Alternative and faster (on gcc x86) plane rotation.

Originally committed as revision 12237 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/faandct.c

@@ -107,9 +107,14 @@ static av_always_inline void row_fdct(FLOAT temp[64], DCTELEM * data)
         tmp5 += tmp6;
         tmp6 += tmp7;
 
+#if 0
         z5= (tmp4 - tmp6) * A5;
         z2= tmp4*A2 + z5;
         z4= tmp6*A4 + z5;
+#else
+        z2= tmp4*(A2+A5) - tmp6*A5;
+        z4= tmp6*(A4-A5) + tmp4*A5;
+#endif
         tmp5*=A1;
 
         z11= tmp7 + tmp5;
@@ -161,9 +166,14 @@ void ff_faandct(DCTELEM * data)
         tmp5 += tmp6;
         tmp6 += tmp7;
 
+#if 0
         z5= (tmp4 - tmp6) * A5;
         z2= tmp4*A2 + z5;
         z4= tmp6*A4 + z5;
+#else
+        z2= tmp4*(A2+A5) - tmp6*A5;
+        z4= tmp6*(A4-A5) + tmp4*A5;
+#endif
         tmp5*=A1;
 
         z11= tmp7 + tmp5;