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         if (texture_num[0] != 0) {
  91                 glDeleteTextures(3, texture_num);
  92                 check_error();
  93         }
  94 }
  95
  96 void YCbCrInput::finalize()
  97 {
  98         // Create the textures themselves.
  99         glGenTextures(3, texture_num);
 100         check_error();
 101
 102         for (unsigned channel = 0; channel < 3; ++channel) {
 103                 glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
 104                 check_error();
 105                 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
 106                 check_error();
 107                 glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE8, widths[channel], heights[channel], 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, NULL);
 108                 check_error();
 109         }
 110
 111         needs_update = true;
 112         finalized = true;
 113 }
 114
 115 void YCbCrInput::set_gl_state(GLuint glsl_program_num, const std::string& prefix, unsigned *sampler_num)
 116 {
 117         for (unsigned channel = 0; channel < 3; ++channel) {
 118                 glActiveTexture(GL_TEXTURE0 + *sampler_num + channel);
 119                 check_error();
 120                 glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
 121                 check_error();
 122
 123                 if (needs_update) {
 124                         // Re-upload the texture.
 125                         // Copy the pixel data into the PBO.
 126                         glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, pbos[channel]);
 127                         check_error();
 128                         glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 129                         check_error();
 130                         glPixelStorei(GL_UNPACK_ROW_LENGTH, pitch[channel]);
 131                         check_error();
 132                         glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, widths[channel], heights[channel], GL_LUMINANCE, GL_UNSIGNED_BYTE, pixel_data[channel]);
 133                         check_error();
 134                         glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
 135                         check_error();
 136                         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
 137                         check_error();
 138                         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 139                         check_error();
 140                 }
 141         }
 142
 143         glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
 144         check_error();
 145
 146         // Bind samplers.
 147         set_uniform_int(glsl_program_num, prefix, "tex_y", *sampler_num + 0);
 148         set_uniform_int(glsl_program_num, prefix, "tex_cb", *sampler_num + 1);
 149         set_uniform_int(glsl_program_num, prefix, "tex_cr", *sampler_num + 2);
 150
 151         *sampler_num += 3;
 152         needs_update = false;
 153 }
 154
 155 std::string YCbCrInput::output_fragment_shader()
 156 {
 157         float coeff[3], offset[3], scale[3];
 158
 159         switch (ycbcr_format.luma_coefficients) {
 160         case YCBCR_REC_601:
 161                 // Rec. 601, page 2.
 162                 coeff[0] = 0.299;
 163                 coeff[1] = 0.587;
 164                 coeff[2] = 0.114;
 165                 break;
 166
 167         case YCBCR_REC_709:
 168                 // Rec. 709, page 19.
 169                 coeff[0] = 0.2126;
 170                 coeff[1] = 0.7152;
 171                 coeff[2] = 0.0722;
 172                 break;
 173
 174         case YCBCR_REC_2020:
 175                 // Rec. 2020, page 4.
 176                 coeff[0] = 0.2627;
 177                 coeff[1] = 0.6780;
 178                 coeff[2] = 0.0593;
 179                 break;
 180
 181         default:
 182                 assert(false);
 183         }
 184
 185         if (ycbcr_format.full_range) {
 186                 offset[0] = 0.0 / 255.0;
 187                 offset[1] = 128.0 / 255.0;
 188                 offset[2] = 128.0 / 255.0;
 189
 190                 scale[0] = 1.0;
 191                 scale[1] = 1.0;
 192                 scale[2] = 1.0;
 193         } else {
 194                 // Rec. 601, page 4; Rec. 709, page 19; Rec. 2020, page 4.
 195                 offset[0] = 16.0 / 255.0;
 196                 offset[1] = 128.0 / 255.0;
 197                 offset[2] = 128.0 / 255.0;
 198
 199                 scale[0] = 255.0 / 219.0;
 200                 scale[1] = 255.0 / 224.0;
 201                 scale[2] = 255.0 / 224.0;
 202         }
 203
 204         // Matrix to convert RGB to YCbCr. See e.g. Rec. 601.
 205         Matrix3d rgb_to_ycbcr;
 206         rgb_to_ycbcr(0,0) = coeff[0];
 207         rgb_to_ycbcr(0,1) = coeff[1];
 208         rgb_to_ycbcr(0,2) = coeff[2];
 209
 210         float cb_fac = (224.0 / 219.0) / (coeff[0] + coeff[1] + 1.0f - coeff[2]);
 211         rgb_to_ycbcr(1,0) = -coeff[0] * cb_fac;
 212         rgb_to_ycbcr(1,1) = -coeff[1] * cb_fac;
 213         rgb_to_ycbcr(1,2) = (1.0f - coeff[2]) * cb_fac;
 214
 215         float cr_fac = (224.0 / 219.0) / (1.0f - coeff[0] + coeff[1] + coeff[2]);
 216         rgb_to_ycbcr(2,0) = (1.0f - coeff[0]) * cr_fac;
 217         rgb_to_ycbcr(2,1) = -coeff[1] * cr_fac;
 218         rgb_to_ycbcr(2,2) = -coeff[2] * cr_fac;
 219
 220         // Inverting the matrix gives us what we need to go from YCbCr back to RGB.
 221         Matrix3d ycbcr_to_rgb = rgb_to_ycbcr.inverse();
 222
 223         std::string frag_shader;
 224
 225         frag_shader = output_glsl_mat3("PREFIX(inv_ycbcr_matrix)", ycbcr_to_rgb);
 226
 227         char buf[256];
 228         sprintf(buf, "const vec3 PREFIX(offset) = vec3(%.8f, %.8f, %.8f);\n",
 229                 offset[0], offset[1], offset[2]);
 230         frag_shader += buf;
 231
 232         sprintf(buf, "const vec3 PREFIX(scale) = vec3(%.8f, %.8f, %.8f);\n",
 233                 scale[0], scale[1], scale[2]);
 234         frag_shader += buf;
 235
 236         float cb_offset_x = compute_chroma_offset(
 237                 ycbcr_format.cb_x_position, ycbcr_format.chroma_subsampling_x, widths[1]);
 238         float cb_offset_y = compute_chroma_offset(
 239                 ycbcr_format.cb_y_position, ycbcr_format.chroma_subsampling_y, heights[1]);
 240         sprintf(buf, "const vec2 PREFIX(cb_offset) = vec2(%.8f, %.8f);\n",
 241                 cb_offset_x, cb_offset_y);
 242         frag_shader += buf;
 243
 244         float cr_offset_x = compute_chroma_offset(
 245                 ycbcr_format.cr_x_position, ycbcr_format.chroma_subsampling_x, widths[2]);
 246         float cr_offset_y = compute_chroma_offset(
 247                 ycbcr_format.cr_y_position, ycbcr_format.chroma_subsampling_y, heights[2]);
 248         sprintf(buf, "const vec2 PREFIX(cr_offset) = vec2(%.8f, %.8f);\n",
 249                 cr_offset_x, cr_offset_y);
 250         frag_shader += buf;
 251
 252         frag_shader += read_file("ycbcr_input.frag");
 253         return frag_shader;
 254 }