GStreamer: use alsasrc/sink when configured for alsa

When configured for alsa, the gstreamer backend used to crash, since
casted to `QGStreamerAudioDeviceInfo`, which was never used. We avoid
this codepath and tirectly construct the alsasrc/alsasink and set the
intendend device explicitly.

Fixes: QTBUG-125080
Pick-to: 6.5 6.7
Change-Id: I95b383df88b8b36de3bc396447176826eae6880d
Reviewed-by: Artem Dyomin <artem.dyomin@qt.io>

2 files changed, 27 insertions, 12 deletions

diff --git a/src/plugins/multimedia/gstreamer/common/qgstreameraudioinput.cpp b/src/plugins/multimedia/gstreamer/common/qgstreameraudioinput.cpp
index 0381b921e..59d40097e 100644
--- a/src/plugins/multimedia/gstreamer/common/qgstreameraudioinput.cpp
+++ b/src/plugins/multimedia/gstreamer/common/qgstreameraudioinput.cpp
@@ -67,21 +67,29 @@ void QGstreamerAudioInput::setAudioDevice(const QAudioDevice &device)
         return;
     qCDebug(qLcMediaAudioInput) << "setAudioInput" << device.description() << device.isNull();
     m_audioDevice = device;
+    const QByteArray &id = m_audioDevice.id();
 
     QGstElement newSrc;
     if constexpr (QT_CONFIG(pulseaudio)) {
-        auto id = m_audioDevice.id();
         newSrc = QGstElement::createFromFactory("pulsesrc", "audiosrc");
-        if (!newSrc.isNull())
+        if (newSrc)
             newSrc.set("device", id.constData());
         else
-            qCWarning(qLcMediaAudioInput) << "Invalid audio device";
-    } else {
-        auto *deviceInfo = static_cast<const QGStreamerAudioDeviceInfo *>(m_audioDevice.handle());
-        if (deviceInfo && deviceInfo->gstDevice)
-            newSrc = QGstElement::createFromDevice(deviceInfo->gstDevice, "audiosrc");
+            qCWarning(qLcMediaAudioInput) << "Cannot create pulsesrc";
+    } else if constexpr (QT_CONFIG(alsa)) {
+        newSrc = QGstElement::createFromFactory("alsasrc", "audiosrc");
+        if (newSrc)
+            newSrc.set("device", id.constData());
         else
+            qCWarning(qLcMediaAudioInput) << "Cannot create alsasrc";
+    } else {
+        auto *gstDeviceInfo =
+                dynamic_cast<const QGStreamerAudioDeviceInfo *>(m_audioDevice.handle());
+        if (gstDeviceInfo && gstDeviceInfo->gstDevice) {
+            newSrc = QGstElement::createFromDevice(gstDeviceInfo->gstDevice, "audiosrc");
+        } else {
             qCWarning(qLcMediaAudioInput) << "Invalid audio device";
+        }
     }
 
     if (newSrc.isNull()) {
diff --git a/src/plugins/multimedia/gstreamer/common/qgstreameraudiooutput.cpp b/src/plugins/multimedia/gstreamer/common/qgstreameraudiooutput.cpp
index f45c371e9..2ad619fb2 100644
--- a/src/plugins/multimedia/gstreamer/common/qgstreameraudiooutput.cpp
+++ b/src/plugins/multimedia/gstreamer/common/qgstreameraudiooutput.cpp
@@ -74,17 +74,23 @@ void QGstreamerAudioOutput::setAudioDevice(const QAudioDevice &info)
         return;
     qCDebug(qLcMediaAudioOutput) << "setAudioOutput" << info.description() << info.isNull();
     m_audioOutput = info;
+    const QByteArray &id = m_audioOutput.id();
 
     QGstElement newSink;
     if constexpr (QT_CONFIG(pulseaudio)) {
-        auto id = m_audioOutput.id();
         newSink = QGstElement::createFromFactory("pulsesink", "audiosink");
-        if (!newSink.isNull())
+        if (newSink)
             newSink.set("device", id.constData());
         else
-            qCWarning(qLcMediaAudioOutput) << "Invalid audio device";
+            qCWarning(qLcMediaAudioOutput) << "Cannot create pulsesink";
+    } else if constexpr (QT_CONFIG(alsa)) {
+        newSink = QGstElement::createFromFactory("alsasink", "audiosink");
+        if (newSink)
+            newSink.set("device", id.constData());
+        else
+            qCWarning(qLcMediaAudioOutput) << "Cannot create alsasink";
     } else {
-        auto *deviceInfo = static_cast<const QGStreamerAudioDeviceInfo *>(m_audioOutput.handle());
+        auto *deviceInfo = dynamic_cast<const QGStreamerAudioDeviceInfo *>(m_audioOutput.handle());
         if (deviceInfo && deviceInfo->gstDevice)
             newSink = QGstElement::createFromDevice(deviceInfo->gstDevice, "audiosink");
         else
@@ -92,7 +98,8 @@ void QGstreamerAudioOutput::setAudioDevice(const QAudioDevice &info)
     }
 
     if (newSink.isNull()) {
-        qCWarning(qLcMediaAudioOutput) << "Failed to create a gst element for the audio device, using a default audio sink";
+        qCWarning(qLcMediaAudioOutput) << "Failed to create a gst element for the audio "
+                                          "device using a default audio sink";
         newSink = QGstElement::createFromFactory("autoaudiosink", "audiosink");
     }