Rename QAudio namespace to QtAudio

With the addition of the QtVideo namespace in Qt 6.7 it becomes
obvious that the existing QAudio namespace is not named according
to the convention for namespaces in Qt.
To fix this, we can rename the QAudio namespace to QtAudio, and
declare the QAudio namespace as an alias for QtAudio. Public APIs
using a QAudio type in their signature need to be exported from a
removed_api.cpp file to maintain binary compatibility.

Two of those are a signal, which leaves one challenge: string-based
connects will have to use the QAudio namespace, in spite of the
documentation, as the signal doesn't exist with a QtAudio parameter.
Add a \note in the signals' documentation.

[ChangeLog][Qt Multimedia][Potentially Source-Incompatible Changes]
The QAudio namespace has been renamed to QtAudio, with QAudio still
being available as an alias. String based connections to
QAudioSink/Source::stateChanged need to continue to use
QAudio::State as the parameter.

Pick-to: 6.7
Change-Id: If49676ee62e048efbed68bb0e4848a5fefaea2f7
Reviewed-by: Lars Knoll <lars@knoll.priv.no>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Artem Dyomin <artem.dyomin@qt.io>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

1 files changed, 241 insertions, 0 deletions

diff --git a/src/multimedia/audio/qtaudio.cpp b/src/multimedia/audio/qtaudio.cpp
new file mode 100644
index 000000000..999248bb6
--- /dev/null
+++ b/src/multimedia/audio/qtaudio.cpp
@@ -0,0 +1,241 @@
+// Copyright (C) 2024 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 <qtaudio.h>
+#include <qmath.h>
+#include <QDebug>
+
+QT_BEGIN_NAMESPACE
+
+#define LOG100 4.60517018599
+
+/*!
+    \namespace QtAudio
+    \ingroup multimedia-namespaces
+    \brief The QtAudio namespace contains enums used by the audio classes.
+    \inmodule QtMultimedia
+    \ingroup multimedia
+    \ingroup multimedia_audio
+*/
+
+/*!
+    \enum QtAudio::Error
+
+    \value NoError         No errors have occurred
+    \value OpenError       An error occurred opening the audio device
+    \value IOError         An error occurred during read/write of audio device
+    \value UnderrunError   Audio data is not being fed to the audio device at a fast enough rate
+    \value FatalError      A non-recoverable error has occurred, the audio device is not usable at this time.
+*/
+
+/*!
+    \enum QtAudio::State
+
+    \value ActiveState       Audio data is being processed, this state is set after start() is called
+                             and while audio data is available to be processed.
+    \value SuspendedState    The audio stream is in a suspended state.  Entered after suspend() is called
+                             or when another stream takes control of the audio device.  In the later case,
+                             a call to resume will return control of the audio device to this stream.  This
+                             should usually only be done upon user request.
+    \value StoppedState      The audio device is closed, and is not processing any audio data
+    \value IdleState         The QIODevice passed in has no data and audio system's buffer is empty, this state
+                             is set after start() is called and while no audio data is available to be processed.
+*/
+
+/*!
+    \enum QtAudio::VolumeScale
+
+    This enum defines the different audio volume scales.
+
+    \value LinearVolumeScale        Linear scale. \c 0.0 (0%) is silence and \c 1.0 (100%) is full
+                                    volume. All Qt Multimedia classes that have an audio volume use
+                                    a linear scale.
+    \value CubicVolumeScale         Cubic scale. \c 0.0 (0%) is silence and \c 1.0 (100%) is full
+                                    volume.
+    \value LogarithmicVolumeScale   Logarithmic Scale. \c 0.0 (0%) is silence and \c 1.0 (100%) is
+                                    full volume. UI volume controls should usually use a logarithmic
+                                    scale.
+    \value DecibelVolumeScale       Decibel (dB, amplitude) logarithmic scale. \c -200 is silence
+                                    and \c 0 is full volume.
+
+    \sa QtAudio::convertVolume()
+*/
+
+namespace QtAudio
+{
+
+/*!
+    Converts an audio \a volume \a from a volume scale \a to another, and returns the result.
+
+    Depending on the context, different scales are used to represent audio volume. All Qt Multimedia
+    classes that have an audio volume use a linear scale, the reason is that the loudness of a
+    speaker is controlled by modulating its voltage on a linear scale. The human ear on the other
+    hand, perceives loudness in a logarithmic way. Using a logarithmic scale for volume controls
+    is therefore appropriate in most applications. The decibel scale is logarithmic by nature and
+    is commonly used to define sound levels, it is usually used for UI volume controls in
+    professional audio applications. The cubic scale is a computationally cheap approximation of a
+    logarithmic scale, it provides more control over lower volume levels.
+
+    The following example shows how to convert the volume value from a slider control before passing
+    it to a QMediaPlayer. As a result, the perceived increase in volume is the same when increasing
+    the volume slider from 20 to 30 as it is from 50 to 60:
+
+    \snippet multimedia-snippets/audio.cpp Volume conversion
+
+    \sa VolumeScale, QAudioSink::setVolume(), QAudioSource::setVolume(),
+    QSoundEffect::setVolume()
+*/
+float convertVolume(float volume, VolumeScale from, VolumeScale to)
+{
+    switch (from) {
+    case LinearVolumeScale:
+        volume = qMax(float(0), volume);
+        switch (to) {
+        case LinearVolumeScale:
+            return volume;
+        case CubicVolumeScale:
+            return qPow(volume, float(1 / 3.0));
+        case LogarithmicVolumeScale:
+            return 1 - std::exp(-volume * LOG100);
+        case DecibelVolumeScale:
+            if (volume < 0.001)
+                return float(-200);
+            else
+                return float(20.0) * std::log10(volume);
+        }
+        break;
+    case CubicVolumeScale:
+        volume = qMax(float(0), volume);
+        switch (to) {
+        case LinearVolumeScale:
+            return volume * volume * volume;
+        case CubicVolumeScale:
+            return volume;
+        case LogarithmicVolumeScale:
+            return 1 - std::exp(-volume * volume * volume * LOG100);
+        case DecibelVolumeScale:
+            if (volume < 0.001)
+                return float(-200);
+            else
+                return float(3.0 * 20.0) * std::log10(volume);
+        }
+        break;
+    case LogarithmicVolumeScale:
+        volume = qMax(float(0), volume);
+        switch (to) {
+        case LinearVolumeScale:
+            if (volume > 0.99)
+                return 1;
+            else
+                return -std::log(1 - volume) / LOG100;
+        case CubicVolumeScale:
+            if (volume > 0.99)
+                return 1;
+            else
+                return qPow(-std::log(1 - volume) / LOG100, float(1 / 3.0));
+        case LogarithmicVolumeScale:
+            return volume;
+        case DecibelVolumeScale:
+            if (volume < 0.001)
+                return float(-200);
+            else if (volume > 0.99)
+                return 0;
+            else
+                return float(20.0) * std::log10(-std::log(1 - volume) / LOG100);
+        }
+        break;
+    case DecibelVolumeScale:
+        switch (to) {
+        case LinearVolumeScale:
+            return qPow(float(10.0), volume / float(20.0));
+        case CubicVolumeScale:
+            return qPow(float(10.0), volume / float(3.0 * 20.0));
+        case LogarithmicVolumeScale:
+            if (qFuzzyIsNull(volume))
+                return 1;
+            else
+                return 1 - std::exp(-qPow(float(10.0), volume / float(20.0)) * LOG100);
+        case DecibelVolumeScale:
+            return volume;
+        }
+        break;
+    }
+
+    return volume;
+}
+
+}
+
+#ifndef QT_NO_DEBUG_STREAM
+QDebug operator<<(QDebug dbg, QAudio::Error error)
+{
+    QDebugStateSaver saver(dbg);
+    dbg.nospace();
+    switch (error) {
+        case QAudio::NoError:
+            dbg << "NoError";
+            break;
+        case QAudio::OpenError:
+            dbg << "OpenError";
+            break;
+        case QAudio::IOError:
+            dbg << "IOError";
+            break;
+        case QAudio::UnderrunError:
+            dbg << "UnderrunError";
+            break;
+        case QAudio::FatalError:
+            dbg << "FatalError";
+            break;
+    }
+    return dbg;
+}
+
+QDebug operator<<(QDebug dbg, QAudio::State state)
+{
+    QDebugStateSaver saver(dbg);
+    dbg.nospace();
+    switch (state) {
+        case QAudio::ActiveState:
+            dbg << "ActiveState";
+            break;
+        case QAudio::SuspendedState:
+            dbg << "SuspendedState";
+            break;
+        case QAudio::StoppedState:
+            dbg << "StoppedState";
+            break;
+        case QAudio::IdleState:
+            dbg << "IdleState";
+            break;
+    }
+    return dbg;
+}
+
+QDebug operator<<(QDebug dbg, QAudio::VolumeScale scale)
+{
+    QDebugStateSaver saver(dbg);
+    dbg.nospace();
+    switch (scale) {
+    case QAudio::LinearVolumeScale:
+        dbg << "LinearVolumeScale";
+        break;
+    case QAudio::CubicVolumeScale:
+        dbg << "CubicVolumeScale";
+        break;
+    case QAudio::LogarithmicVolumeScale:
+        dbg << "LogarithmicVolumeScale";
+        break;
+    case QAudio::DecibelVolumeScale:
+        dbg << "DecibelVolumeScale";
+        break;
+    }
+    return dbg;
+}
+
+#endif
+
+
+QT_END_NAMESPACE
+