
+#define AUDIO_STACK_SIZE 4096
+
+// Shared file playback and bootstrap
+#include "audioworklet_test_shared.inc"
+
+// Callback to process and mix the audio tracks
+bool process(int numInputs, const AudioSampleFrame* inputs, int numOutputs, AudioSampleFrame* outputs, int numParams, const AudioParamFrame* __unused params, void* __unused data) {
+  audioProcessedCount++;
+
+  // Single stereo output
+  assert(numOutputs == 1 && outputs[0].numberOfChannels == 2);
+  for (int n = 0; n < numInputs; n++) {
+    // And all inputs are also stereo
+    assert(inputs[n].numberOfChannels == 2 || inputs[n].numberOfChannels == 0);
+    // This should always be the case
+    assert(inputs[n].samplesPerChannel == outputs[0].samplesPerChannel);
+  }
+  // Interestingly, params won't have a length > 1 unless the value changes, but
+  // we do know two params are incoming
+  assert(numParams = 2);
+  // We can now do a quick mix since we know the layouts
+  if (numInputs > 0) {
+    int totalSamples = outputs[0].samplesPerChannel * outputs[0].numberOfChannels;
+    float* outputData = outputs[0].data;
+    memcpy(outputData, inputs[0].data, totalSamples * sizeof(float));
+    for (int n = 1; n < numInputs; n++) {
+      // It's possible to have an input with no channels
+      if (inputs[n].numberOfChannels == 2) {
+        float* inputData = inputs[n].data;
+        for (int i = totalSamples - 1; i >= 0; i--) {
+          outputData[i] += inputData[i] * params[0].data[(params[0].length > 1) ? i : 0]; // world's worst mixer...
+        }
+      }
+    }
+  }
+  return true;
+}
+
+// Grabs the known worklet parameter and fades in or out (depending on whether
+// it's already fading up or down, we reverse the fade direction).
+EM_JS(void, doFade, (EMSCRIPTEN_AUDIO_WORKLET_NODE_T workletID), {
+  var worklet = emscriptenGetAudioObject(workletID);
+  if (worklet) {
+    // Emscripten's API creates these from a C array, indexing them instead of a
+    // name, so technically 0 is "0" but we might as well use numerical indices.
+    var param = worklet.parameters.get(0);
+    if (param) {
+      param.setTargetAtTime((param.value > 0.5) ? 0 : 1, 0 /* same as context.currentTime */, 0.5);
+    }
+  }
+});
+
+// Registered keypress event to call the JS doFade()
+bool onPress(int __unused type, const EmscriptenKeyboardEvent* e, void* data) {
+  if (!e->repeat && data) {
+    doFade(VOIDP_2_WA(data));
+  }
+  return false;
+}
+
+// Audio processor created, now register the audio callback
+void processorCreated(EMSCRIPTEN_WEBAUDIO_T context, bool success, void* __unused data) {
+  if (!success) {
+    printf("Audio worklet node creation failed\n");
+    return;
+  }
+  printf("Audio worklet processor created\n");
+  printf("Click to toggle audio playback\n");
+  printf("Keypress to fade the baseline in or out\n");
+
+  // Stereo output, two inputs
+  int outputChannelCounts[1] = { 2 };
+  EmscriptenAudioWorkletNodeCreateOptions opts = {
+    .numberOfInputs  = 2,
+    .numberOfOutputs = 1,
+    .outputChannelCounts = outputChannelCounts
+  };
+  EMSCRIPTEN_AUDIO_WORKLET_NODE_T worklet = emscripten_create_wasm_audio_worklet_node(context, "mixer", &opts, &process, NULL);
+  emscripten_audio_node_connect(worklet, context, 0, 0);
+
+  // Create the two stereo source nodes and connect them to the two inputs
+  // Note: we can connect the sources to the same input and it'll get mixed for us, but that's not the point
+  beatID = createTrack(context, "audio_files/emscripten-beat.mp3", true);
+  if (beatID) {
+    emscripten_audio_node_connect(beatID, worklet, 0, 0);
+  }
+  bassID = createTrack(context, "audio_files/emscripten-bass.mp3", true);
+  if (bassID) {
+    emscripten_audio_node_connect(bassID, worklet, 0, 1);
+  }
+
+  // Register a click to start playback
+  emscripten_set_click_callback(EMSCRIPTEN_EVENT_TARGET_DOCUMENT, WA_2_VOIDP(context), false, &onClick);
+  // And a keypress to do affect the fader
+  emscripten_set_keypress_callback(EMSCRIPTEN_EVENT_TARGET_DOCUMENT, WA_2_VOIDP(worklet), false, &onPress);
+
+  // Register the counter that exits the test after one second of mixing
+  emscripten_set_timeout_loop(&playedAndMixed, 16, NULL);
+}
+
+// Worklet thread inited, now create the audio processor
+void initialisedWithParams(EMSCRIPTEN_WEBAUDIO_T context, bool success, void* __unused data) {
+  if (!success) {
+    printf("Audio worklet failed to initialise\n");
+    return;
+  }
+  printf("Audio worklet initialised\n");
+
+  // Custom audio params we'll use as a fader
+  WebAudioParamDescriptor faderParam[] = {
+    {
+      // This a-rate (one entry per sample) is used to set the mix level
+      .defaultValue = 1.0f,
+      .minValue = 0.0f,
+      .maxValue = 1.0f,
+      .automationRate = WEBAUDIO_PARAM_A_RATE
+    }, {
+      // This k-rate (one entry per frame) is used just to test
+      .defaultValue = 0.0f,
+      .minValue = -100.0f,
+      .maxValue = 100.0f,
+      .automationRate = WEBAUDIO_PARAM_K_RATE
+    }
+  };
+  WebAudioWorkletProcessorCreateOptions opts = {
+    .name = "mixer",
+    .numAudioParams = 2,
+    .audioParamDescriptors = faderParam
+  };
+  emscripten_create_wasm_audio_worklet_processor_async(context, &opts, &processorCreated, NULL);
+}
+
+// This implementation has no custom start-up requirements
+EmscriptenStartWebAudioWorkletCallback getStartCallback() {
+  return &initialisedWithParams;
+}

test/webaudio/audioworklet_test_shared.inc

@@ -62,7 +62,7 @@ EM_JS(void, toggleTrack, (EMSCRIPTEN_WEBAUDIO_T srcID), {
   }
 });
 
-// Registered click even to (1) enable audio playback and (2) toggle playing the tracks
+// Registered click event to (1) enable audio playback and (2) toggle playing the tracks
 bool onClick(int __unused type, const EmscriptenMouseEvent* __unused e, void* data) {
   EMSCRIPTEN_WEBAUDIO_T ctx = VOIDP_2_WA(data);
   if (emscripten_audio_context_state(ctx) != AUDIO_CONTEXT_STATE_RUNNING) {