diff --git a/spddiff.avs b/spddiff.avs
index 2b8deed..22955a8 100644
--- a/spddiff.avs
+++ b/spddiff.avs
@@ -1,17 +1,23 @@
-function open(string path)
-{ return AviSource(path, audio=false) }
-
 function DiffClip(clip c, int diff)
 { BlankClip(c, diff).Subtitle(String(-diff), align=5, size=c.Height/8) }
 
 function PadWithDiff(clip c, int len)
 { c.FrameCount < len ? c + DiffClip(c, len - c.FrameCount) : c }
 
+function DualMonoToStereo(clip left, clip right)
+{ MergeChannels(ConvertToMono(left), ConvertToMono(right)) }
+
 function MergeHoriz(clip left, clip right)
-{ Overlay(AddBorders(left, 0, 0, right.Width, 0), right, left.Width, 0) }
+{
+	v = Overlay(AddBorders(left, 0, 0, right.Width, 0), right, left.Width, 0)
+	return AudioDub(v, DualMonoToStereo(left, right))
+}
 
 function MergeVert(clip top, clip bottom)
-{ Overlay(AddBorders(top, 0, 0, 0, bottom.Height), bottom, 0, top.Height) }
+{
+	v = Overlay(AddBorders(top, 0, 0, 0, bottom.Height), bottom, 0, top.Height)
+	return AudioDub(v, DualMonoToStereo(top, bottom))
+}
 
 function Cmp(clip left, clip right)
 {
@@ -22,19 +28,19 @@ function Cmp(clip left, clip right)
 }
 
 # http://tasvideos.org/1072S.html
-open("snes9x\Movies\old.avi")+\
-open("snes9x\Movies\old_part2.avi")+\
-open("snes9x\Movies\old_part3.avi")+\
-open("snes9x\Movies\old_part4.avi")
+AviSource("snes9x\Movies\old.avi")+\
+AviSource("snes9x\Movies\old_part2.avi")+\
+AviSource("snes9x\Movies\old_part3.avi")+\
+AviSource("snes9x\Movies\old_part4.avi")
 Trim(0, 38409)
 AddBorders(0,0,16,0)
 global old = last
 
 # http://tasvideos.org/3346S.html
-open("snes9x\Movies\new.avi")+\
-open("snes9x\Movies\new_part5.avi")+\
-open("snes9x\Movies\new_part6.avi")+\
-open("snes9x\Movies\new_part7.avi")
+AviSource("snes9x\Movies\new.avi")+\
+AviSource("snes9x\Movies\new_part5.avi")+\
+AviSource("snes9x\Movies\new_part6.avi")+\
+AviSource("snes9x\Movies\new_part7.avi")
 Trim(0, 37569)
 global new = last