jpeg2000dec: optimize dequantization_int()

4400->2800 cycles
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/jpeg2000dec.c

@@ -938,13 +938,13 @@ static void dequantization_int(int x, int y, Jpeg2000Cblk *cblk,
                                Jpeg2000Component *comp,
                                Jpeg2000T1Context *t1, Jpeg2000Band *band)
 {
-    int i, j, idx;
-    int32_t *datap = &comp->i_data[(comp->coord[0][1] - comp->coord[0][0]) * y + x];
-    for (j = 0; j < (cblk->coord[1][1] - cblk->coord[1][0]); ++j)
-        for (i = 0; i < (cblk->coord[0][1] - cblk->coord[0][0]); ++i) {
-            idx        = (comp->coord[0][1] - comp->coord[0][0]) * j + i;
-            datap[idx] =
-                ((int32_t)(t1->data[j][i]) * band->i_stepsize + (1 << 15)) >> 16;
+    int i, j;
+    int w = cblk->coord[0][1] - cblk->coord[0][0];
+    for (j = 0; j < (cblk->coord[1][1] - cblk->coord[1][0]); ++j) {
+        int32_t *datap = &comp->i_data[(comp->coord[0][1] - comp->coord[0][0]) * (y + j) + x];
+        int *src = t1->data[j];
+        for (i = 0; i < w; ++i)
+            datap[i] = (src[i] * band->i_stepsize + (1 << 15)) >> 16;
     }
 }