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           needs_pbo_recreate(false),
  66           finalized(false),
  67           needs_mipmaps(false),
  68           width(width),
  69           height(height)
  70 {
  71         pbos[0] = pbos[1] = pbos[2] = 0;
  72         texture_num[0] = texture_num[1] = texture_num[2] = 0;
  73
  74         assert(width % ycbcr_format.chroma_subsampling_x == 0);
  75         pitch[0] = widths[0] = width;
  76         pitch[1] = widths[1] = width / ycbcr_format.chroma_subsampling_x;
  77         pitch[2] = widths[2] = width / ycbcr_format.chroma_subsampling_x;
  78
  79         assert(height % ycbcr_format.chroma_subsampling_y == 0);
  80         heights[0] = height;
  81         heights[1] = height / ycbcr_format.chroma_subsampling_y;
  82         heights[2] = height / ycbcr_format.chroma_subsampling_y;
  83
  84         pixel_data[0] = pixel_data[1] = pixel_data[2] = NULL;
  85
  86         register_int("needs_mipmaps", &needs_mipmaps);
  87 }
  88
  89 YCbCrInput::~YCbCrInput()
  90 {
  91         if (pbos[0] != 0) {
  92                 glDeleteBuffers(3, pbos);
  93                 check_error();
  94         }
  95         if (texture_num[0] != 0) {
  96                 glDeleteTextures(3, texture_num);
  97                 check_error();
  98         }
  99 }
 100
 101 void YCbCrInput::finalize()
 102 {
 103         glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 104         check_error();
 105
 106         // Create PBOs to hold the textures holding the input image, and then the texture itself.
 107         glGenBuffers(3, pbos);
 108         check_error();
 109         glGenTextures(3, texture_num);
 110         check_error();
 111
 112         for (unsigned channel = 0; channel < 3; ++channel) {
 113                 glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, pbos[channel]);
 114                 check_error();
 115                 glBufferData(GL_PIXEL_UNPACK_BUFFER_ARB, pitch[channel] * heights[channel], NULL, GL_STREAM_DRAW);
 116                 check_error();
 117                 glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
 118                 check_error();
 119
 120                 glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
 121                 check_error();
 122                 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
 123                 check_error();
 124                 glPixelStorei(GL_UNPACK_ROW_LENGTH, pitch[channel]);
 125                 check_error();
 126                 glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE8, widths[channel], heights[channel], 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, NULL);
 127                 check_error();
 128                 glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
 129                 check_error();
 130         }
 131
 132         needs_update = true;
 133         finalized = true;
 134 }
 135
 136 void YCbCrInput::set_gl_state(GLuint glsl_program_num, const std::string& prefix, unsigned *sampler_num)
 137 {
 138         for (unsigned channel = 0; channel < 3; ++channel) {
 139                 glActiveTexture(GL_TEXTURE0 + *sampler_num + channel);
 140                 check_error();
 141                 glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
 142                 check_error();
 143
 144                 if (needs_update || needs_pbo_recreate) {
 145                         // Copy the pixel data into the PBO.
 146                         glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, pbos[channel]);
 147                         check_error();
 148
 149                         if (needs_pbo_recreate) {
 150                                 // The pitch has changed; we need to reallocate this PBO.
 151                                 glBufferData(GL_PIXEL_UNPACK_BUFFER_ARB, pitch[channel] * heights[channel], NULL, GL_STREAM_DRAW);
 152                                 check_error();
 153                         }
 154
 155                         void *mapped_pbo = glMapBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, GL_WRITE_ONLY);
 156                         memcpy(mapped_pbo, pixel_data[channel], pitch[channel] * heights[channel]);
 157
 158                         glUnmapBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB);
 159                         check_error();
 160
 161                         // Re-upload the texture from the PBO.
 162                         glPixelStorei(GL_UNPACK_ROW_LENGTH, pitch[channel]);
 163                         check_error();
 164                         glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, widths[channel], heights[channel], GL_LUMINANCE, GL_UNSIGNED_BYTE, BUFFER_OFFSET(0));
 165                         check_error();
 166                         glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
 167                         check_error();
 168                         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
 169                         check_error();
 170                         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 171                         check_error();
 172                         glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
 173                         check_error();
 174                 }
 175         }
 176
 177         // Bind samplers.
 178         set_uniform_int(glsl_program_num, prefix, "tex_y", *sampler_num + 0);
 179         set_uniform_int(glsl_program_num, prefix, "tex_cb", *sampler_num + 1);
 180         set_uniform_int(glsl_program_num, prefix, "tex_cr", *sampler_num + 2);
 181
 182         *sampler_num += 3;
 183         needs_update = false;
 184         needs_pbo_recreate = false;
 185 }
 186
 187 std::string YCbCrInput::output_fragment_shader()
 188 {
 189         float coeff[3], offset[3], scale[3];
 190
 191         switch (ycbcr_format.luma_coefficients) {
 192         case YCBCR_REC_601:
 193                 // Rec. 601, page 2.
 194                 coeff[0] = 0.299;
 195                 coeff[1] = 0.587;
 196                 coeff[2] = 0.114;
 197                 break;
 198
 199         case YCBCR_REC_709:
 200                 // Rec. 709, page 19.
 201                 coeff[0] = 0.2126;
 202                 coeff[1] = 0.7152;
 203                 coeff[2] = 0.0722;
 204                 break;
 205         default:
 206                 assert(false);
 207         }
 208
 209         if (ycbcr_format.full_range) {
 210                 offset[0] = 0.0 / 255.0;
 211                 offset[1] = 128.0 / 255.0;
 212                 offset[2] = 128.0 / 255.0;
 213
 214                 scale[0] = 1.0;
 215                 scale[1] = 1.0;
 216                 scale[2] = 1.0;
 217         } else {
 218                 // Rec. 601, page 4; Rec. 709, page 19.
 219                 offset[0] = 16.0 / 255.0;
 220                 offset[1] = 128.0 / 255.0;
 221                 offset[2] = 128.0 / 255.0;
 222
 223                 scale[0] = 255.0 / 219.0;
 224                 scale[1] = 255.0 / 224.0;
 225                 scale[2] = 255.0 / 224.0;
 226         }
 227
 228         // Matrix to convert RGB to YCbCr. See e.g. Rec. 601.
 229         Matrix3d rgb_to_ycbcr;
 230         rgb_to_ycbcr(0,0) = coeff[0];
 231         rgb_to_ycbcr(0,1) = coeff[1];
 232         rgb_to_ycbcr(0,2) = coeff[2];
 233
 234         float cb_fac = (224.0 / 219.0) / (coeff[0] + coeff[1] + 1.0f - coeff[2]);
 235         rgb_to_ycbcr(1,0) = -coeff[0] * cb_fac;
 236         rgb_to_ycbcr(1,1) = -coeff[1] * cb_fac;
 237         rgb_to_ycbcr(1,2) = (1.0f - coeff[2]) * cb_fac;
 238
 239         float cr_fac = (224.0 / 219.0) / (1.0f - coeff[0] + coeff[1] + coeff[2]);
 240         rgb_to_ycbcr(2,0) = (1.0f - coeff[0]) * cr_fac;
 241         rgb_to_ycbcr(2,1) = -coeff[1] * cr_fac;
 242         rgb_to_ycbcr(2,2) = -coeff[2] * cr_fac;
 243
 244         // Inverting the matrix gives us what we need to go from YCbCr back to RGB.
 245         Matrix3d ycbcr_to_rgb = rgb_to_ycbcr.inverse();
 246
 247         std::string frag_shader;
 248
 249         frag_shader = output_glsl_mat3("PREFIX(inv_ycbcr_matrix)", ycbcr_to_rgb);
 250
 251         char buf[256];
 252         sprintf(buf, "const vec3 PREFIX(offset) = vec3(%.8f, %.8f, %.8f);\n",
 253                 offset[0], offset[1], offset[2]);
 254         frag_shader += buf;
 255
 256         sprintf(buf, "const vec3 PREFIX(scale) = vec3(%.8f, %.8f, %.8f);\n",
 257                 scale[0], scale[1], scale[2]);
 258         frag_shader += buf;
 259
 260         float cb_offset_x = compute_chroma_offset(
 261                 ycbcr_format.cb_x_position, ycbcr_format.chroma_subsampling_x, widths[1]);
 262         float cb_offset_y = compute_chroma_offset(
 263                 ycbcr_format.cb_y_position, ycbcr_format.chroma_subsampling_y, heights[1]);
 264         sprintf(buf, "const vec2 PREFIX(cb_offset) = vec2(%.8f, %.8f);\n",
 265                 cb_offset_x, cb_offset_y);
 266         frag_shader += buf;
 267
 268         float cr_offset_x = compute_chroma_offset(
 269                 ycbcr_format.cr_x_position, ycbcr_format.chroma_subsampling_x, widths[2]);
 270         float cr_offset_y = compute_chroma_offset(
 271                 ycbcr_format.cr_y_position, ycbcr_format.chroma_subsampling_y, heights[2]);
 272         sprintf(buf, "const vec2 PREFIX(cr_offset) = vec2(%.8f, %.8f);\n",
 273                 cr_offset_x, cr_offset_y);
 274         frag_shader += buf;
 275
 276         frag_shader += read_file("ycbcr_input.frag");
 277         return frag_shader;
 278 }