git.sesse.net Git - movit/blob - ycbcr_input.cpp

   1 #include <Eigen/Core>
   2 #include <Eigen/LU>
   3 #include <GL/glew.h>
   4 #include <assert.h>
   5 #include <stdio.h>
   6 #include <string.h>
   7
   8 #include "effect_util.h"
   9 #include "util.h"
  10 #include "ycbcr_input.h"
  11
  12 using namespace Eigen;
  13
  14 namespace {
  15
  16 // OpenGL has texel center in (0.5, 0.5), but different formats have
  17 // chroma in various other places. If luma samples are X, the chroma
  18 // sample is *, and subsampling is 3x3, the situation with chroma
  19 // center in (0.5, 0.5) looks approximately like this:
  20 //
  21 //   X   X
  22 //     *
  23 //   X   X
  24 //
  25 // If, on the other hand, chroma center is in (0.0, 0.5) (common
  26 // for e.g. MPEG-4), the figure changes to:
  27 //
  28 //   X   X
  29 //   *
  30 //   X   X
  31 //
  32 // In other words, (0.0, 0.0) means that the chroma sample is exactly
  33 // co-sited on top of the top-left luma sample. Note, however, that
  34 // this is _not_ 0.5 texels to the left, since the OpenGL's texel center
  35 // is in (0.5, 0.5); it is in (0.25, 0.25). In a sense, the four luma samples
  36 // define a square where chroma position (0.0, 0.0) is in texel position
  37 // (0.25, 0.25) and chroma position (1.0, 1.0) is in texel position (0.75, 0.75)
  38 // (the outer border shows the borders of the texel itself, ie. from
  39 // (0, 0) to (1, 1)):
  40 //
  41 //  ---------
  42 // |         |
  43 // |  X---X  |
  44 // |  | * |  |
  45 // |  X---X  |
  46 // |         |
  47 //  ---------
  48 //
  49 // Also note that if we have no subsampling, the square will have zero
  50 // area and the chroma position does not matter at all.
  51 float compute_chroma_offset(float pos, unsigned subsampling_factor, unsigned resolution)
  52 {
  53         float local_chroma_pos = (0.5 + pos * (subsampling_factor - 1)) / subsampling_factor;
  54         return (0.5 - local_chroma_pos) / resolution;
  55 }
  56
  57 }  // namespace
  58
  59 YCbCrInput::YCbCrInput(const ImageFormat &image_format,
  60                        const YCbCrFormat &ycbcr_format,
  61                        unsigned width, unsigned height)
  62         : image_format(image_format),
  63           ycbcr_format(ycbcr_format),
  64           needs_update(false),
  65           finalized(false),
  66           needs_mipmaps(false),
  67           width(width),
  68           height(height)
  69 {
  70         pbos[0] = pbos[1] = pbos[2] = 0;
  71         texture_num[0] = texture_num[1] = texture_num[2] = 0;
  72
  73         assert(width % ycbcr_format.chroma_subsampling_x == 0);
  74         pitch[0] = widths[0] = width;
  75         pitch[1] = widths[1] = width / ycbcr_format.chroma_subsampling_x;
  76         pitch[2] = widths[2] = width / ycbcr_format.chroma_subsampling_x;
  77
  78         assert(height % ycbcr_format.chroma_subsampling_y == 0);
  79         heights[0] = height;
  80         heights[1] = height / ycbcr_format.chroma_subsampling_y;
  81         heights[2] = height / ycbcr_format.chroma_subsampling_y;
  82
  83         pixel_data[0] = pixel_data[1] = pixel_data[2] = NULL;
  84
  85         register_int("needs_mipmaps", &needs_mipmaps);
  86 }
  87
  88 YCbCrInput::~YCbCrInput()
  89 {
  90         for (unsigned channel = 0; channel < 3; ++channel) {
  91                 if (texture_num[channel] != 0) {
  92                         resource_pool->release_2d_texture(texture_num[channel]);
  93                 }
  94         }
  95 }
  96
  97 void YCbCrInput::finalize()
  98 {
  99         // Create the textures themselves.
 100         for (unsigned channel = 0; channel < 3; ++channel) {
 101                 texture_num[channel] = resource_pool->create_2d_texture(GL_LUMINANCE8, widths[channel], heights[channel]);
 102                 glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
 103                 check_error();
 104                 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
 105                 check_error();
 106         }
 107
 108         needs_update = true;
 109         finalized = true;
 110 }
 111
 112 void YCbCrInput::set_gl_state(GLuint glsl_program_num, const std::string& prefix, unsigned *sampler_num)
 113 {
 114         for (unsigned channel = 0; channel < 3; ++channel) {
 115                 glActiveTexture(GL_TEXTURE0 + *sampler_num + channel);
 116                 check_error();
 117                 glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
 118                 check_error();
 119
 120                 if (needs_update) {
 121                         // Re-upload the texture.
 122                         // Copy the pixel data into the PBO.
 123                         glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, pbos[channel]);
 124                         check_error();
 125                         glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 126                         check_error();
 127                         glPixelStorei(GL_UNPACK_ROW_LENGTH, pitch[channel]);
 128                         check_error();
 129                         glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, widths[channel], heights[channel], GL_LUMINANCE, GL_UNSIGNED_BYTE, pixel_data[channel]);
 130                         check_error();
 131                         glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
 132                         check_error();
 133                         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
 134                         check_error();
 135                         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 136                         check_error();
 137                 }
 138         }
 139
 140         glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
 141         check_error();
 142
 143         // Bind samplers.
 144         set_uniform_int(glsl_program_num, prefix, "tex_y", *sampler_num + 0);
 145         set_uniform_int(glsl_program_num, prefix, "tex_cb", *sampler_num + 1);
 146         set_uniform_int(glsl_program_num, prefix, "tex_cr", *sampler_num + 2);
 147
 148         *sampler_num += 3;
 149         needs_update = false;
 150 }
 151
 152 std::string YCbCrInput::output_fragment_shader()
 153 {
 154         float coeff[3], offset[3], scale[3];
 155
 156         switch (ycbcr_format.luma_coefficients) {
 157         case YCBCR_REC_601:
 158                 // Rec. 601, page 2.
 159                 coeff[0] = 0.299;
 160                 coeff[1] = 0.587;
 161                 coeff[2] = 0.114;
 162                 break;
 163
 164         case YCBCR_REC_709:
 165                 // Rec. 709, page 19.
 166                 coeff[0] = 0.2126;
 167                 coeff[1] = 0.7152;
 168                 coeff[2] = 0.0722;
 169                 break;
 170
 171         case YCBCR_REC_2020:
 172                 // Rec. 2020, page 4.
 173                 coeff[0] = 0.2627;
 174                 coeff[1] = 0.6780;
 175                 coeff[2] = 0.0593;
 176                 break;
 177
 178         default:
 179                 assert(false);
 180         }
 181
 182         if (ycbcr_format.full_range) {
 183                 offset[0] = 0.0 / 255.0;
 184                 offset[1] = 128.0 / 255.0;
 185                 offset[2] = 128.0 / 255.0;
 186
 187                 scale[0] = 1.0;
 188                 scale[1] = 1.0;
 189                 scale[2] = 1.0;
 190         } else {
 191                 // Rec. 601, page 4; Rec. 709, page 19; Rec. 2020, page 4.
 192                 offset[0] = 16.0 / 255.0;
 193                 offset[1] = 128.0 / 255.0;
 194                 offset[2] = 128.0 / 255.0;
 195
 196                 scale[0] = 255.0 / 219.0;
 197                 scale[1] = 255.0 / 224.0;
 198                 scale[2] = 255.0 / 224.0;
 199         }
 200
 201         // Matrix to convert RGB to YCbCr. See e.g. Rec. 601.
 202         Matrix3d rgb_to_ycbcr;
 203         rgb_to_ycbcr(0,0) = coeff[0];
 204         rgb_to_ycbcr(0,1) = coeff[1];
 205         rgb_to_ycbcr(0,2) = coeff[2];
 206
 207         float cb_fac = (224.0 / 219.0) / (coeff[0] + coeff[1] + 1.0f - coeff[2]);
 208         rgb_to_ycbcr(1,0) = -coeff[0] * cb_fac;
 209         rgb_to_ycbcr(1,1) = -coeff[1] * cb_fac;
 210         rgb_to_ycbcr(1,2) = (1.0f - coeff[2]) * cb_fac;
 211
 212         float cr_fac = (224.0 / 219.0) / (1.0f - coeff[0] + coeff[1] + coeff[2]);
 213         rgb_to_ycbcr(2,0) = (1.0f - coeff[0]) * cr_fac;
 214         rgb_to_ycbcr(2,1) = -coeff[1] * cr_fac;
 215         rgb_to_ycbcr(2,2) = -coeff[2] * cr_fac;
 216
 217         // Inverting the matrix gives us what we need to go from YCbCr back to RGB.
 218         Matrix3d ycbcr_to_rgb = rgb_to_ycbcr.inverse();
 219
 220         std::string frag_shader;
 221
 222         frag_shader = output_glsl_mat3("PREFIX(inv_ycbcr_matrix)", ycbcr_to_rgb);
 223
 224         char buf[256];
 225         sprintf(buf, "const vec3 PREFIX(offset) = vec3(%.8f, %.8f, %.8f);\n",
 226                 offset[0], offset[1], offset[2]);
 227         frag_shader += buf;
 228
 229         sprintf(buf, "const vec3 PREFIX(scale) = vec3(%.8f, %.8f, %.8f);\n",
 230                 scale[0], scale[1], scale[2]);
 231         frag_shader += buf;
 232
 233         float cb_offset_x = compute_chroma_offset(
 234                 ycbcr_format.cb_x_position, ycbcr_format.chroma_subsampling_x, widths[1]);
 235         float cb_offset_y = compute_chroma_offset(
 236                 ycbcr_format.cb_y_position, ycbcr_format.chroma_subsampling_y, heights[1]);
 237         sprintf(buf, "const vec2 PREFIX(cb_offset) = vec2(%.8f, %.8f);\n",
 238                 cb_offset_x, cb_offset_y);
 239         frag_shader += buf;
 240
 241         float cr_offset_x = compute_chroma_offset(
 242                 ycbcr_format.cr_x_position, ycbcr_format.chroma_subsampling_x, widths[2]);
 243         float cr_offset_y = compute_chroma_offset(
 244                 ycbcr_format.cr_y_position, ycbcr_format.chroma_subsampling_y, heights[2]);
 245         sprintf(buf, "const vec2 PREFIX(cr_offset) = vec2(%.8f, %.8f);\n",
 246                 cr_offset_x, cr_offset_y);
 247         frag_shader += buf;
 248
 249         frag_shader += read_file("ycbcr_input.frag");
 250         return frag_shader;
 251 }