vf_scale: use sws_init_context()

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

libavfilter/vf_scale.c

@@ -259,25 +259,35 @@ static int config_props(AVFilterLink *outlink)
 
     if (scale->sws)
         sws_freeContext(scale->sws);
-    if (inlink->w == outlink->w && inlink->h == outlink->h &&
-        inlink->format == outlink->format)
-        scale->sws = NULL;
-    else {
-        scale->sws = sws_getContext(inlink ->w, inlink ->h, inlink ->format,
-                                    outlink->w, outlink->h, outfmt,
-                                    scale->flags, NULL, NULL, NULL);
     if (scale->isws[0])
         sws_freeContext(scale->isws[0]);
-        scale->isws[0] = sws_getContext(inlink ->w, inlink ->h/2, inlink ->format,
-                                        outlink->w, outlink->h/2, outfmt,
-                                        scale->flags, NULL, NULL, NULL);
     if (scale->isws[1])
         sws_freeContext(scale->isws[1]);
-        scale->isws[1] = sws_getContext(inlink ->w, inlink ->h/2, inlink ->format,
-                                        outlink->w, outlink->h/2, outfmt,
-                                        scale->flags, NULL, NULL, NULL);
-        if (!scale->sws || !scale->isws[0] || !scale->isws[1])
-            return AVERROR(EINVAL);
+    scale->isws[0] = scale->isws[1] = scale->sws = NULL;
+    if (inlink->w == outlink->w && inlink->h == outlink->h &&
+        inlink->format == outlink->format)
+        ;
+    else {
+        struct SwsContext **swscs[3] = {&scale->sws, &scale->isws[0], &scale->isws[1]};
+        int i;
+
+        for (i = 0; i < 3; i++) {
+            struct SwsContext **s = swscs[i];
+            *s = sws_alloc_context();
+            if (!*s)
+                return AVERROR(ENOMEM);
+
+            av_opt_set_int(*s, "srcw", inlink ->w, 0);
+            av_opt_set_int(*s, "srch", inlink ->h >> !!i, 0);
+            av_opt_set_int(*s, "src_format", inlink->format, 0);
+            av_opt_set_int(*s, "dstw", outlink->w, 0);
+            av_opt_set_int(*s, "dsth", outlink->h >> !!i, 0);
+            av_opt_set_int(*s, "dst_format", outfmt, 0);
+            av_opt_set_int(*s, "sws_flags", scale->flags, 0);
+
+            if ((ret = sws_init_context(*s, NULL, NULL)) < 0)
+                return ret;
+        }
     }
 
     if (inlink->sample_aspect_ratio.num){