diff --git a/sw/airborne/modules/computer_vision/cv/resize.h b/sw/airborne/modules/computer_vision/cv/resize.h
index 22f06888cf..b0524a5270 100644
--- a/sw/airborne/modules/computer_vision/cv/resize.h
+++ b/sw/airborne/modules/computer_vision/cv/resize.h
@@ -23,26 +23,39 @@
 #include <stdint.h>
 #include "image.h"
 
+/** Simplified high-speed low CPU downsample function without averaging
+ *
+ *  downsample factor must be 1, 2, 4, 8 ... 2^X
+ *  image of typ UYVY expected. Only one color UV per 2 pixels
+ *
+ *  we keep the UV color of the first pixel pair
+ *  and sample the intensity evenly 1-3-5-7-... or 1-5-9-...
+ *
+ *  input:         u1y1 v1y2 u3y3 v3y4 u5y5 v5y6 u7y7 v7y8 ...
+ *  downsample=1   u1y1 v1y2 u3y3 v3y4 u5y5 v5y6 u7y7 v7y8 ...
+ *  downsample=2   u1y1v1 (skip2) y3 (skip2) u5y5v5 (skip2 y7 (skip2) ...
+ *  downsample=4   u1y1v1 (skip6) y5 (skip6) ...
+ */
+
 inline void resize_uyuv(struct img_struct *input, struct img_struct *output, int downsample);
 inline void resize_uyuv(struct img_struct *input, struct img_struct *output, int downsample)
 {
   uint8_t *source = input->buf;
   uint8_t *dest = output->buf;
 
-  int pixelskip = downsample - 1;
+  int pixelskip = (downsample - 1) * 2;
   for (int y = 0; y < output->h; y++) {
     for (int x = 0; x < output->w; x += 2) {
       // YUYV
       *dest++ = *source++; // U
       *dest++ = *source++; // Y
-      // now skip 3 pixels
-      source += (pixelskip + 1) * 2;
-      *dest++ = *source++; // U
       *dest++ = *source++; // V
-      source += (pixelskip - 1) * 2;
+      source += pixelskip;
+      *dest++ = *source++; // Y
+      source += pixelskip;
     }
-    // skip 3 rows
-    source += pixelskip * input->w * 2;
+    // read 1 in every 'downsample' rows, so skip (downsample-1) rows after reading the first
+    source += (downsample-1) * input->w * 2;
   }
 }