diff --git a/Filter.md b/Filter.md
index c955fd7..fbc0ddb 100644
--- a/Filter.md
+++ b/Filter.md
@@ -137,7 +137,7 @@ rgaoverlay AVOptions:
 
 ---
 
-* `overlay_rkrga` (Put the 540p image on top of 1080p image and center it. The main image can be YUV or RGB, overlay image must be RGB)
+* `overlay_rkrga` (Put the 540p image on top of 1080p image and center it. The main image can be YUV or RGB, overlay image MUST be RGB)
 ```shell
 ./ffmpeg -init_hw_device rkmpp=hw -filter_hw_device hw -f lavfi -i color=c=cyan:s=1920x1080,format=nv12 -f lavfi -i testsrc2=s=960x540,format=bgra \
 -filter_complex "[0:v]hwupload[main];[1:v]hwupload[overlay];[main][overlay]overlay_rkrga=eof_action=pass:repeatlast=0:format=nv12:x=(W-w)/2:y=(H-h)/2" \