1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
|
/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* Copyright (C) 2021, Ideas On Board
*
* ipu3_agc.cpp - AGC/AEC control algorithm
*/
#include "agc.h"
#include "awb.h"
#include <algorithm>
#include <chrono>
#include <cmath>
#include <libcamera/base/log.h>
#include <libcamera/ipa/core_ipa_interface.h>
#include "libipa/histogram.h"
namespace libcamera {
using namespace std::literals::chrono_literals;
namespace ipa::ipu3::algorithms {
LOG_DEFINE_CATEGORY(IPU3Agc)
/* Number of frames to wait before calculating stats on minimum exposure */
static constexpr uint32_t kInitialFrameMinAECount = 4;
/* Number of frames to wait between new gain/exposure estimations */
static constexpr uint32_t kFrameSkipCount = 6;
/* Maximum ISO value for analogue gain */
static constexpr uint32_t kMinISO = 100;
static constexpr uint32_t kMaxISO = 1500;
/* Maximum analogue gain value
* \todo grab it from a camera helper */
static constexpr uint32_t kMinGain = kMinISO / 100;
static constexpr uint32_t kMaxGain = kMaxISO / 100;
/* \todo use calculated value based on sensor */
static constexpr uint32_t kMinExposure = 1;
static constexpr uint32_t kMaxExposure = 1976;
/* Histogram constants */
static constexpr uint32_t knumHistogramBins = 256;
static constexpr double kEvGainTarget = 0.5;
Agc::Agc()
: frameCount_(0), lastFrame_(0), iqMean_(0.0), lineDuration_(0s),
maxExposureTime_(0s), prevExposure_(0s), prevExposureNoDg_(0s),
currentExposure_(0s), currentExposureNoDg_(0s)
{
}
int Agc::configure(IPAContext &context, const IPAConfigInfo &configInfo)
{
stride_ = context.configuration.grid.stride;
lineDuration_ = configInfo.sensorInfo.lineLength * 1.0s
/ configInfo.sensorInfo.pixelRate;
maxExposureTime_ = kMaxExposure * lineDuration_;
return 0;
}
void Agc::processBrightness(const ipu3_uapi_stats_3a *stats,
const ipu3_uapi_grid_config &grid)
{
uint32_t hist[knumHistogramBins] = { 0 };
for (unsigned int cellY = 0; cellY < grid.height; cellY++) {
for (unsigned int cellX = 0; cellX < grid.width; cellX++) {
uint32_t cellPosition = (cellY * stride_ + cellX)
* sizeof(Ipu3AwbCell);
const Ipu3AwbCell *cell =
reinterpret_cast<const Ipu3AwbCell *>(
&stats->awb_raw_buffer.meta_data[cellPosition]
);
if (cell->satRatio == 0) {
uint8_t gr = cell->greenRedAvg;
uint8_t gb = cell->greenBlueAvg;
hist[(gr + gb) / 2]++;
}
}
}
/* Estimate the quantile mean of the top 2% of the histogram */
iqMean_ = Histogram(Span<uint32_t>(hist)).interQuantileMean(0.98, 1.0);
}
void Agc::filterExposure()
{
double speed = 0.2;
if (prevExposure_ == 0s) {
/* DG stands for digital gain.*/
prevExposure_ = currentExposure_;
prevExposureNoDg_ = currentExposureNoDg_;
} else {
/*
* If we are close to the desired result, go faster to avoid making
* multiple micro-adjustments.
* \ todo: Make this customisable?
*/
if (prevExposure_ < 1.2 * currentExposure_ &&
prevExposure_ > 0.8 * currentExposure_)
speed = sqrt(speed);
prevExposure_ = speed * currentExposure_ +
prevExposure_ * (1.0 - speed);
prevExposureNoDg_ = speed * currentExposureNoDg_ +
prevExposureNoDg_ * (1.0 - speed);
}
/*
* We can't let the no_dg exposure deviate too far below the
* total exposure, as there might not be enough digital gain available
* in the ISP to hide it (which will cause nasty oscillation).
*/
double fastReduceThreshold = 0.4;
if (prevExposureNoDg_ <
prevExposure_ * fastReduceThreshold)
prevExposureNoDg_ = prevExposure_ * fastReduceThreshold;
LOG(IPU3Agc, Debug) << "After filtering, total_exposure " << prevExposure_;
}
void Agc::lockExposureGain(uint32_t &exposure, double &gain)
{
/* Algorithm initialization should wait for first valid frames */
/* \todo - have a number of frames given by DelayedControls ?
* - implement a function for IIR */
if ((frameCount_ < kInitialFrameMinAECount) || (frameCount_ - lastFrame_ < kFrameSkipCount))
return;
/* Are we correctly exposed ? */
if (std::abs(iqMean_ - kEvGainTarget * knumHistogramBins) <= 1) {
LOG(IPU3Agc, Debug) << "!!! Good exposure with iqMean = " << iqMean_;
} else {
double newGain = kEvGainTarget * knumHistogramBins / iqMean_;
/* extracted from Rpi::Agc::computeTargetExposure */
libcamera::utils::Duration currentShutter = exposure * lineDuration_;
currentExposureNoDg_ = currentShutter * gain;
LOG(IPU3Agc, Debug) << "Actual total exposure " << currentExposureNoDg_
<< " Shutter speed " << currentShutter
<< " Gain " << gain;
currentExposure_ = currentExposureNoDg_ * newGain;
libcamera::utils::Duration maxTotalExposure = maxExposureTime_ * kMaxGain;
currentExposure_ = std::min(currentExposure_, maxTotalExposure);
LOG(IPU3Agc, Debug) << "Target total exposure " << currentExposure_;
/* \todo: estimate if we need to desaturate */
filterExposure();
libcamera::utils::Duration newExposure = 0.0s;
if (currentShutter < maxExposureTime_) {
exposure = std::clamp(static_cast<uint32_t>(exposure * currentExposure_ / currentExposureNoDg_), kMinExposure, kMaxExposure);
newExposure = currentExposure_ / exposure;
gain = std::clamp(static_cast<uint32_t>(gain * currentExposure_ / newExposure), kMinGain, kMaxGain);
} else if (currentShutter >= maxExposureTime_) {
gain = std::clamp(static_cast<uint32_t>(gain * currentExposure_ / currentExposureNoDg_), kMinGain, kMaxGain);
newExposure = currentExposure_ / gain;
exposure = std::clamp(static_cast<uint32_t>(exposure * currentExposure_ / newExposure), kMinExposure, kMaxExposure);
}
LOG(IPU3Agc, Debug) << "Adjust exposure " << exposure * lineDuration_ << " and gain " << gain;
}
lastFrame_ = frameCount_;
}
void Agc::process(IPAContext &context, const ipu3_uapi_stats_3a *stats)
{
uint32_t &exposure = context.frameContext.agc.exposure;
double &gain = context.frameContext.agc.gain;
processBrightness(stats, context.configuration.grid.bdsGrid);
lockExposureGain(exposure, gain);
frameCount_++;
}
} /* namespace ipa::ipu3::algorithms */
} /* namespace libcamera */
|
