Convert SUB/IDX to SRT

Convert SUB/IDX (VobSub) subtitle files to SRT format using OCR technology.

Supports: .sub, .idxMax 10 filesOutput: SRTFree Online Tool
Tool Options

Select the primary language of the subtitles for better OCR accuracy

Selected Settings

OCR Language: English

Note: SUB/IDX processing requires both files and may take 5-15 minutes depending on complexity

Select your files
About SUB/IDX to SRT conversion

SUB/IDX files are a dual-file subtitle format commonly known as VobSub. The IDX file contains timing information, color palettes, and metadata, while the SUB file contains the actual subtitle images. This format requires OCR (Optical Character Recognition) to extract text from the image data.

This tool processes both files to:

  • Extract timing information from IDX files
  • Process subtitle images from SUB files using OCR
  • Combine timing and text data into SRT format
  • Handle multiple languages and character encodings
Understanding SUB/IDX format

IDX File (.idx)

  • Contains subtitle timing information
  • Stores color palette data
  • Includes language and encoding metadata
  • References corresponding SUB file

SUB File (.sub)

  • Contains compressed subtitle image data
  • Stores bitmap representations of text
  • Uses run-length encoding compression
  • Requires IDX file for proper interpretation
File upload requirements

Important: Dual-file format

SUB/IDX subtitles require both files to work properly. For best results, upload both the .sub and .idx files together. The tool will attempt to process single files but may have limited functionality.

Upload options:

  • Both files: Upload both .sub and .idx files for complete processing
  • Single file: Upload either file - tool will work with available data
  • Batch processing: Upload multiple SUB/IDX pairs simultaneously
  • File naming: Files with matching names will be automatically paired
OCR processing and accuracy

Optimal conditions:

  • High-resolution source material
  • Clear, high-contrast text
  • Standard fonts and character sizes
  • Minimal image compression artifacts
  • Proper color palette information

Challenging scenarios:

  • Low-resolution or pixelated text
  • Decorative or stylized fonts
  • Complex scripts (Arabic, Chinese, etc.)
  • Corrupted or incomplete files
  • Missing color palette data
Processing specifications

Performance:

  • Processing time: 3-15 minutes per file pair
  • Maximum file size: 100MB per file
  • Batch limit: 10 file pairs maximum
  • Memory usage: High during OCR processing

Output quality:

  • Timing accuracy: Preserved from IDX
  • Text accuracy: 85-98% depending on source
  • Language support: 100+ languages
  • Format: Standard SRT with UTF-8 encoding
Common use cases

DVD Subtitle Extraction

Convert subtitles extracted from DVD movies using tools like MakeMKV or DVD Decrypter into editable SRT format.

Legacy Format Migration

Modernize old subtitle collections by converting VobSub format to widely-supported SRT format.

Subtitle Editing

Enable editing of image-based subtitles by converting them to text-based format for translation or correction.

Tips for best results

Before uploading:

  • Ensure both SUB and IDX files are from the same source
  • Check that files are not corrupted or truncated
  • Use files with matching base names (e.g., movie.sub + movie.idx)

After conversion:

  • Review the SRT output for OCR accuracy
  • Check timing synchronization with your video
  • Manually correct any recognition errors
  • Verify special characters and formatting
Alternative tools

If you have SUP files (single-file format) instead of SUB/IDX pairs, please use our dedicated SUP to SRT converter tool for better compatibility and processing efficiency.

Why Choose Our Convert SUB/IDX to SRT?
  • Free and Online: No software installation required
  • Fast Processing: Quick conversion and processing
  • Multiple Formats: Support for .sub, .idx files
  • Batch Processing: Handle up to 10 files at once
  • Privacy Focused: Your files are processed securely
  • No Registration: Start using immediately
How to Use Convert SUB/IDX to SRT
  1. Upload your subtitle files by dragging and dropping or clicking "Choose Files"
  2. Configure any tool-specific options if available
  3. Click "Process Files" to start the conversion
  4. Download your processed files when ready

The tool supports files up to 50MB for image-based subtitles (.sup, .sub, .idx) and 5MB for text-based formats. Processing usually takes just a few seconds depending on file size and complexity.