From 2440d0aa3f0ca38f27fc739e56e55a754fe411ae Mon Sep 17 00:00:00 2001
From: Felix The Cat <ftc.denis@gmail.com>
Date: Wed, 6 Jan 2021 11:28:33 +0300
Subject: [PATCH] Improved handling of starting and ending silence

---
 Measurer.cpp | 22 ++++++++++++++++++++--
 Measurer.h   |  1 +
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/Measurer.cpp b/Measurer.cpp
index 3e00e23..a6d7db7 100644
--- a/Measurer.cpp
+++ b/Measurer.cpp
@@ -83,11 +83,19 @@ float Measurer::ProcessData(QByteArray data)
 		}
 		cerr << "Samples read: " << oss.str() << "\n";
 	}
+	// determine silence threshold (will consider signal less than SILENCE of maximum as silence)
+	float max_sample = abs(samples[0]);
+	for (int i = 1; i < (int)samples.size(); i++)
+	{
+		float q = abs(samples[i]);
+		if (q > max_sample) max_sample = q;
+	}
+	float silence_level = SILENCE_LEVEL * max_sample;
 	// cut off starting and ending silence
 	int left_pos = 0;
-	while (left_pos < (int)samples.size() && abs(samples[left_pos]) < 1e-4) left_pos++;
+	while (left_pos < (int)samples.size() && abs(samples[left_pos]) < silence_level) left_pos++;
 	int right_pos = (int)samples.size() - 1;
-	while (right_pos >= 0 && abs(samples[right_pos]) < 1e-4) right_pos--;
+	while (right_pos >= 0 && abs(samples[right_pos]) < silence_level) right_pos--;
 	int len = right_pos - left_pos + 1;
 	int pow = 1, m = 0;
 	while (2 * pow <= len)
@@ -101,6 +109,16 @@ float Measurer::ProcessData(QByteArray data)
 		d[i] = Complex(samples[left_pos + i], 0);
 	}
 	FFT(d, pow, false);
+	if (debug)
+	{
+		ostringstream oss;
+		for (int i = 0; i < pow; i++)
+		{
+			float amp = (float)sqrt(d[i].real() * d[i].real() + d[i].imag() * d[i].imag());
+			oss << amp << " ";
+		}
+		cerr << "Spectrum: " << oss.str() << "\n";
+	}
 	float max = -1;
 	int argmax = 0;
 	for (int i = 0; i < pow; i++)
diff --git a/Measurer.h b/Measurer.h
index 461e152..37aa04a 100644
--- a/Measurer.h
+++ b/Measurer.h
@@ -13,6 +13,7 @@ class Measurer
 {
 	const int TONE_FREQUENCY = 6000;
 	const int SAMPLE_RATE = 44100;
+	const float SILENCE_LEVEL = 0.3;
 
 	MeasureChannel channel;
 	QAudioDeviceInfo input, output;