Convert SUB/IDX to SRT

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

Supports: .sub, .idxMax 20 filesOutput: SRTFree Online Tool
Tool Options

Select the primary language to boost OCR accuracy.

Selected settings

OCR language: English

SUB/IDX processing may take 5–15 minutes depending on video length.

Select your files
How SUB/IDX conversion works

SUB/IDX (VobSub) subtitles store timing in the .idx file and bitmap images in the .sub file. The converter reads both, runs OCR on the images, and rebuilds an editable SRT file.

During processing we:

  • Extract timing and palette data from the IDX file
  • Perform OCR on the SUB images to capture text
  • Merge timing with recognised text into SRT cues
  • Respect language metadata to choose the right OCR model
Understanding the file pair
  • IDX files contain timestamp, color, and language information
  • SUB files hold compressed bitmap frames of each subtitle
  • Both files must originate from the same source rip to align
File upload requirements
  • Filenames must match except for the extension (movie.sub + movie.idx)
  • Upload up to ten pairs (20 files) per batch
  • Corrupted or truncated files may fail during OCR

Both files required

Upload matching .sub and .idx files that share the same filename. Without the pair, OCR cannot map text to the right timestamps.

Optimal conditions
  • High-resolution sources with clear text
  • Standard fonts and strong contrast
  • Complete palette information in the IDX file
  • Minimal compression artifacts
Challenging scenarios
  • Low-resolution or noisy subtitles
  • Decorative or stylised fonts
  • Complex character sets without language metadata
  • Missing palette data or incomplete rips
Processing performance
  • Processing time: roughly 3–15 minutes per pair depending on length
  • Maximum size: 100 MB per file
  • Batch limit: 10 pairs per run
  • Memory usage peaks during OCR decoding
Output quality
  • Timing accuracy comes directly from the IDX file
  • Text accuracy typically ranges between 85–98%
  • Supports 100+ languages via OCR
  • Exports UTF-8 encoded SRT files
Common use cases

DVD subtitle extraction

Convert VobSub rips from DVDs into editable text.

Legacy archive migration

Modernise old subtitle libraries by moving away from image-based formats.

Editable OCR output

Translate or correct subtitles after they become text.

Best practices
  • Double-check both files belong to the same video
  • Review the SRT output for OCR mistakes and fix manually
  • Verify timing against the video before final delivery
  • Confirm special characters display correctly
Working with SUP files

If you are dealing with SUP subtitles instead, use the dedicated SUP to SRT converter for faster OCR and better accuracy.

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 20 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.

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