Fix orientation

Author: wysaid

src/ccap_imp_windows.cpp

@@ -761,13 +761,24 @@ HRESULT STDMETHODCALLTYPE ProviderDirectShow::SampleCB(double sampleTime, IMedia
             // biHeight may be negative. Negative height indicates top-to-bottom orientation.
             // Positive height indicates bottom-to-top orientation (standard Windows DIB format).
             m_frameProp.height = abs(vih->bmiHeader.biHeight);
-            if (vih->bmiHeader.biHeight < 0) {
+            
+            // For YUV formats, always assume TopToBottom orientation regardless of biHeight
+            // This fixes issues with some virtual cameras (like OBS) that report positive biHeight
+            // but actually deliver TopToBottom data
+            auto info = findPixelFormatInfo(mt.subtype);
+            bool isYUVFormat = (info.pixelFormat & kPixelFormatYUVColorBit) != 0;
+            
+            if (isYUVFormat) {
+                // YUV data is typically TopToBottom, ignore biHeight sign
+                m_inputOrientation = FrameOrientation::TopToBottom;
+                CCAP_LOG_V("ccap: YUV format detected, using TopToBottom orientation (biHeight=%d)\n", vih->bmiHeader.biHeight);
+            } else if (vih->bmiHeader.biHeight < 0) {
                 m_inputOrientation = FrameOrientation::TopToBottom;
             } else {
                 m_inputOrientation = FrameOrientation::BottomToTop;
             }
+            
             m_frameProp.fps = 10000000.0 / vih->AvgTimePerFrame;
-            auto info = findPixelFormatInfo(mt.subtype);
             if (info.pixelFormat != PixelFormat::Unknown) {
                 m_frameProp.cameraPixelFormat = info.pixelFormat;
             }

src/ccap_imp_windows.h

@@ -118,8 +118,9 @@ class ProviderDirectShow : public ProviderImp, public ISampleGrabberCB {
     std::vector<std::string> m_allDeviceNames;
 
     std::chrono::steady_clock::time_point m_startTime{};
-    bool m_firstFrameArrived = false;
     FrameOrientation m_inputOrientation = FrameOrientation::TopToBottom;
+    
+    bool m_firstFrameArrived = false;
 
     // State variables
     bool m_didSetup{ false };