vo_opengl: add Super-xBR filter for upscaling

Add the Super-xBR filter for image doubling, and the prescaling framework
to support it.

The shader code was ported from MPDN extensions project, with
modification to process luma only.

This commit is largely inspired by code from #2266, with
`gl_transform_trans()` authored by @haasn taken directly.

DOCS/man/vo.rst

@@ -549,6 +549,46 @@ Available video output drivers are:
         feature doesn't work correctly with different scale factors in
         different directions.
 
+    ``prescale=<filter>``
+        This option provides non-convolution-based filters for upscaling. These
+        filters resize the video to multiple of the original size (all currently
+        supported prescalers can only perform image doubling a single pass).
+        Generally another convolution based filter (the main scaler) will be
+        applied after prescaler to match the target display size.
+
+        ``none`` (default)
+            Disable all prescalers.
+
+        ``superxbr``
+            A relatively fast prescaler, produces sharp image with less
+            aliasing.
+
+            Some parameters can be tuned with ``superxbr-sharpness`` and
+            ``superxbr-edge-strength`` options.
+
+        Note that all above filters are designed (or implemented) to process
+        luma plane only and probably won't work as intended for video in RGB
+        format. A workaround is to add a ``format`` video filter to convert
+        video to YUV first.
+
+    ``prescale-passes=<1..5>``
+        The number of times to apply the prescaler (defaults to be 1). Setting
+        it to 2 will perform a 4x upscaling.
+
+    ``prescale-downscaling-threshold=<0..32>``
+        This option prevents "overkill" use of prescalers, which can be caused
+        by misconfiguration, or user trying to play a video with much larger
+        size. With this option, user can specify the maximal allowed downscaling
+        ratio in both dimention. To satisfy it, the number of passes for
+        prescaler will be reduced, and if necessary prescaler could also be
+        disabled.
+
+        The default value is 2.0, and should be able to prevent most seemingly
+        unreasonable use of prescalers. Most user would probably want to set it
+        to a smaller value between 1.0 and 1.5 for better performance.
+
+        A value less than 1.0 will disable the check.
+
     ``pre-shaders=<files>``, ``post-shaders=<files>``, ``scale-shader=<file>``
         Custom GLSL fragment shaders.
 

video/out/opengl/superxbr.c

@@ -0,0 +1,227 @@
+/*
+ * This file is part of mpv.
+ *
+ * mpv is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * mpv is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with mpv.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * You can alternatively redistribute this file and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ */
+
+#include "superxbr.h"
+
+#include <assert.h>
+
+#define GLSL(x) gl_sc_add(sc, #x "\n");
+#define GLSLF(...) gl_sc_addf(sc, __VA_ARGS__)
+#define GLSLH(x) gl_sc_hadd(sc, #x "\n");
+#define GLSLHF(...) gl_sc_haddf(sc, __VA_ARGS__)
+
+struct superxbr_opts {
+    float sharpness;
+    float edge_strength;
+};
+
+const struct superxbr_opts superxbr_opts_def = {
+    .sharpness = 1.0f,
+    .edge_strength = 1.0f,
+};
+
+#define OPT_BASE_STRUCT struct superxbr_opts
+const struct m_sub_options superxbr_conf = {
+    .opts = (const m_option_t[]) {
+        OPT_FLOATRANGE("sharpness", sharpness, 0, 0.0, 2.0),
+        OPT_FLOATRANGE("edge-strength", edge_strength, 0, 0.0, 1.0),
+        {0}
+    },
+    .size = sizeof(struct superxbr_opts),
+    .defaults = &superxbr_opts_def,
+};
+
+/*
+
+    *******  Super XBR Shader  *******
+
+    Copyright (c) 2015 Hyllian - sergiogdb@gmail.com
+
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in
+    all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+    THE SOFTWARE.
+
+*/
+
+void pass_superxbr(struct gl_shader_cache *sc, int planes, int tex_num,
+                   int step, const struct superxbr_opts *conf,
+                   struct gl_transform *transform)
+{
+    assert(0 <= step && step < 2);
+    GLSLF("// superxbr (tex %d, step %d)\n", tex_num, step + 1);
+
+    if (!conf)
+        conf = &superxbr_opts_def;
+
+    if (step == 0) {
+        *transform = (struct gl_transform){{{2.0,0.0}, {0.0,2.0}}, {-0.5,-0.5}};
+
+        GLSLH(#define wp1  2.0)
+        GLSLH(#define wp2  1.0)
+        GLSLH(#define wp3 -1.0)
+        GLSLH(#define wp4  4.0)
+        GLSLH(#define wp5 -1.0)
+        GLSLH(#define wp6  1.0)
+
+        GLSLHF("#define weight1 (%f*1.29633/10.0)\n", conf->sharpness);
+        GLSLHF("#define weight2 (%f*1.75068/10.0/2.0)\n", conf->sharpness);
+
+        GLSLH(#define Get(x, y) (texture(tex, pos + (vec2(x, y) - vec2(0.25, 0.25)) / tex_size)[plane]))
+    } else {
+        *transform = (struct gl_transform){{{1.0,0.0}, {0.0,1.0}}, {0.0,0.0}};
+
+        GLSLH(#define wp1  2.0)
+        GLSLH(#define wp2  0.0)
+        GLSLH(#define wp3  0.0)
+        GLSLH(#define wp4  0.0)
+        GLSLH(#define wp5  0.0)
+        GLSLH(#define wp6  0.0)
+
+        GLSLHF("#define weight1 (%f*1.75068/10.0)\n", conf->sharpness);
+        GLSLHF("#define weight2 (%f*1.29633/10.0/2.0)\n", conf->sharpness);
+
+        GLSLH(#define Get(x, y) (texture(tex, pos + (vec2((x) + (y) - 1, (y) - (x))) / tex_size)[plane]))
+    }
+    GLSLH(float df(float A, float B)
+          {
+              return abs(A-B);
+          });
+
+    GLSLH(float d_wd(float b0, float b1, float c0, float c1, float c2,
+                     float d0, float d1, float d2, float d3, float e1,
+                     float e2, float e3, float f2, float f3)
+          {
+              return (wp1*(df(c1,c2) + df(c1,c0) + df(e2,e1) + df(e2,e3)) +
+                      wp2*(df(d2,d3) + df(d0,d1)) +
+                      wp3*(df(d1,d3) + df(d0,d2)) +
+                      wp4*df(d1,d2) +
+                      wp5*(df(c0,c2) + df(e1,e3)) +
+                      wp6*(df(b0,b1) + df(f2,f3)));
+          })
+
+    GLSLH(float hv_wd(float i1, float i2, float i3, float i4,
+                      float e1, float e2, float e3, float e4)
+          {
+              return (wp4*(df(i1,i2)+df(i3,i4)) +
+                      wp1*(df(i1,e1)+df(i2,e2)+df(i3,e3)+df(i4,e4)) +
+                      wp3*(df(i1,e2)+df(i3,e4)+df(e1,i2)+df(e3,i4)));
+          })
+
+    GLSLHF("float superxbr(sampler2D tex, vec2 pos, vec2 tex_size, int plane) {\n");
+
+    if (step == 0) {
+        GLSLH(vec2 dir = fract(pos * tex_size) - 0.5;)
+        GLSLH(if (dir.x < 0 || dir.y < 0)
+                  return texture(tex, pos - dir / tex_size)[plane];)
+    } else {
+        GLSLH(vec2 dir = fract(pos * tex_size / 2) - 0.5;)
+        GLSLH(if (dir.x * dir.y > 0)
+                  return texture(tex, pos)[plane];)
+    }
+
+    GLSLH(float P0 = Get(-1,-1);
+          float P1 = Get( 2,-1);
+          float P2 = Get(-1, 2);
+          float P3 = Get( 2, 2);
+
+          float  B = Get( 0,-1);
+          float  C = Get( 1,-1);
+          float  D = Get(-1, 0);
+          float  E = Get( 0, 0);
+          float  F = Get( 1, 0);
+          float  G = Get(-1, 1);
+          float  H = Get( 0, 1);
+          float  I = Get( 1, 1);
+
+          float F4 = Get(2, 0);
+          float I4 = Get(2, 1);
+          float H5 = Get(0, 2);
+          float I5 = Get(1, 2);)
+
+/*
+                                  P1
+         |P0|B |C |P1|         C     F4          |a0|b1|c2|d3|
+         |D |E |F |F4|      B     F     I4       |b0|c1|d2|e3|   |e1|i1|i2|e2|
+         |G |H |I |I4|   P0    E  A  I     P3    |c0|d1|e2|f3|   |e3|i3|i4|e4|
+         |P2|H5|I5|P3|      D     H     I5       |d0|e1|f2|g3|
+                               G     H5
+                                  P2
+*/
+
+    /* Calc edgeness in diagonal directions. */
+    GLSLH(float d_edge = (d_wd( D, B, G, E, C, P2, H, F, P1, H5, I, F4, I5, I4 ) -
+                          d_wd( C, F4, B, F, I4, P0, E, I, P3, D, H, I5, G, H5 ));)
+
+    /* Calc edgeness in horizontal/vertical directions. */
+    GLSLH(float hv_edge = (hv_wd(F, I, E, H, C, I5, B, H5) -
+                           hv_wd(E, F, H, I, D, F4, G, I4));)
+
+    /* Filter weights. Two taps only. */
+    GLSLH(vec4 w1 = vec4(-weight1, weight1+0.5, weight1+0.5, -weight1);
+          vec4 w2 = vec4(-weight2, weight2+0.25, weight2+0.25, -weight2);)
+
+    /* Filtering and normalization in four direction generating four colors. */
+    GLSLH(float c1 = dot(vec4(P2, H, F, P1), w1);
+          float c2 = dot(vec4(P0, E, I, P3), w1);
+          float c3 = dot(vec4( D+G, E+H, F+I, F4+I4), w2);
+          float c4 = dot(vec4( C+B, F+E, I+H, I5+H5), w2);)
+
+    GLSLHF("float limits = %f + 0.000001;\n", conf->edge_strength);
+    GLSLH(float edge_strength = smoothstep(0.0, limits, abs(d_edge));)
+
+    /* Smoothly blends the two strongest directions(one in diagonal and the
+     * other in vert/horiz direction). */
+    GLSLHF("float color =  mix(mix(c1, c2, step(0.0, d_edge)),"
+                              "mix(c3, c4, step(0.0, hv_edge)), 1 - %f);\n",
+           conf->edge_strength);
+    /* Anti-ringing code. */
+    GLSLH(float min_sample = min(min(E, F), min(H, I));
+          float max_sample = max(max(E, F), max(H, I));
+          float aux = color;
+          color = clamp(color, min_sample, max_sample);)
+    GLSLHF("color = mix(aux, color, 1-2.0*abs(%f-0.5));\n", conf->edge_strength);
+
+    GLSLH(return color;)
+
+    GLSLHF("}");  // superxbr()
+
+    GLSL(vec4 color = vec4(1.0);)
+
+    for (int i = 0; i < planes; i++) {
+        GLSLF("color[%d] = superxbr(texture%d, texcoord%d, texture_size%d, %d);\n",
+              i, tex_num, tex_num, tex_num, i);
+    }
+}

video/out/opengl/superxbr.h

@@ -0,0 +1,36 @@
+/*
+ * This file is part of mpv.
+ *
+ * mpv is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * mpv is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with mpv.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * You can alternatively redistribute this file and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ */
+
+#ifndef MP_GL_SUPERXBR_H
+#define MP_GL_SUPERXBR_H
+
+#include "common.h"
+#include "utils.h"
+
+extern const struct superxbr_opts superxbr_opts_def;
+extern const struct m_sub_options superxbr_conf;
+
+void pass_superxbr(struct gl_shader_cache *sc, int planes, int tex_num,
+                   int step, const struct superxbr_opts *conf,
+                   struct gl_transform *transform);
+
+#endif

video/out/opengl/utils.c

@@ -435,6 +435,18 @@ void gl_transform_ortho(struct gl_transform *t, float x0, float x1,
     t->t[1] = -(y1 + y0) / (y1 - y0);
 }
 
+// Apply the effects of one transformation to another, transforming it in the
+// process. In other words: post-composes t onto x
+void gl_transform_trans(struct gl_transform t, struct gl_transform *x)
+{
+    float x00 = x->m[0][0], x01 = x->m[0][1], x10 = x->m[1][0], x11 = x->m[1][1];
+    x->m[0][0] = t.m[0][0] * x00 + t.m[0][1] * x10;
+    x->m[1][0] = t.m[0][0] * x01 + t.m[0][1] * x11;
+    x->m[0][1] = t.m[1][0] * x00 + t.m[1][1] * x10;
+    x->m[1][1] = t.m[1][0] * x01 + t.m[1][1] * x11;
+    gl_transform_vec(t, &x->t[0], &x->t[1]);
+}
+
 static void GLAPIENTRY gl_debug_cb(GLenum source, GLenum type, GLuint id,
                                    GLenum severity, GLsizei length,
                                    const GLchar *message, const void *userParam)
@@ -462,7 +474,7 @@ void gl_set_debug_logger(GL *gl, struct mp_log *log)
     }
 }
 
-#define SC_ENTRIES 16
+#define SC_ENTRIES 32
 #define SC_UNIFORM_ENTRIES 20
 
 enum uniform_type {

video/out/opengl/utils.h

@@ -117,6 +117,8 @@ static inline void gl_transform_rect(struct gl_transform t, struct mp_rect_f *r)
     gl_transform_vec(t, &r->x1, &r->y1);
 }
 
+void gl_transform_trans(struct gl_transform t, struct gl_transform *x);
+
 void gl_set_debug_logger(GL *gl, struct mp_log *log);
 
 struct gl_shader_cache;