PulseAudio: change the way volume is applied.

We used to change the PulseAudio sink input volume. Doing so had
some potential unwanted side effects depending on the PulseAudio server
configuration. When flat volumes were enabled, it would affect the
global system volume. It could also affect the volume of other streams
having the same audio role.
Volumes in Qt Multimedia are supposed to be relative to the application
volume and should not affect anything else than the object on which it
was changed. To guarantee that, PulseAudio volume APIs are not used
anymore. Instead, software-based volume attenuation is applied on the
audio samples before being passed to PulseAudio.

Applies to QSoundEffect, QAudioOutput and QAudioInput.

Task-number: QTBUG-40823
Task-number: QTBUG-49461
Change-Id: I690716976bda8fe666969ca2cbdf6d8d0b419733
Reviewed-by: Christian Stromme <christian.stromme@theqtcompany.com>

1 files changed, 22 insertions, 77 deletions

diff --git a/src/plugins/pulseaudio/qaudioinput_pulse.cpp b/src/plugins/pulseaudio/qaudioinput_pulse.cpp
index 77b438ff9..93d410598 100644
--- a/src/plugins/pulseaudio/qaudioinput_pulse.cpp
+++ b/src/plugins/pulseaudio/qaudioinput_pulse.cpp
@@ -34,6 +34,7 @@
 #include <QtCore/qcoreapplication.h>
 #include <QtCore/qdebug.h>
 #include <QtCore/qmath.h>
+#include <private/qaudiohelpers_p.h>
 
 #include "qaudioinput_pulse.h"
 #include "qaudiodeviceinfo_pulse.h"
@@ -118,39 +119,12 @@ static void inputStreamSuccessCallback(pa_stream *stream, int success, void *use
     pa_threaded_mainloop_signal(pulseEngine->mainloop(), 0);
 }
 
-void QPulseAudioInput::sourceInfoCallback(pa_context *context, const pa_source_info *i, int eol, void *userdata)
-{
-    Q_UNUSED(context);
-    Q_UNUSED(eol);
-
-    Q_ASSERT(userdata);
-    if (i) {
-        QPulseAudioInput *that = reinterpret_cast<QPulseAudioInput*>(userdata);
-        that->m_volume = pa_sw_volume_to_linear(pa_cvolume_avg(&i->volume));
-    }
-}
-
-void QPulseAudioInput::inputVolumeCallback(pa_context *context, int success, void *userdata)
-{
-    Q_UNUSED(success);
-
-    if (!success)
-        qWarning() << "QAudioInput: failed to set input volume";
-
-    QPulseAudioInput *that = reinterpret_cast<QPulseAudioInput*>(userdata);
-
-    // Regardless of success or failure, we update the volume property
-    if (that->m_stream)
-        pa_context_get_source_info_by_index(context, pa_stream_get_device_index(that->m_stream), sourceInfoCallback, userdata);
-}
-
 QPulseAudioInput::QPulseAudioInput(const QByteArray &device)
     : m_totalTimeValue(0)
     , m_audioSource(0)
     , m_errorState(QAudio::NoError)
     , m_deviceState(QAudio::StoppedState)
     , m_volume(qreal(1.0f))
-    , m_customVolumeRequired(false)
     , m_pullMode(true)
     , m_opened(false)
     , m_bytesAvailable(0)
@@ -356,9 +330,6 @@ bool QPulseAudioInput::open()
     if (actualBufferAttr->tlength != (uint32_t)-1)
         m_bufferSize = actualBufferAttr->tlength;
 
-    if (m_customVolumeRequired)
-        setPulseVolume();
-
     pulseEngine->unlock();
 
     connect(pulseEngine, &QPulseAudioEngine::contextFailed, this, &QPulseAudioInput::onPulseContextFailed);
@@ -407,32 +378,6 @@ void QPulseAudioInput::close()
     m_opened = false;
 }
 
-/* Call this with the stream opened and the mainloop locked */
-void QPulseAudioInput::setPulseVolume()
-{
-    QPulseAudioEngine *pulseEngine = QPulseAudioEngine::instance();
-    Q_ASSERT(pulseEngine->context() != 0);
-
-    pa_cvolume cvolume;
-
-    if (qFuzzyCompare(m_volume, 0.0)) {
-        pa_cvolume_mute(&cvolume, m_spec.channels);
-    } else {
-        pa_cvolume_set(&cvolume, m_spec.channels, pa_sw_volume_from_linear(m_volume));
-    }
-
-    pa_operation *op = pa_context_set_source_volume_by_index(pulseEngine->context(),
-            pa_stream_get_device_index(m_stream),
-            &cvolume,
-            inputVolumeCallback,
-            this);
-
-    if (op == NULL)
-        qWarning() << "QAudioInput: Failed to set volume";
-    else
-        pa_operation_unref(op);
-}
-
 int QPulseAudioInput::checkBytesReady()
 {
     if (m_deviceState != QAudio::ActiveState && m_deviceState != QAudio::IdleState) {
@@ -494,7 +439,9 @@ qint64 QPulseAudioInput::read(char *data, qint64 len)
 
         qint64 actualLength = 0;
         if (m_pullMode) {
-            actualLength = m_audioSource->write(static_cast<const char *>(audioBuffer), readLength);
+            QByteArray adjusted(readLength, Qt::Uninitialized);
+            applyVolume(audioBuffer, adjusted.data(), readLength);
+            actualLength = m_audioSource->write(adjusted);
 
             if (actualLength < qint64(readLength)) {
                 pulseEngine->unlock();
@@ -506,7 +453,7 @@ qint64 QPulseAudioInput::read(char *data, qint64 len)
             }
         } else {
             actualLength = qMin(static_cast<int>(len - readBytes), static_cast<int>(readLength));
-            memcpy(data + readBytes, audioBuffer, actualLength);
+            applyVolume(audioBuffer, data + readBytes, actualLength);
         }
 
 #ifdef DEBUG_PULSE
@@ -517,7 +464,10 @@ qint64 QPulseAudioInput::read(char *data, qint64 len)
 #ifdef DEBUG_PULSE
             qDebug() << "QPulseAudioInput::read -- appending " << readLength - actualLength << " bytes of data to temp buffer";
 #endif
-            m_tempBuffer.append(static_cast<const char *>(audioBuffer) + actualLength, readLength - actualLength);
+            int diff = readLength - actualLength;
+            int oldSize = m_tempBuffer.size();
+            m_tempBuffer.resize(m_tempBuffer.size() + diff);
+            applyVolume(static_cast<const char *>(audioBuffer) + actualLength, m_tempBuffer.data() + oldSize, diff);
             QMetaObject::invokeMethod(this, "userFeed", Qt::QueuedConnection);
         }
 
@@ -544,6 +494,14 @@ qint64 QPulseAudioInput::read(char *data, qint64 len)
     return readBytes;
 }
 
+void QPulseAudioInput::applyVolume(const void *src, void *dest, int len)
+{
+    if (m_volume < 1.f)
+        QAudioHelperInternal::qMultiplySamples(m_volume, m_format, src, dest, len);
+    else
+        memcpy(dest, src, len);
+}
+
 void QPulseAudioInput::resume()
 {
     if (m_deviceState == QAudio::SuspendedState || m_deviceState == QAudio::IdleState) {
@@ -567,30 +525,17 @@ void QPulseAudioInput::resume()
 
 void QPulseAudioInput::setVolume(qreal vol)
 {
-    if (vol >= 0.0 && vol <= 1.0) {
-        QPulseAudioEngine *pulseEngine = QPulseAudioEngine::instance();
-        pulseEngine->lock();
-        m_customVolumeRequired = true;
-        if (!qFuzzyCompare(m_volume, vol)) {
-            m_volume = vol;
-            if (m_opened) {
-                setPulseVolume();
-            }
-        }
-        pulseEngine->unlock();
-    }
+    if (qFuzzyCompare(m_volume, vol))
+        return;
+
+    m_volume = qBound(qreal(0), vol, qreal(1));
 }
 
 qreal QPulseAudioInput::volume() const
 {
-    QPulseAudioEngine *pulseEngine = QPulseAudioEngine::instance();
-    pulseEngine->lock();
-    qreal vol = m_volume;
-    pulseEngine->unlock();
-    return vol;
+    return m_volume;
 }
 
-
 void QPulseAudioInput::setBufferSize(int value)
 {
     m_bufferSize = value;