diff --git a/.gitignore b/.gitignore
index 28c58b9..adc7fdc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,6 +5,9 @@ debug
 11025.ppm
 11025.wav
 11025.dat
+16000.ppm
+16000.wav
+16000.dat
 40000.ppm
 40000.wav
 40000.dat
diff --git a/Makefile b/Makefile
index f0a2d0d..6c7e261 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
 
-CFLAGS = -DUP=1 -DDN=1 -D_GNU_SOURCE=1 -W -Wall -O3 -std=c99 -ffast-math
+CFLAGS = -DUP=0 -DDN=1 -D_GNU_SOURCE=1 -W -Wall -O3 -std=c99 -ffast-math
 LDFLAGS = -lm -lasound
 
 all: encode decode debug
@@ -7,11 +7,13 @@ all: encode decode debug
 test: all
 	./encode smpte.ppm 8000.wav 8000
 	./encode smpte.ppm 11025.wav 11025
+	./encode smpte.ppm 16000.wav 16000
 	./encode smpte.ppm 40000.wav 40000
 	./encode smpte.ppm 44100.wav 44100
 	./encode smpte.ppm 48000.wav 48000
 	./decode 8000.wav 8000.ppm
 	./decode 11025.wav 11025.ppm
+	./decode 16000.wav 16000.ppm
 	./decode 40000.wav 40000.ppm
 	./decode 44100.wav 44100.ppm
 	./decode 48000.wav 48000.ppm
@@ -19,17 +21,19 @@ test: all
 fun: all
 	./encode smpte.ppm 8000.wav 8000
 	./encode smpte.ppm 11025.wav 11025
+	./encode smpte.ppm 16000.wav 16000
 	./encode smpte.ppm 40000.wav 40000
 	./encode smpte.ppm 44100.wav 44100
 	./encode smpte.ppm 48000.wav 48000
 	./debug 8000.wav 8000.ppm > 8000.dat
 	./debug 11025.wav 11025.ppm > 11025.dat
+	./debug 16000.wav 16000.ppm > 16000.dat
 	./debug 40000.wav 40000.ppm > 40000.dat
 	./debug 44100.wav 44100.ppm > 44100.dat
 	./debug 48000.wav 48000.ppm > 48000.dat
 
 clean:
-	rm -f encode decode debug *.o {8000,11025,40000,44100,48000}.{ppm,wav,dat}
+	rm -f encode decode debug *.o {8000,11025,16000,40000,44100,48000}.{ppm,wav,dat}
 
 encode: encode.o mmap_file.o pcm.o wav.o alsa.o yuv.o
 
diff --git a/debug.c b/debug.c
index 05be10e..63a79b0 100644
--- a/debug.c
+++ b/debug.c
@@ -92,7 +92,7 @@ int main(int argc, char **argv)
 #if DN && !UP
 	int64_t factor_L = 1;
 	// factor_M * step should be smaller than pixel length
-	int64_t factor_M = rate * 0.088 / 320.0;
+	int64_t factor_M = rate * 0.088 / 320.0 / 2;
 #endif
 #if !DN
 	int64_t factor_L = 1;
diff --git a/decode.c b/decode.c
index c65ff56..60668d4 100644
--- a/decode.c
+++ b/decode.c
@@ -121,7 +121,7 @@ int main(int argc, char **argv)
 #if DN && !UP
 	int64_t factor_L = 1;
 	// factor_M * step should be smaller than pixel length
-	int64_t factor_M = rate * 0.088 / 320.0;
+	int64_t factor_M = rate * 0.088 / 320.0 / 2;
 #endif
 #if !DN
 	int64_t factor_L = 1;