vf_vapoursynth: pass image properties from input

This might not always be correct depending on filtering done in VS. But
unless VS send us all the metadata we have to get it from somewhere.

Fixes dynamic frame metadata, which was copied from fmt_in, initialized
only upon reinitialization.

Fixes crashes caused by the use of stale pointers.

Fixes: #13956

video/filter/vf_vapoursynth.c

@@ -209,6 +209,10 @@ static void copy_mp_to_vs_frame_props_map(struct priv *p, VSMap *map,
     if (img->fields & MP_IMGFIELD_INTERLACED)
         field = img->fields & MP_IMGFIELD_TOP_FIRST ? 2 : 1;
     p->vsapi->propSetInt(map, "_FieldBased", field, 0);
+
+    // Don't ref passed frame, it is not meant to be read externally and we know
+    // it will be alive once we get it back.
+    p->vsapi->propSetData(map, "_MP_IMAGE", (const char *)img, sizeof(*img), 0);
 }
 
 static int set_vs_frame_props(struct priv *p, VSFrameRef *frame,
@@ -271,10 +275,6 @@ static void VS_CC vs_frame_done(void *userData, const VSFrameRef *f, int n,
     struct mp_image *res = NULL;
     if (f) {
         struct mp_image img = map_vs_frame(p, f, false);
-        struct mp_image dummy = {.params = p->fmt_in};
-        if (p->fmt_in.w != img.w || p->fmt_in.h != img.h)
-            dummy.params.crop = (struct mp_rect){0, 0, img.w, img.h};
-        mp_image_copy_attributes(&img, &dummy);
         img.pkt_duration = -1;
         const VSMap *map = p->vsapi->getFramePropsRO(f);
         if (map) {
@@ -283,6 +283,18 @@ static void VS_CC vs_frame_done(void *userData, const VSFrameRef *f, int n,
             int den = p->vsapi->propGetInt(map, "_DurationDen", 0, &err2);
             if (!err1 && !err2)
                 img.pkt_duration = num / (double)den;
+
+            const struct mp_image *mpi = (void *)p->vsapi->propGetData(map, "_MP_IMAGE", 0, &err1);
+            if (!err1) {
+                // mp_image_new_copy will add new refs to it
+                img.params = mpi->params;
+                if (mpi->params.w != img.w || mpi->params.h != img.h)
+                    img.params.crop = (struct mp_rect){0, 0, img.w, img.h};
+            } else {
+                MP_ERR(p, "Failed to get mp_image attributes!");
+            }
+        } else {
+            MP_ERR(p, "Failed to get frame properties!");
         }
         if (img.pkt_duration < 0) {
             MP_ERR(p, "No PTS after filter at frame %d!\n", n);