--- old/quantize_mpeg_mmx.asm	Thu Sep 21 08:56:24 2006
+++ new/quantize_mpeg_mmx.asm	Thu Sep 21 09:19:14 2006
@@ -221,21 +221,19 @@
   ; calculate DC
   movsx eax, word [eax]     ; data[0]
   mov ecx, [esp + 4 + 16]   ; dcscalar
-  mov edx, ecx
-  shr edx, 1                ; edx = dcscalar /2
-  mov edi, edx
-  neg edi
+  mov edx, eax
+  mov edi, ecx
+  shr ecx, 1                ; ecx = dcscalar/2
+  sar edx, 31               ; edx = sign extend of eax (ready for division too)
+  xor ecx, edx              ; adjust ecx according to the sign of data[0]
+  sub ecx, edx
+  add eax, ecx
   
-  cmp eax, 0
-  cmovg edx, edi
-  sub eax, edx
+  mov ecx, [esp + 4 + 4]	; coeff again
 
-  mov edi, [esp + 4 + 4]	; coeff again
+  idiv edi                  ; eax = edx:eax / dcscalar
 
-  cdq                       ; expand eax -> edx:eax
-  idiv ecx                  ; eax = edx:eax / dcscalar
-
-  mov [edi], ax             ; coeff[0] = ax
+  mov [ecx], ax             ; coeff[0] = ax
 
   pop edi