Detect DirectShow bottom-up frames by format

Author: richiemcilroy

crates/camera-windows/src/lib.rs

@@ -367,7 +367,7 @@ impl VideoDeviceInfo {
                         };
 
                         let bi_height = video_info.bmiHeader.biHeight;
-                        let is_bottom_up = bi_height > 0;
+                        let is_bottom_up = directshow_frame_is_bottom_up(format, bi_height);
                         let height = bi_height.unsigned_abs() as usize;
 
                         callback(Frame {
@@ -503,6 +503,10 @@ impl PixelFormat {
     }
 }
 
+fn directshow_frame_is_bottom_up(pixel_format: PixelFormat, bi_height: i32) -> bool {
+    bi_height > 0 && pixel_format.is_traditionally_bottom_up()
+}
+
 #[derive(Clone)]
 enum VideoDeviceInfoInner {
     MediaFoundation {
@@ -706,18 +710,19 @@ impl VideoFormat {
         }
 
         let video_info = unsafe { inner.video_info() };
+        let pixel_format = DSPixelFormat::new(&inner)
+            .ok_or(VideoFormatError::InvalidPixelFormat(inner.subtype))?
+            .format;
         let bi_height = video_info.bmiHeader.biHeight;
-        let is_bottom_up = bi_height > 0;
+        let is_bottom_up = directshow_frame_is_bottom_up(pixel_format, bi_height);
         let height = bi_height.unsigned_abs();
 
         Ok(VideoFormat {
             width: video_info.bmiHeader.biWidth as u32,
             height,
             frame_rate: ((10_000_000.0 / video_info.AvgTimePerFrame as f32) * 100.0).round()
                 / 100.0,
-            pixel_format: DSPixelFormat::new(&inner)
-                .ok_or(VideoFormatError::InvalidPixelFormat(inner.subtype))?
-                .format,
+            pixel_format,
             is_bottom_up,
             inner: VideoFormatInner::DirectShow(inner),
         })
@@ -817,3 +822,24 @@ impl DSPixelFormat {
         })
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::{PixelFormat, directshow_frame_is_bottom_up};
+
+    #[test]
+    fn directshow_rgb_with_positive_height_is_bottom_up() {
+        assert!(directshow_frame_is_bottom_up(PixelFormat::RGB32, 1080));
+    }
+
+    #[test]
+    fn directshow_yuv_with_positive_height_is_not_bottom_up() {
+        assert!(!directshow_frame_is_bottom_up(PixelFormat::YUYV422, 1080));
+        assert!(!directshow_frame_is_bottom_up(PixelFormat::NV12, 1080));
+    }
+
+    #[test]
+    fn directshow_negative_height_is_not_bottom_up() {
+        assert!(!directshow_frame_is_bottom_up(PixelFormat::RGB32, -1080));
+    }
+}