error message for decoding image

filter/knn.go

@@ -29,6 +29,7 @@ LICENSE
 package filter
 
 import (
+	"fmt"
 	"image"
 	"image/color"
 	"io"
@@ -74,7 +75,10 @@ func (m *KNNFilter) Close() error {
 // Write applies the motion filter to the video stream. Only frames with motion
 // are written to the destination encoder, frames without are discarded.
 func (m *KNNFilter) Write(f []byte) (int, error) {
-	img, _ := gocv.IMDecode(f, gocv.IMReadColor)
+	img, err := gocv.IMDecode(f, gocv.IMReadColor)
+	if err != nil {
+		return 0, fmt.Errorf("can't decode image: %w", err)
+	}
 	defer img.Close()
 
 	imgDelta := gocv.NewMat()