SRT to 3D Subtitles

Convert standard .srt subtitles into .ass format, offset so they display correctly in 3D video playback.

The Problem

When watching 3D movies (Side-by-Side, Over-Under, Anaglyph), centered subtitles get split between the left and right eye views, making them disorienting to read. This tool converts standard .srt subtitles into a 3D-compatible .ass format that keeps each eye's subtitles in the correct position.

Features

• SBS (Side-by-Side) — subtitles split left/right for each eye
• OU (Over-Under) — subtitles split top/bottom for each eye
• Anaglyph (Red/Green) — subtitles offset with red/green color channels
• CLI — full command-line interface with configurable options
• GUI — lightweight Windows interface for easier mode selection
• Formatting support — converts HTML tags (<b>, <i>, <u>, <font color>) to ASS format codes
• Resolution scaling — adjusts subtitle positioning based on target resolution

Usage

The application runs in two modes — GUI (no arguments) and CLI (with arguments).

GUI

1. Launch ConvertSRTto3DASS.exe (or the Linux/macOS binary)
2. Select your .srt input file
3. Choose your 3D mode (SBS, OU, or Anaglyph)
4. Adjust settings as needed
5. Click Convert

Command Line

Pass any argument to trigger CLI mode:

ConvertSRTto3DASS.exe input.srt [options]

Or drag and drop an .srt file onto the executable.

Available options:

--mode sbs|ou|rg              3D mode (default: sbs)
--resx <number>               Output width
--resy <number>               Output height
--baseresx <number>           Scaling reference width (default: 1280)
--baseresy <number>           Scaling reference height (default: 720)
--fontsize <number>           Font size (default: 16)
--offsetx <number>            RG eye separation
--bottomoffset <number>       RG bottom offset
--sbssidemargin <number>      SBS side margin
--outopmargin <number>        OU top subtitle margin
--verticalmargin <number>     General vertical margin
--output <path>               Output file path
--help, -h, /?                Show help

Examples:

ConvertSRTto3DASS.exe movie.srt --mode sbs
ConvertSRTto3DASS.exe movie.srt --mode ou --resx 1920 --resy 1080
ConvertSRTto3DASS.exe movie.srt --mode rg --offsetx 6 --bottomoffset 24

Note: The GUI is experimental. Feedback and bug reports are welcome!

Known Issues

• Plex Transcoder has issues with the converted subtitles. VLC works correctly.
• Subtitle positional data from .srt files is stripped during conversion.

Requirements

• .NET 8 SDK — required to build
• Windows — the GUI runs on Windows
• Linux/macOS — the CLI runs cross-platform

Building

# Build all projects
dotnet build

# Publish CLI (cross-platform)
dotnet publish ConvertSRTto3DASS.Cli -c Release -r linux-x64 --self-contained false -p:PublishSingleFile=true
dotnet publish ConvertSRTto3DASS.Cli -c Release -r osx-x64 --self-contained false -p:PublishSingleFile=true
dotnet publish ConvertSRTto3DASS.Cli -c Release -r win-x64 --self-contained false -p:PublishSingleFile=true

# Publish GUI (Windows only)
dotnet publish ConvertSRTto3DASS.Gui -c Release -r win-x64 --self-contained false -p:PublishSingleFile=true

License

MIT License — Copyright © imrayya 2021-2026

Contributing

Contributions are welcome. Please open an issue or submit a pull request.

Contributors

• imrayya — project owner
• jae0815
• fabio-noga
• kaiju466

Disclaimer

This is a personal hobby project. The codebase is functional but not production-grade — minimal comments, no tests, and some rough edges. Use at your own discretion.