SrtExtractor

A powerful and easy-to-use desktop application for extracting subtitles from MKV and MP4 video files and converting them to SRT format.

🎯 Overview

SrtExtractor simplifies the process of extracting subtitles from your video files. Whether you're dealing with MKV containers or MP4 files with embedded "Timed Text" subtitles, SrtExtractor provides a seamless experience to convert them into the widely compatible SRT format.

✨ Features

• Multi-format Support: Handles both MKV and MP4 video files
• Batch Processing: Process multiple files simultaneously with drag & drop support
• Network File Detection: Automatically detects network drives with performance estimates
• Automatic Tool Management: Detects and auto-downloads necessary external tools
• Smart Subtitle Detection: Automatically finds and lists available subtitle tracks
• Intelligent Track Recommendation: Prioritizes SubRip/SRT subtitles over HDMV PGS when both are available
• Flexible Output: Generates SRT files with customizable naming patterns
• Real-time Logging: Provides detailed logs of all operations
• User-friendly Interface: Clean, intuitive WPF interface with modern design
• OCR Support: Converts image-based subtitles (PGS) to text using Subtitle Edit
• Smart OCR Correction: Automatically fixes common OCR errors in subtitle text
• Multi-Pass Correction: Advanced correction system with multiple passes to catch different OCR errors
• Standalone Correction Tool: Correct existing SRT files independently
• Batch SRT Correction: Process hundreds of SRT files simultaneously with bulk correction
• Preference Settings: Choose between forced subtitles or closed captions
• Process Cancellation: Cancel long-running operations with proper cleanup
• Temporary File Management: Automatic cleanup of temporary files during processing
• High Performance: Optimized regex patterns, intelligent caching, and efficient memory management
• Responsive UI: Debounced window operations and optimized batch processing for smooth experience

🛠️ Supported Subtitle Formats

Direct Text Extraction

• S_TEXT/UTF8 - UTF-8 encoded text subtitles
• SubRip/SRT - Standard SRT format
• S_TEXT/3GPP - 3GPP Timed Text (MP4)
• S_TEXT/ASS - Advanced SubStation Alpha
• S_TEXT/SSA - SubStation Alpha
• S_TEXT/VTT - WebVTT format

OCR Conversion

• S_HDMV/PGS - Blu-ray PGS subtitles (converted via OCR)

🎯 Smart Track Recommendation

SrtExtractor features an intelligent recommendation engine that automatically selects the best subtitle track based on your preferences and available options:

Priority Order

1. SubRip/SRT Tracks (Highest Priority) - Direct text extraction, no OCR required
2. Other Text-based Tracks (ASS, SSA, VTT) - Also direct extraction
3. HDMV PGS Tracks (Lower Priority) - Requires OCR conversion

Smart Selection Logic

• When both SubRip/SRT and HDMV PGS are available: SubRip/SRT is automatically recommended
• Quality-based selection: Within each priority group, tracks are ranked by bitrate and frame count
• User preferences respected: Forced subtitles and closed captions are prioritized based on settings
• Comprehensive logging: Track selection decisions are logged for transparency

Example Scenarios

• File with SubRip/SRT + HDMV PGS: SubRip/SRT track recommended (faster extraction, no OCR)
• File with only HDMV PGS: HDMV PGS track recommended (with OCR processing)
• Multiple SubRip/SRT tracks: Highest quality SubRip/SRT track recommended

🔧 Requirements

• Windows 10/11 (x64)
• .NET 9.0 Runtime
• External Tools (auto-detected and managed):
  • MKVToolNix (for MKV processing)
  • Subtitle Edit CLI (for OCR conversion)
  • FFmpeg (for MP4 processing)

⚠️ Windows 10 Users

Important: The automatic tool installation via winget requires Windows 10 version 1809 (build 17763) or later. If you're using an older version of Windows 10, you'll need to manually install MKVToolNix:

1. Download MKVToolNix from: https://mkvtoolnix.download/downloads.html
2. Install it to the default location
3. SrtExtractor will automatically detect the installation

The app will show a helpful dialog with download instructions if winget is not available.

To check your Windows 10 version: Press Win + R, type winver, and press Enter.

📦 Installation

1. Download the latest release from the Releases page
2. Extract the ZIP file to your desired location
3. Run SrtExtractor.exe

The application will automatically detect and download required external tools on first run.

🚀 Usage

Single File Processing

1. Select Video File: Click "Pick Video..." to choose your MKV or MP4 file
2. Probe Tracks: Click "Probe Tracks" to analyze the file for subtitle tracks
3. Review Recommendation: The smart recommendation engine automatically selects the best track (SubRip/SRT preferred over HDMV PGS)
4. Select Track: Choose your preferred subtitle track from the list, or use the recommended one
5. Extract: Click "Extract Selected → SRT" to generate the SRT file
6. Multi-Pass Correction: OCR errors are automatically corrected using advanced multi-pass correction

Batch Processing

Process multiple files efficiently with the new batch mode:

1. Enable Batch Mode: Check "🎬 Enable Batch Mode" in the Settings panel
2. Confirm Settings: Review your preferred subtitle settings (forced/CC, OCR language)
3. Add Files: Drag & drop MKV/MP4 files anywhere on the window to add them to the queue
4. Review Queue: Check the batch queue panel showing file sizes, network indicators (🌐), and estimated processing times
5. Process Batch: Click "🚀 Process Batch" to extract subtitles from all files
6. Monitor Progress: Watch real-time progress with detailed status updates
7. Review Results: Get a comprehensive summary of successful, failed, and cancelled files

Batch Mode Features

• Network Detection: Files on network drives show 🌐 indicator with realistic time estimates
• Drag & Drop: Simply drag files onto the application window to add them to the queue
• Progress Tracking: Real-time progress bar and "Processing X of Y files" counter
• Cancellation Support: Cancel batch processing at any time with proper cleanup
• Detailed Summary: Complete breakdown of processing results when finished
• Automatic Cleanup: Temporary files are automatically cleaned up during and after processing

Standalone SRT Correction

Use the "🔧 Correct SRT File" button to fix OCR errors in existing SRT files:

1. Click "🔧 Correct SRT File"
2. Select your SRT file
3. Common OCR errors are automatically fixed
4. File is updated in-place with corrections

Batch SRT Correction

Process hundreds of SRT files simultaneously with the new batch correction feature:

1. Open Batch Tool: Click "Batch SRT Correction" button in the main window
2. Select Folder: Choose a folder containing SRT files (with option to include subfolders)
3. Scan Files: Click "🔍 Scan for SRT Files" to discover all SRT files
4. Configure Options:
   • Include subfolders (recommended for large collections)
   • Create backup copies (recommended for safety)
5. Start Processing: Click "🚀 Start Batch Correction" to process all files
6. Monitor Progress: Watch real-time progress with file-by-file status updates
7. Review Results: Get detailed statistics on corrections applied per file

Batch SRT Correction Features

• Lightning Fast: Process hundreds of SRT files in minutes
• Massive Corrections: Typical results of 1000+ corrections per file
• Safe Processing: Optional backup creation before correction
• Progress Tracking: Real-time progress bar and file-by-file status
• Cancellation Support: Stop processing at any time
• Detailed Results: See exact correction count per file
• Professional Output: Clean, properly formatted SRT files

Example Results: 79 SRT files processed with 81,000+ total corrections applied!

Settings

• Subtitle Preference: Choose between "Prefer forced subtitles" or "Prefer CC (Closed Captions)"
• OCR Language: Set the language for OCR conversion (default: English)
• File Pattern: Customize output filename pattern (default: {basename}.{lang}{forced}{cc}.srt)
• Multi-Pass Correction: Configure advanced correction settings:
  • Enable Multi-Pass: Toggle advanced multi-pass correction (recommended)
  • Correction Mode: Choose between Quick (1 pass), Standard (3 passes), or Thorough (5 passes)
  • Smart Convergence: Automatically stop when no more corrections are found
  • Max Passes: Set maximum number of correction passes

File Naming Pattern

The output filename follows this pattern:

• {basename} - Original video filename (without extension)
• {lang} - Subtitle language code
• {forced} - ".forced" if it's a forced subtitle
• {cc} - ".cc" if it's a closed caption

Example: Movie.eng.forced.srt or Show.eng.cc.srt

🏗️ Architecture

Built with modern .NET 9 and WPF, SrtExtractor follows the MVVM pattern with intelligent subtitle recommendation:

• Models: Data structures for tracks, settings, and tool status
• ViewModels: Business logic, UI state management, and smart track recommendation
• Views: XAML-based user interface with recommendation indicators
• Services: External tool integration and file operations
• State: Observable state management for data binding
• Recommendation Engine: Intelligent track selection prioritizing SubRip/SRT over HDMV PGS

🔧 External Tools

MKVToolNix

• Purpose: MKV file probing and subtitle extraction
• Installation: Auto-detected or installed via winget
• Tools Used: mkvmerge.exe, mkvextract.exe

Subtitle Edit CLI

• Purpose: OCR conversion of image-based subtitles
• Installation: Auto-built from source during development
• Tool Used: seconv.exe

FFmpeg

• Purpose: MP4 file processing and subtitle extraction
• Installation: Auto-downloaded during development
• Tools Used: ffmpeg.exe, ffprobe.exe

🧠 Smart OCR Correction

SrtExtractor includes an intelligent OCR correction system that automatically fixes common errors:

Automatic Fixes

• Extra Spaces: T he → The, sh it → shit
• Missing Spaces: Yougotanybiscuits → You got any biscuits
• Character Substitutions: RipIey → Ripley, feeIdead → feel dead
• Apostrophe Issues: you)re → you're, won)t → won't
• Contractions: I am → I'm, you are → you're
• Common Phrases: Whatyoudoing → What you doing

Correction Patterns

The system uses regex-based patterns to identify and fix over 100 common OCR errors, ensuring your subtitles are clean and professional.

🚀 Multi-Pass Correction System

SrtExtractor now features an advanced multi-pass correction system that significantly improves subtitle quality:

Why Multi-Pass?

OCR errors often come in different types that require multiple passes to catch:

• First Pass: Catches obvious spacing and character issues
• Second Pass: Identifies missed contractions and phrase corrections
• Third Pass: Finds subtle character substitutions and remaining errors

Correction Modes

• Quick Mode: 1 pass (fastest, catches obvious errors)
• Standard Mode: 3 passes with smart convergence (recommended)
• Thorough Mode: 5 passes without convergence (maximum quality)

Smart Convergence

The system automatically detects when no more corrections are needed and stops early, saving processing time while ensuring quality.

Real-World Results

Multi-pass correction has been proven to find additional corrections on subsequent passes:

• Example: Blade (1998) subtitle file showed improvements across multiple correction runs
• Typical Results: Each pass finds 5-15% additional corrections missed by previous passes
• Quality Improvement: Significantly cleaner, more professional subtitle output

Batch Correction Results

The correction system is incredibly effective when processing large collections:

• Average: 1000+ corrections per SRT file
• Large Collections: 80,000+ total corrections across 79 files
• Processing Speed: Hundreds of files processed in minutes
• Quality Improvement: Professional-grade subtitle formatting

📝 Logging

SrtExtractor provides comprehensive logging:

• UI Log: Real-time display in the application
• File Log: Rolling daily logs saved to C:\ProgramData\ZentrixLabs\SrtExtractor\Logs\
• Log Format: srt_YYYYMMDD.txt
• Recommendation Logging: Track selection decisions and reasoning are logged for transparency

🎨 User Interface

• Clean Design: Modern, intuitive interface with optimized layout
• Real-time Feedback: Progress indicators and status updates
• Tool Status: Visual indicators for external tool availability
• Batch Queue Panel: Dedicated panel for managing multiple files with drag & drop
• Network Indicators: Visual indicators (🌐) for network files with time estimates
• Progress Tracking: Real-time progress bars and counters for batch operations
• Batch SRT Correction Window: Dedicated interface for bulk SRT file processing
• File List Display: Shows discovered SRT files with status and correction counts
• About Window: Branding and credits information

🐛 Troubleshooting

Common Issues

1. Tools Not Found: Use "Re-detect Tools" button or check tool installation
2. Extraction Fails: Verify the selected track is a supported format
3. OCR Issues: Ensure Subtitle Edit CLI is properly built and available
4. Batch Mode Not Working: Ensure you've enabled batch mode and added files to the queue
5. Network Files Slow: Files on network drives will take longer - this is normal
6. Temporary Files Left Behind: Use the "🧹 Cleanup Temp Files" button if needed
7. Cancellation Issues: If processes don't stop, restart the application
8. Batch SRT Correction Shows "None Found": Ensure you've selected a folder and clicked "Scan for SRT Files"
9. SRT Files Not Updating: Check that files aren't read-only or locked by another application
10. Wrong Track Recommended: Check the log for recommendation decisions; you can manually select a different track

Log Files

Check the log files in C:\ProgramData\ZentrixLabs\SrtExtractor\Logs\ for detailed error information.

🤝 Contributing

Contributions are welcome! Please feel free to submit issues and pull requests.

📄 License

This project is licensed under the MIT License - see the LICENSE.txt file for details.

🙏 Acknowledgments

• MKVToolNix - Matroska tools for video container operations
• Subtitle Edit - OCR conversion for image-based subtitles
• FFmpeg - Complete multimedia framework for MP4 processing

🔗 Links

• Project Repository: https://github.com/ZentrixLabs/SrtExtractor
• ZentrixLabs Website: https://zentrixlabs.net/

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Developed by ZentrixLabs - Making video processing simple and efficient.