From 9e62fbe2ac764479c449472d8bda52ac4df0de91 Mon Sep 17 00:00:00 2001 From: "Steinar H. Gunderson" Date: Wed, 17 Oct 2012 01:34:22 +0200 Subject: [PATCH] Support different chroma positioning for Cb and Cr. The test is slightly shaky, so it needs high tolerances, but at least there is a test. --- ycbcr_input.cpp | 20 ++++++--- ycbcr_input.frag | 4 +- ycbcr_input.h | 3 +- ycbcr_input_test.cpp | 101 ++++++++++++++++++++++++++++++++++++++----- 4 files changed, 109 insertions(+), 19 deletions(-) diff --git a/ycbcr_input.cpp b/ycbcr_input.cpp index 374237e..fe36eb0 100644 --- a/ycbcr_input.cpp +++ b/ycbcr_input.cpp @@ -253,12 +253,20 @@ std::string YCbCrInput::output_fragment_shader() scale[0], scale[1], scale[2]); frag_shader += buf; - float chroma_offset_x = compute_chroma_offset( - ycbcr_format.chroma_x_position, ycbcr_format.chroma_subsampling_x, widths[1]); - float chroma_offset_y = compute_chroma_offset( - ycbcr_format.chroma_y_position, ycbcr_format.chroma_subsampling_y, 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"); diff --git a/ycbcr_input.frag b/ycbcr_input.frag index 13e44b0..8da8256 100644 --- a/ycbcr_input.frag +++ b/ycbcr_input.frag @@ -10,8 +10,8 @@ vec4 FUNCNAME(vec2 tc) { vec3 ycbcr; ycbcr.x = texture2D(PREFIX(tex_y), tc).x; - ycbcr.y = texture2D(PREFIX(tex_cb), tc + PREFIX(chroma_offset)).x; - ycbcr.z = texture2D(PREFIX(tex_cr), tc + PREFIX(chroma_offset)).x; + ycbcr.y = texture2D(PREFIX(tex_cb), tc + PREFIX(cb_offset)).x; + ycbcr.z = texture2D(PREFIX(tex_cr), tc + PREFIX(cr_offset)).x; ycbcr -= PREFIX(offset); ycbcr *= PREFIX(scale); diff --git a/ycbcr_input.h b/ycbcr_input.h index 6c33cec..fba5588 100644 --- a/ycbcr_input.h +++ b/ycbcr_input.h @@ -22,7 +22,8 @@ struct YCbCrFormat { // Positioning of the chroma samples. MPEG-1 and JPEG is (0.5, 0.5); // MPEG-2 and newer typically are (0.0, 0.5). - float chroma_x_position, chroma_y_position; + float cb_x_position, cb_y_position; + float cr_x_position, cr_y_position; }; class YCbCrInput : public Input { diff --git a/ycbcr_input_test.cpp b/ycbcr_input_test.cpp index 7b2a6fd..5bd052b 100644 --- a/ycbcr_input_test.cpp +++ b/ycbcr_input_test.cpp @@ -40,8 +40,10 @@ TEST(YCbCrInput, Simple444) { ycbcr_format.full_range = false; ycbcr_format.chroma_subsampling_x = 1; ycbcr_format.chroma_subsampling_y = 1; - ycbcr_format.chroma_x_position = 0.5f; - ycbcr_format.chroma_y_position = 0.5f; + ycbcr_format.cb_x_position = 0.5f; + ycbcr_format.cb_y_position = 0.5f; + ycbcr_format.cr_x_position = 0.5f; + ycbcr_format.cr_y_position = 0.5f; YCbCrInput *input = new YCbCrInput(format, ycbcr_format, width, height); input->set_pixel_data(0, y); @@ -92,8 +94,10 @@ TEST(YCbCrInput, FullRangeRec601) { ycbcr_format.full_range = true; ycbcr_format.chroma_subsampling_x = 1; ycbcr_format.chroma_subsampling_y = 1; - ycbcr_format.chroma_x_position = 0.5f; - ycbcr_format.chroma_y_position = 0.5f; + ycbcr_format.cb_x_position = 0.5f; + ycbcr_format.cb_y_position = 0.5f; + ycbcr_format.cr_x_position = 0.5f; + ycbcr_format.cr_y_position = 0.5f; YCbCrInput *input = new YCbCrInput(format, ycbcr_format, width, height); input->set_pixel_data(0, y); @@ -143,8 +147,10 @@ TEST(YCbCrInput, Rec709) { ycbcr_format.full_range = false; ycbcr_format.chroma_subsampling_x = 1; ycbcr_format.chroma_subsampling_y = 1; - ycbcr_format.chroma_x_position = 0.5f; - ycbcr_format.chroma_y_position = 0.5f; + ycbcr_format.cb_x_position = 0.5f; + ycbcr_format.cb_y_position = 0.5f; + ycbcr_format.cr_x_position = 0.5f; + ycbcr_format.cr_y_position = 0.5f; YCbCrInput *input = new YCbCrInput(format, ycbcr_format, width, height); input->set_pixel_data(0, y); @@ -202,8 +208,10 @@ TEST(YCbCrInput, Subsampling420) { ycbcr_format.full_range = false; ycbcr_format.chroma_subsampling_x = 2; ycbcr_format.chroma_subsampling_y = 2; - ycbcr_format.chroma_x_position = 0.5f; - ycbcr_format.chroma_y_position = 0.5f; + ycbcr_format.cb_x_position = 0.5f; + ycbcr_format.cb_y_position = 0.5f; + ycbcr_format.cr_x_position = 0.5f; + ycbcr_format.cr_y_position = 0.5f; YCbCrInput *input = new YCbCrInput(format, ycbcr_format, width, height); input->set_pixel_data(0, y); @@ -261,8 +269,10 @@ TEST(YCbCrInput, Subsampling420WithNonCenteredSamples) { ycbcr_format.full_range = false; ycbcr_format.chroma_subsampling_x = 2; ycbcr_format.chroma_subsampling_y = 2; - ycbcr_format.chroma_x_position = 0.0f; - ycbcr_format.chroma_y_position = 0.5f; + ycbcr_format.cb_x_position = 0.0f; + ycbcr_format.cb_y_position = 0.5f; + ycbcr_format.cr_x_position = 0.0f; + ycbcr_format.cr_y_position = 0.5f; YCbCrInput *input = new YCbCrInput(format, ycbcr_format, width, height); input->set_pixel_data(0, y); @@ -276,3 +286,74 @@ TEST(YCbCrInput, Subsampling420WithNonCenteredSamples) { // so we need some leeway. expect_equal(expected_data, out_data, width, height, 0.01, 0.001); } + +// Yes, some 4:2:2 formats actually have this craziness. +TEST(YCbCrInput, DifferentCbAndCrPositioning) { + const int width = 4; + const int height = 4; + + unsigned char y[width * height] = { + 126, 126, 126, 126, + 126, 126, 126, 126, + 126, 126, 126, 126, + 126, 126, 126, 126, + }; + unsigned char cb[(width/2) * height] = { + 64, 128, + 128, 192, + 128, 128, + 128, 128, + }; + unsigned char cr[(width/2) * height] = { + 48, 128, + 128, 208, + 128, 128, + 128, 128, + }; + + // Chroma samples in this csae are always co-sited with a luma sample; + // their associated color values and position are marked off in comments. + float expected_data_blue[width * height] = { + 0.000 /* 0.0 */, 0.250, 0.500 /* 0.5 */, 0.500, + 0.500 /* 0.5 */, 0.750, 1.000 /* 1.0 */, 1.000, + 0.500 /* 0.5 */, 0.500, 0.500 /* 0.5 */, 0.500, + 0.500 /* 0.5 */, 0.500, 0.500 /* 0.5 */, 0.500, + }; + float expected_data_red[width * height] = { + 0.000, 0.000 /* 0.0 */, 0.250, 0.500 /* 0.5 */, + 0.500, 0.500 /* 0.5 */, 0.750, 1.000 /* 1.0 */, + 0.500, 0.500 /* 0.5 */, 0.500, 0.500 /* 0.5 */, + 0.500, 0.500 /* 0.5 */, 0.500, 0.500 /* 0.5 */, + }; + float out_data[width * height]; + + EffectChainTester tester(NULL, width, height); + + ImageFormat format; + format.color_space = COLORSPACE_sRGB; + format.gamma_curve = GAMMA_sRGB; + + YCbCrFormat ycbcr_format; + ycbcr_format.luma_coefficients = YCBCR_REC_601; + ycbcr_format.full_range = false; + ycbcr_format.chroma_subsampling_x = 2; + ycbcr_format.chroma_subsampling_y = 1; + ycbcr_format.cb_x_position = 0.0f; + ycbcr_format.cb_y_position = 0.5f; + ycbcr_format.cr_x_position = 1.0f; + ycbcr_format.cr_y_position = 0.5f; + + YCbCrInput *input = new YCbCrInput(format, ycbcr_format, width, height); + input->set_pixel_data(0, y); + input->set_pixel_data(1, cb); + input->set_pixel_data(2, cr); + tester.get_chain()->add_input(input); + + // Y'CbCr isn't 100% accurate (the input values are rounded), + // so we need some leeway. + tester.run(out_data, GL_RED, COLORSPACE_sRGB, GAMMA_sRGB); + expect_equal(expected_data_red, out_data, width, height, 0.02, 0.002); + + tester.run(out_data, GL_BLUE, COLORSPACE_sRGB, GAMMA_sRGB); + expect_equal(expected_data_blue, out_data, width, height, 0.01, 0.001); +} -- 2.39.2