diff options
Diffstat (limited to 'src/ipa/ipu3/algorithms/agc.cpp')
| -rw-r--r-- | src/ipa/ipu3/algorithms/agc.cpp | 44 |
1 files changed, 22 insertions, 22 deletions
diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp index 43a39ffd..9cd2ded5 100644 --- a/src/ipa/ipu3/algorithms/agc.cpp +++ b/src/ipa/ipu3/algorithms/agc.cpp @@ -62,12 +62,12 @@ static constexpr double kEvGainTarget = 0.5; static constexpr uint32_t kNumStartupFrames = 10; /* - * Normalized luma value target. + * Relative luminance target. * * It's a number that's chosen so that, when the camera points at a grey * target, the resulting image brightness is considered right. */ -static constexpr double kNormalizedLumaTarget = 0.16; +static constexpr double kRelativeLuminanceTarget = 0.16; Agc::Agc() : frameCount_(0), iqMean_(0.0), lineDuration_(0s), minShutterSpeed_(0s), @@ -250,12 +250,12 @@ void Agc::computeExposure(IPAFrameContext &frameContext, double currentYGain) } /** - * \brief Estimate the average brightness of the frame + * \brief Estimate the relative luminance of the frame with a given gain * \param[in] frameContext The shared IPA frame context * \param[in] grid The grid used to store the statistics in the IPU3 * \param[in] stats The IPU3 statistics and ISP results * \param[in] currentYGain The gain calculated on the current brightness level - * \return The normalized luma + * \return The relative luminance * * Luma is the weighted sum of gamma-compressed R′G′B′ components of a color * video. The luma values are normalized as 0.0 to 1.0, with 1.0 being a @@ -263,12 +263,12 @@ void Agc::computeExposure(IPAFrameContext &frameContext, double currentYGain) * luma here. * * More detailed information can be found in: - * https://en.wikipedia.org/wiki/Luma_(video) + * https://en.wikipedia.org/wiki/Relative_luminance */ -double Agc::computeInitialY(IPAFrameContext &frameContext, - const ipu3_uapi_grid_config &grid, - const ipu3_uapi_stats_3a *stats, - double currentYGain) +double Agc::estimateLuminance(IPAFrameContext &frameContext, + const ipu3_uapi_grid_config &grid, + const ipu3_uapi_stats_3a *stats, + double currentYGain) { double redSum = 0, greenSum = 0, blueSum = 0; @@ -288,14 +288,14 @@ double Agc::computeInitialY(IPAFrameContext &frameContext, } /* - * Estimate the sum of the brightness values, weighted with the gains - * applied on the channels in AWB as the Rec. 601 luma. + * Apply the AWB gains to approximate colours correctly, use the Rec. + * 601 formula to calculate the relative luminance, and normalize it. */ - double Y_sum = redSum * frameContext.awb.gains.red * .299 + - greenSum * frameContext.awb.gains.green * .587 + - blueSum * frameContext.awb.gains.blue * .114; + double ySum = redSum * frameContext.awb.gains.red * 0.299 + + greenSum * frameContext.awb.gains.green * 0.587 + + blueSum * frameContext.awb.gains.blue * 0.114; - return Y_sum / (grid.height * grid.width) / 255; + return ySum / (grid.height * grid.width) / 255; } /** @@ -311,22 +311,22 @@ void Agc::process(IPAContext &context, const ipu3_uapi_stats_3a *stats) measureBrightness(stats, context.configuration.grid.bdsGrid); double currentYGain = 1.0; - double targetY = kNormalizedLumaTarget; + double yTarget = kRelativeLuminanceTarget; /* * Do this calculation a few times as brightness increase can be * non-linear when there are saturated regions. */ - for (int i = 0; i < 8; i++) { - double initialY = computeInitialY(context.frameContext, + for (unsigned int i = 0; i < 8; i++) { + double yValue = estimateLuminance(context.frameContext, context.configuration.grid.bdsGrid, stats, currentYGain); - double extra_gain = std::min(10.0, targetY / (initialY + .001)); + double extra_gain = std::min(10.0, yTarget / (yValue + .001)); currentYGain *= extra_gain; - LOG(IPU3Agc, Debug) << "Initial Y " << initialY - << " target " << targetY - << " gives gain " << currentYGain; + LOG(IPU3Agc, Debug) << "Y value: " << yValue + << ", Y target: " << yTarget + << ", gives gain " << currentYGain; if (extra_gain < 1.01) break; } |