CoreAudio: fix supported channel count.

We were using the number of channels actually used by audio devices as
the maximum channel count. This is wrong as CoreAudio can automatically
split or merge channels in order to accommodate the device.
We now assume all channel configurations are valid.

Task-number: QTBUG-37956
Change-Id: Ia8e8bbea8543caa7fecda305be74a2953b92fd25
Reviewed-by: Andy Nichols <andy.nichols@digia.com>

src/plugins/coreaudio/coreaudiodeviceinfo.mm

@@ -196,38 +196,14 @@ QList<int> CoreAudioDeviceInfo::supportedSampleRates()
 
 QList<int> CoreAudioDeviceInfo::supportedChannelCounts()
 {
-    QList<int> supportedChannels;
+    static QList<int> supportedChannels;
-    int maxChannels = 0;
 
-#if defined(Q_OS_OSX)
+    if (supportedChannels.isEmpty()) {
-    UInt32 propSize = 0;
+        // If the number of channels is not supported by an audio device, Core Audio will
-    AudioObjectPropertyScope scope = m_mode == QAudio::AudioInput ? kAudioDevicePropertyScopeInput : kAudioDevicePropertyScopeOutput;
+        // automatically convert the audio data.
-    AudioObjectPropertyAddress streamConfigurationPropertyAddress = { kAudioDevicePropertyStreamConfiguration,
+        for (int i = 1; i <= 16; ++i)
-                                                                      scope,
+            supportedChannels.append(i);
-                                                                      kAudioObjectPropertyElementMaster };
-
-    if (AudioObjectGetPropertyDataSize(m_deviceId, &streamConfigurationPropertyAddress, 0, NULL, &propSize) == noErr) {
-        AudioBufferList* audioBufferList = static_cast<AudioBufferList*>(malloc(propSize));
-
-        if (audioBufferList != 0) {
-            if (AudioObjectGetPropertyData(m_deviceId, &streamConfigurationPropertyAddress, 0, NULL, &propSize, audioBufferList) == noErr) {
-                for (int i = 0; i < int(audioBufferList->mNumberBuffers); ++i)
-                    maxChannels += audioBufferList->mBuffers[i].mNumberChannels;
-            }
-
-            free(audioBufferList);
-        }
     }
-#else //iOS
-    if (m_mode == QAudio::AudioInput)
-        maxChannels = CoreAudioSessionManager::instance().inputChannelCount();
-    else if (m_mode == QAudio::AudioOutput)
-        maxChannels = CoreAudioSessionManager::instance().outputChannelCount();
-#endif
-
-    // Assume all channel configurations are supported up to the maximum number of channels
-    for (int i = 1; i <= maxChannels; ++i)
-        supportedChannels.append(i);
 
     return supportedChannels;
 }

src/plugins/coreaudio/coreaudiosessionmanager.h

@@ -92,9 +92,6 @@ public:
     QList<QByteArray> inputDevices();
     QList<QByteArray> outputDevices();
 
-    int inputChannelCount();
-    int outputChannelCount();
-
     float currentIOBufferDuration();
     float preferredSampleRate();
 

src/plugins/coreaudio/coreaudiosessionmanager.mm

@@ -377,16 +377,6 @@ QList<QByteArray> CoreAudioSessionManager::outputDevices()
     return outputDevices;
 }
 
-int CoreAudioSessionManager::inputChannelCount()
-{
-    return [[m_sessionObserver audioSession] inputNumberOfChannels];
-}
-
-int CoreAudioSessionManager::outputChannelCount()
-{
-    return [[m_sessionObserver audioSession] outputNumberOfChannels];
-}
-
 float CoreAudioSessionManager::currentIOBufferDuration()
 {
     return [[m_sessionObserver audioSession] IOBufferDuration];