How to convert SUP (Blu-ray PGS) subtitles to SRT

Blu-ray subtitles are stored as PGS (Presentation Graphic Stream) — literally pictures of text saved in a .sup file. To edit, translate or use them on devices that only accept text subtitles, they must be OCR-converted to SRT. AI Subtitle Studio handles both steps with no external software: extract the track, then run the built-in OCR converter.

What is a SUP file?

A .sup file contains bitmap images of each subtitle line together with the timestamps for showing and hiding them (codec id: hdmv_pgs_subtitle). Because there is no text inside — only pixels — you cannot open a SUP in a text editor, load it into most translation tools, or restyle it. Many streaming boxes and TVs will not render SUP files at all.

Converting to SRT requires OCR (Optical Character Recognition): software reads each image and turns it back into text with the original timing.

How AI Subtitle Studio converts SUP to SRT

Extracting a PGS track (from the Dashboard, using mkvextract for MKV sources) gives you the raw .sup file — extraction on its own does not produce text, so this is not the finished subtitle yet. Take that .sup to the Convert screen and click Convert: the app's own bundled OCR engine (hardware-accelerated with DirectML on Windows or CoreML on Mac, CPU otherwise) reads the images and writes out a clean, fully timed .srt. No external OCR software or internet connection is needed for this. Common OCR mistakes — confused characters like l/I, stray SDH tags, broken line breaks — can be fixed afterwards with the built-in Cleanup tool's OCR-error option, a local pattern-based pass that runs instantly offline (no AI model needed).

Convert SUP to SRT step by step

Load the video or the .sup file Drag your MKV/Blu-ray rip into the Dashboard. Embedded PGS tracks are detected and labeled automatically. A standalone .sup file next to the video is picked up as an external track.
Extract the PGS track Click Extract on the PGS subtitle track. For MKV sources the app uses mkvextract for maximum reliability. This produces a .sup file, not yet an .srt.
Convert it to SRT on the Convert screen Open the .sup file on the Convert screen and click Convert. The built-in OCR engine processes the images into text with the original timestamps, producing an editable .srt file.
Clean up and save Optionally run the Cleanup tool to fix OCR misreads and formatting, then save — your Blu-ray subtitles are now universal SRT text.

Convert your Blu-ray subtitles to SRT

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Frequently asked questions

Why can't I just rename .sup to .srt?

Because a SUP file contains images, not text. The file structure is completely different — it must be OCR-converted, which AI Subtitle Studio's Convert screen does for you.

Does extracting a PGS track automatically give me an SRT?

No. Extraction only pulls the raw .sup image file out of the video — you then need to run it through OCR separately on the Convert screen to get a text .srt.

Do I need to install Subtitle Edit or another OCR tool?

No. OCR runs using AI Subtitle Studio's own bundled engine on the Convert screen — no external software or installation required.

How accurate is the OCR?

Blu-ray PGS images are high resolution, so OCR accuracy is typically very high. The Cleanup tool's OCR-error option catches the remaining classic misreads (like “I” vs “l”) automatically and locally.

Can I translate the subtitles after converting?

Yes. Once the track is SRT text you can translate it into another language directly in the app while keeping all timing.

Does this work without internet?

Yes — extraction and OCR run entirely on your machine. Nothing is uploaded.