qwasmaudiodevice.cpp

Go to the documentation of this file.

// 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>
 
#include <AL/al.h>
#include <AL/alc.h>
 
QT_BEGIN_NAMESPACE
 
namespace {
 
QAudioDevicePrivate::AudioDeviceFormat createDefaultWasmAudioDeviceFormat()
{
    QAudioDevicePrivate::AudioDeviceFormat format;
 
    format.minimumChannelCount = 1;
    format.maximumChannelCount = 2;
    format.minimumSampleRate = 8000;
    format.maximumSampleRate = 96000; // js AudioContext max according to docs
 
    // native openAL formats
    format.supportedSampleFormats.append(QAudioFormat::UInt8);
    format.supportedSampleFormats.append(QAudioFormat::Int16);
 
    // Browsers use 32bit floats as native, but emscripten reccomends checking for the exension.
    if (alIsExtensionPresent("AL_EXT_float32"))
        format.supportedSampleFormats.append(QAudioFormat::Float);
 
    format.preferredFormat.setChannelCount(2);
 
    // FIXME: firefox
    // An AudioContext was prevented from starting automatically.
    // It must be created or resumed after a user gesture on the page.
    emscripten::val audioContext = emscripten::val::global("window")["AudioContext"].new_();
    if (audioContext == emscripten::val::undefined())
        audioContext = emscripten::val::global("window")["webkitAudioContext"].new_();
 
    if (audioContext != emscripten::val::undefined()) {
        int sRate = audioContext["sampleRate"].as<int>();
        audioContext.call<void>("close");
        format.preferredFormat.setSampleRate(sRate);
    }
 
    auto f = QAudioFormat::Float;
 
    if (!format.supportedSampleFormats.contains(f))
        f = QAudioFormat::Int16;
    format.preferredFormat.setSampleFormat(f);
 
    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