diff --git a/CHANGELOG.md b/CHANGELOG.md
index b03ec32..b643967 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Fixed
+
+- The issue of decreasing PTS precision with increasing video duration (#1269).
+
 ## [6.3.0] - 2024-12-20
 
 ### Added
diff --git a/src/encoder.cpp b/src/encoder.cpp
index f0c67d1..7b732f3 100644
--- a/src/encoder.cpp
+++ b/src/encoder.cpp
@@ -262,8 +262,7 @@ int Encoder::write_frame(AVFrame *frame, int64_t frame_idx) {
     frame->pict_type = AV_PICTURE_TYPE_NONE;
 
     // Calculate this frame's presentation timestamp (PTS)
-    frame->pts = frame_idx * (enc_ctx_->time_base.den * enc_ctx_->framerate.den /
-                              (enc_ctx_->time_base.num * enc_ctx_->framerate.num));
+    frame->pts = av_rescale_q(frame_idx, av_inv_q(enc_ctx_->framerate), enc_ctx_->time_base);
 
     // Convert the frame to the encoder's pixel format if needed
     if (frame->format != enc_ctx_->pix_fmt) {