/** @brief Compute decimation factor for 3A statistics and shading correction.
*
* @param[in] width Frame width in pixels.
* @param[in] height Frame height in pixels.
* @return Log2 of decimation factor (= grid cell size) in bayer quads.
*/
static int
binary_grid_deci_factor_log2(int width, int height)
{
/* 3A/Shading decimation factor spcification (at August 2008)
* ------------------------------------------------------------------
* [Image Width (BQ)] [Decimation Factor (BQ)] [Resulting grid cells]
* 1280 ~ 32 40 ~
* 640 ~ 1279 16 40 ~ 80
* ~ 639 8 ~ 80
* ------------------------------------------------------------------
*/
/* Maximum and minimum decimation factor by the specification */
#define MAX_SPEC_DECI_FACT_LOG2 5
#define MIN_SPEC_DECI_FACT_LOG2 3
/* the smallest frame width in bayer quads when decimation factor (log2) is 5 or 4, by the specification */
#define DECI_FACT_LOG2_5_SMALLEST_FRAME_WIDTH_BQ 1280
#define DECI_FACT_LOG2_4_SMALLEST_FRAME_WIDTH_BQ 640
int smallest_factor; /* the smallest factor (log2) where the number of cells does not exceed the limitation */
int spec_factor; /* the factor (log2) which satisfies the specification */
/* Currently supported maximum width and height are 5120(=80*64) and 3840(=60*64). */
assert(ISP_BQ_GRID_WIDTH(width, MAX_SPEC_DECI_FACT_LOG2) <= SH_CSS_MAX_BQ_GRID_WIDTH);
assert(ISP_BQ_GRID_HEIGHT(height, MAX_SPEC_DECI_FACT_LOG2) <= SH_CSS_MAX_BQ_GRID_HEIGHT);
/* Compute the smallest factor. */
smallest_factor = MAX_SPEC_DECI_FACT_LOG2;
while (ISP_BQ_GRID_WIDTH(width, smallest_factor - 1) <= SH_CSS_MAX_BQ_GRID_WIDTH &&
ISP_BQ_GRID_HEIGHT(height, smallest_factor - 1) <= SH_CSS_MAX_BQ_GRID_HEIGHT
&& smallest_factor > MIN_SPEC_DECI_FACT_LOG2)
smallest_factor--;
/* Get the factor by the specification. */
if (_ISP_BQS(width) >= DECI_FACT_LOG2_5_SMALLEST_FRAME_WIDTH_BQ)
spec_factor = 5;
else if (_ISP_BQS(width) >= DECI_FACT_LOG2_4_SMALLEST_FRAME_WIDTH_BQ)
spec_factor = 4;
else
spec_factor = 3;
/* If smallest_factor is smaller than or equal to spec_factor, choose spec_factor to follow the specification.
If smallest_factor is larger than spec_factor, choose smallest_factor.
ex. width=2560, height=1920
smallest_factor=4, spec_factor=5
smallest_factor < spec_factor -> return spec_factor
ex. width=300, height=3000
smallest_factor=5, spec_factor=3
smallest_factor > spec_factor -> return smallest_factor
*/
return max(smallest_factor, spec_factor);
#undef MAX_SPEC_DECI_FACT_LOG2
#undef MIN_SPEC_DECI_FACT_LOG2
#undef DECI_FACT_LOG2_5_SMALLEST_FRAME_WIDTH_BQ
#undef DECI_FACT_LOG2_4_SMALLEST_FRAME_WIDTH_BQ
}
static int
sh_css_grid_deci_factor_log2(int width, int height)
{
int fact, fact1;
fact = 5;
while (ISP_BQ_GRID_WIDTH(width, fact - 1) <= SH_CSS_MAX_BQ_GRID_WIDTH &&
ISP_BQ_GRID_HEIGHT(height, fact - 1) <= SH_CSS_MAX_BQ_GRID_HEIGHT
&& fact > 3)
fact--;
/* fact1 satisfies the specification of grid size. fact and fact1 is
not the same for some resolution (fact=4 and fact1=5 for 5mp). */
if (width >= 2560)
fact1 = 5;
else if (width >= 1280)
fact1 = 4;
else
fact1 = 3;
return max(fact, fact1);
}