From 32a58a93a6c479e430e349895807ec6f7ab8b3d2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ge=CC=81ry=20Casiez?= <=>
Date: Tue, 13 Aug 2024 17:55:32 +0200
Subject: [PATCH] Integrating the use case where the new timestamp is equal or
 even smaller than the last timestamp and causing incorrect freq update

---
 C/SF1eFilter.c                        | 2 +-
 CppUsingTemplates/1efilter.cc         | 2 +-
 java/OneEuroFilter.java               | 2 +-
 javascript/OneEuroFilter.js           | 2 +-
 python/OneEuroFilter/OneEuroFilter.py | 2 +-
 typescript/src/OneEuroFilter.ts       | 2 +-
 6 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/C/SF1eFilter.c b/C/SF1eFilter.c
index c114e9d..17fd731 100644
--- a/C/SF1eFilter.c
+++ b/C/SF1eFilter.c
@@ -112,7 +112,7 @@ float SF1eFilterDo(SF1eFilter *filter, float x)
 
 float SF1eFilterDoAtTime(SF1eFilter *filter, float x, double timestamp)
 {
-	if(filter->lastTime != 0) {
+	if(filter->lastTime != 0 && timestamp > filter->lastTime) {
 		filter->frequency = 1.0f / (timestamp - filter->lastTime);
 	}
 	filter->lastTime = timestamp;
diff --git a/CppUsingTemplates/1efilter.cc b/CppUsingTemplates/1efilter.cc
index 09098a7..e587e31 100644
--- a/CppUsingTemplates/1efilter.cc
+++ b/CppUsingTemplates/1efilter.cc
@@ -56,7 +56,7 @@ struct one_euro_filter {
 	T operator()(T x, timestamp_t t = -1) {
 		T dx = 0;
 		
-		if(last_time_ != -1 && t != -1 && t != last_time_) {
+		if(last_time_ != -1 && t != -1 && t != last_time_ && t > last_time_) {
 			freq = 1.0 / (t - last_time_);
 		}
 		last_time_ = t;
diff --git a/java/OneEuroFilter.java b/java/OneEuroFilter.java
index ddf1197..61ed2dc 100755
--- a/java/OneEuroFilter.java
+++ b/java/OneEuroFilter.java
@@ -159,7 +159,7 @@ private void init(double freq,
 
     double filter(double value, double timestamp) throws Exception {
         // update the sampling frequency based on timestamps
-        if (lasttime != UndefinedTime && timestamp != UndefinedTime) {
+        if (lasttime != UndefinedTime && timestamp != UndefinedTime && timestamp > lasttime) {
             freq = 1.0 / (timestamp - lasttime);
         }
         
diff --git a/javascript/OneEuroFilter.js b/javascript/OneEuroFilter.js
index 388bd4d..cbdf0ae 100755
--- a/javascript/OneEuroFilter.js
+++ b/javascript/OneEuroFilter.js
@@ -125,7 +125,7 @@ export class OneEuroFilter {
 
   filter(value, timestamp=undefined) {
     // update the sampling frequency based on timestamps
-    if (this.lasttime!=undefined && timestamp!=undefined)
+    if (this.lasttime!=undefined && timestamp!=undefined && timestamp > this.lasttime)
       this.freq = 1.0 / (timestamp-this.lasttime) ;
     this.lasttime = timestamp ;
     // estimate the current variation per second 
diff --git a/python/OneEuroFilter/OneEuroFilter.py b/python/OneEuroFilter/OneEuroFilter.py
index 581022b..7b01b8f 100644
--- a/python/OneEuroFilter/OneEuroFilter.py
+++ b/python/OneEuroFilter/OneEuroFilter.py
@@ -124,7 +124,7 @@ def __call__(self, x:float, timestamp:float=None) -> float:
         """
 
         # ---- update the sampling frequency based on timestamps
-        if self.__lasttime and timestamp:
+        if self.__lasttime and timestamp and timestamp>self.__lasttime:
             self.__freq = 1.0 / (timestamp-self.__lasttime)
         self.__lasttime = timestamp
         # ---- estimate the current variation per second
diff --git a/typescript/src/OneEuroFilter.ts b/typescript/src/OneEuroFilter.ts
index dc792b7..e461f55 100755
--- a/typescript/src/OneEuroFilter.ts
+++ b/typescript/src/OneEuroFilter.ts
@@ -195,7 +195,7 @@ export class OneEuroFilter {
 
   public filter(value : number, timestamp : number | undefined) : number {
     // update the sampling frequency based on timestamps
-    if (this.lasttime!=undefined && timestamp!=undefined)
+    if (this.lasttime!=undefined && timestamp!=undefined && timestamp>this.lasttime)
       this.freq = 1.0 / (timestamp-this.lasttime) ;
     this.lasttime = timestamp ;
     // estimate the current variation per second