[libcamera-devel,v1,5/5] ipa: raspberrypi: Normalise region sums to 16-bits

17834 diff mbox series

The VC4 ISP uses a pipeline bit-depth of 13-bits. The AGC algorithm needs to
know this bit-depth when computing the Y value for the image.

Instead of hardcoding the VC4 bit-depth in the AGC source code, normalise all
region sums to 16-bits when filling the Statistics structure. AWB and ALSC are
agonistic about pipline depth, so do not need chaning.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
---
 src/ipa/raspberrypi/controller/rpi/agc.cpp | 10 ++++------
 src/ipa/raspberrypi/raspberrypi.cpp        | 21 ++++++++++++++-------
 2 files changed, 18 insertions(+), 13 deletions(-)

Hi Naush

Thanks for the patch.

On Tue, 22 Nov 2022 at 11:22, Naushir Patuck via libcamera-devel
<libcamera-devel@lists.libcamera.org> wrote:
>
> The VC4 ISP uses a pipeline bit-depth of 13-bits. The AGC algorithm needs to
> know this bit-depth when computing the Y value for the image.
>
> Instead of hardcoding the VC4 bit-depth in the AGC source code, normalise all
> region sums to 16-bits when filling the Statistics structure. AWB and ALSC are
> agonistic about pipline depth, so do not need chaning.

Ooh, this line went a bit wrong :)
s/agonistic/agnostic/   (trying to imagine what an "agonistic"
algorithm might be!!)
s/pipline/pipeline/
s/chaning/changing.

But apart from that:

Reviewed-by: David Plowman <david.plowman@raspberrypi.com>

Thanks!
David

>
> Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
> ---
>  src/ipa/raspberrypi/controller/rpi/agc.cpp | 10 ++++------
>  src/ipa/raspberrypi/raspberrypi.cpp        | 21 ++++++++++++++-------
>  2 files changed, 18 insertions(+), 13 deletions(-)
>
> diff --git a/src/ipa/raspberrypi/controller/rpi/agc.cpp b/src/ipa/raspberrypi/controller/rpi/agc.cpp
> index 79c83e0a9eae..358af8f2544b 100644
> --- a/src/ipa/raspberrypi/controller/rpi/agc.cpp
> +++ b/src/ipa/raspberrypi/controller/rpi/agc.cpp
> @@ -28,8 +28,6 @@ LOG_DEFINE_CATEGORY(RPiAgc)
>
>  #define NAME "rpi.agc"
>
> -static constexpr unsigned int PipelineBits = 13; /* seems to be a 13-bit pipeline */
> -
>  int AgcMeteringMode::read(const libcamera::YamlObject &params)
>  {
>         const YamlObject &yamlWeights = params["weights"];
> @@ -593,9 +591,9 @@ static double computeInitialY(StatisticsPtr &stats, AwbStatus const &awb,
>         for (unsigned int i = 0; i < stats->agcRegions.numRegions(); i++) {
>                 uint32_t counted, uncounted;
>                 auto s = stats->agcRegions.get(i, counted, uncounted);
> -               double rAcc = std::min<double>(s.rSum * gain, ((1 << PipelineBits) - 1) * counted);
> -               double gAcc = std::min<double>(s.gSum * gain, ((1 << PipelineBits) - 1) * counted);
> -               double bAcc = std::min<double>(s.bSum * gain, ((1 << PipelineBits) - 1) * counted);
> +               double rAcc = std::min<double>(s.rSum * gain, ((1 << 16) - 1) * counted);
> +               double gAcc = std::min<double>(s.gSum * gain, ((1 << 16) - 1) * counted);
> +               double bAcc = std::min<double>(s.bSum * gain, ((1 << 16) - 1) * counted);
>                 rSum += rAcc * weights[i];
>                 gSum += gAcc * weights[i];
>                 bSum += bAcc * weights[i];
> @@ -608,7 +606,7 @@ static double computeInitialY(StatisticsPtr &stats, AwbStatus const &awb,
>         double ySum = rSum * awb.gainR * .299 +
>                       gSum * awb.gainG * .587 +
>                       bSum * awb.gainB * .114;
> -       return ySum / pixelSum / (1 << PipelineBits);
> +       return ySum / pixelSum / (1 << 16);
>  }
>
>  /*
> diff --git a/src/ipa/raspberrypi/raspberrypi.cpp b/src/ipa/raspberrypi/raspberrypi.cpp
> index 8fcfa0b3ea50..fcecd60bcf6d 100644
> --- a/src/ipa/raspberrypi/raspberrypi.cpp
> +++ b/src/ipa/raspberrypi/raspberrypi.cpp
> @@ -1132,19 +1132,26 @@ RPiController::StatisticsPtr IPARPi::fillStatistics(bcm2835_isp_stats *stats) co
>         /* RGB histograms are not used, so do not populate them. */
>         statistics->yHist = std::move(RPiController::Histogram(stats->hist[0].g_hist, NUM_HISTOGRAM_BINS));
>
> +       /*
> +        * All region sums are based on a 13-bit pipeline bit-depth. Normalise
> +        * this to 16-bits for the AGC/AWB/ALSC algorithms.
> +        */
>         statistics->awbRegions.init(DEFAULT_AWB_REGIONS_X, DEFAULT_AWB_REGIONS_Y);
>         for (i = 0; i < statistics->awbRegions.numRegions(); i++)
> -               statistics->awbRegions.set(i, { stats->awb_stats[i].r_sum,
> -                                               stats->awb_stats[i].g_sum,
> -                                               stats->awb_stats[i].b_sum },
> +               statistics->awbRegions.set(i, { stats->awb_stats[i].r_sum << 3,
> +                                               stats->awb_stats[i].g_sum << 3,
> +                                               stats->awb_stats[i].b_sum << 3 },
>                                            stats->awb_stats[i].counted, stats->awb_stats[i].notcounted);
>
> -       /* There are only ever 15 regions computed by the firmware, but the HW defines AGC_REGIONS == 16! */
> +       /*
> +        * There are only ever 15 regions computed by the firmware due to zoning,
> +        * but the HW defines AGC_REGIONS == 16!
> +        */
>         statistics->agcRegions.init(15);
>         for (i = 0; i < statistics->agcRegions.numRegions(); i++)
> -               statistics->agcRegions.set(i, { stats->agc_stats[i].r_sum,
> -                                               stats->agc_stats[i].g_sum,
> -                                               stats->agc_stats[i].b_sum },
> +               statistics->agcRegions.set(i, { stats->agc_stats[i].r_sum << 3,
> +                                               stats->agc_stats[i].g_sum << 3,
> +                                               stats->agc_stats[i].b_sum << 3 },
>                                            stats->agc_stats[i].counted, 0);
>
>         statistics->focusRegions.init(4, 3);
> --
> 2.25.1
>