+#define GL_GLEXT_PROTOTYPES 1
+
+#include <string.h>
+#include <GL/gl.h>
+#include <GL/glext.h>
+#include <assert.h>
+
+#include "ycbcr_input.h"
+#include "util.h"
+
+YCbCrInput::YCbCrInput(const ImageFormat &image_format,
+ const YCbCrFormat &ycbcr_format,
+ unsigned width, unsigned height)
+ : image_format(image_format),
+ ycbcr_format(ycbcr_format),
+ needs_update(false),
+ finalized(false),
+ needs_mipmaps(false),
+ width(width),
+ height(height)
+{
+ pitch[0] = pitch[1] = pitch[2] = width;
+
+ assert(width % ycbcr_format.chroma_subsampling_x == 0);
+ widths[0] = width;
+ widths[1] = width / ycbcr_format.chroma_subsampling_x;
+ widths[2] = width / ycbcr_format.chroma_subsampling_x;
+
+ assert(height % ycbcr_format.chroma_subsampling_y == 0);
+ heights[0] = height;
+ heights[1] = height / ycbcr_format.chroma_subsampling_y;
+ heights[2] = height / ycbcr_format.chroma_subsampling_y;
+
+ register_int("needs_mipmaps", &needs_mipmaps);
+}
+
+void YCbCrInput::finalize()
+{
+ // Create PBOs to hold the textures holding the input image, and then the texture itself.
+ glGenBuffers(3, pbos);
+ check_error();
+ glGenTextures(3, texture_num);
+ check_error();
+
+ for (unsigned channel = 0; channel < 3; ++channel) {
+ glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, pbos[channel]);
+ check_error();
+ glBufferData(GL_PIXEL_UNPACK_BUFFER_ARB, pitch[channel] * heights[channel], NULL, GL_STREAM_DRAW);
+ check_error();
+ glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
+ check_error();
+
+ glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
+ check_error();
+ glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+ check_error();
+ glPixelStorei(GL_UNPACK_ROW_LENGTH, pitch[channel]);
+ check_error();
+ glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE8, widths[channel], heights[channel], 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, NULL);
+ check_error();
+ glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
+ check_error();
+ }
+
+ needs_update = false;
+ finalized = true;
+}
+
+void YCbCrInput::set_gl_state(GLuint glsl_program_num, const std::string& prefix, unsigned *sampler_num)
+{
+ for (unsigned channel = 0; channel < 3; ++channel) {
+ glActiveTexture(GL_TEXTURE0 + *sampler_num + channel);
+ check_error();
+ glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
+ check_error();
+
+ if (needs_update) {
+ // Copy the pixel data into the PBO.
+ glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, pbos[channel]);
+ check_error();
+ void *mapped_pbo = glMapBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, GL_WRITE_ONLY);
+ memcpy(mapped_pbo, pixel_data[channel], pitch[channel] * heights[channel]);
+ glUnmapBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB);
+ check_error();
+
+ // Re-upload the texture from the PBO.
+ glPixelStorei(GL_UNPACK_ROW_LENGTH, pitch[channel]);
+ check_error();
+ glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, widths[channel], heights[channel], GL_LUMINANCE, GL_UNSIGNED_BYTE, BUFFER_OFFSET(0));
+ check_error();
+ glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
+ check_error();
+ glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+ check_error();
+ glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+ check_error();
+ glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
+ check_error();
+ }
+ }
+
+ // Bind samplers.
+ set_uniform_int(glsl_program_num, prefix, "tex_y", *sampler_num + 0);
+ set_uniform_int(glsl_program_num, prefix, "tex_cb", *sampler_num + 1);
+ set_uniform_int(glsl_program_num, prefix, "tex_cr", *sampler_num + 2);
+
+ *sampler_num += 3;
+ needs_update = false;
+}
+
+std::string YCbCrInput::output_fragment_shader()
+{
+ float coeff[3], offset[3], scale[3];
+
+ switch (ycbcr_format.luma_coefficients) {
+ case YCBCR_REC_601:
+ // Rec. 601, page 2.
+ coeff[0] = 0.299;
+ coeff[1] = 0.587;
+ coeff[2] = 0.114;
+ break;
+
+ case YCBCR_REC_709:
+ // Rec. 709, page 19.
+ coeff[0] = 0.2126;
+ coeff[1] = 0.7152;
+ coeff[2] = 0.0722;
+ break;
+ default:
+ assert(false);
+ }
+
+ if (ycbcr_format.full_range) {
+ offset[0] = 0.0 / 255.0;
+ offset[1] = 128.0 / 255.0;
+ offset[2] = 128.0 / 255.0;
+
+ scale[0] = 1.0;
+ scale[1] = 1.0;
+ scale[2] = 1.0;
+ } else {
+ // Rec. 601, page 4; Rec. 709, page 19.
+ offset[0] = 16.0 / 255.0;
+ offset[1] = 128.0 / 255.0;
+ offset[2] = 128.0 / 255.0;
+
+ scale[0] = 255.0 / 219.0;
+ scale[1] = 255.0 / 224.0;
+ scale[2] = 255.0 / 224.0;
+ }
+
+ // Matrix to convert RGB to YCbCr. See e.g. Rec. 601.
+ Matrix3x3 rgb_to_ycbcr;
+ rgb_to_ycbcr[0] = coeff[0];
+ rgb_to_ycbcr[3] = coeff[1];
+ rgb_to_ycbcr[6] = coeff[2];
+
+ float cb_fac = (224.0 / 219.0) / (coeff[0] + coeff[1] + 1.0f - coeff[2]);
+ rgb_to_ycbcr[1] = -coeff[0] * cb_fac;
+ rgb_to_ycbcr[4] = -coeff[1] * cb_fac;
+ rgb_to_ycbcr[7] = (1.0f - coeff[2]) * cb_fac;
+
+ float cr_fac = (224.0 / 219.0) / (1.0f - coeff[0] + coeff[1] + coeff[2]);
+ rgb_to_ycbcr[2] = (1.0f - coeff[0]) * cr_fac;
+ rgb_to_ycbcr[5] = -coeff[1] * cr_fac;
+ rgb_to_ycbcr[8] = -coeff[2] * cr_fac;
+
+ // Inverting the matrix gives us what we need to go from YCbCr back to RGB.
+ Matrix3x3 ycbcr_to_rgb;
+ invert_3x3_matrix(rgb_to_ycbcr, ycbcr_to_rgb);
+
+ std::string frag_shader;
+
+ char buf[1024];
+ sprintf(buf,
+ "const mat3 PREFIX(inv_ycbcr_matrix) = mat3(\n"
+ " %.8f, %.8f, %.8f,\n"
+ " %.8f, %.8f, %.8f,\n"
+ " %.8f, %.8f, %.8f);\n",
+ ycbcr_to_rgb[0], ycbcr_to_rgb[1], ycbcr_to_rgb[2],
+ ycbcr_to_rgb[3], ycbcr_to_rgb[4], ycbcr_to_rgb[5],
+ ycbcr_to_rgb[6], ycbcr_to_rgb[7], ycbcr_to_rgb[8]);
+ frag_shader = buf;
+
+ sprintf(buf, "const vec3 PREFIX(offset) = vec3(%.8f, %.8f, %.8f);\n",
+ offset[0], offset[1], offset[2]);
+ frag_shader += buf;
+
+ sprintf(buf, "const vec3 PREFIX(scale) = vec3(%.8f, %.8f, %.8f);\n",
+ scale[0], scale[1], scale[2]);
+ frag_shader += buf;
+
+ // OpenGL has texel center in (0.5, 0.5), but different formats have
+ // chroma in various other places. If luma samples are X, the chroma
+ // sample is *, and subsampling is 3x3, the situation with chroma
+ // center in (0.5, 0.5) looks approximately like this:
+ //
+ // X X
+ // *
+ // X X
+ //
+ // If, on the other hand, chroma center is in (0.0, 0.5) (common
+ // for e.g. MPEG-4), the figure changes to:
+ //
+ // X X
+ // *
+ // X X
+ //
+ // Obviously, the chroma plane here needs to be moved to the left,
+ // which means _adding_ 0.5 to the texture coordinates when sampling
+ // chroma.
+ float chroma_offset_x = (0.5f - ycbcr_format.chroma_x_position) / widths[1];
+ float chroma_offset_y = (0.5f - ycbcr_format.chroma_y_position) / heights[1];
+ sprintf(buf, "const vec2 PREFIX(chroma_offset) = vec2(%.8f, %.8f);\n",
+ chroma_offset_x, chroma_offset_y);
+ frag_shader += buf;
+
+ frag_shader += read_file("ycbcr_input.frag");
+ return frag_shader;
+}