From e6058d3dc30ca8160ebeb8bba562ba08574164bb Mon Sep 17 00:00:00 2001
From: Bin Jin <bjin1990@gmail.com>
Date: Sat, 5 Dec 2015 19:14:23 +0000
Subject: vo_opengl: make LOOKUP_TEXTURE_SIZE configurable

---
 DOCS/man/vo.rst          | 9 +++++++++
 video/out/opengl/video.c | 8 ++++----
 video/out/opengl/video.h | 1 +
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/DOCS/man/vo.rst b/DOCS/man/vo.rst
index c8f484aa72..56339f1468 100644
--- a/DOCS/man/vo.rst
+++ b/DOCS/man/vo.rst
@@ -431,6 +431,15 @@ Available video output drivers are:
             Scale parameter (t). Increasing this makes the window wider.
             Defaults to 1.
 
+    ``scaler-lut-size=<4..10>``
+        Set the size of the lookup texture for scaler kernels (default: 8).
+        The actual size of the texture is ``2^N`` for an option value of ``N``.
+        So the lookup texture with the default setting uses 256 samples.
+
+        All weights are bilinearly interpolated from those samples, so
+        increasing the size of lookup table might improve the accuracy of
+        scaler.
+
     ``scaler-resizes-only``
         Disable the scaler if the video image is not resized. In that case,
         ``bilinear`` is used instead whatever is set with ``scale``. Bilinear
diff --git a/video/out/opengl/video.c b/video/out/opengl/video.c
index de20984cdc..0fdc4df0a2 100644
--- a/video/out/opengl/video.c
+++ b/video/out/opengl/video.c
@@ -49,9 +49,6 @@
 #include "video/out/dither.h"
 #include "video/out/vo.h"
 
-// Pixel width of 1D lookup textures.
-#define LOOKUP_TEXTURE_SIZE 256
-
 // Maximal number of passes that prescaler can be applied.
 #define MAX_PRESCALE_PASSES 5
 
@@ -348,6 +345,7 @@ const struct gl_video_opts gl_video_opts_def = {
         {{"mitchell",   .params={NAN, NAN}}, {.params = {NAN, NAN}},
          .clamp = 1, }, // tscale
     },
+    .scaler_lut_size = 8,
     .alpha_mode = 2,
     .background = {0, 0, 0, 255},
     .gamma = 1.0f,
@@ -371,6 +369,7 @@ const struct gl_video_opts gl_video_opts_hq_def = {
         {{"mitchell",   .params={NAN, NAN}}, {.params = {NAN, NAN}},
          .clamp = 1, }, // tscale
     },
+    .scaler_lut_size = 8,
     .alpha_mode = 2,
     .background = {0, 0, 0, 255},
     .gamma = 1.0f,
@@ -412,6 +411,7 @@ const struct m_sub_options gl_video_conf = {
         SCALER_OPTS("dscale", 1),
         SCALER_OPTS("cscale", 2),
         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("linear-scaling", linear_scaling, 0),
         OPT_FLAG("correct-downscaling", correct_downscaling, 0),
@@ -1081,7 +1081,7 @@ static void reinit_scaler(struct gl_video *p, struct scaler *scaler,
 
     gl->BindTexture(target, scaler->gl_lut);
 
-    scaler->lut_size = LOOKUP_TEXTURE_SIZE;
+    scaler->lut_size = 1 << p->opts.scaler_lut_size;
 
     float *weights = talloc_array(NULL, float, scaler->lut_size * size);
     mp_compute_lut(scaler->kernel, scaler->lut_size, weights);
diff --git a/video/out/opengl/video.h b/video/out/opengl/video.h
index a56c0c1c09..4dab617cda 100644
--- a/video/out/opengl/video.h
+++ b/video/out/opengl/video.h
@@ -71,6 +71,7 @@ struct scaler {
 struct gl_video_opts {
     int dumb_mode;
     struct scaler_config scaler[4];
+    int scaler_lut_size;
     float gamma;
     int gamma_auto;
     int target_prim;
-- 
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