X-Git-Url: https://git.sesse.net/?p=movit;a=blobdiff_plain;f=ycbcr_input.cpp;h=958b9167f2ede78eba5b543f9eae54053d908de5;hp=8d58c7de8ab10c6d09adf68fa0bc8ef467f8be51;hb=29072985d0a00a53e5b578a1444cee61a0c9e1f2;hpb=af39090a8902411ffc0c89f296a0f8bde9229f60 diff --git a/ycbcr_input.cpp b/ycbcr_input.cpp index 8d58c7d..958b916 100644 --- a/ycbcr_input.cpp +++ b/ycbcr_input.cpp @@ -1,9 +1,58 @@ #include #include +#include + +#include #include "ycbcr_input.h" #include "util.h" -#include "opengl.h" + +using namespace Eigen; + +namespace { + +// 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 +// +// In other words, (0.0, 0.0) means that the chroma sample is exactly +// co-sited on top of the top-left luma sample. Note, however, that +// this is _not_ 0.5 texels to the left, since the OpenGL's texel center +// is in (0.5, 0.5); it is in (0.25, 0.25). In a sense, the four luma samples +// define a square where chroma position (0.0, 0.0) is in texel position +// (0.25, 0.25) and chroma position (1.0, 1.0) is in texel position (0.75, 0.75) +// (the outer border shows the borders of the texel itself, ie. from +// (0, 0) to (1, 1)): +// +// --------- +// | | +// | X---X | +// | | * | | +// | X---X | +// | | +// --------- +// +// Also note that if we have no subsampling, the square will have zero +// area and the chroma position does not matter at all. +float compute_chroma_offset(float pos, unsigned subsampling_factor, unsigned resolution) +{ + float local_chroma_pos = (0.5 + pos * (subsampling_factor - 1)) / subsampling_factor; + return (0.5 - local_chroma_pos) / resolution; +} + +} // namespace YCbCrInput::YCbCrInput(const ImageFormat &image_format, const YCbCrFormat &ycbcr_format, @@ -20,12 +69,10 @@ YCbCrInput::YCbCrInput(const ImageFormat &image_format, pbos[0] = pbos[1] = pbos[2] = 0; texture_num[0] = texture_num[1] = texture_num[2] = 0; - 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; + pitch[0] = widths[0] = width; + pitch[1] = widths[1] = width / ycbcr_format.chroma_subsampling_x; + pitch[2] = widths[2] = width / ycbcr_format.chroma_subsampling_x; assert(height % ycbcr_format.chroma_subsampling_y == 0); heights[0] = height; @@ -78,7 +125,7 @@ void YCbCrInput::finalize() check_error(); } - needs_update = false; + needs_update = true; finalized = true; } @@ -175,38 +222,29 @@ std::string YCbCrInput::output_fragment_shader() } // 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]; + Matrix3d rgb_to_ycbcr; + rgb_to_ycbcr(0,0) = coeff[0]; + rgb_to_ycbcr(0,1) = coeff[1]; + rgb_to_ycbcr(0,2) = 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; + rgb_to_ycbcr(1,0) = -coeff[0] * cb_fac; + rgb_to_ycbcr(1,1) = -coeff[1] * cb_fac; + rgb_to_ycbcr(1,2) = (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; + rgb_to_ycbcr(2,0) = (1.0f - coeff[0]) * cr_fac; + rgb_to_ycbcr(2,1) = -coeff[1] * cr_fac; + rgb_to_ycbcr(2,2) = -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); + Matrix3d ycbcr_to_rgb = rgb_to_ycbcr.inverse(); 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; + frag_shader = output_glsl_mat3("PREFIX(inv_ycbcr_matrix)", ycbcr_to_rgb); + char buf[256]; sprintf(buf, "const vec3 PREFIX(offset) = vec3(%.8f, %.8f, %.8f);\n", offset[0], offset[1], offset[2]); frag_shader += buf; @@ -215,29 +253,20 @@ std::string YCbCrInput::output_fragment_shader() 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); + float cb_offset_x = compute_chroma_offset( + ycbcr_format.cb_x_position, ycbcr_format.chroma_subsampling_x, widths[1]); + float cb_offset_y = compute_chroma_offset( + ycbcr_format.cb_y_position, ycbcr_format.chroma_subsampling_y, heights[1]); + sprintf(buf, "const vec2 PREFIX(cb_offset) = vec2(%.8f, %.8f);\n", + cb_offset_x, cb_offset_y); + frag_shader += buf; + + float cr_offset_x = compute_chroma_offset( + ycbcr_format.cr_x_position, ycbcr_format.chroma_subsampling_x, widths[2]); + float cr_offset_y = compute_chroma_offset( + ycbcr_format.cr_y_position, ycbcr_format.chroma_subsampling_y, heights[2]); + sprintf(buf, "const vec2 PREFIX(cr_offset) = vec2(%.8f, %.8f);\n", + cr_offset_x, cr_offset_y); frag_shader += buf; frag_shader += read_file("ycbcr_input.frag");