vo_opengl: add tscale-interpolates-only sub-option

DOCS/interface-changes.rst

@@ -28,6 +28,7 @@ Interface changes
     - VO opengl custom shaders must now use "sample_pixel" as function name,
       instead of "sample"
     - change VO opengl scaler-resizes-only default to enabled
+    - add VO opengl "tscale-interpolates-only" suboption
  --- mpv 0.15.0 ---
     - change "yadif" video filter defaults
  --- mpv 0.14.0 ---

DOCS/man/vo.rst

@@ -549,6 +549,10 @@ Available video output drivers are:
         manifest themselves as short flashes or fringes of black, mostly
         around moving edges) in exchange for potentially adding more blur.
 
+    ``tscale-interpolates-only=<yes|no>``
+        If set, then don't perform interpolation if the playback rate matches
+        the the display refresh rate (default: yes).
+
     ``dscale-radius``, ``cscale-radius``, ``tscale-radius``, etc.
         Set filter parameters for ``dscale``, ``cscale`` and ``tscale``,
         respectively.

video/out/opengl/video.c

@@ -338,6 +338,7 @@ const struct gl_video_opts gl_video_opts_def = {
          .clamp = 1, }, // tscale
     },
     .scaler_resizes_only = 1,
+    .tscale_interpolates_only = 1,
     .scaler_lut_size = 6,
     .alpha_mode = 3,
     .background = {0, 0, 0, 255},
@@ -363,6 +364,7 @@ const struct gl_video_opts gl_video_opts_hq_def = {
          .clamp = 1, }, // tscale
     },
     .scaler_resizes_only = 1,
+    .tscale_interpolates_only = 1,
     .scaler_lut_size = 6,
     .alpha_mode = 3,
     .background = {0, 0, 0, 255},
@@ -406,6 +408,7 @@ const struct m_sub_options gl_video_conf = {
         SCALER_OPTS("tscale", 3),
         OPT_INTRANGE("scaler-lut-size", scaler_lut_size, 0, 4, 10),
         OPT_FLAG("scaler-resizes-only", scaler_resizes_only, 0),
+        OPT_FLAG("tscale-interpolates-only", tscale_interpolates_only, 0),
         OPT_FLAG("linear-scaling", linear_scaling, 0),
         OPT_FLAG("correct-downscaling", correct_downscaling, 0),
         OPT_FLAG("sigmoid-upscaling", sigmoid_upscaling, 0),
@@ -2182,8 +2185,11 @@ void gl_video_render_frame(struct gl_video *p, struct vo_frame *frame, int fbo)
     if (has_frame) {
         gl_sc_set_vao(p->sc, &p->vao);
 
+        bool same_rate = !(frame->repeat || frame->num_vsyncs > 1);
+
         if (p->opts.interpolation && frame->display_synced &&
-            (p->frames_drawn || !frame->still))
+            (p->frames_drawn || !frame->still) &&
+            (!same_rate || !p->opts.tscale_interpolates_only))
         {
             gl_video_interpolate_frame(p, frame, fbo);
         } else {

video/out/opengl/video.h

@@ -83,6 +83,7 @@ struct gl_video_opts {
     float sigmoid_center;
     float sigmoid_slope;
     int scaler_resizes_only;
+    int tscale_interpolates_only;
     int pbo;
     int dither_depth;
     int dither_algo;