Auto-Subtitle-Sync (VLC Addon)

A lightweight "one-button" VLC Media Player addon that perfectly synchronizes your out-of-sync subtitles with the actual speech in the video.

It listens to the audio track, performs voice activity detection, and aligns the .srt timings directly inside VLC!

Note: This extension was coded entirely by AI using Gemini's Antigravity assistant.

Features

• One-Click Sync: Select your subtitle, hit sync, and the extension does the rest.
• Audio-Based Alignment: It doesn't just shift timestamps by a fixed amount; it listens to when people are speaking in the video to find the exact alignment.
• Auto-Loads: Once synced, the new subtitle is automatically loaded into your playing video in VLC.
• Multiple Engines Supported: Supports ffsubsync for standard drift correction and alass for advanced sync problems (like theatrical subtitles on extended/director's cut movies).

How It Works

VLC Lua extensions are somewhat sandboxed, so this addon uses a powerful external synchronization engine under the hood. You can choose between:

1. ffsubsync: Great for standard subtitle shifts and speed/drift corrections.
2. alass (Automatic Language-Agnostic Subtitle Synchronization): Best for complex scenarios like Director's Cuts or Extended Editions where scenes have been added or removed in the middle. It automatically splits subtitles and introduces padding gaps to maintain alignment.

Installation

1. Install the Sync Engine(s)

You can choose to use either one or both engines.

Option A: ffsubsync (Standard)

1. Download the latest Windows binary: qwqcode/ffsubsync-bin Releases
2. Extract the file, rename it to ffsubsync.exe and place it in a folder (e.g., C:\ffsubsync\ffsubsync.exe).

Option B: alass (For Extended/Director's Cuts)

1. Download the latest Windows release binary: kaegi/alass Releases (or download alass-windows64.zip)
2. Extract alass.exe and place it in a folder (e.g., C:\alass\alass.exe).

Note: Both engines require ffmpeg and ffprobe to be installed on your computer and added to your system's PATH.

2. Install the VLC Addon

1. Download the subsync_addon.lua file from this repository.
2. Open File Explorer and navigate to your VLC extensions folder:
   • Type %APPDATA%\vlc\lua\extensions in the address bar. (Create the lua and extensions folders if they don't exist).
3. Place subsync_addon.lua into that extensions folder.
4. Restart VLC Media Player.

Usage

1. Open a movie in VLC.
2. In the top menu bar, click View -> Auto-Sync Subtitle.
3. A dialog box will appear.
   • The Video Path will automatically detect the playing movie.
   • Subtitle Path (.srt): Paste the full path to your out-of-sync .srt file.
   • Engine: Select ffsubsync or alass (use alass if you are syncing a theatrical subtitle with an extended cut movie).
   • Path to Executable: Paste the location of the selected engine's .exe file.
4. Click Sync Subtitle.
5. Wait a moment (a terminal window will briefly run).
6. Once completed, a .synced.srt file is created next to your original subtitle, and VLC will automatically load it!

Requirements

• VLC Media Player (Windows)
• ffmpeg installed and in your system PATH.
• ffsubsync.exe or alass.exe binary.

License

MIT