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 "resource_pool.h"
  10 #include "util.h"
  11 #include "ycbcr_input.h"
  12
  13 using namespace Eigen;
  14
  15 namespace {
  16
  17 // OpenGL has texel center in (0.5, 0.5), but different formats have
  18 // chroma in various other places. If luma samples are X, the chroma
  19 // sample is *, and subsampling is 3x3, the situation with chroma
  20 // center in (0.5, 0.5) looks approximately like this:
  21 //
  22 //   X   X
  23 //     *
  24 //   X   X
  25 //
  26 // If, on the other hand, chroma center is in (0.0, 0.5) (common
  27 // for e.g. MPEG-4), the figure changes to:
  28 //
  29 //   X   X
  30 //   *
  31 //   X   X
  32 //
  33 // In other words, (0.0, 0.0) means that the chroma sample is exactly
  34 // co-sited on top of the top-left luma sample. Note, however, that
  35 // this is _not_ 0.5 texels to the left, since the OpenGL's texel center
  36 // is in (0.5, 0.5); it is in (0.25, 0.25). In a sense, the four luma samples
  37 // define a square where chroma position (0.0, 0.0) is in texel position
  38 // (0.25, 0.25) and chroma position (1.0, 1.0) is in texel position (0.75, 0.75)
  39 // (the outer border shows the borders of the texel itself, ie. from
  40 // (0, 0) to (1, 1)):
  41 //
  42 //  ---------
  43 // |         |
  44 // |  X---X  |
  45 // |  | * |  |
  46 // |  X---X  |
  47 // |         |
  48 //  ---------
  49 //
  50 // Also note that if we have no subsampling, the square will have zero
  51 // area and the chroma position does not matter at all.
  52 float compute_chroma_offset(float pos, unsigned subsampling_factor, unsigned resolution)
  53 {
  54         float local_chroma_pos = (0.5 + pos * (subsampling_factor - 1)) / subsampling_factor;
  55         return (0.5 - local_chroma_pos) / resolution;
  56 }
  57
  58 }  // namespace
  59
  60 YCbCrInput::YCbCrInput(const ImageFormat &image_format,
  61                        const YCbCrFormat &ycbcr_format,
  62                        unsigned width, unsigned height)
  63         : image_format(image_format),
  64           ycbcr_format(ycbcr_format),
  65           needs_update(false),
  66           finalized(false),
  67           needs_mipmaps(false),
  68           width(width),
  69           height(height),
  70           resource_pool(NULL)
  71 {
  72         pbos[0] = pbos[1] = pbos[2] = 0;
  73         texture_num[0] = texture_num[1] = texture_num[2] = 0;
  74
  75         assert(width % ycbcr_format.chroma_subsampling_x == 0);
  76         pitch[0] = widths[0] = width;
  77         pitch[1] = widths[1] = width / ycbcr_format.chroma_subsampling_x;
  78         pitch[2] = widths[2] = width / ycbcr_format.chroma_subsampling_x;
  79
  80         assert(height % ycbcr_format.chroma_subsampling_y == 0);
  81         heights[0] = height;
  82         heights[1] = height / ycbcr_format.chroma_subsampling_y;
  83         heights[2] = height / ycbcr_format.chroma_subsampling_y;
  84
  85         pixel_data[0] = pixel_data[1] = pixel_data[2] = NULL;
  86
  87         register_int("needs_mipmaps", &needs_mipmaps);
  88 }
  89
  90 YCbCrInput::~YCbCrInput()
  91 {
  92         for (unsigned channel = 0; channel < 3; ++channel) {
  93                 if (texture_num[channel] != 0) {
  94                         resource_pool->release_2d_texture(texture_num[channel]);
  95                 }
  96         }
  97 }
  98
  99 void YCbCrInput::finalize()
 100 {
 101         // Create the textures themselves.
 102         for (unsigned channel = 0; channel < 3; ++channel) {
 103                 texture_num[channel] = resource_pool->create_2d_texture(GL_LUMINANCE8, widths[channel], heights[channel]);
 104                 glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
 105                 check_error();
 106                 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
 107                 check_error();
 108         }
 109
 110         needs_update = true;
 111         finalized = true;
 112 }
 113
 114 void YCbCrInput::set_gl_state(GLuint glsl_program_num, const std::string& prefix, unsigned *sampler_num)
 115 {
 116         for (unsigned channel = 0; channel < 3; ++channel) {
 117                 glActiveTexture(GL_TEXTURE0 + *sampler_num + channel);
 118                 check_error();
 119                 glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
 120                 check_error();
 121
 122                 if (needs_update) {
 123                         // Re-upload the texture.
 124                         // Copy the pixel data into the PBO.
 125                         glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, pbos[channel]);
 126                         check_error();
 127                         glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 128                         check_error();
 129                         glPixelStorei(GL_UNPACK_ROW_LENGTH, pitch[channel]);
 130                         check_error();
 131                         glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, widths[channel], heights[channel], GL_LUMINANCE, GL_UNSIGNED_BYTE, pixel_data[channel]);
 132                         check_error();
 133                         glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
 134                         check_error();
 135                         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
 136                         check_error();
 137                         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 138                         check_error();
 139                 }
 140         }
 141
 142         glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
 143         check_error();
 144
 145         // Bind samplers.
 146         set_uniform_int(glsl_program_num, prefix, "tex_y", *sampler_num + 0);
 147         set_uniform_int(glsl_program_num, prefix, "tex_cb", *sampler_num + 1);
 148         set_uniform_int(glsl_program_num, prefix, "tex_cr", *sampler_num + 2);
 149
 150         *sampler_num += 3;
 151         needs_update = false;
 152 }
 153
 154 std::string YCbCrInput::output_fragment_shader()
 155 {
 156         float coeff[3], offset[3], scale[3];
 157
 158         switch (ycbcr_format.luma_coefficients) {
 159         case YCBCR_REC_601:
 160                 // Rec. 601, page 2.
 161                 coeff[0] = 0.299;
 162                 coeff[1] = 0.587;
 163                 coeff[2] = 0.114;
 164                 break;
 165
 166         case YCBCR_REC_709:
 167                 // Rec. 709, page 19.
 168                 coeff[0] = 0.2126;
 169                 coeff[1] = 0.7152;
 170                 coeff[2] = 0.0722;
 171                 break;
 172
 173         case YCBCR_REC_2020:
 174                 // Rec. 2020, page 4.
 175                 coeff[0] = 0.2627;
 176                 coeff[1] = 0.6780;
 177                 coeff[2] = 0.0593;
 178                 break;
 179
 180         default:
 181                 assert(false);
 182         }
 183
 184         if (ycbcr_format.full_range) {
 185                 offset[0] = 0.0 / 255.0;
 186                 offset[1] = 128.0 / 255.0;
 187                 offset[2] = 128.0 / 255.0;
 188
 189                 scale[0] = 1.0;
 190                 scale[1] = 1.0;
 191                 scale[2] = 1.0;
 192         } else {
 193                 // Rec. 601, page 4; Rec. 709, page 19; Rec. 2020, page 4.
 194                 offset[0] = 16.0 / 255.0;
 195                 offset[1] = 128.0 / 255.0;
 196                 offset[2] = 128.0 / 255.0;
 197
 198                 scale[0] = 255.0 / 219.0;
 199                 scale[1] = 255.0 / 224.0;
 200                 scale[2] = 255.0 / 224.0;
 201         }
 202
 203         // Matrix to convert RGB to YCbCr. See e.g. Rec. 601.
 204         Matrix3d rgb_to_ycbcr;
 205         rgb_to_ycbcr(0,0) = coeff[0];
 206         rgb_to_ycbcr(0,1) = coeff[1];
 207         rgb_to_ycbcr(0,2) = coeff[2];
 208
 209         float cb_fac = (224.0 / 219.0) / (coeff[0] + coeff[1] + 1.0f - coeff[2]);
 210         rgb_to_ycbcr(1,0) = -coeff[0] * cb_fac;
 211         rgb_to_ycbcr(1,1) = -coeff[1] * cb_fac;
 212         rgb_to_ycbcr(1,2) = (1.0f - coeff[2]) * cb_fac;
 213
 214         float cr_fac = (224.0 / 219.0) / (1.0f - coeff[0] + coeff[1] + coeff[2]);
 215         rgb_to_ycbcr(2,0) = (1.0f - coeff[0]) * cr_fac;
 216         rgb_to_ycbcr(2,1) = -coeff[1] * cr_fac;
 217         rgb_to_ycbcr(2,2) = -coeff[2] * cr_fac;
 218
 219         // Inverting the matrix gives us what we need to go from YCbCr back to RGB.
 220         Matrix3d ycbcr_to_rgb = rgb_to_ycbcr.inverse();
 221
 222         std::string frag_shader;
 223
 224         frag_shader = output_glsl_mat3("PREFIX(inv_ycbcr_matrix)", ycbcr_to_rgb);
 225
 226         char buf[256];
 227         sprintf(buf, "const vec3 PREFIX(offset) = vec3(%.8f, %.8f, %.8f);\n",
 228                 offset[0], offset[1], offset[2]);
 229         frag_shader += buf;
 230
 231         sprintf(buf, "const vec3 PREFIX(scale) = vec3(%.8f, %.8f, %.8f);\n",
 232                 scale[0], scale[1], scale[2]);
 233         frag_shader += buf;
 234
 235         float cb_offset_x = compute_chroma_offset(
 236                 ycbcr_format.cb_x_position, ycbcr_format.chroma_subsampling_x, widths[1]);
 237         float cb_offset_y = compute_chroma_offset(
 238                 ycbcr_format.cb_y_position, ycbcr_format.chroma_subsampling_y, heights[1]);
 239         sprintf(buf, "const vec2 PREFIX(cb_offset) = vec2(%.8f, %.8f);\n",
 240                 cb_offset_x, cb_offset_y);
 241         frag_shader += buf;
 242
 243         float cr_offset_x = compute_chroma_offset(
 244                 ycbcr_format.cr_x_position, ycbcr_format.chroma_subsampling_x, widths[2]);
 245         float cr_offset_y = compute_chroma_offset(
 246                 ycbcr_format.cr_y_position, ycbcr_format.chroma_subsampling_y, heights[2]);
 247         sprintf(buf, "const vec2 PREFIX(cr_offset) = vec2(%.8f, %.8f);\n",
 248                 cr_offset_x, cr_offset_y);
 249         frag_shader += buf;
 250
 251         frag_shader += read_file("ycbcr_input.frag");
 252         return frag_shader;
 253 }