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cwoffendencwoffenden
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Work-in-progress (fails with wasm64)
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‎src/audio_worklet.js

Lines changed: 108 additions & 39 deletions
Original file line numberDiff line numberDiff line change
@@ -28,11 +28,43 @@ function createWasmAudioWorkletProcessor(audioParams) {
2828
this.callback = {{{ makeDynCall('iipipipp', 'opts.callback') }}};
2929
this.userData = opts.userData;
3030
// Then the samples per channel to process, fixed for the lifetime of the
31-
// context that created this processor. Note for when moving to Web Audio
32-
// 1.1: the typed array passed to process() should be the same size as this
33-
// 'render quantum size', and this exercise of passing in the value
34-
// shouldn't be required (to be verified)
31+
// context that created this processor. Even though this 'render quantum
32+
// size' is fixed at 128 samples in the 1.0 spec, it will be variable in
33+
// the 1.1 spec. It's passed in now, just to prove it's settable, but will
34+
// eventually be a property of the AudioWorkletGlobalScope (globalThis).
3535
this.samplesPerChannel = opts.samplesPerChannel;
36+
this.bytesPerChannel = this.samplesPerChannel * {{{ getNativeTypeSize('float') }}};
37+
38+
// Create up-front as many typed views for marshalling the output data as
39+
// may be required (with an arbitrary maximum of 16, for the case where a
40+
// multi-MB stack is passed), allocated at the *top* of the worklet's
41+
// stack (and whose addresses are fixed). The 'minimum alloc' firstly
42+
// stops STACK_OVERFLOW_CHECK failing (since the stack will be full, and
43+
// 16 being the minimum allocation size due to alignments) and leaves room
44+
// for a single AudioSampleFrame as a minumum.
45+
this.maxBuffers = Math.min(((wwParams.stackSize - /*minimum alloc*/ 16) / this.bytesPerChannel) | 0, /*sensible limit*/ 16);
46+
#if ASSERTIONS
47+
console.assert(this.maxBuffers > 0, `AudioWorklet needs more stack allocating (at least ${this.bytesPerChannel})`);
48+
#endif
49+
// These are still alloc'd to take advantage of the overflow checks, etc.
50+
var oldStackPtr = stackSave();
51+
var viewDataIdx = {{{ getHeapOffset('stackAlloc(this.maxBuffers * this.bytesPerChannel)', 'float') }}};
52+
#if WEBAUDIO_DEBUG
53+
console.log(`AudioWorklet creating ${this.maxBuffers} buffer one-time views (for a stack size of ${wwParams.stackSize} at address 0x${(viewDataIdx * 4).toString(16)})`);
54+
#endif
55+
this.outputViews = [];
56+
for (var n = this.maxBuffers; n > 0; n--) {
57+
// Added in reverse so the lowest indices are closest to the stack top
58+
this.outputViews.unshift(
59+
HEAPF32.subarray(viewDataIdx, viewDataIdx += this.samplesPerChannel)
60+
);
61+
}
62+
stackRestore(oldStackPtr);
63+
64+
#if ASSERTIONS
65+
// Explicitly verify this later in process()
66+
this.ctorOldStackPtr = oldStackPtr;
67+
#endif
3668
}
3769

3870
static get parameterDescriptors() {
@@ -53,26 +85,42 @@ function createWasmAudioWorkletProcessor(audioParams) {
5385
var entry; // reused list entry or index
5486
var subentry; // reused channel or other array in each list entry or index
5587

56-
// Calculate how much stack space is needed.
57-
var bytesPerChannel = this.samplesPerChannel * {{{ getNativeTypeSize('float') }}};
88+
// Calculate the required stack and output buffer views
5889
var stackMemoryNeeded = (numInputs + numOutputs) * {{{ C_STRUCTS.AudioSampleFrame.__size__ }}};
90+
for (entry of inputList) {
91+
stackMemoryNeeded += entry.length * this.bytesPerChannel;
92+
}
93+
var outputViewsNeeded = 0;
94+
for (entry of outputList) {
95+
outputViewsNeeded += entry.length;
96+
}
97+
stackMemoryNeeded += outputViewsNeeded * this.bytesPerChannel;
5998
var numParams = 0;
60-
for (entry of inputList) stackMemoryNeeded += entry.length * bytesPerChannel;
61-
for (entry of outputList) stackMemoryNeeded += entry.length * bytesPerChannel;
6299
for (entry in parameters) {
63100
stackMemoryNeeded += parameters[entry].byteLength + {{{ C_STRUCTS.AudioParamFrame.__size__ }}};
64101
++numParams;
65102
}
103+
#if ASSERTIONS
104+
console.assert(outputViewsNeeded <= this.outputViews.length, `Too many AudioWorklet outputs (need ${outputViewsNeeded} but have stack space for ${this.outputViews.length})`);
105+
#endif
66106

67-
// Allocate the necessary stack space.
68107
var oldStackPtr = stackSave();
69-
var inputsPtr = stackAlloc(stackMemoryNeeded);
108+
// Allocate the necessary stack space. All pointer variables are always in
109+
// bytes; 'dataPtr' is the start of the data section, and advances as
110+
// space for structs and data is taken; 'structPtr' is reused as the
111+
// working start to each struct record.
112+
// Here 'dataPtr' will be 16-byte aligned, from _emscripten_stack_alloc(),
113+
// as were the output views, so we round up and advance the required bytes
114+
// to ensure the addresses all work out at the end.
115+
entry = (stackMemoryNeeded + 15) & ~15;
116+
var dataPtr = stackAlloc(entry) + (entry - stackMemoryNeeded);
70117

71-
// Copy input audio descriptor structs and data to Wasm ('structPtr' is
72-
// reused as the working start to each struct record, 'dataPtr' start of
73-
// the data section, usually after all structs).
118+
// Copy input audio descriptor structs and data to Wasm (recall, structs
119+
// first, audio data after). 'inputsPtr' is the start of the C callback's
120+
// input AudioSampleFrame.
121+
var /*const*/ inputsPtr = dataPtr;
74122
var structPtr = inputsPtr;
75-
var dataPtr = inputsPtr + numInputs * {{{ C_STRUCTS.AudioSampleFrame.__size__ }}};
123+
dataPtr += numInputs * {{{ C_STRUCTS.AudioSampleFrame.__size__ }}};
76124
for (entry of inputList) {
77125
// Write the AudioSampleFrame struct instance
78126
{{{ makeSetValue('structPtr', C_STRUCTS.AudioSampleFrame.numberOfChannels, 'entry.length', 'u32') }}};
@@ -82,26 +130,13 @@ function createWasmAudioWorkletProcessor(audioParams) {
82130
// Marshal the input audio sample data for each audio channel of this input
83131
for (subentry of entry) {
84132
HEAPF32.set(subentry, {{{ getHeapOffset('dataPtr', 'float') }}});
85-
dataPtr += bytesPerChannel;
133+
dataPtr += this.bytesPerChannel;
86134
}
87135
}
88136

89-
// Copy output audio descriptor structs to Wasm
90-
var outputsPtr = dataPtr;
91-
structPtr = outputsPtr;
92-
var outputDataPtr = (dataPtr += numOutputs * {{{ C_STRUCTS.AudioSampleFrame.__size__ }}});
93-
for (entry of outputList) {
94-
// Write the AudioSampleFrame struct instance
95-
{{{ makeSetValue('structPtr', C_STRUCTS.AudioSampleFrame.numberOfChannels, 'entry.length', 'u32') }}};
96-
{{{ makeSetValue('structPtr', C_STRUCTS.AudioSampleFrame.samplesPerChannel, 'this.samplesPerChannel', 'u32') }}};
97-
{{{ makeSetValue('structPtr', C_STRUCTS.AudioSampleFrame.data, 'dataPtr', '*') }}};
98-
structPtr += {{{ C_STRUCTS.AudioSampleFrame.__size__ }}};
99-
// Reserve space for the output data
100-
dataPtr += bytesPerChannel * entry.length;
101-
}
102-
103-
// Copy parameters descriptor structs and data to Wasm
104-
var paramsPtr = dataPtr;
137+
// Copy parameters descriptor structs and data to Wasm. 'paramsPtr' is the
138+
// start of the C callback's input AudioParamFrame.
139+
var /*const*/ paramsPtr = dataPtr;
105140
structPtr = paramsPtr;
106141
dataPtr += numParams * {{{ C_STRUCTS.AudioParamFrame.__size__ }}};
107142
for (entry = 0; subentry = parameters[entry++];) {
@@ -114,20 +149,54 @@ function createWasmAudioWorkletProcessor(audioParams) {
114149
dataPtr += subentry.length * {{{ getNativeTypeSize('float') }}};
115150
}
116151

152+
// Copy output audio descriptor structs to Wasm. 'outputsPtr' is the start
153+
// of the C callback's output AudioSampleFrame.
154+
// Note: dataPtr after the struct offsets should now be 16-byte aligned.
155+
var /*const*/ outputsPtr = dataPtr;
156+
structPtr = outputsPtr;
157+
dataPtr += numOutputs * {{{ C_STRUCTS.AudioSampleFrame.__size__ }}};
158+
for (entry of outputList) {
159+
// Write the AudioSampleFrame struct instance
160+
{{{ makeSetValue('structPtr', C_STRUCTS.AudioSampleFrame.numberOfChannels, 'entry.length', 'u32') }}};
161+
{{{ makeSetValue('structPtr', C_STRUCTS.AudioSampleFrame.samplesPerChannel, 'this.samplesPerChannel', 'u32') }}};
162+
{{{ makeSetValue('structPtr', C_STRUCTS.AudioSampleFrame.data, 'dataPtr', '*') }}};
163+
structPtr += {{{ C_STRUCTS.AudioSampleFrame.__size__ }}};
164+
// Advance the output pointer to the next output (matching the pre-allocated views)
165+
dataPtr += this.bytesPerChannel * entry.length;
166+
}
167+
168+
#if ASSERTIONS
169+
// If all the maths worked out, we arrived at the original stack address
170+
console.assert(dataPtr == oldStackPtr, `AudioWorklet stack missmatch (audio data finishes at ${dataPtr} instead of ${oldStackPtr})`);
171+
172+
// Sanity checks. If these trip the most likely cause, beyond unforeseen
173+
// stack shenanigans, is that the 'render quantum size' changed after
174+
// construction (which shouldn't be possible).
175+
if (numOutputs) {
176+
// First that the output view addresses match the stack positions
177+
dataPtr -= this.bytesPerChannel;
178+
for (entry = 0; entry < outputViewsNeeded; entry++) {
179+
console.assert(dataPtr == this.outputViews[entry].byteOffset, 'AudioWorklet internal error in addresses of the output array views');
180+
dataPtr -= this.bytesPerChannel;
181+
}
182+
// And that the views' size match the passed in output buffers
183+
for (entry of outputList) {
184+
for (subentry of entry) {
185+
console.assert(subentry.byteLength == this.bytesPerChannel, `AudioWorklet unexpected output buffer size (expected ${this.bytesPerChannel} got ${subentry.byteLength})`);
186+
}
187+
}
188+
}
189+
#endif
190+
117191
// Call out to Wasm callback to perform audio processing
118192
var didProduceAudio = this.callback(numInputs, inputsPtr, numOutputs, outputsPtr, numParams, paramsPtr, this.userData);
119193
if (didProduceAudio) {
120194
// Read back the produced audio data to all outputs and their channels.
121-
// (A garbage-free function TypedArray.copy(dstTypedArray, dstOffset,
122-
// srcTypedArray, srcOffset, count) would sure be handy.. but web does
123-
// not have one, so manually copy all bytes in)
124-
outputDataPtr = {{{ getHeapOffset('outputDataPtr', 'float') }}};
195+
// The preallocated 'outputViews' already have the correct offsets and
196+
// sizes into the stack (recall from the ctor that they run backwards).
125197
for (entry of outputList) {
126198
for (subentry of entry) {
127-
// repurposing structPtr for now
128-
for (structPtr = 0; structPtr < this.samplesPerChannel; ++structPtr) {
129-
subentry[structPtr] = HEAPF32[outputDataPtr++];
130-
}
199+
subentry.set(this.outputViews[--outputViewsNeeded]);
131200
}
132201
}
133202
}

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