command: add vsync-ratio property

This is very "illustrative", unlike the video-speed-correction
property, and thus useful. It can also be used to observe scheduling
errors, which are not detected by the core. (These happen due to
rounding errors; possibly not evne our fault, but coming from
files with rounded timestamps and so on.)

3 files changed, 33 insertions, 6 deletions

diff --git a/player/command.c b/player/command.c
index e3b8feab98..eadcc27296 100644
--- a/player/command.c
+++ b/player/command.c
@@ -567,12 +567,34 @@ static int mp_property_mistimed_frame_count(void *ctx, struct m_property *prop,
                                             int action, void *arg)
 {
     MPContext *mpctx = ctx;
-     if (!mpctx->d_video || !mpctx->display_sync_active)
+    if (!mpctx->d_video || !mpctx->display_sync_active)
         return M_PROPERTY_UNAVAILABLE;
 
     return m_property_int_ro(action, arg, mpctx->mistimed_frames_total);
 }
 
+static int mp_property_vsync_ratio(void *ctx, struct m_property *prop,
+                                   int action, void *arg)
+{
+    MPContext *mpctx = ctx;
+    if (!mpctx->d_video || !mpctx->display_sync_active)
+        return M_PROPERTY_UNAVAILABLE;
+
+    int vsyncs = 0, frames = 0;
+    for (int n = 0; n < mpctx->num_past_frames; n++) {
+        int vsync = mpctx->past_frames[n].num_vsyncs;
+        if (vsync < 0)
+            break;
+        vsyncs += vsync;
+        frames += 1;
+    }
+
+    if (!frames)
+        return M_PROPERTY_UNAVAILABLE;
+
+    return m_property_double_ro(action, arg, vsyncs / (double)frames);
+}
+
 static int mp_property_vo_drop_frame_count(void *ctx, struct m_property *prop,
                                            int action, void *arg)
 {
@@ -3394,6 +3416,7 @@ static const struct m_property mp_properties[] = {
     {"total-avsync-change", mp_property_total_avsync_change},
     {"drop-frame-count", mp_property_drop_frame_cnt},
     {"mistimed-frame-count", mp_property_mistimed_frame_count},
+    {"vsync-ratio", mp_property_vsync_ratio},
     {"vo-drop-frame-count", mp_property_vo_drop_frame_count},
     {"vo-delayed-frame-count", mp_property_vo_delayed_frame_count},
     {"percent-pos", mp_property_percent_pos},
@@ -3612,7 +3635,7 @@ static const char *const *const mp_event_property_change[] = {
       "percent-pos", "time-remaining", "playtime-remaining", "playback-time",
       "estimated-vf-fps", "drop-frame-count", "vo-drop-frame-count",
       "total-avsync-change", "audio-speed-correction", "video-speed-correction",
-      "vo-delayed-frame-count", "mistimed-frame-count"),
+      "vo-delayed-frame-count", "mistimed-frame-count", "vsync-ratio"),
     E(MPV_EVENT_VIDEO_RECONFIG, "video-out-params", "video-params",
       "video-format", "video-codec", "video-bitrate", "dwidth", "dheight",
       "width", "height", "fps", "aspect", "vo-configured", "current-vo",
diff --git a/player/core.h b/player/core.h
index fcdf0e3595..7031efc107 100644
--- a/player/core.h
+++ b/player/core.h
@@ -99,6 +99,7 @@ struct frame_info {
     double pts;
     double duration;        // PTS difference to next frame
     double approx_duration; // possibly fixed/smoothed out duration
+    int num_vsyncs;         // scheduled vsyncs, if using display-sync
 };
 
 struct track {
diff --git a/player/video.c b/player/video.c
index 8ee9c87e93..5ef327aa09 100644
--- a/player/video.c
+++ b/player/video.c
@@ -1001,6 +1001,8 @@ static void handle_display_sync_frame(struct MPContext *mpctx,
     mpctx->total_avsync_change = 0;
     update_av_diff(mpctx, time_left * opts->playback_speed);
 
+    mpctx->past_frames[0].num_vsyncs = num_vsyncs;
+
     if (resample)
         adjust_audio_speed(mpctx, vsync);
 
@@ -1177,9 +1179,10 @@ void write_video(struct MPContext *mpctx, double endpts)
         mpctx->num_past_frames--;
     MP_TARRAY_INSERT_AT(mpctx, mpctx->past_frames, mpctx->num_past_frames, 0,
                         (struct frame_info){0});
-    struct frame_info *frame_info = &mpctx->past_frames[0];
-
-    frame_info->pts = mpctx->next_frames[0]->pts;
+    mpctx->past_frames[0] = (struct frame_info){
+        .pts = mpctx->next_frames[0]->pts,
+        .num_vsyncs = -1,
+    };
     calculate_frame_duration(mpctx);
 
     struct vo_frame dummy = {
@@ -1193,7 +1196,7 @@ void write_video(struct MPContext *mpctx, double endpts)
         dummy.frames[n] = mpctx->next_frames[n];
     struct vo_frame *frame = vo_frame_ref(&dummy);
 
-    double diff = frame_info->approx_duration;
+    double diff = mpctx->past_frames[0].approx_duration;
     if (opts->untimed || vo->driver->untimed)
         diff = -1; // disable frame dropping and aspects of frame timing
     if (diff >= 0) {