SubtitleEdit/subtitleedit

Export to Blu-ray SUP produces an incorrect file

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#10219 opened on Feb 18, 2026

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 (6 comments) (0 reactions) (0 assignees)C# (12,864 stars) (1,206 forks)batch import
help wanted

Description

Steps to reproduce:

  1. Download https://github.com/user-attachments/files/25347090/Subpictures_21.zip (it's a SUP file ripped from the DVD).
  2. Open it in SE.
  3. In Import/OCR VobSub window, select all lines, right-click on them, select Export - Blu-ray sup..., save the file.
  4. Go to Katai, drag-n-drop ksy file there, then drag-n-drop the subtitle file you just saved.
  5. In object tree, expand segment, then [0 … 99]. In SupSegment 3, PTS is 0, DTS is 13097155.

According to the docs: The DTS should indicate a time when the decoding of the sub picture starts, and the PTS indicates a time when the decoding ends and the sub picture is shown on the screen.

It's obvious that DTS should not be greater than PTS. This inconsistency leads to an issue when applying a negative delay to SUP file with SupMover.

Contributor guide

Tech stack
csharp
Domain
desktop
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
C#
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60
Research direction
Investigate the Blu ray SUP export code in SubtitleEdit, likely in the export related classes. The issue requires ensuring that when writing SUP segments, the DTS (decode time stamp) is not greater than PTS (presentation time stamp). Review the linked documentation and the ksy parser for reference. Check the code that calculates and writes these timestamps, and ensure correct ordering.