player: update meaning of drop_frame_cnt

Rename the variable, update comments, and update the documentation of
the property which returns its value.

DOCS/man/input.rst

@@ -688,9 +688,10 @@ Property list
     disabled.
 
 ``drop-frame-count``
-    Frames dropped because they arrived too late. Doesn't necessarily indicate
-    actual frame-drops, just the number of times the decoder was asked to drop.
-    Unavailable if video is disabled
+    Video frames dropped by decoder, because video is too far behind audio (when
+    using ``--framedrop=decoder``). Sometimes, this may be incremented in other
+    situations, e.g. when video packets are damaged, or the decoder doesn't
+    follow the usual rules. Unavailable if video is disabled.
 
 ``vo-drop-frame-count``
     Frames dropped by VO (when using ``--framedrop=vo``).

player/command.c

@@ -524,7 +524,7 @@ static int mp_property_drop_frame_cnt(void *ctx, struct m_property *prop,
      if (!mpctx->d_video)
         return M_PROPERTY_UNAVAILABLE;
 
-    return m_property_int_ro(action, arg, mpctx->drop_frame_cnt);
+    return m_property_int_ro(action, arg, mpctx->dropped_frames_total);
 }
 
 static int mp_property_vo_drop_frame_count(void *ctx, struct m_property *prop,

player/core.h

@@ -246,9 +246,8 @@ typedef struct MPContext {
     // How much video timing has been changed to make it match the audio
     // timeline. Used for status line information only.
     double total_avsync_change;
-    // Total number of dropped frames that were "approved" to be dropped.
-    // Actual dropping depends on --framedrop and decoder internals.
-    int drop_frame_cnt;
+    // Total number of dropped frames that were dropped by decoder.
+    int dropped_frames_total;
     // Number of frames dropped in a row.
     int dropped_frames;
     // A-V sync difference when last frame was displayed. Kept to display

player/osd.c

@@ -230,10 +230,10 @@ static void print_status(struct MPContext *mpctx)
         // VO stats
         if (mpctx->d_video) {
             int64_t c = vo_get_drop_count(mpctx->video_out);
-            if (c > 0 || mpctx->drop_frame_cnt > 0) {
+            if (c > 0 || mpctx->dropped_frames_total > 0) {
                 saddf(&line, " Dropped: %"PRId64, c);
-                if (mpctx->drop_frame_cnt)
-                    saddf(&line, "/%d", mpctx->drop_frame_cnt);
+                if (mpctx->dropped_frames_total)
+                    saddf(&line, "/%d", mpctx->dropped_frames_total);
             }
         }
     }

player/video.c

@@ -223,7 +223,7 @@ void reset_video_state(struct MPContext *mpctx)
     mpctx->video_pts = MP_NOPTS_VALUE;
     mpctx->video_next_pts = MP_NOPTS_VALUE;
     mpctx->total_avsync_change = 0;
-    mpctx->drop_frame_cnt = 0;
+    mpctx->dropped_frames_total = 0;
     mpctx->dropped_frames = 0;
     mpctx->drop_message_shown = 0;
 
@@ -400,7 +400,7 @@ static int decode_image(struct MPContext *mpctx)
     if (had_packet && !d_video->waiting_decoded_mpi &&
         mpctx->video_status == STATUS_PLAYING)
     {
-        mpctx->drop_frame_cnt++;
+        mpctx->dropped_frames_total++;
         mpctx->dropped_frames++;
     }