#include <string.h>
#include <assert.h>
+#include <GL/glew.h>
+
+#include <Eigen/LU>
#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,
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;
check_error();
}
- needs_update = false;
+ needs_update = true;
finalized = true;
}
}
// 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;
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");
projects / movit / blobdiff