Fix GetFrameRateList checks and memory leak

GetFrameRateList passes an unmanaged pointer to the caller which must be
manually freed with CoTaskMemFree. Additionally the Chromium project
notes that some drivers cause quirky return values which we would not
catch without stricter checks. See: https://chromium.googlesource.com/chromium/src/media/+/8cc93abd7339eeb9b7c2a12cca07b3dc245b2139/video/capture/win/video_capture_device_win.cc#484

Change-Id: I6aa4a6ea1ac0241e585e98cf9ff63240bacd3956
Reviewed-by: Christian Strømme <christian.stromme@qt.io>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/plugins/directshow/camera/dscamerasession.cpp b/src/plugins/directshow/camera/dscamerasession.cpp
index 5ab9f67d8..a237811ae 100644
--- a/src/plugins/directshow/camera/dscamerasession.cpp
+++ b/src/plugins/directshow/camera/dscamerasession.cpp
@@ -1137,8 +1137,8 @@ void DSCameraSession::updateSourceCapabilities()
                         long listSize = 0;
                         LONGLONG *frameRates = 0;
                         SIZE size = { resolution.width(), resolution.height() };
-                        if (SUCCEEDED(pVideoControl->GetFrameRateList(pPin, iIndex, size,
-                                                                      &listSize, &frameRates))) {
+                        hr = pVideoControl->GetFrameRateList(pPin, iIndex, size, &listSize, &frameRates);
+                        if (hr == S_OK && listSize > 0 && frameRates) {
                             for (long i = 0; i < listSize; ++i) {
                                 qreal fr = qreal(10000000) / frameRates[i];
                                 frameRateRanges.append(QCamera::FrameRateRange(fr, fr));
@@ -1147,6 +1147,8 @@ void DSCameraSession::updateSourceCapabilities()
                             // Make sure higher frame rates come first
                             std::sort(frameRateRanges.begin(), frameRateRanges.end(), qt_frameRateRangeGreaterThan);
                         }
+
+                        CoTaskMemFree(frameRates);
                         pPin->Release();
                     }
                 }