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 "util.h"
   9 #include "ycbcr_input.h"
  10
  11 using namespace Eigen;
  12
  13 namespace {
  14
  15 // OpenGL has texel center in (0.5, 0.5), but different formats have
  16 // chroma in various other places. If luma samples are X, the chroma
  17 // sample is *, and subsampling is 3x3, the situation with chroma
  18 // center in (0.5, 0.5) looks approximately like this:
  19 //
  20 //   X   X
  21 //     *
  22 //   X   X
  23 //
  24 // If, on the other hand, chroma center is in (0.0, 0.5) (common
  25 // for e.g. MPEG-4), the figure changes to:
  26 //
  27 //   X   X
  28 //   *
  29 //   X   X
  30 //
  31 // In other words, (0.0, 0.0) means that the chroma sample is exactly
  32 // co-sited on top of the top-left luma sample. Note, however, that
  33 // this is _not_ 0.5 texels to the left, since the OpenGL's texel center
  34 // is in (0.5, 0.5); it is in (0.25, 0.25). In a sense, the four luma samples
  35 // define a square where chroma position (0.0, 0.0) is in texel position
  36 // (0.25, 0.25) and chroma position (1.0, 1.0) is in texel position (0.75, 0.75)
  37 // (the outer border shows the borders of the texel itself, ie. from
  38 // (0, 0) to (1, 1)):
  39 //
  40 //  ---------
  41 // |         |
  42 // |  X---X  |
  43 // |  | * |  |
  44 // |  X---X  |
  45 // |         |
  46 //  ---------
  47 //
  48 // Also note that if we have no subsampling, the square will have zero
  49 // area and the chroma position does not matter at all.
  50 float compute_chroma_offset(float pos, unsigned subsampling_factor, unsigned resolution)
  51 {
  52         float local_chroma_pos = (0.5 + pos * (subsampling_factor - 1)) / subsampling_factor;
  53         return (0.5 - local_chroma_pos) / resolution;
  54 }
  55
  56 }  // namespace
  57
  58 YCbCrInput::YCbCrInput(const ImageFormat &image_format,
  59                        const YCbCrFormat &ycbcr_format,
  60                        unsigned width, unsigned height)
  61         : image_format(image_format),
  62           ycbcr_format(ycbcr_format),
  63           needs_update(false),
  64           needs_pbo_recreate(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 (pbos[0] != 0) {
  91                 glDeleteBuffers(3, pbos);
  92                 check_error();
  93         }
  94         if (texture_num[0] != 0) {
  95                 glDeleteTextures(3, texture_num);
  96                 check_error();
  97         }
  98 }
  99
 100 void YCbCrInput::finalize()
 101 {
 102         glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 103         check_error();
 104
 105         // Create PBOs to hold the textures holding the input image, and then the texture itself.
 106         glGenBuffers(3, pbos);
 107         check_error();
 108         glGenTextures(3, texture_num);
 109         check_error();
 110
 111         for (unsigned channel = 0; channel < 3; ++channel) {
 112                 glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, pbos[channel]);
 113                 check_error();
 114                 glBufferData(GL_PIXEL_UNPACK_BUFFER_ARB, pitch[channel] * heights[channel], NULL, GL_STREAM_DRAW);
 115                 check_error();
 116                 glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
 117                 check_error();
 118
 119                 glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
 120                 check_error();
 121                 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
 122                 check_error();
 123                 glPixelStorei(GL_UNPACK_ROW_LENGTH, pitch[channel]);
 124                 check_error();
 125                 glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE8, widths[channel], heights[channel], 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, NULL);
 126                 check_error();
 127                 glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
 128                 check_error();
 129         }
 130
 131         needs_update = true;
 132         finalized = true;
 133 }
 134
 135 void YCbCrInput::set_gl_state(GLuint glsl_program_num, const std::string& prefix, unsigned *sampler_num)
 136 {
 137         for (unsigned channel = 0; channel < 3; ++channel) {
 138                 glActiveTexture(GL_TEXTURE0 + *sampler_num + channel);
 139                 check_error();
 140                 glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
 141                 check_error();
 142
 143                 if (needs_update || needs_pbo_recreate) {
 144                         // Copy the pixel data into the PBO.
 145                         glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, pbos[channel]);
 146                         check_error();
 147
 148                         if (needs_pbo_recreate) {
 149                                 // The pitch has changed; we need to reallocate this PBO.
 150                                 glBufferData(GL_PIXEL_UNPACK_BUFFER_ARB, pitch[channel] * heights[channel], NULL, GL_STREAM_DRAW);
 151                                 check_error();
 152                         }
 153
 154                         void *mapped_pbo = glMapBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, GL_WRITE_ONLY);
 155                         memcpy(mapped_pbo, pixel_data[channel], pitch[channel] * heights[channel]);
 156
 157                         glUnmapBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB);
 158                         check_error();
 159
 160                         // Re-upload the texture from the PBO.
 161                         glPixelStorei(GL_UNPACK_ROW_LENGTH, pitch[channel]);
 162                         check_error();
 163                         glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, widths[channel], heights[channel], GL_LUMINANCE, GL_UNSIGNED_BYTE, BUFFER_OFFSET(0));
 164                         check_error();
 165                         glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
 166                         check_error();
 167                         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
 168                         check_error();
 169                         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 170                         check_error();
 171                         glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
 172                         check_error();
 173                 }
 174         }
 175
 176         // Bind samplers.
 177         set_uniform_int(glsl_program_num, prefix, "tex_y", *sampler_num + 0);
 178         set_uniform_int(glsl_program_num, prefix, "tex_cb", *sampler_num + 1);
 179         set_uniform_int(glsl_program_num, prefix, "tex_cr", *sampler_num + 2);
 180
 181         *sampler_num += 3;
 182         needs_update = false;
 183         needs_pbo_recreate = false;
 184 }
 185
 186 std::string YCbCrInput::output_fragment_shader()
 187 {
 188         float coeff[3], offset[3], scale[3];
 189
 190         switch (ycbcr_format.luma_coefficients) {
 191         case YCBCR_REC_601:
 192                 // Rec. 601, page 2.
 193                 coeff[0] = 0.299;
 194                 coeff[1] = 0.587;
 195                 coeff[2] = 0.114;
 196                 break;
 197
 198         case YCBCR_REC_709:
 199                 // Rec. 709, page 19.
 200                 coeff[0] = 0.2126;
 201                 coeff[1] = 0.7152;
 202                 coeff[2] = 0.0722;
 203                 break;
 204         default:
 205                 assert(false);
 206         }
 207
 208         if (ycbcr_format.full_range) {
 209                 offset[0] = 0.0 / 255.0;
 210                 offset[1] = 128.0 / 255.0;
 211                 offset[2] = 128.0 / 255.0;
 212
 213                 scale[0] = 1.0;
 214                 scale[1] = 1.0;
 215                 scale[2] = 1.0;
 216         } else {
 217                 // Rec. 601, page 4; Rec. 709, page 19.
 218                 offset[0] = 16.0 / 255.0;
 219                 offset[1] = 128.0 / 255.0;
 220                 offset[2] = 128.0 / 255.0;
 221
 222                 scale[0] = 255.0 / 219.0;
 223                 scale[1] = 255.0 / 224.0;
 224                 scale[2] = 255.0 / 224.0;
 225         }
 226
 227         // Matrix to convert RGB to YCbCr. See e.g. Rec. 601.
 228         Matrix3d rgb_to_ycbcr;
 229         rgb_to_ycbcr(0,0) = coeff[0];
 230         rgb_to_ycbcr(0,1) = coeff[1];
 231         rgb_to_ycbcr(0,2) = coeff[2];
 232
 233         float cb_fac = (224.0 / 219.0) / (coeff[0] + coeff[1] + 1.0f - coeff[2]);
 234         rgb_to_ycbcr(1,0) = -coeff[0] * cb_fac;
 235         rgb_to_ycbcr(1,1) = -coeff[1] * cb_fac;
 236         rgb_to_ycbcr(1,2) = (1.0f - coeff[2]) * cb_fac;
 237
 238         float cr_fac = (224.0 / 219.0) / (1.0f - coeff[0] + coeff[1] + coeff[2]);
 239         rgb_to_ycbcr(2,0) = (1.0f - coeff[0]) * cr_fac;
 240         rgb_to_ycbcr(2,1) = -coeff[1] * cr_fac;
 241         rgb_to_ycbcr(2,2) = -coeff[2] * cr_fac;
 242
 243         // Inverting the matrix gives us what we need to go from YCbCr back to RGB.
 244         Matrix3d ycbcr_to_rgb = rgb_to_ycbcr.inverse();
 245
 246         std::string frag_shader;
 247
 248         frag_shader = output_glsl_mat3("PREFIX(inv_ycbcr_matrix)", ycbcr_to_rgb);
 249
 250         char buf[256];
 251         sprintf(buf, "const vec3 PREFIX(offset) = vec3(%.8f, %.8f, %.8f);\n",
 252                 offset[0], offset[1], offset[2]);
 253         frag_shader += buf;
 254
 255         sprintf(buf, "const vec3 PREFIX(scale) = vec3(%.8f, %.8f, %.8f);\n",
 256                 scale[0], scale[1], scale[2]);
 257         frag_shader += buf;
 258
 259         float cb_offset_x = compute_chroma_offset(
 260                 ycbcr_format.cb_x_position, ycbcr_format.chroma_subsampling_x, widths[1]);
 261         float cb_offset_y = compute_chroma_offset(
 262                 ycbcr_format.cb_y_position, ycbcr_format.chroma_subsampling_y, heights[1]);
 263         sprintf(buf, "const vec2 PREFIX(cb_offset) = vec2(%.8f, %.8f);\n",
 264                 cb_offset_x, cb_offset_y);
 265         frag_shader += buf;
 266
 267         float cr_offset_x = compute_chroma_offset(
 268                 ycbcr_format.cr_x_position, ycbcr_format.chroma_subsampling_x, widths[2]);
 269         float cr_offset_y = compute_chroma_offset(
 270                 ycbcr_format.cr_y_position, ycbcr_format.chroma_subsampling_y, heights[2]);
 271         sprintf(buf, "const vec2 PREFIX(cr_offset) = vec2(%.8f, %.8f);\n",
 272                 cr_offset_x, cr_offset_y);
 273         frag_shader += buf;
 274
 275         frag_shader += read_file("ycbcr_input.frag");
 276         return frag_shader;
 277 }