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 <paul.kocialkowski@xxxxxxxxxxxxxxx>
---
configure.ac | 1 +
lib/Makefile.am | 2 +
lib/igt_frame.c | 131 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
lib/igt_frame.h | 2 +
4 files changed, 136 insertions(+)
diff --git a/configure.ac b/configure.ac
index 5b41f333..db0015e5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -178,6 +178,7 @@ if test x"$udev" = xyes; then
AC_DEFINE(HAVE_UDEV,1,[Enable udev-based monitor hotplug detection])
fi
PKG_CHECK_MODULES(GLIB, glib-2.0)
+PKG_CHECK_MODULES(GSL, gsl)
# for chamelium
AC_ARG_ENABLE(chamelium, AS_HELP_STRING([--disable-chamelium],
diff --git a/lib/Makefile.am b/lib/Makefile.am
index d4f41128..fb922ced 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -35,6 +35,7 @@ AM_CFLAGS = \
$(DRM_CFLAGS) \
$(PCIACCESS_CFLAGS) \
$(LIBUNWIND_CFLAGS) \
+ $(GSL_CFLAGS) \
$(KMOD_CFLAGS) \
$(PROCPS_CFLAGS) \
$(DEBUG_CFLAGS) \
@@ -54,6 +55,7 @@ libintel_tools_la_LIBADD = \
$(DRM_LIBS) \
$(PCIACCESS_LIBS) \
$(PROCPS_LIBS) \
+ $(GSL_LIBS) \
$(KMOD_LIBS) \
$(CAIRO_LIBS) \
$(LIBUDEV_LIBS) \
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 <fcntl.h>
#include <pixman.h>
#include <cairo.h>
+#include <gsl/gsl_statistics_double.h>
+#include <gsl/gsl_fit.h>
#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;
+}
diff --git a/lib/igt_frame.h b/lib/igt_frame.h
index ec6a1643..1d9bbf6a 100644
--- a/lib/igt_frame.h
+++ b/lib/igt_frame.h
@@ -39,5 +39,7 @@ void igt_write_compared_frames_to_png(cairo_surface_t *reference,
cairo_surface_t *capture,
const char *reference_suffix,
const char *capture_suffix);
+bool igt_check_analog_frame_match(cairo_surface_t *reference,
+ cairo_surface_t *capture);
#endif
--
2.13.2
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