options: deprecate --video-sync=display-adrop

A stupid thing that will probably be in the way.

DOCS/interface-changes.rst

@@ -36,6 +36,8 @@ Interface changes
       outputs like vo_x11 and vo_drm, and screenshots, but not much else.
     - deprecate --input-file (there are no plans to remove this short-term,
       but it will probably eventually go away)
+    - deprecate --video-sync=display-adrop (might be removed if it's in the way;
+      undeprecated or readded if it's not too much of a problem)
  --- mpv 0.30.0 ---
     - add `--d3d11-output-format` to enable explicit selection of a D3D11
       swap chain format.

player/core.h

@@ -341,6 +341,7 @@ typedef struct MPContext {
     // Timing error (in seconds) due to rounding on vsync boundaries
     double display_sync_error;
     double audio_drop_throttle;
+    bool audio_drop_deprecated_msg;
     // Number of mistimed frames.
     int mistimed_frames_total;
     bool hrseek_active;     // skip all data until hrseek_pts

player/video.c

@@ -784,6 +784,12 @@ static void handle_display_sync_frame(struct MPContext *mpctx,
 
     mpctx->display_sync_active = false;
 
+    if (mode == VS_DISP_ADROP && !mpctx->audio_drop_deprecated_msg) {
+        MP_WARN(mpctx, "video-sync=display-adrop mode is deprecated and will "
+                       "be removed in the future.\n");
+        mpctx->audio_drop_deprecated_msg = true;
+    }
+
     if (!VS_IS_DISP(mode))
         return;
     bool resample = mode == VS_DISP_RESAMPLE || mode == VS_DISP_RESAMPLE_VDROP ||