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

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

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.