From 8cf32fe06c8f54bca11c485ccc1cc3899f9d81db Mon Sep 17 00:00:00 2001 From: Paul Kocialkowski Date: Thu, 20 Jul 2017 18:13:36 +0300 Subject: lib/igt_frame: Add support for analog frame comparison testing This adds support for analog frame comparison check, as used in VGA. Since VGA uses a DAC-ADC chain, its data cannot be expected to be pixel perfect. Thus, it is impossible to uses a CRC check and full frames have to be analyzed instead. Such an analysis is implemented, based on both an absolute error threshold and a correlation with the expected error trend for a DAC-ADC chain. It was tested with a couple encoders and provides reliable error detection with few false positives. Signed-off-by: Paul Kocialkowski Reviewed-by: Lyude --- lib/igt_frame.c | 131 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 131 insertions(+) (limited to 'lib/igt_frame.c') diff --git a/lib/igt_frame.c b/lib/igt_frame.c index dfafe53d..222a45f8 100644 --- a/lib/igt_frame.c +++ b/lib/igt_frame.c @@ -29,6 +29,8 @@ #include #include #include +#include +#include #include "igt.h" @@ -135,3 +137,132 @@ void igt_write_compared_frames_to_png(cairo_surface_t *reference, close(fd); } + +/** + * igt_check_analog_frame_match: + * @reference: The reference cairo surface + * @capture: The captured cairo surface + * + * Checks that the analog image contained in the chamelium frame dump matches + * the given framebuffer. + * + * In order to determine whether the frame matches the reference, the following + * reasoning is implemented: + * 1. The absolute error for each color value of the reference is collected. + * 2. The average absolute error is calculated for each color value of the + * reference and must not go above 60 (23.5 % of the total range). + * 3. A linear fit for the average absolute error from the pixel value is + * calculated, as a DAC-ADC chain is expected to have a linear error curve. + * 4. The linear fit is correlated with the actual average absolute error for + * the frame and the correlation coefficient is checked to be > 0.985, + * indicating a match with the expected error trend. + * + * Most errors (e.g. due to scaling, rotation, color space, etc) can be + * reliably detected this way, with a minimized number of false-positives. + * However, the brightest values (250 and up) are ignored as the error trend + * is often not linear there in practice due to clamping. + * + * Returns: a boolean indicating whether the frames match + */ + +bool igt_check_analog_frame_match(cairo_surface_t *reference, + cairo_surface_t *capture) +{ + pixman_image_t *reference_src, *capture_src; + int w, h; + int error_count[3][256][2] = { 0 }; + double error_average[4][250]; + double error_trend[250]; + double c0, c1, cov00, cov01, cov11, sumsq; + double correlation; + unsigned char *reference_pixels, *capture_pixels; + unsigned char *p; + unsigned char *q; + bool match = true; + int diff; + int x, y; + int i, j; + + w = cairo_image_surface_get_width(reference); + h = cairo_image_surface_get_height(reference); + + reference_src = pixman_image_create_bits( + PIXMAN_x8r8g8b8, w, h, + (void*)cairo_image_surface_get_data(reference), + cairo_image_surface_get_stride(reference)); + reference_pixels = (unsigned char *) pixman_image_get_data(reference_src); + + capture_src = pixman_image_create_bits( + PIXMAN_x8r8g8b8, w, h, + (void*)cairo_image_surface_get_data(capture), + cairo_image_surface_get_stride(capture)); + capture_pixels = (unsigned char *) pixman_image_get_data(capture_src); + + /* Collect the absolute error for each color value */ + for (x = 0; x < w; x++) { + for (y = 0; y < h; y++) { + p = &capture_pixels[(x + y * w) * 4]; + q = &reference_pixels[(x + y * w) * 4]; + + for (i = 0; i < 3; i++) { + diff = (int) p[i] - q[i]; + if (diff < 0) + diff = -diff; + + error_count[i][q[i]][0] += diff; + error_count[i][q[i]][1]++; + } + } + } + + /* Calculate the average absolute error for each color value */ + for (i = 0; i < 250; i++) { + error_average[0][i] = i; + + for (j = 1; j < 4; j++) { + error_average[j][i] = (double) error_count[j-1][i][0] / + error_count[j-1][i][1]; + + if (error_average[j][i] > 60) { + igt_warn("Error average too high (%f)\n", + error_average[j][i]); + + match = false; + goto complete; + } + } + } + + /* + * Calculate error trend from linear fit. + * A DAC-ADC chain is expected to have a linear absolute error on + * most of its range + */ + for (i = 1; i < 4; i++) { + gsl_fit_linear((const double *) &error_average[0], 1, + (const double *) &error_average[i], 1, 250, + &c0, &c1, &cov00, &cov01, &cov11, &sumsq); + + for (j = 0; j < 250; j++) + error_trend[j] = c0 + j * c1; + + correlation = gsl_stats_correlation((const double *) &error_trend, + 1, + (const double *) &error_average[i], + 1, 250); + + if (correlation < 0.985) { + igt_warn("Error with reference not correlated (%f)\n", + correlation); + + match = false; + goto complete; + } + } + +complete: + pixman_image_unref(reference_src); + pixman_image_unref(capture_src); + + return match; +} -- cgit v1.2.3