AVFoundation: correctly set the activeFormat on the AVCaptureDevice.

According to the AVCaptureDevice documentation, the device must be
locked before starting the capture session to prevent the activeFormat
from being overridden. We now do that, but only if we explicitly set
an activeFormat. Otherwise the device is not locked, which allows
the session to find an appropriate format for the capture device.
The device is also locked when enabling video capture, as doing so
might also reset the activeFormat.

Task-number: QTBUG-49170
Change-Id: I75478fd4bbfec96cd2abd2c3ae2951088b38978e
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@theqtcompany.com>

1 files changed, 13 insertions, 17 deletions

diff --git a/src/plugins/avfoundation/camera/avfcameraviewfindersettingscontrol.mm b/src/plugins/avfoundation/camera/avfcameraviewfindersettingscontrol.mm
index 95fadb816..3c20801e5 100644
--- a/src/plugins/avfoundation/camera/avfcameraviewfindersettingscontrol.mm
+++ b/src/plugins/avfoundation/camera/avfcameraviewfindersettingscontrol.mm
@@ -384,11 +384,6 @@ QCameraViewfinderSettings AVFCameraViewfinderSettingsControl2::viewfinderSetting
 
 void AVFCameraViewfinderSettingsControl2::setViewfinderSettings(const QCameraViewfinderSettings &settings)
 {
-    if (settings.isNull()) {
-        qDebugCamera() << Q_FUNC_INFO << "empty viewfinder settings";
-        return;
-    }
-
     if (m_settings == settings)
         return;
 
@@ -454,7 +449,7 @@ bool AVFCameraViewfinderSettingsControl2::CVPixelFormatFromQtFormat(QVideoFrame:
 AVCaptureDeviceFormat *AVFCameraViewfinderSettingsControl2::findBestFormatMatch(const QCameraViewfinderSettings &settings) const
 {
     AVCaptureDevice *captureDevice = m_service->session()->videoCaptureDevice();
-    if (!captureDevice)
+    if (!captureDevice || settings.isNull())
         return nil;
 
 #if QT_MAC_PLATFORM_SDK_EQUAL_OR_ABOVE(__MAC_10_7, __IPHONE_7_0)
@@ -553,32 +548,30 @@ bool AVFCameraViewfinderSettingsControl2::convertPixelFormatIfSupported(QVideoFr
     return found;
 }
 
-void AVFCameraViewfinderSettingsControl2::applySettings()
+bool AVFCameraViewfinderSettingsControl2::applySettings()
 {
-    if (m_settings.isNull())
-        return;
-
     if (m_service->session()->state() != QCamera::LoadedState &&
         m_service->session()->state() != QCamera::ActiveState) {
-        return;
+        return false;
     }
 
     AVCaptureDevice *captureDevice = m_service->session()->videoCaptureDevice();
     if (!captureDevice)
-        return;
+        return false;
+
+    bool activeFormatChanged = false;
 
-    NSMutableDictionary *videoSettings = [NSMutableDictionary dictionaryWithCapacity:1];
 #if QT_MAC_PLATFORM_SDK_EQUAL_OR_ABOVE(__MAC_10_7, __IPHONE_7_0)
     AVCaptureDeviceFormat *match = findBestFormatMatch(m_settings);
     if (match) {
         if (match != captureDevice.activeFormat) {
             const AVFConfigurationLock lock(captureDevice);
-            if (!lock) {
+            if (lock) {
+                captureDevice.activeFormat = match;
+                activeFormatChanged = true;
+            } else {
                 qDebugCamera() << Q_FUNC_INFO << "failed to lock for configuration";
-                return;
             }
-
-            captureDevice.activeFormat = match;
         }
     } else {
         qDebugCamera() << Q_FUNC_INFO << "matching device format not found";
@@ -617,6 +610,7 @@ void AVFCameraViewfinderSettingsControl2::applySettings()
         }
 
         if (avfPixelFormat != 0) {
+            NSMutableDictionary *videoSettings = [NSMutableDictionary dictionaryWithCapacity:1];
             [videoSettings setObject:[NSNumber numberWithUnsignedInt:avfPixelFormat]
                                       forKey:(id)kCVPixelBufferPixelFormatTypeKey];
 
@@ -625,6 +619,8 @@ void AVFCameraViewfinderSettingsControl2::applySettings()
     }
 
     qt_set_framerate_limits(captureDevice, videoConnection(), m_settings);
+
+    return activeFormatChanged;
 }
 
 QCameraViewfinderSettings AVFCameraViewfinderSettingsControl2::requestedSettings() const