Index: firmware/target/arm/sandisk/sansa-c200/lcd-as-c200.S
===================================================================
--- firmware/target/arm/sandisk/sansa-c200/lcd-as-c200.S	(revision 15102)
+++ firmware/target/arm/sandisk/sansa-c200/lcd-as-c200.S	(working copy)
@@ -59,8 +59,7 @@
     ldrb        r8, [r5], #1            @ r8 = *Cb_p++;
     ldrb        r9, [r6], #1            @ r9 = *Cr_p++;
                                         @
-    sub         r7, r7, #16             @ r7 = Y = (Y' - 16)*74
-    add         r12, r7, r7, asl #2     @ actually (Y' - 16)*37 and shift right
+    add         r12, r7, r7, asl #2     @ r7 = Y = (Y')*74 actually (Y')*37 and shift right
     add         r7, r12, r7, asl #5     @ by one less when adding - same for all
                                         @
     sub         r8, r8, #128            @ Cb -= 128
@@ -75,12 +74,13 @@
     add         r11, r11, r9, asl #5    @
     add         r9, r11, r9, asl #6     @
                                         @
-    add         r8, r8, #2              @ r8 = bu = (Cb*128 + 128) >> 8
-    mov         r8, r8, asr #2          @
-    add         r9, r9, #256            @ r9 = rv = (r9 + 256) >> 9
-    mov         r9, r9, asr #9          @
-    rsb         r10, r10, #128          @ r10 = guv = (-r10 + 128) >> 8
-    mov         r10, r10, asr #8        @
+    mov r8, r8, asl #2 @ r8 = bu = (Cb*128 + ROUNDOFFB) >> 9
+    sub r8, r8, #541 @
+    mov r8, r8, asr #4 @
+    sub r9, r9, #13856 @ r9 = rv = (r9 + ROUNDOFFR) >> 9
+    mov r9, r9, asr #9 @
+    rsb r10, r10, #8544 @ r10 = guv = (-r10 + ROUNDOFFG) >> 8
+    mov r10, r10, asr #8 @
                                         @ compute R, G, and B
     add         r0, r8, r7, asr #8      @ r0  = b = (Y >> 9) + bu
     add         r11, r9, r7, asr #8     @ r11 = r = (Y >> 9) + rv
@@ -117,9 +117,8 @@
     bne         1b                      @
     str         r0, [r3, #0x10]         @ send LSB
                                         @
-    sub         r7, r12, #16            @ r7 = Y = (Y' - 16)*74
-    add         r12, r7, r7, asl #2     @
-    add         r7, r12, r7, asl #5     @
+    add         r11, r12, r12, asl #2   @ r7 = Y = (Y')*74
+    add         r7, r11, r12, asl #5    @
                                         @ compute R, G, and B
     add         r0, r8, r7, asr #8      @ r0  = b = (Y >> 9) + bu
     add         r11, r9, r7, asr #8     @ r11 = r = (Y >> 9) + rv
@@ -156,9 +155,8 @@
     bne         1b                      @
     str         r0, [r3, #0x10]         @ send LSB
                                         @
-    sub         r7, r12, #16            @ r7 = Y = (Y' - 16)*74
-    add         r12, r7, r7, asl #2     @
-    add         r7, r12, r7, asl #5     @
+    add         r11, r12, r12, asl #2   @ r7 = Y = (Y')*74
+    add         r7, r11, r12, asl #5    @
                                         @ compute R, G, and B
     add         r0, r8, r7, asr #8      @ r0  = b = (Y >> 9) + bu
     add         r11, r9, r7, asr #8     @ r11 = r = (Y >> 9) + rv
@@ -196,9 +194,8 @@
     bne         1b                      @
     str         r0, [r3, #0x10]         @ send LSB
                                         @
-    sub         r7, r12, #16            @ r7 = Y = (Y' - 16)*74
-    add         r12, r7, r7, asl #2     @
-    add         r7, r12, r7, asl #5     @
+    add         r11, r12, r12, asl #2   @ r7 = Y = (Y')*74
+    add         r7, r11, r12, asl #5    @
                                         @ compute R, G, and B
     add         r0, r8, r7, asr #8      @ r0  = b = (Y >> 9) + bu
     add         r11, r9, r7, asr #8     @ r11 = r = (Y >> 9) + rv