avutil/softfloat: fix av_sincos_sf()

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit d84677abd8)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavutil/softfloat.h

@@ -281,7 +281,7 @@ static av_unused void av_sincos_sf(int a, int *s, int *c)
                 (int64_t)av_sintbl_4_sf[(idx & 0x1f) + 1] * (a & 0x7ff) +
                 0x400) >> 11);
 
-    *c = (int)(((int64_t)cv * ct + (int64_t)sv * st + 0x20000000) >> 30);
+    *c = (int)(((int64_t)cv * ct - (int64_t)sv * st + 0x20000000) >> 30);
 
     *s = (int)(((int64_t)cv * st + (int64_t)sv * ct + 0x20000000) >> 30);
 }

libavutil/tests/softfloat.c

@@ -148,7 +148,7 @@ int main(void){
         av_sincos_sf(i*(1ULL<<32)/36/4, &s, &c);
         errs = (double)s/ (1<<30) - sin(i*M_PI/36);
         errc = (double)c/ (1<<30) - cos(i*M_PI/36);
-        if (fabs(errs) > 0.00000002 || fabs(errc) >0.001) {
+        if (fabs(errs) > 0.000000004 || fabs(errc) >0.000000004) {
             printf("sincos FAIL %d %f %f %f %f\n", i, (float)s/ (1<<30), (float)c/ (1<<30), sin(i*M_PI/36), cos(i*M_PI/36));
         }