summaryrefslogtreecommitdiff
path: root/drivers/media/video/omap3isp/ispresizer.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/media/video/omap3isp/ispresizer.c')
-rw-r--r--drivers/media/video/omap3isp/ispresizer.c75
1 files changed, 60 insertions, 15 deletions
diff --git a/drivers/media/video/omap3isp/ispresizer.c b/drivers/media/video/omap3isp/ispresizer.c
index 653f88ba56db..0bb0f8cd36f5 100644
--- a/drivers/media/video/omap3isp/ispresizer.c
+++ b/drivers/media/video/omap3isp/ispresizer.c
@@ -714,19 +714,50 @@ static void resizer_print_status(struct isp_res_device *res)
* iw and ih are the input width and height after cropping. Those equations need
* to be satisfied exactly for the resizer to work correctly.
*
- * Reverting the equations, we can compute the resizing ratios with
+ * The equations can't be easily reverted, as the >> 8 operation is not linear.
+ * In addition, not all input sizes can be achieved for a given output size. To
+ * get the highest input size lower than or equal to the requested input size,
+ * we need to compute the highest resizing ratio that satisfies the following
+ * inequality (taking the 4-tap mode width equation as an example)
+ *
+ * iw >= (32 * sph + (ow - 1) * hrsz + 16) >> 8 - 7
+ *
+ * (where iw is the requested input width) which can be rewritten as
+ *
+ * iw - 7 >= (32 * sph + (ow - 1) * hrsz + 16) >> 8
+ * (iw - 7) << 8 >= 32 * sph + (ow - 1) * hrsz + 16 - b
+ * ((iw - 7) << 8) + b >= 32 * sph + (ow - 1) * hrsz + 16
+ *
+ * where b is the value of the 8 least significant bits of the right hand side
+ * expression of the last inequality. The highest resizing ratio value will be
+ * achieved when b is equal to its maximum value of 255. That resizing ratio
+ * value will still satisfy the original inequality, as b will disappear when
+ * the expression will be shifted right by 8.
+ *
+ * The reverted the equations thus become
*
* - 8-phase, 4-tap mode
- * hrsz = ((iw - 7) * 256 - 16 - 32 * sph) / (ow - 1)
- * vrsz = ((ih - 4) * 256 - 16 - 32 * spv) / (oh - 1)
+ * hrsz = ((iw - 7) * 256 + 255 - 16 - 32 * sph) / (ow - 1)
+ * vrsz = ((ih - 4) * 256 + 255 - 16 - 32 * spv) / (oh - 1)
* - 4-phase, 7-tap mode
- * hrsz = ((iw - 7) * 256 - 32 - 64 * sph) / (ow - 1)
- * vrsz = ((ih - 7) * 256 - 32 - 64 * spv) / (oh - 1)
+ * hrsz = ((iw - 7) * 256 + 255 - 32 - 64 * sph) / (ow - 1)
+ * vrsz = ((ih - 7) * 256 + 255 - 32 - 64 * spv) / (oh - 1)
*
- * The ratios are integer values, and must be rounded down to ensure that the
- * cropped input size is not bigger than the uncropped input size. As the ratio
- * in 7-tap mode is always smaller than the ratio in 4-tap mode, we can use the
- * 7-tap mode equations to compute a ratio approximation.
+ * The ratios are integer values, and are rounded down to ensure that the
+ * cropped input size is not bigger than the uncropped input size.
+ *
+ * As the number of phases/taps, used to select the correct equations to compute
+ * the ratio, depends on the ratio, we start with the 4-tap mode equations to
+ * compute an approximation of the ratio, and switch to the 7-tap mode equations
+ * if the approximation is higher than the ratio threshold.
+ *
+ * As the 7-tap mode equations will return a ratio smaller than or equal to the
+ * 4-tap mode equations, the resulting ratio could become lower than or equal to
+ * the ratio threshold. This 'equations loop' isn't an issue as long as the
+ * correct equations are used to compute the final input size. Starting with the
+ * 4-tap mode equations ensure that, in case of values resulting in a 'ratio
+ * loop', the smallest of the ratio values will be used, never exceeding the
+ * requested input size.
*
* We first clamp the output size according to the hardware capabilitie to avoid
* auto-cropping the input more than required to satisfy the TRM equations. The
@@ -775,6 +806,8 @@ static void resizer_calc_ratios(struct isp_res_device *res,
unsigned int max_width;
unsigned int max_height;
unsigned int width_alignment;
+ unsigned int width;
+ unsigned int height;
/*
* Clamp the output height based on the hardware capabilities and
@@ -786,19 +819,22 @@ static void resizer_calc_ratios(struct isp_res_device *res,
max_height = min_t(unsigned int, max_height, MAX_OUT_HEIGHT);
output->height = clamp(output->height, min_height, max_height);
- ratio->vert = ((input->height - 7) * 256 - 32 - 64 * spv)
+ ratio->vert = ((input->height - 4) * 256 + 255 - 16 - 32 * spv)
/ (output->height - 1);
+ if (ratio->vert > MID_RESIZE_VALUE)
+ ratio->vert = ((input->height - 7) * 256 + 255 - 32 - 64 * spv)
+ / (output->height - 1);
ratio->vert = clamp_t(unsigned int, ratio->vert,
MIN_RESIZE_VALUE, MAX_RESIZE_VALUE);
if (ratio->vert <= MID_RESIZE_VALUE) {
upscaled_height = (output->height - 1) * ratio->vert
+ 32 * spv + 16;
- input->height = (upscaled_height >> 8) + 4;
+ height = (upscaled_height >> 8) + 4;
} else {
upscaled_height = (output->height - 1) * ratio->vert
+ 64 * spv + 32;
- input->height = (upscaled_height >> 8) + 7;
+ height = (upscaled_height >> 8) + 7;
}
/*
@@ -854,20 +890,29 @@ static void resizer_calc_ratios(struct isp_res_device *res,
max_width & ~(width_alignment - 1));
output->width = ALIGN(output->width, width_alignment);
- ratio->horz = ((input->width - 7) * 256 - 32 - 64 * sph)
+ ratio->horz = ((input->width - 7) * 256 + 255 - 16 - 32 * sph)
/ (output->width - 1);
+ if (ratio->horz > MID_RESIZE_VALUE)
+ ratio->horz = ((input->width - 7) * 256 + 255 - 32 - 64 * sph)
+ / (output->width - 1);
ratio->horz = clamp_t(unsigned int, ratio->horz,
MIN_RESIZE_VALUE, MAX_RESIZE_VALUE);
if (ratio->horz <= MID_RESIZE_VALUE) {
upscaled_width = (output->width - 1) * ratio->horz
+ 32 * sph + 16;
- input->width = (upscaled_width >> 8) + 7;
+ width = (upscaled_width >> 8) + 7;
} else {
upscaled_width = (output->width - 1) * ratio->horz
+ 64 * sph + 32;
- input->width = (upscaled_width >> 8) + 7;
+ width = (upscaled_width >> 8) + 7;
}
+
+ /* Center the new crop rectangle. */
+ input->left += (input->width - width) / 2;
+ input->top += (input->height - height) / 2;
+ input->width = width;
+ input->height = height;
}
/*