Index: os.h
===================================================================
--- os.h	(revision 14848)
+++ os.h	(working copy)
@@ -113,10 +113,11 @@
   __asm__("fistl %0": "=m"(i) : "t"(f));
   return(i);
 }
-#endif
 
+#endif /* Special i386 GCC implementation */
 
-#if defined(_WIN32) && !defined(__GNUC__) && !defined(__BORLANDC__)
+/* Win32 implementation for Visual C++ (any others with this combination of flags?) */
+#if defined(_WIN32) && !defined(_WIN64) && !defined(__GNUC__) && !defined(__BORLANDC__)
 #  define VORBIS_FPU_CONTROL
 
 typedef ogg_int16_t vorbis_fpu_control;
@@ -136,15 +137,43 @@
 static __inline void vorbis_fpu_restore(vorbis_fpu_control fpu){
 }
 
-#endif
+#endif /* Special Win32 Visual C++ implementation */
 
+/* Win64 implementation using SSE intrinsics for Visual C++ 2005 and above */
+/* Any CPU supporting x64 also supports SSE, so this is safe and will not lead
+   to issues with users that do not have an SSE-capable CPU
+*/
+#if defined(_WIN32) && defined(_WIN64) && defined(_MSC_VER) && (_MSC_VER >= 1400)
+#  define VORBIS_FPU_CONTROL
+
+typedef ogg_int16_t vorbis_fpu_control;
+
+/* Special implementation for msvc x64 where inline asm doesn't work */
+#include <emmintrin.h> 
+static int vorbis_ftoi(double f){
+  return _mm_cvtsd_si32(_mm_load_sd(&f));
+}
+
+static __inline void vorbis_fpu_setround(vorbis_fpu_control *fpu){
+}
 
+static __inline void vorbis_fpu_restore(vorbis_fpu_control fpu){
+}
+
+#endif /* Special Win64 (64-bit) Visual C++ implementation */
+
+/* If no special implementation was found for the current compiler / platform,
+   use the default implementation here: */
 #ifndef VORBIS_FPU_CONTROL
 
 typedef int vorbis_fpu_control;
 
 static int vorbis_ftoi(double f){
-  return (int)(f+.5);
+  /* Old implementation (only correct when no negative numbers encountered): */
+  /* return (int)(f+.5); */
+
+  /* Proper but slower implementation */
+  return (f < 0) ? (int)(f - 0.5) : (int)(f + 0.5);
 }
 
 /* We don't have special code for this compiler/arch, so do it the slow way */