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

   1 #define GL_GLEXT_PROTOTYPES 1
   2
   3 #include <string.h>
   4 #include <GL/gl.h>
   5 #include <GL/glext.h>
   6 #include <assert.h>
   7
   8 #include "ycbcr_input.h"
   9 #include "util.h"
  10
  11 YCbCrInput::YCbCrInput(const ImageFormat &image_format,
  12                        const YCbCrFormat &ycbcr_format,
  13                        unsigned width, unsigned height)
  14         : image_format(image_format),
  15           ycbcr_format(ycbcr_format),
  16           needs_update(false),
  17           finalized(false),
  18           needs_mipmaps(false),
  19           width(width),
  20           height(height)
  21 {
  22         pitch[0] = pitch[1] = pitch[2] = width;
  23
  24         assert(width % ycbcr_format.chroma_subsampling_x == 0);
  25         widths[0] = width;
  26         widths[1] = width / ycbcr_format.chroma_subsampling_x;
  27         widths[2] = width / ycbcr_format.chroma_subsampling_x;
  28
  29         assert(height % ycbcr_format.chroma_subsampling_y == 0);
  30         heights[0] = height;
  31         heights[1] = height / ycbcr_format.chroma_subsampling_y;
  32         heights[2] = height / ycbcr_format.chroma_subsampling_y;
  33
  34         register_int("needs_mipmaps", &needs_mipmaps);
  35 }
  36
  37 void YCbCrInput::finalize()
  38 {
  39         // Create PBOs to hold the textures holding the input image, and then the texture itself.
  40         glGenBuffers(3, pbos);
  41         check_error();
  42         glGenTextures(3, texture_num);
  43         check_error();
  44
  45         for (unsigned channel = 0; channel < 3; ++channel) {
  46                 glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, pbos[channel]);
  47                 check_error();
  48                 glBufferData(GL_PIXEL_UNPACK_BUFFER_ARB, pitch[channel] * heights[channel], NULL, GL_STREAM_DRAW);
  49                 check_error();
  50                 glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
  51                 check_error();
  52
  53                 glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
  54                 check_error();
  55                 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  56                 check_error();
  57                 glPixelStorei(GL_UNPACK_ROW_LENGTH, pitch[channel]);
  58                 check_error();
  59                 glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE8, widths[channel], heights[channel], 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, NULL);
  60                 check_error();
  61                 glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
  62                 check_error();
  63         }
  64
  65         needs_update = false;
  66         finalized = true;
  67 }
  68
  69 void YCbCrInput::set_gl_state(GLuint glsl_program_num, const std::string& prefix, unsigned *sampler_num)
  70 {
  71         for (unsigned channel = 0; channel < 3; ++channel) {
  72                 glActiveTexture(GL_TEXTURE0 + *sampler_num + channel);
  73                 check_error();
  74                 glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
  75                 check_error();
  76
  77                 if (needs_update) {
  78                         // Copy the pixel data into the PBO.
  79                         glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, pbos[channel]);
  80                         check_error();
  81                         void *mapped_pbo = glMapBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, GL_WRITE_ONLY);
  82                         memcpy(mapped_pbo, pixel_data[channel], pitch[channel] * heights[channel]);
  83                         glUnmapBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB);
  84                         check_error();
  85
  86                         // Re-upload the texture from the PBO.
  87                         glPixelStorei(GL_UNPACK_ROW_LENGTH, pitch[channel]);
  88                         check_error();
  89                         glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, widths[channel], heights[channel], GL_LUMINANCE, GL_UNSIGNED_BYTE, BUFFER_OFFSET(0));
  90                         check_error();
  91                         glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
  92                         check_error();
  93                         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
  94                         check_error();
  95                         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
  96                         check_error();
  97                         glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
  98                         check_error();
  99                 }
 100         }
 101
 102         // Bind samplers.
 103         set_uniform_int(glsl_program_num, prefix, "tex_y", *sampler_num + 0);
 104         set_uniform_int(glsl_program_num, prefix, "tex_cb", *sampler_num + 1);
 105         set_uniform_int(glsl_program_num, prefix, "tex_cr", *sampler_num + 2);
 106
 107         *sampler_num += 3;
 108         needs_update = false;
 109 }
 110
 111 std::string YCbCrInput::output_fragment_shader()
 112 {
 113         float coeff[3], offset[3], scale[3];
 114
 115         switch (ycbcr_format.luma_coefficients) {
 116         case YCBCR_REC_601:
 117                 // Rec. 601, page 2.
 118                 coeff[0] = 0.299;
 119                 coeff[1] = 0.587;
 120                 coeff[2] = 0.114;
 121                 break;
 122
 123         case YCBCR_REC_709:
 124                 // Rec. 709, page 19.
 125                 coeff[0] = 0.2126;
 126                 coeff[1] = 0.7152;
 127                 coeff[2] = 0.0722;
 128                 break;
 129         default:
 130                 assert(false);
 131         }
 132
 133         if (ycbcr_format.full_range) {
 134                 offset[0] = 0.0 / 255.0;
 135                 offset[1] = 128.0 / 255.0;
 136                 offset[2] = 128.0 / 255.0;
 137
 138                 scale[0] = 1.0;
 139                 scale[1] = 1.0;
 140                 scale[2] = 1.0;
 141         } else {
 142                 // Rec. 601, page 4; Rec. 709, page 19.
 143                 offset[0] = 16.0 / 255.0;
 144                 offset[1] = 128.0 / 255.0;
 145                 offset[2] = 128.0 / 255.0;
 146
 147                 scale[0] = 255.0 / 219.0;
 148                 scale[1] = 255.0 / 224.0;
 149                 scale[2] = 255.0 / 224.0;
 150         }
 151
 152         // Matrix to convert RGB to YCbCr. See e.g. Rec. 601.
 153         Matrix3x3 rgb_to_ycbcr;
 154         rgb_to_ycbcr[0] = coeff[0];
 155         rgb_to_ycbcr[3] = coeff[1];
 156         rgb_to_ycbcr[6] = coeff[2];
 157
 158         float cb_fac = (224.0 / 219.0) / (coeff[0] + coeff[1] + 1.0f - coeff[2]);
 159         rgb_to_ycbcr[1] = -coeff[0] * cb_fac;
 160         rgb_to_ycbcr[4] = -coeff[1] * cb_fac;
 161         rgb_to_ycbcr[7] = (1.0f - coeff[2]) * cb_fac;
 162
 163         float cr_fac = (224.0 / 219.0) / (1.0f - coeff[0] + coeff[1] + coeff[2]);
 164         rgb_to_ycbcr[2] = (1.0f - coeff[0]) * cr_fac;
 165         rgb_to_ycbcr[5] = -coeff[1] * cr_fac;
 166         rgb_to_ycbcr[8] = -coeff[2] * cr_fac;
 167
 168         // Inverting the matrix gives us what we need to go from YCbCr back to RGB.
 169         Matrix3x3 ycbcr_to_rgb;
 170         invert_3x3_matrix(rgb_to_ycbcr, ycbcr_to_rgb);
 171
 172         std::string frag_shader;
 173
 174         char buf[1024];
 175         sprintf(buf,
 176                 "const mat3 PREFIX(inv_ycbcr_matrix) = mat3(\n"
 177                 "    %.8f, %.8f, %.8f,\n"
 178                 "    %.8f, %.8f, %.8f,\n"
 179                 "    %.8f, %.8f, %.8f);\n",
 180                 ycbcr_to_rgb[0], ycbcr_to_rgb[1], ycbcr_to_rgb[2],
 181                 ycbcr_to_rgb[3], ycbcr_to_rgb[4], ycbcr_to_rgb[5],
 182                 ycbcr_to_rgb[6], ycbcr_to_rgb[7], ycbcr_to_rgb[8]);
 183         frag_shader = buf;
 184
 185         sprintf(buf, "const vec3 PREFIX(offset) = vec3(%.8f, %.8f, %.8f);\n",
 186                 offset[0], offset[1], offset[2]);
 187         frag_shader += buf;
 188
 189         sprintf(buf, "const vec3 PREFIX(scale) = vec3(%.8f, %.8f, %.8f);\n",
 190                 scale[0], scale[1], scale[2]);
 191         frag_shader += buf;
 192
 193         // OpenGL has texel center in (0.5, 0.5), but different formats have
 194         // chroma in various other places. If luma samples are X, the chroma
 195         // sample is *, and subsampling is 3x3, the situation with chroma
 196         // center in (0.5, 0.5) looks approximately like this:
 197         //
 198         //   X     X
 199         //      *
 200         //   X     X
 201         //
 202         // If, on the other hand, chroma center is in (0.0, 0.5) (common
 203         // for e.g. MPEG-4), the figure changes to:
 204         //
 205         //   X     X
 206         //   *
 207         //   X     X
 208         //
 209         // Obviously, the chroma plane here needs to be moved to the left,
 210         // which means _adding_ 0.5 to the texture coordinates when sampling
 211         // chroma.
 212         float chroma_offset_x = (0.5f - ycbcr_format.chroma_x_position) / widths[1];
 213         float chroma_offset_y = (0.5f - ycbcr_format.chroma_y_position) / heights[1];
 214         sprintf(buf, "const vec2 PREFIX(chroma_offset) = vec2(%.8f, %.8f);\n",
 215                 chroma_offset_x, chroma_offset_y);
 216         frag_shader += buf;
 217
 218         frag_shader += read_file("ycbcr_input.frag");
 219         return frag_shader;
 220 }