vo_gpu: warn if correct-downscaling is ignored

And document that it's ignored with bilinear scaler.

1 files changed, 11 insertions, 0 deletions

diff --git a/video/out/gpu/video.c b/video/out/gpu/video.c
index 3c06751959..539934fe67 100644
--- a/video/out/gpu/video.c
+++ b/video/out/gpu/video.c
@@ -292,6 +292,7 @@ struct gl_video {
     bool broken_frame; // temporary error state
 
     bool colorspace_override_warned;
+    bool correct_downscaling_warned;
 };
 
 static const struct gl_video_opts gl_video_opts_def = {
@@ -4022,6 +4023,16 @@ static void reinit_from_options(struct gl_video *p)
                    "E.g.: --video-sync=display-resample\n");
         p->dsi_warned = true;
     }
+
+    if (p->opts.correct_downscaling && !p->correct_downscaling_warned) {
+        const char *name = p->opts.scaler[SCALER_DSCALE].kernel.name;
+        if (!name)
+            name = p->opts.scaler[SCALER_SCALE].kernel.name;
+        if (!name || !strcmp(name, "bilinear")) {
+            MP_WARN(p, "correct-downscaling requires non-bilinear scaler.\n");
+            p->correct_downscaling_warned = true;
+        }
+    }
 }
 
 void gl_video_configure_queue(struct gl_video *p, struct vo *vo)