avfilter/vf_traspose: move switch out of loop

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavfilter/vf_transpose.c

@@ -174,38 +174,46 @@ static int filter_slice(AVFilterContext *ctx, void *arg, int jobnr,
             dstlinesize *= -1;
         }
 
-        for (y = start; y < end; y++) {
-            switch (pixstep) {
-            case 1:
+        switch (pixstep) {
+        case 1:
+            for (y = start; y < end; y++, dst += dstlinesize)
                 for (x = 0; x < outw; x++)
                     dst[x] = src[x*srclinesize + y];
-                break;
-            case 2:
+            break;
+        case 2:
+            for (y = start; y < end; y++, dst += dstlinesize) {
                 for (x = 0; x < outw; x++)
                     *((uint16_t *)(dst + 2*x)) = *((uint16_t *)(src + x*srclinesize + y*2));
-                break;
-            case 3:
+            }
+            break;
+        case 3:
+            for (y = start; y < end; y++, dst += dstlinesize) {
                 for (x = 0; x < outw; x++) {
                     int32_t v = AV_RB24(src + x*srclinesize + y*3);
                     AV_WB24(dst + 3*x, v);
                 }
-                break;
-            case 4:
+            }
+            break;
+        case 4:
+            for (y = start; y < end; y++, dst += dstlinesize) {
                 for (x = 0; x < outw; x++)
                     *((uint32_t *)(dst + 4*x)) = *((uint32_t *)(src + x*srclinesize + y*4));
-                break;
-            case 6:
+            }
+            break;
+        case 6:
+            for (y = start; y < end; y++, dst += dstlinesize) {
                 for (x = 0; x < outw; x++) {
                     int64_t v = AV_RB48(src + x*srclinesize + y*6);
                     AV_WB48(dst + 6*x, v);
                 }
-                break;
-            case 8:
+            }
+            break;
+        case 8:
+            for (y = start; y < end; y++, dst += dstlinesize) {
                 for (x = 0; x < outw; x++)
                     *((uint64_t *)(dst + 8*x)) = *((uint64_t *)(src + x*srclinesize + y*8));
-                break;
             }
-            dst += dstlinesize;
+            break;
         }
     }