Minor loop optimization in libfaad's is/ms decoding.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@29837 a1c6a512-1295-4272-9138-f99709370657

1 files changed, 4 insertions, 5 deletions

diff --git a/apps/codecs/libfaad/ms.c b/apps/codecs/libfaad/ms.c
index f01e5caa07..b42e95a408 100644
--- a/apps/codecs/libfaad/ms.c
+++ b/apps/codecs/libfaad/ms.c
@@ -41,7 +41,6 @@ void ms_decode(ic_stream *ics, ic_stream *icsr, real_t *l_spec, real_t *r_spec,
     uint16_t nshort = frame_len/8;
 
     uint16_t i, k;
-    real_t tmp;
 
     if (ics->ms_mask_present >= 1)
     {
@@ -58,12 +57,12 @@ void ms_decode(ic_stream *ics, ic_stream *icsr, real_t *l_spec, real_t *r_spec,
                     if ((ics->ms_used[g][sfb] || ics->ms_mask_present == 2) &&
                         !is_intensity(icsr, g, sfb) && !is_noise(ics, g, sfb))
                     {
-                        for (i = ics->swb_offset[sfb]; i < ics->swb_offset[sfb+1]; i++)
+                        k = (group*nshort) + ics->swb_offset[sfb];
+                        for (i = ics->swb_offset[sfb]; i < ics->swb_offset[sfb+1]; i++, k++)
                         {
-                            k = (group*nshort) + i;
-                            tmp = l_spec[k] - r_spec[k];
+                            /* L' = L+R, R' = L-R */
                             l_spec[k] = l_spec[k] + r_spec[k];
-                            r_spec[k] = tmp;
+                            r_spec[k] = l_spec[k] - (r_spec[k]<<1);
                         }
                     }
                 }