lavfi/vf_libplacebo: fix side data stripping logic

This was accidentally comparing s->colorspace against out->colorspace,
which is wrong - the intent was to compare in->colorspace against
out->colorspace.

We also forgot to strip mastering metadata. Finally, the order is sort
of wrong - we should strip this side data *before* process_frames,
because otherwise it may end up being seen and used by libplacebo.

Signed-off-by: Niklas Haas <git@haasn.dev>

libavfilter/vf_libplacebo.c

@@ -390,7 +390,7 @@ fail:
 
 static int filter_frame(AVFilterLink *link, AVFrame *in)
 {
-    int err, changed;
+    int err, changed_csp;
     AVFilterContext *ctx = link->dst;
     LibplaceboContext *s = ctx->priv;
     AVFilterLink *outlink = ctx->outputs[0];
@@ -426,22 +426,25 @@ static int filter_frame(AVFilterLink *link, AVFrame *in)
     if (s->color_primaries >= 0)
         out->color_primaries = s->color_primaries;
 
-    RET(process_frames(ctx, out, in));
-
-    int changed_csp = s->colorspace      != out->colorspace     ||
-                      s->color_range     != out->color_range    ||
-                      s->color_trc       != out->color_trc      ||
-                      s->color_primaries != out->color_primaries;
+    changed_csp = in->colorspace      != out->colorspace     ||
+                  in->color_range     != out->color_range    ||
+                  in->color_trc       != out->color_trc      ||
+                  in->color_primaries != out->color_primaries;
 
-    if (s->apply_dovi || changed_csp) {
     /* Strip side data if no longer relevant */
+    if (changed_csp) {
+        av_frame_remove_side_data(out, AV_FRAME_DATA_MASTERING_DISPLAY_METADATA);
+        av_frame_remove_side_data(out, AV_FRAME_DATA_CONTENT_LIGHT_LEVEL);
+    }
+    if (s->apply_dovi || changed_csp) {
         av_frame_remove_side_data(out, AV_FRAME_DATA_DOVI_RPU_BUFFER);
         av_frame_remove_side_data(out, AV_FRAME_DATA_DOVI_METADATA);
     }
-
     if (s->apply_filmgrain)
         av_frame_remove_side_data(out, AV_FRAME_DATA_FILM_GRAIN_PARAMS);
 
+    RET(process_frames(ctx, out, in));
+
     av_frame_free(&in);
 
     return ff_filter_frame(outlink, out);