From c62c23eff1ba994d5c10b9255f467704de4da148 Mon Sep 17 00:00:00 2001
From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
Date: Wed, 11 Nov 2015 20:00:29 +0100
Subject: [PATCH] Rate-limit VU and LRA meter updates.

---
 mainwindow.cpp | 12 ++++++++++++
 mainwindow.h   |  2 ++
 2 files changed, 14 insertions(+)

diff --git a/mainwindow.cpp b/mainwindow.cpp
index de0b4da..34db733 100644
--- a/mainwindow.cpp
+++ b/mainwindow.cpp
@@ -151,6 +151,18 @@ void MainWindow::reset_meters_button_clicked()
 
 void MainWindow::audio_level_callback(float level_lufs, float peak_db, float global_level_lufs, float range_low_lufs, float range_high_lufs, float auto_gain_staging_db)
 {
+	timeval now;
+	gettimeofday(&now, nullptr);
+
+	// The meters are somewhat inefficient to update. Only update them
+	// every 100 ms or so (we get updates every 5–20 ms).
+	double last_update_age = now.tv_sec - last_audio_level_callback.tv_sec +
+		1e-6 * (now.tv_usec - last_audio_level_callback.tv_usec);
+	if (last_update_age < 0.100) {
+		return;
+	}
+	last_audio_level_callback = now;
+
 	post_to_main_thread([=]() {
 		ui->vu_meter->set_level(level_lufs);
 		ui->lra_meter->set_levels(global_level_lufs, range_low_lufs, range_high_lufs);
diff --git a/mainwindow.h b/mainwindow.h
index b88324a..4c4c3f0 100644
--- a/mainwindow.h
+++ b/mainwindow.h
@@ -4,6 +4,7 @@
 #include <QMainWindow>
 #include <string>
 #include <vector>
+#include <sys/time.h>
 
 class GLWidget;
 class QResizeEvent;
@@ -42,6 +43,7 @@ private:
 
 	// Called from the mixer.
 	void audio_level_callback(float level_lufs, float peak_db, float global_level_lufs, float range_low_lufs, float range_high_lufs, float auto_gain_staging_db);
+	timeval last_audio_level_callback{0, 0};
 
 	Ui::MainWindow *ui;
 	QPushButton *transition_btn1, *transition_btn2, *transition_btn3;
-- 
2.39.2