pica-client: more improvements of echo cancellation

1 files changed, 56 insertions, 9 deletions

diff --git a/pica-client/audiovideocallcontroller.h b/pica-client/audiovideocallcontroller.h
index e30f4c1..f7c9e37 100644
--- a/pica-client/audiovideocallcontroller.h
+++ b/pica-client/audiovideocallcontroller.h
@@ -85,20 +85,64 @@ private:
 	//
 	// m_savedCaptureGain is where the control was found at the start of the
 	// call, put back in stopAudioPipeline(): this is the user's own setting
-	// and we are only borrowing it. m_captureGainSteps bounds how far we will
-	// go, so a microphone that clips for some reason turning it down cannot
-	// fix - a broken preamp, someone shouting into it - ends up quiet rather
-	// than muted.
+	// and we are only borrowing it.
 	CaptureGainControl *m_captureGain;
 	double m_savedCaptureGain;
 	bool m_haveSavedCaptureGain;
-	int m_captureGainSteps;
 
-	static const int kMaxCaptureGainSteps = 12;
+	// This is a calibration that runs at the start of a call and then stops -
+	// NOT a gain control that rides the level for the call's duration. The
+	// difference matters: an adaptive echo canceller can only track a
+	// stationary echo path, and moving the microphone gain moves that path.
+	// See the AGC comment in EchoCanceller's constructor, which says the same
+	// thing about the reason speexdsp's own AGC is left switched off.
+	//
+	// So every adjustment resets the canceller, and once m_gainCalibrating is
+	// false nothing touches the control again until the call ends.
+	bool m_gainCalibrating;
+	int m_captureGainSteps;
 
-	// Never go below this fraction of the control's travel; past it we are
-	// making the user inaudible to fix a problem they can hear about instead.
-	static constexpr double kMinCaptureGain = 0.05;
+	// dB reading when calibration opened, and whether the platform would give
+	// us one. Bounding the total cut in decibels rather than as a fraction of
+	// the control's travel is the whole point: a fraction means different
+	// things on a hardware mixer (linear in dB) and on a sound server or
+	// WASAPI endpoint (roughly cubic), which is how an earlier version of this
+	// managed to wind a microphone down to silence.
+	double m_gainStartDb;
+	bool m_haveGainDb;
+
+	// Consecutive adjustments that moved the control but did not reduce the
+	// clipping. Means the stage actually overloading is one we cannot reach -
+	// an analog mic boost ahead of the converter, or Windows' separate
+	// "Microphone Boost" - and that turning our control down further will
+	// silence the user without ever fixing it.
+	int m_gainIneffectiveSteps;
+	double m_lastPinnedPercent;
+
+	// Reports to ignore after an adjustment, while audio captured at the old
+	// setting drains out of the pipeline.
+	int m_gainSettleReports;
+
+	static const int kMaxCaptureGainSteps = 6;
+
+	// Bound used when the control will not report decibels at all, where we
+	// are working blind and a wrong guess is what silences a microphone.
+	static const int kMaxBlindGainSteps = 2;
+	static const int kMaxGainIneffectiveSteps = 2;
+	static const int kGainSettleReports = 1;
+
+	// How long the calibration window stays open, in milliseconds of call
+	// time. Long enough that someone who says nothing for the first few
+	// seconds still gets calibrated, short enough to be over before the
+	// conversation proper.
+	static const int kGainCalibrationMs = 20000;
+
+	// Hard ceiling on the total cut, in dB below where the user had it. Past
+	// this the problem is not one we are going to fix by turning a knob.
+	static constexpr double kMaxGainReductionDb = 24.0;
+
+	// An adjustment that achieves less than this much is not doing anything.
+	static constexpr double kMinEffectiveStepDb = 0.5;
 
 	// Sequence number / capture-clock timestamp stamped onto outgoing
 	// 0x76 audio packets (see PICA_PROTO_CALL_PACKET_HDRSIZE).
@@ -123,6 +167,9 @@ private:
 	void startCaptureGainControl(const QString &captureDevice);
 	void stopCaptureGainControl();
 
+	// Ends the calibration window, logging why. Idempotent.
+	void closeGainCalibration(const QString &why);
+
 	void playEarpieceTone(void (TonePlayer::*tone)());
 	void playRingTone();
 	void stopTones();