working :)

run.sh

@@ -7,18 +7,18 @@ Y=70
 convert \
 	-background none -fill black \
 	-pointsize 60 -size ${X}x${Y} -gravity center \
-	label:TEST1 mask.png
+	label:123456 mask.png
 
 # Create large static image
 convert -size 2000x${Y} canvas: +noise Random -monochrome -alpha off background.png
 
 # Create video
-ffmpeg -y -framerate 60 -loop true -t 10 -i background.png -i mask.png \
+ffmpeg -loglevel error -hide_banner -y -framerate 60 -loop true -t 10 -i background.png -i mask.png \
 	-filter_complex "
-		[0] crop=x=n:w=${X}:h=${Y} [bg];
-		[0] crop=x=out_w-n:w=${X}:h=${Y} [fg];
+		[0] crop=x=n:w=${X}:h=${Y},split[bg][a];
+		[a] hflip [flip];
 		[1] alphaextract [mask];
-		[fg][mask] alphamerge [text];
+		[flip][mask] alphamerge [text];
 		[bg][text] overlay"\
 	-c:v libx264 -crf 10 -an out.mp4