swr: reorder the operations in the noise shaping code

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libswresample/dither.c

@@ -118,6 +118,7 @@ int swri_dither_init(SwrContext *s, enum AVSampleFormat out_fmt, enum AVSampleFo
     if (s->dither.method > SWR_DITHER_NS) {
         s->dither.noise.bps = 4;
         s->dither.noise.fmt = AV_SAMPLE_FMT_FLTP;
+        s->dither.noise_scale = 1;
     }
 
     return 0;

libswresample/dither_template.c

@@ -34,12 +34,13 @@ void RENAME(swri_noise_shaping)(SwrContext *s, AudioData *srcs, AudioData *noise
         DELEM *data = (DELEM*)srcs->ch[ch];
         pos  = s->dither.ns_pos;
         for (i=0; i<count; i++) {
-            double d1, d = data[i];
+            double d1, d = data[i]*S_1;
             for(j=0; j<taps; j++)
                 d -= s->dither.ns_coeffs[j] * s->dither.ns_errors[ch][pos + j];
             pos = pos ? pos - 1 : pos - 1 + taps;
-            d1 = rint((d + noise[i]) * S_1)*S;
+            d1 = rint(d + noise[i]);
             s->dither.ns_errors[ch][pos + taps] = s->dither.ns_errors[ch][pos] = d1 - d;
+            d1 *= S;
             CLIP(d1);
             data[i] = d1;
         }