6 #include "ycbcr_input.h"
10 using namespace Eigen;
12 YCbCrInput::YCbCrInput(const ImageFormat &image_format,
13 const YCbCrFormat &ycbcr_format,
14 unsigned width, unsigned height)
15 : image_format(image_format),
16 ycbcr_format(ycbcr_format),
18 needs_pbo_recreate(false),
24 pbos[0] = pbos[1] = pbos[2] = 0;
25 texture_num[0] = texture_num[1] = texture_num[2] = 0;
27 assert(width % ycbcr_format.chroma_subsampling_x == 0);
28 pitch[0] = widths[0] = width;
29 pitch[1] = widths[1] = width / ycbcr_format.chroma_subsampling_x;
30 pitch[2] = widths[2] = width / ycbcr_format.chroma_subsampling_x;
32 assert(height % ycbcr_format.chroma_subsampling_y == 0);
34 heights[1] = height / ycbcr_format.chroma_subsampling_y;
35 heights[2] = height / ycbcr_format.chroma_subsampling_y;
37 register_int("needs_mipmaps", &needs_mipmaps);
40 YCbCrInput::~YCbCrInput()
43 glDeleteBuffers(3, pbos);
46 if (texture_num[0] != 0) {
47 glDeleteTextures(3, texture_num);
52 void YCbCrInput::finalize()
54 glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
57 // Create PBOs to hold the textures holding the input image, and then the texture itself.
58 glGenBuffers(3, pbos);
60 glGenTextures(3, texture_num);
63 for (unsigned channel = 0; channel < 3; ++channel) {
64 glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, pbos[channel]);
66 glBufferData(GL_PIXEL_UNPACK_BUFFER_ARB, pitch[channel] * heights[channel], NULL, GL_STREAM_DRAW);
68 glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
71 glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
73 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
75 glPixelStorei(GL_UNPACK_ROW_LENGTH, pitch[channel]);
77 glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE8, widths[channel], heights[channel], 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, NULL);
79 glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
87 void YCbCrInput::set_gl_state(GLuint glsl_program_num, const std::string& prefix, unsigned *sampler_num)
89 for (unsigned channel = 0; channel < 3; ++channel) {
90 glActiveTexture(GL_TEXTURE0 + *sampler_num + channel);
92 glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
95 if (needs_update || needs_pbo_recreate) {
96 // Copy the pixel data into the PBO.
97 glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, pbos[channel]);
100 if (needs_pbo_recreate) {
101 // The pitch has changed; we need to reallocate this PBO.
102 glBufferData(GL_PIXEL_UNPACK_BUFFER_ARB, pitch[channel] * heights[channel], NULL, GL_STREAM_DRAW);
106 void *mapped_pbo = glMapBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, GL_WRITE_ONLY);
107 memcpy(mapped_pbo, pixel_data[channel], pitch[channel] * heights[channel]);
109 glUnmapBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB);
112 // Re-upload the texture from the PBO.
113 glPixelStorei(GL_UNPACK_ROW_LENGTH, pitch[channel]);
115 glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, widths[channel], heights[channel], GL_LUMINANCE, GL_UNSIGNED_BYTE, BUFFER_OFFSET(0));
117 glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
119 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
121 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
123 glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
129 set_uniform_int(glsl_program_num, prefix, "tex_y", *sampler_num + 0);
130 set_uniform_int(glsl_program_num, prefix, "tex_cb", *sampler_num + 1);
131 set_uniform_int(glsl_program_num, prefix, "tex_cr", *sampler_num + 2);
134 needs_update = false;
135 needs_pbo_recreate = false;
138 std::string YCbCrInput::output_fragment_shader()
140 float coeff[3], offset[3], scale[3];
142 switch (ycbcr_format.luma_coefficients) {
151 // Rec. 709, page 19.
160 if (ycbcr_format.full_range) {
161 offset[0] = 0.0 / 255.0;
162 offset[1] = 128.0 / 255.0;
163 offset[2] = 128.0 / 255.0;
169 // Rec. 601, page 4; Rec. 709, page 19.
170 offset[0] = 16.0 / 255.0;
171 offset[1] = 128.0 / 255.0;
172 offset[2] = 128.0 / 255.0;
174 scale[0] = 255.0 / 219.0;
175 scale[1] = 255.0 / 224.0;
176 scale[2] = 255.0 / 224.0;
179 // Matrix to convert RGB to YCbCr. See e.g. Rec. 601.
180 Matrix3d rgb_to_ycbcr;
181 rgb_to_ycbcr(0,0) = coeff[0];
182 rgb_to_ycbcr(0,1) = coeff[1];
183 rgb_to_ycbcr(0,2) = coeff[2];
185 float cb_fac = (224.0 / 219.0) / (coeff[0] + coeff[1] + 1.0f - coeff[2]);
186 rgb_to_ycbcr(1,0) = -coeff[0] * cb_fac;
187 rgb_to_ycbcr(1,1) = -coeff[1] * cb_fac;
188 rgb_to_ycbcr(1,2) = (1.0f - coeff[2]) * cb_fac;
190 float cr_fac = (224.0 / 219.0) / (1.0f - coeff[0] + coeff[1] + coeff[2]);
191 rgb_to_ycbcr(2,0) = (1.0f - coeff[0]) * cr_fac;
192 rgb_to_ycbcr(2,1) = -coeff[1] * cr_fac;
193 rgb_to_ycbcr(2,2) = -coeff[2] * cr_fac;
195 // Inverting the matrix gives us what we need to go from YCbCr back to RGB.
196 Matrix3d ycbcr_to_rgb = rgb_to_ycbcr.inverse();
198 std::string frag_shader;
200 frag_shader = output_glsl_mat3("PREFIX(inv_ycbcr_matrix)", ycbcr_to_rgb);
203 sprintf(buf, "const vec3 PREFIX(offset) = vec3(%.8f, %.8f, %.8f);\n",
204 offset[0], offset[1], offset[2]);
207 sprintf(buf, "const vec3 PREFIX(scale) = vec3(%.8f, %.8f, %.8f);\n",
208 scale[0], scale[1], scale[2]);
211 // OpenGL has texel center in (0.5, 0.5), but different formats have
212 // chroma in various other places. If luma samples are X, the chroma
213 // sample is *, and subsampling is 3x3, the situation with chroma
214 // center in (0.5, 0.5) looks approximately like this:
220 // If, on the other hand, chroma center is in (0.0, 0.5) (common
221 // for e.g. MPEG-4), the figure changes to:
227 // In other words, (0.0, 0.0) means that the chroma sample is exactly
228 // co-sited on top of the top-left luma sample. Note, however, that
229 // this is _not_ 0.5 texels to the left, since the OpenGL's texel center
230 // is in (0.5, 0.5); it is in (0.25, 0.25). In a sense, the four luma samples
231 // define a square where chroma position (0.0, 0.0) is in texel position
232 // (0.25, 0.25) and chroma position (1.0, 1.0) is in texel position (0.75, 0.75)
233 // (the outer border shows the borders of the texel itself, ie. from
234 // (0, 0) to (1, 1)):
244 // Also note that if we have no subsampling, the square will have zero
245 // area and the chroma position does not matter at all.
246 float chroma_x_local_position =
247 (0.5 + ycbcr_format.chroma_x_position * (ycbcr_format.chroma_subsampling_x - 1)) /
248 ycbcr_format.chroma_subsampling_x;
249 float chroma_y_local_position =
250 (0.5 + ycbcr_format.chroma_y_position * (ycbcr_format.chroma_subsampling_y - 1)) /
251 ycbcr_format.chroma_subsampling_y;
253 float chroma_offset_x = (0.5f - chroma_x_local_position) / widths[1];
254 float chroma_offset_y = (0.5f - chroma_y_local_position) / heights[1];
255 sprintf(buf, "const vec2 PREFIX(chroma_offset) = vec2(%.8f, %.8f);\n",
256 chroma_offset_x, chroma_offset_y);
259 frag_shader += read_file("ycbcr_input.frag");