Use refresh rate instead of core fps for frameskip timing (#15666)

gfx/video_driver.c

@@ -3409,6 +3409,10 @@ void video_driver_frame(const void *data, unsigned width,
 
    video_driver_build_info(&video_info);
 
+   /* Take target refresh rate as initial FPS value instead of 0.00 */
+   if (!last_fps)
+      last_fps = video_info.refresh_rate;
+
    /* If fast forward is active and fast forward
     * frame skipping is enabled, drop any frames
     * that occur at a rate higher than the core-set
@@ -3426,6 +3430,7 @@ void video_driver_frame(const void *data, unsigned width,
    {
       retro_time_t frame_time_accumulator_prev = frame_time_accumulator;
       retro_time_t frame_time_delta            = new_time - last_time;
+      retro_time_t frame_time_target           = 1000000.0f / video_info.refresh_rate;
 
       /* Ignore initial previous frame time
        * to prevent rubber band startup */
@@ -3434,28 +3439,29 @@ void video_driver_frame(const void *data, unsigned width,
       else if (nonblock_active < 0)
          nonblock_active = 1;
 
-      /* Accumulate the elapsed time since the
+      /* Accumulate the elapsed time since the last frame */
-       * last frame */
       if (nonblock_active > 0)
          frame_time_accumulator += frame_time_delta;
 
       /* Render frame if the accumulated time is
        * greater than or equal to the expected
        * core frame time */
-      render_frame = frame_time_accumulator >=
+      render_frame = frame_time_accumulator >= frame_time_target;
-            video_st->core_frame_time;
 
       /* If frame is to be rendered, subtract
        * expected frame time from accumulator */
       if (render_frame)
       {
-         frame_time_accumulator -= video_st->core_frame_time;
+         frame_time_accumulator -= frame_time_target;
 
          /* Prevent external frame limiters from
           * pushing fast forward ratio down to 1x */
-         if (frame_time_accumulator + frame_time_accumulator_prev < video_st->core_frame_time)
+         if (frame_time_accumulator_prev - frame_time_accumulator >= frame_time_delta)
             frame_time_accumulator -= frame_time_delta;
 
+         if (frame_time_accumulator < 0)
+            frame_time_accumulator = 0;
+
          /* If fast forward is working correctly,
           * the actual frame time will always be
           * less than the expected frame time.
@@ -3465,7 +3471,7 @@ void video_driver_frame(const void *data, unsigned width,
           * will never empty and may potentially
           * overflow. If a 'runaway' accumulator
           * is detected, we simply reset it */
-         if (frame_time_accumulator > video_st->core_frame_time)
+         if (frame_time_accumulator > frame_time_target)
             frame_time_accumulator = 0;
       }
    }

gfx/video_driver.h

@@ -772,7 +772,6 @@ typedef struct
 #endif
    struct retro_system_av_info av_info; /* double alignment */
    retro_time_t frame_time_samples[MEASURE_FRAME_TIME_SAMPLES_COUNT];
-   retro_time_t core_frame_time;
    uint64_t frame_time_count;
    uint64_t frame_count;
    uint8_t *record_gpu_buffer;

runloop.c

@@ -2674,9 +2674,6 @@ bool runloop_environment_cb(unsigned cmd, void *data)
                   (*info)->timing.sample_rate);
 
             memcpy(av_info, *info, sizeof(*av_info));
-            video_st->core_frame_time = 1000000 /
-                  ((video_st->av_info.timing.fps > 0.0) ?
-                        video_st->av_info.timing.fps : 60.0);
 
             command_event(CMD_EVENT_REINIT, &reinit_flags);
 
@@ -4587,9 +4584,6 @@ static bool runloop_event_load_core(runloop_state_t *runloop_st,
    core_init_libretro_cbs(runloop_st, &runloop_st->retro_ctx);
 
    runloop_st->current_core.retro_get_system_av_info(&video_st->av_info);
-   video_st->core_frame_time = 1000000 /
-         ((video_st->av_info.timing.fps > 0.0) ?
-               video_st->av_info.timing.fps : 60.0);
 
    RARCH_LOG("[Core]: Geometry: %ux%u, Aspect: %.3f, FPS: %.2f, Sample rate: %.2f Hz.\n",
          video_st->av_info.geometry.base_width, video_st->av_info.geometry.base_height,