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// Copyright (C) 2021 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
#include "qwasmaudiodevice_p.h"
#include <emscripten.h>
#include <emscripten/val.h>
#include <emscripten/bind.h>
QT_BEGIN_NAMESPACE
namespace {
// Probe the hardware sample rate once and cache it. The rate is the same for
// all devices, so creating a temporary AudioContext per enumerated device is
// wasteful and can cause browser device errors from overlapping contexts.
int probeHardwareSampleRate()
{
static int cachedRate = 0;
if (cachedRate > 0)
return cachedRate;
// FIXME: firefox
// An AudioContext was prevented from starting automatically.
// It must be created or resumed after a user gesture on the page.
emscripten::val ctx = emscripten::val::global("window")["AudioContext"].new_();
if (ctx == emscripten::val::undefined())
ctx = emscripten::val::global("window")["webkitAudioContext"].new_();
if (ctx != emscripten::val::undefined()) {
cachedRate = ctx["sampleRate"].as<int>();
ctx.call<void>("close");
}
return cachedRate;
}
QAudioDevicePrivate::AudioDeviceFormat createDefaultWasmAudioDeviceFormat()
{
QAudioDevicePrivate::AudioDeviceFormat format;
format.minimumChannelCount = 1;
format.maximumChannelCount = 2;
format.minimumSampleRate = 8000;
format.maximumSampleRate = 96000; // js AudioContext max according to docs
// WebAudio natively supports all these formats via AudioWorklet.
format.supportedSampleFormats.append(QAudioFormat::UInt8);
format.supportedSampleFormats.append(QAudioFormat::Int16);
format.supportedSampleFormats.append(QAudioFormat::Int32);
format.supportedSampleFormats.append(QAudioFormat::Float);
format.preferredFormat.setChannelCount(2);
if (int sRate = probeHardwareSampleRate(); sRate > 0)
format.preferredFormat.setSampleRate(sRate);
format.preferredFormat.setSampleFormat(QAudioFormat::Float);
return format;
}
} // namespace
QWasmAudioDevice::QWasmAudioDevice(const char *device, const char *desc, bool isDef,
QAudioDevice::Mode mode)
: QAudioDevicePrivate(device, mode, QString::fromUtf8(desc), isDef,
createDefaultWasmAudioDeviceFormat())
{
}
QT_END_NAMESPACE