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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