macSubtitleOCR / VobSub to SRT

DVD bitmap subtitle guide

How to convert VobSub SUB/IDX subtitles to SRT on Mac

VobSub stores DVD subtitles as pictures in a SUB file and timing, palette, and language information in an IDX file. macSubtitleOCR reads the pair — or an embedded VobSub track — and turns each cue into editable SRT text locally.

Download macSubtitleOCRStart the guide

Free and open source · macOS 15+ · Apple silicon and Intel

What you need

You need a Mac running macOS 15 or newer, the free macSubtitleOCR app, and either a standalone VobSub pair or a Matroska file with VobSub tracks:

SourceWhat the app reads
Movie.sub + Movie.idxThe SUB contains DVD subtitle images; the matching IDX supplies timing, colors, and track languages.
.mkv or .mksEmbedded VobSub tracks and their Matroska language, title, default, and forced flags.

For standalone VobSub, both files are required. Keep Movie.sub and Movie.idx in the same folder with the same base name. Opening either one opens the pair.

Convert SUB/IDX to SRT step by step

  1. Check the pair. Make sure the SUB and IDX filenames match and are in the same folder. If your VobSub track is in MKV or MKS, you can skip this step.
  2. Open the source. Drag either paired file, the MKV, or the MKS into macSubtitleOCR. Add a folder when you want to queue many sources.
  3. Select a language track. An IDX can describe several subtitle languages in one SUB file. Expand the source, verify the language, and tick only the tracks you need.
  4. Make subtitles. Choose the destination and start recognition. The app decodes the DVD subpictures using their palette and sends the rendered text images to Apple Vision.
  5. Review the SRT. Check flagged cues and compare each recognized line with its original bitmap. Correct text inline; changes are saved to the SRT.

Why are there two VobSub files?

The binary .sub file holds compressed subtitle pictures. The text .idx file tells software when each picture appears, which palette to use, and which language tracks exist. A SUB file by itself does not contain enough information for reliable conversion.

If one file is missing, return to the original rip or extract the VobSub track again as a complete SUB/IDX pair. Renaming unrelated files to match will not repair the metadata.

What file do you get?

The SRT contains timing and recognized text, not the original DVD pixels, palette, or screen position. Output names use language and track information to avoid collisions:

Movie.sub
Movie.idx
Movie.eng.srt
Movie.spa.forced.srt

Keep the SRT beside the video for compatible players, edit it in any subtitle editor, or mux it as a text subtitle into another container.

What should you review?

DVD subtitles have lower resolution than Blu-ray PGS, so thin strokes, italics, punctuation, and accented characters may need more checking. Start with cues the app flags as low confidence. The review table keeps the bitmap, timing, and editable result together.

Try Invert images before recognition when a particular palette renders poorly for OCR. Add names and repeated unusual terms to Custom words before running the track again.

Do you need another subtitle tool?

No companion tool is required for SUB/IDX or VobSub-in-MKV input. macSubtitleOCR includes the Matroska reader, VobSub parser, palette rendering, and OCR path. A larger editor can still be useful later if you want to retime or restyle the resulting text subtitles.

Does conversion upload the subtitles?

No. VobSub decoding and Vision recognition run on your Mac. Optional clean-up and translation are local too. Only the optional update check contacts GitHub.

Ready to convert?

Download the signed and notarized app, then open either file in your SUB/IDX pair.

Get the latest releaseNeed PGS instead?