video: add --display-fps switch to control framedrop FPS

Since the display FPS is currently detected on X11 only (and even there
it's known to be wrong on certain setups), it seems like a good idea to
make this user-configurable.

4 files changed, 17 insertions, 3 deletions

diff --git a/DOCS/man/options.rst b/DOCS/man/options.rst
index fa4dcd3b8b..9320a244ac 100644
--- a/DOCS/man/options.rst
+++ b/DOCS/man/options.rst
@@ -464,6 +464,13 @@ Video
         mode enabled. It doesn't increment the ``D:`` field in the statusline
         either.
 
+``--display-fps=<fps>``
+    Set the maximum assumed display FPS used with ``--framedrop``. By default
+    a detected value is used (X11 only, not correct on multi-monitor systems),
+    or infinite display FPS if that fails. Infinite FPS means only frames too
+    late are dropped. If a correct FPS is provided, frames that are predicted
+    to be too late are dropped too.
+
 ``--hwdec=<api>``
     Specify the hardware video decoding API that should be used if possible.
     Whether hardware decoding is actually done depends on the video codec. If
diff --git a/options/options.c b/options/options.c
index 58e8d9dec4..aacb1b725a 100644
--- a/options/options.c
+++ b/options/options.c
@@ -462,6 +462,8 @@ const m_option_t mp_opts[] = {
                 {"decoder", 2},
                 {"decoder+vo", 3})),
 
+    OPT_DOUBLE("display-fps", frame_drop_fps, M_OPT_MIN, .min = 0),
+
     OPT_FLAG("audiodrop", insert_silence, 0),
 
     OPT_FLAG("untimed", untimed, M_OPT_FIXED),
diff --git a/options/options.h b/options/options.h
index 9b48a0162e..65007bd22e 100644
--- a/options/options.h
+++ b/options/options.h
@@ -137,6 +137,7 @@ typedef struct MPOpts {
     float default_max_pts_correction;
     int autosync;
     int frame_dropping;
+    double frame_drop_fps;
     int insert_silence;
     int term_osd;
     int term_osd_bar;
diff --git a/video/out/vo.c b/video/out/vo.c
index 72f98e8859..bb98160883 100644
--- a/video/out/vo.c
+++ b/video/out/vo.c
@@ -332,8 +332,12 @@ static void run_reconfig(void *p)
     forget_frames(vo); // implicitly synchronized
 
     double display_fps = 1000.0; // assume infinite if unset
-    vo->driver->control(vo, VOCTRL_GET_DISPLAY_FPS, &display_fps);
-    vo->in->vsync_interval = 1e6 / display_fps;
+    if (vo->global->opts->frame_drop_fps > 0) {
+        display_fps = vo->global->opts->frame_drop_fps;
+    } else {
+        vo->driver->control(vo, VOCTRL_GET_DISPLAY_FPS, &display_fps);
+    }
+    vo->in->vsync_interval = MPMAX((int64_t)(1e6 / display_fps), 1);
     MP_VERBOSE(vo, "Assuming %f FPS for framedrop.\n", display_fps);
 }
 
@@ -515,7 +519,7 @@ static int64_t prev_sync(struct vo *vo, int64_t ts)
     struct vo_internal *in = vo->in;
 
     int64_t diff = (int64_t)(ts - in->last_flip);
-    int64_t offset = diff % MPMAX(in->vsync_interval, 1);
+    int64_t offset = diff % in->vsync_interval;
     if (offset < 0)
         offset += in->vsync_interval;
     return ts - offset;