Commit graph

31 commits

Author SHA1 Message Date
Jesús de Vicente Peña
7d0203c723 AEC3: adding a milder exponential decay parameter that is used for dominant nearend regions when enabled.
Bug: webrtc:13143
Change-Id: Iedc6ff39ed5c7cd372b54a82c86354957c8852de
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/231131
Commit-Queue: Per Åhgren <peah@webrtc.org>
Reviewed-by: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#34947}
2021-09-08 11:36:50 +00:00
Gustaf Ullberg
a63d152423 AEC3: Unbounded echo spectrum for dominant nearend detection.
The dominant nearend detector uses the residual echo spectrum for
determining whether in nearend state. The residual echo spectrum in
computed using the ERLE. To reduce the risk of echo leaks in the
suppressor, the ERLE is capped. While minimizing echo leaks, the
capping of the ERLE can affect the dominant nearend classification
negatively as the residual echo spectrum is often over estimated.

This change enables the dominant nearend detector to use a residual
echo spectrum computed with a virtually non-capped ERLE. This ERLE
is only used for dominant nearend detection and leads to increased
transparency.

The feature is currently disabled by default and can be enabled
with the field trial "WebRTC-Aec3UseUnboundedEchoSpectrum".

Bug: webrtc:12870
Change-Id: Icb675c6f5d42ab9286e623b5fb38424d5c9cbee4
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/221920
Reviewed-by: Jesus de Vicente Pena <devicentepena@webrtc.org>
Commit-Queue: Gustaf Ullberg <gustaf@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34270}
2021-06-11 13:30:00 +00:00
Gustaf Ullberg
437d129ef5 AEC3: Avoid overcompensating for render onsets during dominant nearend
The ERLE is used to estimate residual echo for echo suppression. The
ERLE is reduced during far-end offset to avoid echo leakage. When there
is a strong near-end present this can cause unnecessary transparency loss.

This change adds an ERLE estimation that does not compensate for onsets and
uses it for residual echo estimation when the suppressor considers the near-end to be dominant.

Bug: webrtc:12686
Change-Id: Ida78eeacf1f95c6e62403f86ba3f2ff055898a84
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/215323
Commit-Queue: Gustaf Ullberg <gustaf@webrtc.org>
Reviewed-by: Jesus de Vicente Pena <devicentepena@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33786}
2021-04-20 12:33:02 +00:00
Sam Zackrisson
389bf0feb8 AEC3: Move option for reverb model in nonlinaer mode into AEC3 config
This adds a config parameter for reverb modelling in nonlinear mode.
The killswitch is preserved, and will have the same effect before and after this CL.

Tested: Bitexact on a large number of aecdumps both with and without WebRTC-Aec3NonlinearModeReverbKillSwitch.
Bug: webrtc:8671
Change-Id: I7b2fa92307af5316dbe895392367abb8d15f06bf
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/183541
Commit-Queue: Sam Zackrisson <saza@webrtc.org>
Reviewed-by: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32298}
2020-10-02 20:27:47 +00:00
Per Åhgren
d8d09c3c5a AEC3: Add transparency-related killswitches
This CL adds a number of kill-switches to the AEC3 code to be used as
safe fallbacks to increase AEC transparency.

The changes have been shown to be bitexact for a test dataset.

Bug: webrtc:11475,chromium:1066836
Change-Id: Ibebcbbfbbd958cb6fcc6993247e3030fa65b582c
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/172600
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Commit-Queue: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30964}
2020-04-01 17:32:36 +00:00
Per Åhgren
b4161d3c0d AEC3: Add multichannel support to the residual echo estimator
This CL adds support for multichannel in the residual echo
estimator code. It also adds placeholder functionality in
the surrounding code to ensure that the residual echo
estimator receives the require inputs.

The changes in the CL has been shown to be bitexact on a
large set of mono recordings.

Bug: webrtc:10913
Change-Id: I726128ca928648b1dcf36c5f479eb243f3ff3f96
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/155361
Commit-Queue: Per Åhgren <peah@webrtc.org>
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29400}
2019-10-08 11:18:35 +00:00
Sam Zackrisson
f3f6159114 Rename VectorBuffer->SpectrumBuffer, MatrixBuffer->BlockBuffer, BlockBuffer->Aec2BlockBuffer
The VectorBuffer and MatrixBuffer names are too generic for their use case.

Bug: webrtc:10913
Change-Id: Ideecd0d27e07487a85a61dc6474e69733d07dcd6
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/151602
Reviewed-by: Per Åhgren <peah@webrtc.org>
Commit-Queue: Sam Zackrisson <saza@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29076}
2019-09-05 10:53:24 +00:00
Per Åhgren
eac47f7fae Removing unused fallback variant for the reverb computation
This CL removes a long unused fallback behavior for the reverb
computation.

Bug: webrtc:8671
Change-Id: I4b57795a9bb33769237858f40392881ee235653e
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/148520
Commit-Queue: Gustaf Ullberg <gustaf@webrtc.org>
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28802}
2019-08-08 08:00:38 +00:00
Gustaf Ullberg
98da0bd54a AEC3: Remove unused code from residual echo estimator
Bug: webrtc:8671
Change-Id: Id2f711223826e71072dda343fc22ee996532a33a
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/132793
Reviewed-by: Per Åhgren <peah@webrtc.org>
Commit-Queue: Gustaf Ullberg <gustaf@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27611}
2019-04-15 10:22:45 +00:00
Gustaf Ullberg
68d6d44197 AEC3: Remove remaining kill-switches
This CL concludes the post-launch removal of kill-switches is AEC3.

Kill-switches removed:
WebRTC-Aec3AdaptErleOnLowRenderKillSwitch
WebRTC-Aec3AgcGainChangeResponseKillSwitch
WebRTC-Aec3BoundedNearendKillSwitch
WebRTC-Aec3EarlyShadowFilterJumpstartKillSwitch
WebRTC-Aec3EnableAdaptiveEchoReverbEstimation
WebRTC-Aec3EnforceSkewHysteresis1
WebRTC-Aec3EnforceSkewHysteresis2
WebRTC-Aec3FilterAnalyzerPreprocessorKillSwitch
WebRTC-Aec3MisadjustmentEstimatorKillSwitch
WebRTC-Aec3OverrideEchoPathGainKillSwitch
WebRTC-Aec3RapidAgcGainRecoveryKillSwitch
WebRTC-Aec3ResetErleAtGainChangesKillSwitch
WebRTC-Aec3ShadowFilterBoostedJumpstartKillSwitch
WebRTC-Aec3ShadowFilterJumpstartKillSwitch
WebRTC-Aec3SmoothSignalTransitionsKillSwitch
WebRTC-Aec3SmoothUpdatesTailFreqRespKillSwitch
WebRTC-Aec3SoftTransparentModeKillSwitch
WebRTC-Aec3StandardNonlinearReverbModelKillSwitch
WebRTC-Aec3StrictDivergenceCheckKillSwitch
WebRTC-Aec3UseOffsetBlocks
WebRTC-Aec3UseStationarityPropertiesKillSwitch
WebRTC-Aec3UtilizeShadowFilterOutputKillSwitch
WebRTC-Aec3ZeroExternalDelayHeadroomKillSwitch
WebRTC-Aec3FilterQualityStateKillSwitch
WebRTC-Aec3NewSaturationBehaviorKillSwitch
WebRTC-Aec3GainLimiterDeactivationKillSwitch
WebRTC-Aec3EnableErleUpdatesDuringReverbKillSwitch

The change has been tested for bit-exactness.

Bug: webrtc:8671
Change-Id: I42816b9d1c875cec0347034c6e2ed4ff5db6ec0f
Reviewed-on: https://webrtc-review.googlesource.com/c/119942
Commit-Queue: Gustaf Ullberg <gustaf@webrtc.org>
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26443}
2019-01-29 10:31:45 +00:00
Steve Anton
10542f21c8 (4) Rename files to snake_case: update BUILD.gn, include paths, header guards, and DEPS entries
Mechanically generated by running this command:

tools_webrtc/do-renames.sh update all-renames.txt && git cl format

Then manually updating:

tools_webrtc/sanitizers/tsan_suppressions_webrtc.cc

Bug: webrtc:10159
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: I54824cd91dada8fc3ee3d098f971bc319d477833
Reviewed-on: https://webrtc-review.googlesource.com/c/115653
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26226}
2019-01-11 17:11:39 +00:00
Yves Gerey
988cc0870b [Cleanup] Add missing #include. Remove useless ones.
This CL is the result of running include-what-you-use tool on part
of the code base (audio target and dependencies) plus manual fixes.

bug: webrtc:8311
Change-Id: I277d281ce943c3ecc1bd45fd8d83055931743604
Reviewed-on: https://webrtc-review.googlesource.com/c/106280
Commit-Queue: Yves Gerey <yvesg@google.com>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25311}
2018-10-23 11:32:56 +00:00
Jesús de Vicente Peña
c98849cf92 AEC3: changes the signal used for deciding when to update the erle so the reverb render signal is now used
In this CL we change the signal that controls the updates of the ERLE estimator. Until now, the render signal was used which is not optimum for reverberant signals. In this CL, a reverberation has been added to the the render signal and this new signal has been used for controlling when to update the ERLE estimator.

Bug: webrtc:9873
Change-Id: I0ebea3fc208f97aa237af015ba543015d49ed978
Reviewed-on: https://webrtc-review.googlesource.com/c/105660
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Commit-Queue: Jesus de Vicente Pena <devicentepena@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25285}
2018-10-22 10:30:12 +00:00
Per Åhgren
f954ba5c11 AEC3: Increasing the transparency during call startup
This CL increases the AEC3 transparency during call
startup and after echo path delay changes in 3 ways:
1. The exit requirements for the initial mode is
made less strict.
2. The requirements for using the linear echo model
are made less strict.
3. The duplicated reverb modelling in the linear mode
removed.


Bug: webrtc:9572,chromium:868329
Change-Id: I79ea0796ed26408e35576bb39eaae4e4848b4f83
Reviewed-on: https://webrtc-review.googlesource.com/90868
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Commit-Queue: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24132}
2018-07-27 14:18:42 +00:00
Gustaf Ullberg
6c618c7002 AEC3: Avoid entering non-linear mode when the filter is slightly diverged
This CL changes the behavior when the main filter diverges.
Instead of entering non-linear mode, the AEC continues to operate in
linear mode but estimates the residual echo differently. R2 is S2
scaled by a factor of 10.

Bug: chromium:857018,webrtc:9462
Change-Id: I41212efe164ad319cf38a163cdf9d3ea151e0997
Reviewed-on: https://webrtc-review.googlesource.com/85981
Commit-Queue: Gustaf Ullberg <gustaf@webrtc.org>
Reviewed-by: Jesus de Vicente Pena <devicentepena@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23772}
2018-06-28 13:35:18 +00:00
Jesús de Vicente Peña
075cb2b2f7 AEC3: Changes to how the reverberation decay is applied.
In this work we introduce some changes on how the reverberation model for AEC3 is applied. Currently, the exponential modelling of the tails is applied over the linear echo estimates. That might result  in an overestimation of the reverberation tails under certain conditions. In this work, the reverberation model is instead applied over an estimate of the energies at the tails of the linear estimate.

Additionally, the stationary estimator is changed so it does not disable the aec immediately after a burst of activity.

Bug: webrtc:9384,webrtc:9400,chromium:852257
Change-Id: Ia486694ed326cfe231fc688877c0b9b6e2c450ff
Reviewed-on: https://webrtc-review.googlesource.com/82161
Reviewed-by: Per Åhgren <peah@webrtc.org>
Commit-Queue: Jesus de Vicente Pena <devicentepena@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23599}
2018-06-13 14:54:04 +00:00
Jesús de Vicente Peña
dd09287514 AEC3: Gain limiter: Improving the behavior of the gain limiter.
In this work, we change the behavior of the gain limiter so it also looks at the energy
 on farend around the default delay for deciding the suppression gain
that should be applied at the initial portion of the call.

Bug: webrtc:9311,chromium:846724
Change-Id: I0b777cedbbd7fd689e72070f72237296ce120d3c
Reviewed-on: https://webrtc-review.googlesource.com/78960
Reviewed-by: Per Åhgren <peah@webrtc.org>
Commit-Queue: Jesus de Vicente Pena <devicentepena@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23400}
2018-05-25 15:49:38 +00:00
Per Åhgren
ced31ba1cf Correcting the usage of the estimated echo path gain in AEC3
This CL corrects the usage of the estimated echo path gain to not be
hardcoded to 1. In order to retain the tuned behavior, the CL for now
maintains the former behavior in the code.

Bug: webrtc:9255,chromium:851187
Change-Id: I7f91c72e476680a8a854c22b74b1771fae446110
Reviewed-on: https://webrtc-review.googlesource.com/75510
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Commit-Queue: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23190}
2018-05-09 12:35:31 +00:00
Per Åhgren
9ad845d2ab Soften the AEC3 transparent mode to handle broken headsets
This CL softens the effect of the AEC3 transparent mode to also handle
headsets that leak low-level echoes in a nonlinear way.
This is handled by reintroducing the limit in the echo path gain for the
nonlinear mode. Due to recent improvements in echo suppressor behavior
this is now possible to do with a limited impact on the near-end speech.

Bug: webrtc:9246,chromium:840347
Change-Id: I0ca5157160d1884ba93b962323b56016756986d3
Reviewed-on: https://webrtc-review.googlesource.com/74703
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Commit-Queue: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23145}
2018-05-07 13:52:08 +00:00
Jesús de Vicente Peña
65ddf07219 AEC3: not applying noise gating when using the stationarity properties of the render signal
Bug: webrtc:9193,chromium:836790
Change-Id: I87ded1d33869037420c435155bd084f6fc3efdb0
Reviewed-on: https://webrtc-review.googlesource.com/73740
Reviewed-by: Per Åhgren <peah@webrtc.org>
Commit-Queue: Jesus de Vicente Pena <devicentepena@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23111}
2018-05-04 09:14:24 +00:00
Per Åhgren
31122d6c5f Correct and soften the AEC3 handling of saturated mic signals
This CL changes the handling of saturated microphone signals in AEC3.

Some of the changes included are
-Make the detection of saturated echoes depend on the echo path gain
 estimate.
-Remove redundant code related to echo saturation.
-Correct the computation of residual echoes when the echo is saturated.
-Soften the echo removal during echo saturation.

Bug: webrtc:9119
Change-Id: I5cb11cd449de552ab670beeb24ed8112f8beb734
Reviewed-on: https://webrtc-review.googlesource.com/67220
Commit-Queue: Per Åhgren <peah@webrtc.org>
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22809}
2018-04-10 15:28:45 +00:00
Per Åhgren
251c7355aa Add a specific AEC3 behavior for setups with known clock-drift
TBR=gustaf@webrtc.org

Change-Id: I9c726fc8e1b010255a1bee166c99fe6cb75d7658
Bug: chromium:826655,webrtc:9079
Reviewed-on: https://webrtc-review.googlesource.com/64982
Commit-Queue: Per Åhgren <peah@webrtc.org>
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22657}
2018-03-28 16:51:57 +00:00
Per Åhgren
5c532d3774 Robustification of the echo suppression behavior during headset usage.
This CL robustifies the echo removal behavior when headsets are used.
In particular it:
-Introduces a secondary, more refined alignment when no alignment can
be found using the delay estimator.
-Changes decision logic for when to use the linear filter output.
-Changes the decision logic for when to be transparent.
-Changes the way that the transparent mode works.
-Makes the nonlinear mode less aggressive.
-Removes the detector for non-audible echoes.
-Makes the attenuation when there are signals with strong narrowband
characteristics more mild in scenarios with low render.

Furthermore the CL:
-Removes the input of external echo leakage information.


Bug: webrtc:9047,chromium:824111,webrtc:8314,webrtc:8671,webrtc:5201,webrtc:5919
Change-Id: Ied1fe0c0a35d3c31b47606ed2db319a73644d406
Reviewed-on: https://webrtc-review.googlesource.com/60866
Commit-Queue: Per Åhgren <peah@webrtc.org>
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22548}
2018-03-22 00:23:23 +00:00
Gustaf Ullberg
3646f973c2 AEC3 includes echo_canceller3_config.h directly
Avoid including audio_processing.h from within AEC3.

Bug: webrtc:8844
Change-Id: I02c475c2fb84e2c24eac86baac3c7edaa08bebc0
Reviewed-on: https://webrtc-review.googlesource.com/53065
Commit-Queue: Gustaf Ullberg <gustaf@webrtc.org>
Reviewed-by: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22029}
2018-02-15 08:30:14 +00:00
Per Åhgren
60e8965b6b Removed the redundant functionality for the initial state in AEC3
Bug: webrtc:8671
Change-Id: I93412675a6b56c20c8d866e64e24560a4546dc66
Reviewed-on: https://webrtc-review.googlesource.com/35200
Commit-Queue: Per Åhgren <peah@webrtc.org>
Reviewed-by: Per Åhgren <peah@webrtc.org>
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21391}
2017-12-20 16:54:48 +00:00
Per Åhgren
09a718accd Added the ability to more easily adjust the filter length in AEC3
Bug: webrtc:8609
Change-Id: If060b332993c2c98d7a12608ab31f4da858b8016
Reviewed-on: https://webrtc-review.googlesource.com/28620
Commit-Queue: Per Åhgren <peah@webrtc.org>
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21216}
2017-12-11 22:02:46 +00:00
Gustaf Ullberg
bd83b914c3 Separate AEC3 config from AudioProcessing::Config.
The struct containing the config for AEC3 is removed from
AudioProcessing::Config and is put in a new struct called
EchoCanceller3Config.

AEC3 should no longer be activated through
AudioProcessing::ApplyConfig. Instead an EchoCanceller3Factory
can be injected at AudioProcessing creation.

Bug: webrtc:8346
Change-Id: I27e3592e675eec3632a60c45d9e0d12514c2c567
Reviewed-on: https://webrtc-review.googlesource.com/11420
Reviewed-by: Per Åhgren <peah@webrtc.org>
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Commit-Queue: Gustaf Ullberg <gustaf@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20342}
2017-10-19 08:19:52 +00:00
Per Åhgren
1b4059e84f Transparency improvements for AEC3 during call start and after resets
This CL changes the AEC3 behavior to be more transparent when there 
is uncertainty about the amount of echo in the microphone signal.

Bug: webrtc:8398, chromium:774868
Change-Id: I88e681f8decd892f44397b753df371a1c4b90af0
Reviewed-on: https://webrtc-review.googlesource.com/10801
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Commit-Queue: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20319}
2017-10-17 06:00:50 +00:00
Per Åhgren
c65ce78027 Separated the NLP behavior in AEC3 for different echo estimates.
This CL separates the NLP gain computation for the different variants
of echo estimation. This simplifies the setting of tuning 
parameters, with resulting transparency improvements and increased
echo removal performance.

Bug: webrtc:8359
Change-Id: I9b97064396fb6f6e2f418ce534573f68694390a1
Reviewed-on: https://webrtc-review.googlesource.com/7613
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Commit-Queue: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20209}
2017-10-09 13:16:37 +00:00
Mirko Bonadei
92ea95e34a Fixing WebRTC after moving from src/webrtc to src/
In https://webrtc-review.googlesource.com/c/src/+/1560 we moved WebRTC
from src/webrtc to src/ (in order to preserve an healthy git history).
This CL takes care of fixing header guards, #include paths, etc...

NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
TBR=tommi@webrtc.org


Bug: chromium:611808
Change-Id: Iea91618212bee0af16aa3f05071eab8f93706578
Reviewed-on: https://webrtc-review.googlesource.com/1561
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Henrik Kjellander <kjellander@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#19846}
2017-09-15 05:02:56 +00:00
Mirko Bonadei
bb547203bf Moving src/webrtc into src/.
In order to eliminate the WebRTC Subtree mirror in Chromium, 
WebRTC is moving the content of the src/webrtc directory up
to the src/ directory.

NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
TBR=tommi@webrtc.org

Bug: chromium:611808
Change-Id: Iac59c5b51b950f174119565bac87955a7994bc38
Reviewed-on: https://webrtc-review.googlesource.com/1560
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Henrik Kjellander <kjellander@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#19845}
2017-09-15 04:25:06 +00:00
Renamed from webrtc/modules/audio_processing/aec3/residual_echo_estimator.h (Browse further)