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
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
|
/* 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 <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 analogue gain value
* \todo grab it from a camera helper */
static constexpr double kMinGain = 1.0;
static constexpr double kMaxGain = 8.0;
/* 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),
minExposureLines_(0), maxExposureLines_(0), filteredExposure_(0s),
currentExposure_(0s), prevExposureValue_(0s)
{
}
int Agc::configure(IPAContext &context, const IPAConfigInfo &configInfo)
{
stride_ = context.configuration.grid.stride;
lineDuration_ = configInfo.sensorInfo.lineLength * 1.0s
/ configInfo.sensorInfo.pixelRate;
/* \todo replace the exposure in lines storage with time based ones. */
minExposureLines_ = context.configuration.agc.minShutterSpeed / lineDuration_;
maxExposureLines_ = context.configuration.agc.maxShutterSpeed / lineDuration_;
/* Configure the default exposure and gain. */
context.frameContext.agc.gain =
context.configuration.agc.minAnalogueGain;
context.frameContext.agc.exposure = minExposureLines_;
prevExposureValue_ = context.frameContext.agc.gain
* context.frameContext.agc.exposure
* 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;
const ipu3_uapi_awb_set_item *cell =
reinterpret_cast<const ipu3_uapi_awb_set_item *>(
&stats->awb_raw_buffer.meta_data[cellPosition]
);
if (cell->sat_ratio == 0) {
uint8_t gr = cell->Gr_avg;
uint8_t gb = cell->Gb_avg;
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 (filteredExposure_ == 0s) {
/* DG stands for digital gain.*/
filteredExposure_ = currentExposure_;
} else {
/*
* If we are close to the desired result, go faster to avoid making
* multiple micro-adjustments.
* \ todo: Make this customisable?
*/
if (filteredExposure_ < 1.2 * currentExposure_ &&
filteredExposure_ > 0.8 * currentExposure_)
speed = sqrt(speed);
filteredExposure_ = speed * currentExposure_ +
filteredExposure_ * (1.0 - speed);
}
LOG(IPU3Agc, Debug) << "After filtering, total_exposure " << filteredExposure_;
}
void Agc::lockExposureGain(uint32_t &exposure, double &analogueGain)
{
/* 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;
lastFrame_ = frameCount_;
/* Are we correctly exposed ? */
if (std::abs(iqMean_ - kEvGainTarget * knumHistogramBins) <= 1) {
LOG(IPU3Agc, Debug) << "We are well exposed (iqMean = "
<< iqMean_ << ")";
return;
}
double evGain = kEvGainTarget * knumHistogramBins / iqMean_;
/* extracted from Rpi::Agc::computeTargetExposure */
utils::Duration currentShutter = exposure * lineDuration_;
LOG(IPU3Agc, Debug) << "Actual total exposure " << currentShutter * analogueGain
<< " Shutter speed " << currentShutter
<< " Gain " << analogueGain
<< " Needed ev gain " << evGain;
currentExposure_ = prevExposureValue_ * evGain;
utils::Duration minShutterSpeed = minExposureLines_ * lineDuration_;
utils::Duration maxShutterSpeed = maxExposureLines_ * lineDuration_;
utils::Duration maxTotalExposure = maxShutterSpeed * kMaxGain;
currentExposure_ = std::min(currentExposure_, maxTotalExposure);
LOG(IPU3Agc, Debug) << "Target total exposure " << currentExposure_
<< ", maximum is " << maxTotalExposure;
/* \todo: estimate if we need to desaturate */
filterExposure();
utils::Duration exposureValue = filteredExposure_;
utils::Duration shutterTime = minShutterSpeed;
/*
* Push the shutter time up to the maximum first, and only then
* increase the gain.
*/
shutterTime = std::clamp<utils::Duration>(exposureValue / kMinGain,
minShutterSpeed, maxShutterSpeed);
double stepGain = std::clamp(exposureValue / shutterTime,
kMinGain, kMaxGain);
LOG(IPU3Agc, Debug) << "Divided up shutter and gain are "
<< shutterTime << " and "
<< stepGain;
exposure = shutterTime / lineDuration_;
analogueGain = stepGain;
/*
* Update the exposure value for the next process call.
*
* \todo Obtain the values of the exposure time and analog gain
* that were actually used by the sensor, either from embedded
* data when available, or from the delayed controls
* infrastructure in case a slow down caused a mismatch.
*/
prevExposureValue_ = shutterTime * analogueGain;
}
void Agc::process(IPAContext &context, const ipu3_uapi_stats_3a *stats)
{
uint32_t &exposure = context.frameContext.agc.exposure;
double &analogueGain = context.frameContext.agc.gain;
processBrightness(stats, context.configuration.grid.bdsGrid);
lockExposureGain(exposure, analogueGain);
frameCount_++;
}
} /* namespace ipa::ipu3::algorithms */
} /* namespace libcamera */
|
