swscale/swscale: combine the input/output checks in sws_frame_setup()

Cosmetic change in preparation for the next commit.

Signed-off-by: James Almer <jamrial@gmail.com>

libswscale/swscale.c

@@ -1442,6 +1442,7 @@ int sws_frame_setup(SwsContext *ctx, const AVFrame *dst, const AVFrame *src)
     for (int field = 0; field < 2; field++) {
         SwsFormat src_fmt = ff_fmt_from_frame(src, field);
         SwsFormat dst_fmt = ff_fmt_from_frame(dst, field);
+        int src_ok, dst_ok;
 
         if ((src->flags ^ dst->flags) & AV_FRAME_FLAG_INTERLACED) {
             err_msg = "Cannot convert interlaced to progressive frames or vice versa.\n";
@@ -1449,14 +1450,10 @@ int sws_frame_setup(SwsContext *ctx, const AVFrame *dst, const AVFrame *src)
             goto fail;
         }
 
-        if (!ff_test_fmt(&src_fmt, 0)) {
-            err_msg = "Unsupported input";
-            ret = AVERROR(ENOTSUP);
-            goto fail;
-        }
-
-        if (!ff_test_fmt(&dst_fmt, 1)) {
-            err_msg = "Unsupported output";
+        src_ok = ff_test_fmt(&src_fmt, 0);
+        dst_ok = ff_test_fmt(&dst_fmt, 1);
+        if ((!src_ok || !dst_ok)) {
+            err_msg = src_ok ? "Unsupported output" : "Unsupported input";
             ret = AVERROR(ENOTSUP);
             goto fail;
         }