Fix redundant warning output on macOS

Redundant warnings were reproduced with specific installed sowtware,
e.g. Soundflower. The software is able to create 64 audio channels and
customize them. Basically, all the channels have unknown label,
so we should filter the warnings.

The logic of channels detection is not changed: only a little bit
refactored.

See dump of audio channels on client's PC:
bugreports.qt.io/secure/attachment/132568/dump_audio_res2.txt

Pick-to: 6.4
Task-number: QTBUG-107678
Change-Id: I85b63d39b71aa09b28d47bf5bf7d40d1e8a1328b
Reviewed-by: Doris Verria <doris.verria@qt.io>

2 files changed, 19 insertions, 11 deletions

diff --git a/src/multimedia/audio/qaudiodevice_p.h b/src/multimedia/audio/qaudiodevice_p.h
index ff9d061da..575a9edc5 100644
--- a/src/multimedia/audio/qaudiodevice_p.h
+++ b/src/multimedia/audio/qaudiodevice_p.h
@@ -40,7 +40,7 @@ public:
     int minimumChannelCount = 0;
     int maximumChannelCount = 0;
     QList<QAudioFormat::SampleFormat> supportedSampleFormats;
-    QAudioFormat::ChannelConfig channelConfiguration;
+    QAudioFormat::ChannelConfig channelConfiguration = QAudioFormat::ChannelConfigUnknown;
 
     QAudioDevice create() { return QAudioDevice(this); }
 };
diff --git a/src/multimedia/darwin/qcoreaudioutils.mm b/src/multimedia/darwin/qcoreaudioutils.mm
index f8095b2b9..369adad24 100644
--- a/src/multimedia/darwin/qcoreaudioutils.mm
+++ b/src/multimedia/darwin/qcoreaudioutils.mm
@@ -232,19 +232,27 @@ QAudioFormat::ChannelConfig CoreAudioUtils::fromAudioChannelLayout(const AudioCh
             return QAudioFormat::ChannelConfigStereo;
 
         for (uint i = 0; i < layout->mNumberChannelDescriptions; ++i) {
-            bool found = false;
-            for (const auto &m : channelMap) {
-                if (layout->mChannelDescriptions[i].mChannelLabel == m.label) {
-                    channels |= QAudioFormat::channelConfig(m.pos);
-                    found = true;
-                    break;
-                }
+            const auto channelLabel = layout->mChannelDescriptions[i].mChannelLabel;
+            if (channelLabel == kAudioChannelLabel_Unknown) {
+                // Any number of unknown channel labels occurs for loopback audio devices.
+                // E.g. the case is reproduced with installed software Soundflower.
+                continue;
             }
-            if (!found)
-                qWarning() << "audio device has unknown channel" << layout->mChannelDescriptions[i].mChannelLabel;
+
+            const auto found = std::find_if(channelMap, std::end(channelMap),
+                                            [channelLabel](const auto &labelWithPos) {
+                                                return labelWithPos.label == channelLabel;
+                                            });
+
+            if (found == std::end(channelMap))
+                qWarning() << "audio device has unrecognized channel, index:" << i
+                           << "label:" << channelLabel;
+            else
+                channels |= QAudioFormat::channelConfig(found->pos);
         }
     } else {
-        qWarning() << "Channel layout uses unimplemented format";
+        qWarning() << "Channel layout uses unimplemented format, channelLayoutTag:"
+                   << layout->mChannelLayoutTag;
     }
     return QAudioFormat::ChannelConfig(channels);
 }