Add missing options to EmscriptenAudioWorkletNodeCreateOptions (#25497)

## Problem Description
The EmscriptenAudioWorkletNodeCreateOptions struct currently only
exposes options specific to AudioWorkletNode itself (numberOfInputs,
numberOfOutputs, outputChannelCounts), but AudioWorkletNode inherits
from AudioNode which has additional properties:

- channelCount 
- channelCountMode 
- channelInterpretation 

## Fix 

- Extend the C struct in `system/include/emscripten/webaudio.h`.
- Update the JavaScript implementation in `src/lib/libwebaudio.js` to
pass these options to the `AudioWorkletNode` constructor.

Fixes: #23982

---------

Co-authored-by: Nikitha Mohithe <nikithamohite@Nikithas-MacBook-Air.local>

Author: nikitha-m

src/lib/libwebaudio.js

@@ -318,6 +318,9 @@ var LibraryWebAudio = {
       numberOfInputs: {{{ makeGetValue('options', C_STRUCTS.EmscriptenAudioWorkletNodeCreateOptions.numberOfInputs, 'i32') }}},
       numberOfOutputs: optionsOutputs,
       outputChannelCount: readChannelCountArray({{{ makeGetValue('options', C_STRUCTS.EmscriptenAudioWorkletNodeCreateOptions.outputChannelCounts, 'i32*') }}}, optionsOutputs),
+      channelCount: {{{ makeGetValue('options', C_STRUCTS.EmscriptenAudioWorkletNodeCreateOptions.channelCount, 'u32') }}} || undefined,
+      channelCountMode: [/*'max'*/,'clamped-max','explicit'][{{{ makeGetValue('options', C_STRUCTS.EmscriptenAudioWorkletNodeCreateOptions.channelCountMode, 'i32') }}}],
+      channelInterpretation: [/*'speakers'*/,'discrete'][{{{ makeGetValue('options', C_STRUCTS.EmscriptenAudioWorkletNodeCreateOptions.channelInterpretation, 'i32') }}}],
       processorOptions: {
         callback,
         userData,

src/struct_info.json

@@ -1293,7 +1293,10 @@
             "EmscriptenAudioWorkletNodeCreateOptions": [
               "numberOfInputs",
               "numberOfOutputs",
-              "outputChannelCounts"
+              "outputChannelCounts",
+              "channelCount",
+              "channelCountMode",
+              "channelInterpretation"
             ]
         }
     },

src/struct_info_generated.json

@@ -535,7 +535,10 @@
             "samplesPerChannel": 4
         },
         "EmscriptenAudioWorkletNodeCreateOptions": {
-            "__size__": 12,
+            "__size__": 24,
+            "channelCount": 12,
+            "channelCountMode": 16,
+            "channelInterpretation": 20,
             "numberOfInputs": 0,
             "numberOfOutputs": 4,
             "outputChannelCounts": 8

src/struct_info_generated_wasm64.json

@@ -535,7 +535,10 @@
             "samplesPerChannel": 4
         },
         "EmscriptenAudioWorkletNodeCreateOptions": {
-            "__size__": 16,
+            "__size__": 32,
+            "channelCount": 16,
+            "channelCountMode": 24,
+            "channelInterpretation": 28,
             "numberOfInputs": 0,
             "numberOfOutputs": 4,
             "outputChannelCounts": 8

system/include/emscripten/webaudio.h

@@ -126,6 +126,17 @@ typedef struct AudioParamFrame
 
 typedef bool (*EmscriptenWorkletNodeProcessCallback)(int numInputs, const AudioSampleFrame *inputs, int numOutputs, AudioSampleFrame *outputs, int numParams, const AudioParamFrame *params, void *userData4);
 
+typedef enum {
+    WEBAUDIO_CHANNEL_COUNT_MODE_MAX = 0,
+    WEBAUDIO_CHANNEL_COUNT_MODE_CLAMPED_MAX = 1,
+    WEBAUDIO_CHANNEL_COUNT_MODE_EXPLICIT = 2
+} WEBAUDIO_CHANNEL_COUNT_MODE;
+
+typedef enum {
+    WEBAUDIO_CHANNEL_INTERPRETATION_SPEAKERS = 0,
+    WEBAUDIO_CHANNEL_INTERPRETATION_DISCRETE = 1
+} WEBAUDIO_CHANNEL_INTERPRETATION;
+
 typedef struct EmscriptenAudioWorkletNodeCreateOptions
 {
 	// How many audio nodes does this node take inputs from? Default=1
@@ -134,6 +145,13 @@ typedef struct EmscriptenAudioWorkletNodeCreateOptions
 	int numberOfOutputs;
 	// For each output, specifies the number of audio channels (1=mono/2=stereo/etc.) for that output. Default=an array of ones for each output channel.
 	int *outputChannelCounts;
+	// Number of channels used when up-mixing and down-mixing connections to any inputs to the node. Default=2
+	unsigned long channelCount;
+	// How channels will be counted when up-mixing and down-mixing connections to any inputs to the node? Default=max
+	WEBAUDIO_CHANNEL_COUNT_MODE channelCountMode;
+	// How individual channels will be treated when up-mixing and down-mixing connections to any inputs to the node? Default=speakers
+	WEBAUDIO_CHANNEL_INTERPRETATION channelInterpretation;
+
 } EmscriptenAudioWorkletNodeCreateOptions;
 
 // Instantiates the given AudioWorkletProcessor as an AudioWorkletNode, which continuously calls the specified processCallback() function on the browser's audio thread to perform audio processing.

test/webaudio/audioworklet.c

@@ -92,7 +92,10 @@ void AudioWorkletProcessorCreated(EMSCRIPTEN_WEBAUDIO_T audioContext, bool succe
   EmscriptenAudioWorkletNodeCreateOptions options = {
     .numberOfInputs = 0,
     .numberOfOutputs = 1,
-    .outputChannelCounts = outputChannelCounts
+    .outputChannelCounts = outputChannelCounts,
+    .channelCount = 1,
+    .channelCountMode = WEBAUDIO_CHANNEL_COUNT_MODE_EXPLICIT,
+    .channelInterpretation = WEBAUDIO_CHANNEL_INTERPRETATION_SPEAKERS,
   };
 
   // Instantiate the noise-generator Audio Worklet Processor.