8 #include "effect_util.h"
9 #include "resource_pool.h"
11 #include "ycbcr_input.h"
13 using namespace Eigen;
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:
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:
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
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)
54 float local_chroma_pos = (0.5 + pos * (subsampling_factor - 1)) / subsampling_factor;
55 return (0.5 - local_chroma_pos) / resolution;
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),
71 pbos[0] = pbos[1] = pbos[2] = 0;
72 texture_num[0] = texture_num[1] = texture_num[2] = 0;
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;
79 assert(height % ycbcr_format.chroma_subsampling_y == 0);
81 heights[1] = height / ycbcr_format.chroma_subsampling_y;
82 heights[2] = height / ycbcr_format.chroma_subsampling_y;
84 pixel_data[0] = pixel_data[1] = pixel_data[2] = NULL;
86 register_int("needs_mipmaps", &needs_mipmaps);
89 YCbCrInput::~YCbCrInput()
91 for (unsigned channel = 0; channel < 3; ++channel) {
92 if (texture_num[channel] != 0) {
93 resource_pool->release_2d_texture(texture_num[channel]);
98 void YCbCrInput::finalize()
100 // Create the textures themselves.
101 for (unsigned channel = 0; channel < 3; ++channel) {
102 texture_num[channel] = resource_pool->create_2d_texture(GL_LUMINANCE8, widths[channel], heights[channel]);
103 glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
105 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
113 void YCbCrInput::set_gl_state(GLuint glsl_program_num, const std::string& prefix, unsigned *sampler_num)
115 for (unsigned channel = 0; channel < 3; ++channel) {
116 glActiveTexture(GL_TEXTURE0 + *sampler_num + channel);
118 glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
122 // Re-upload the texture.
123 // Copy the pixel data into the PBO.
124 glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, pbos[channel]);
126 glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
128 glPixelStorei(GL_UNPACK_ROW_LENGTH, pitch[channel]);
130 glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, widths[channel], heights[channel], GL_LUMINANCE, GL_UNSIGNED_BYTE, pixel_data[channel]);
132 glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
134 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
136 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
141 glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
145 set_uniform_int(glsl_program_num, prefix, "tex_y", *sampler_num + 0);
146 set_uniform_int(glsl_program_num, prefix, "tex_cb", *sampler_num + 1);
147 set_uniform_int(glsl_program_num, prefix, "tex_cr", *sampler_num + 2);
150 needs_update = false;
153 std::string YCbCrInput::output_fragment_shader()
155 float coeff[3], offset[3], scale[3];
157 switch (ycbcr_format.luma_coefficients) {
166 // Rec. 709, page 19.
173 // Rec. 2020, page 4.
183 if (ycbcr_format.full_range) {
184 offset[0] = 0.0 / 255.0;
185 offset[1] = 128.0 / 255.0;
186 offset[2] = 128.0 / 255.0;
192 // Rec. 601, page 4; Rec. 709, page 19; Rec. 2020, page 4.
193 offset[0] = 16.0 / 255.0;
194 offset[1] = 128.0 / 255.0;
195 offset[2] = 128.0 / 255.0;
197 scale[0] = 255.0 / 219.0;
198 scale[1] = 255.0 / 224.0;
199 scale[2] = 255.0 / 224.0;
202 // Matrix to convert RGB to YCbCr. See e.g. Rec. 601.
203 Matrix3d rgb_to_ycbcr;
204 rgb_to_ycbcr(0,0) = coeff[0];
205 rgb_to_ycbcr(0,1) = coeff[1];
206 rgb_to_ycbcr(0,2) = coeff[2];
208 float cb_fac = (224.0 / 219.0) / (coeff[0] + coeff[1] + 1.0f - coeff[2]);
209 rgb_to_ycbcr(1,0) = -coeff[0] * cb_fac;
210 rgb_to_ycbcr(1,1) = -coeff[1] * cb_fac;
211 rgb_to_ycbcr(1,2) = (1.0f - coeff[2]) * cb_fac;
213 float cr_fac = (224.0 / 219.0) / (1.0f - coeff[0] + coeff[1] + coeff[2]);
214 rgb_to_ycbcr(2,0) = (1.0f - coeff[0]) * cr_fac;
215 rgb_to_ycbcr(2,1) = -coeff[1] * cr_fac;
216 rgb_to_ycbcr(2,2) = -coeff[2] * cr_fac;
218 // Inverting the matrix gives us what we need to go from YCbCr back to RGB.
219 Matrix3d ycbcr_to_rgb = rgb_to_ycbcr.inverse();
221 std::string frag_shader;
223 frag_shader = output_glsl_mat3("PREFIX(inv_ycbcr_matrix)", ycbcr_to_rgb);
226 sprintf(buf, "const vec3 PREFIX(offset) = vec3(%.8f, %.8f, %.8f);\n",
227 offset[0], offset[1], offset[2]);
230 sprintf(buf, "const vec3 PREFIX(scale) = vec3(%.8f, %.8f, %.8f);\n",
231 scale[0], scale[1], scale[2]);
234 float cb_offset_x = compute_chroma_offset(
235 ycbcr_format.cb_x_position, ycbcr_format.chroma_subsampling_x, widths[1]);
236 float cb_offset_y = compute_chroma_offset(
237 ycbcr_format.cb_y_position, ycbcr_format.chroma_subsampling_y, heights[1]);
238 sprintf(buf, "const vec2 PREFIX(cb_offset) = vec2(%.8f, %.8f);\n",
239 cb_offset_x, cb_offset_y);
242 float cr_offset_x = compute_chroma_offset(
243 ycbcr_format.cr_x_position, ycbcr_format.chroma_subsampling_x, widths[2]);
244 float cr_offset_y = compute_chroma_offset(
245 ycbcr_format.cr_y_position, ycbcr_format.chroma_subsampling_y, heights[2]);
246 sprintf(buf, "const vec2 PREFIX(cr_offset) = vec2(%.8f, %.8f);\n",
247 cr_offset_x, cr_offset_y);
250 frag_shader += read_file("ycbcr_input.frag");