Subtitle Edit

the subtitle editor :)

OCR (Optical Character Recognition)

Subtitle Edit can convert image-based subtitle formats to text using OCR.

OCR Window

Supported Image Formats

OCR Engines

Tesseract

Open-source OCR engine with language packs.

nOCR (Nikse OCR)

Built-in trainable OCR engine.

Binary OCR

Binary image comparison engine.

Google Lens Sharp / Google Lens Standalone

Cloud-based OCR using Google Lens (free, but capped).

Google Vision

Cloud-based OCR using Google Cloud Vision API.

Ollama

Local LLM-based OCR via an Ollama server (e.g. with a vision model).

llama.cpp

Local LLM-based OCR using a llama.cpp-compatible server. Subtitle Edit can download llama.cpp and the model for you, or talk to a server you run yourself.

CrispEmbed

Local OCR engine with multiple model backends (free/open source).

Mistral OCR

Cloud-based OCR using Mistral API.

Paddle OCR Standalone / Paddle OCR Python

Local OCR engine.

Engine Setup Notes

How to Use

  1. Open an image-based subtitle file
  2. The OCR window opens automatically
  3. Select an OCR engine
  4. Configure engine-specific settings
  5. Click Start OCR
  6. Review and correct any errors
  7. Click OK to import the text subtitles

Saving the Images

The subtitle list’s right-click menu has Save all images with HTML index…. Pick a folder and Subtitle Edit writes index.html plus images/0001.png, 0002.png, … — every subtitle bitmap next to the text OCR produced for it, which is the quickest way to proof-read a run against the originals.

The page is self-contained (no external css, js or fonts), so it opens straight off the file system. It follows the reader’s light/dark preference, with an Auto/Light/Dark override, and adds a text filter, an “only lines without text” filter for spotting images that produced nothing, a dark/light/checkerboard backdrop for the transparent bitmaps, click-to-zoom, and each line’s number, time codes, duration and image size.

Keyboard Shortcuts

General

Shortcut Action
Escape Cancel OCR / Close window
Ctrl+G Go to line number
Ctrl++ Zoom in (images in grid)
Ctrl+- Zoom out (images in grid)
F1 Show help

Subtitle Grid

Shortcut Action
Ctrl+I Toggle italic formatting
Ctrl+P View selected image (use arrow keys to navigate)
Delete Delete selected line(s)
Home Jump to first line
End Jump to last line
Double-click Inspect line (nOCR/Binary OCR only)

Unknown Words List

Shortcut Action
Enter Jump to subtitle line containing the selected unknown word

Note: All shortcuts can be customized. Go to Options → Shortcuts to view and change key bindings.

Pre-processing

Before OCR, you can apply image pre-processing:

Batch OCR

Batch Convert can process image-based subtitle files with OCR. Subtitle Edit 5 includes Binary OCR in Batch Convert and can auto-detect several nOCR/Binary OCR settings such as language and pixels-are-space values.

For VobSub files, Batch Convert isolates the glyph color before OCR (on by default, configurable in the Batch Convert settings): the subpicture is rebuilt as a crisp black-on-white bitmap from pixel frequency, so outline and anti-alias colors no longer melt adjacent characters together.

For command-line workflows, see Command Line (seconv), which documents OCR engines and options for headless conversion.

OCR Pre-processing

Unknown Words

When the OCR engine encounters uncertain characters, you can:

What is remembered

Some of the choices in the unknown-word prompt are saved to disk and reused on later OCR runs; others only last as long as the OCR window is open.

Choice Remembered? Stored in
Change all Yes {language}_OCRFixReplaceList.xml
Add to names list Yes {language}_names.xml
Add to user dictionary Yes {language}_user.xml
Skip once No —
Skip all No — current OCR session only —

“Skip all” is deliberately temporary. It silences a word for the rest of the current OCR session and is forgotten when the OCR window closes, so a mis-click never has lasting consequences. If you want a word to be accepted permanently, use Add to user dictionary (or Add to names list for proper nouns) instead, and use Change all for a correction that should be applied automatically from now on.

OCR Fix Replacement Lists

Subtitle Edit uses language-specific XML files to automatically correct common OCR errors. These files are named {language}_OCRFixReplaceList.xml (e.g., eng_OCRFixReplaceList.xml for English) and are located in the Dictionaries folder.

See the example file: Dictionaries/eng_OCRFixReplaceList.xml

XML Structure

The OCR fix replacement list contains several sections that handle different types of corrections:

1. WholeWords

Replaces entire words that match exactly. This is the most common section for fixing OCR mistakes.

<WholeWords>
    <Word from="tñere" to="there" />
    <Word from="ri9ht" to="right" />
    <Word from="0f" to="of" />
    <Word from="alot" to="a lot" />
    <Word from="becuase" to="because" />
</WholeWords>

Use cases:

2. PartialWordsAlways

Replaces character sequences within words, always applied without spell checking.

<PartialWordsAlways>
    <WordPart from="¤" to="o" />
    <WordPart from="lVI" to="M" />
    <WordPart from="IVl" to="M" />
</PartialWordsAlways>

Use cases:

3. WholeLines

Replaces entire lines that match exactly (including formatting tags).

<WholeLines>
    <Line from="[chitte rs]" to="[chitters]" />
    <Line from="Hil' it!" to="Hit it!" />
    <Line from="&lt;i&gt;Hil' it!&lt;/i&gt;" to="&lt;i&gt;Hit it!&lt;/i&gt;" />
    <Line from="ISIGHS]" to="[SIGHS]" />
</WholeLines>

Use cases:

4. PartialLinesAlways

Replaces text fragments within lines, always applied without spell checking.

<PartialLinesAlways>
    <LinePart from="Apollo 1 3" to="Apollo 13" />
    <LinePart from=",.," to="..." />
    <LinePart from=" lt " to=" it " />
    <LinePart from=" lf " to=" if " />
</PartialLinesAlways>

Use cases:

5. PartialLines

Replaces text fragments within lines (may be spell-checked).

<PartialLines>
    <LinePart from=" /be " to=" I be " />
    <LinePart from=" aren '1'" to=" aren't" />
    <LinePart from=" aren'tyou" to=" aren't you" />
</PartialLines>

6. RegularExpressionsIfSpelledCorrectly

Uses regex patterns to fix errors, but only applies the replacement if the corrected word is in the dictionary.

<RegularExpressionsIfSpelledCorrectly>
    <!-- Fix lowercase 'l' to uppercase 'I' if result is a valid word -->
    <RegEx find="\bl([A-Z]+)\b" spellCheck="I$1" replaceWith="I$1" />
    <RegEx find="\b([A-Z]+)l\b" spellCheck="$1I" replaceWith="$1I" />

    <!-- Fix possessive forms: David's, there's -->
    <RegEx find="\b([A-Z][a-z]+)['']s\b" spellCheck="$1" replaceWith="$1's" />
    <RegEx find="\b([a-z]+)['']s\b" spellCheck="$1" replaceWith="$1's" />

    <!-- Fix missing spaces: ofDavid → of David -->
    <RegEx find="\bof([A-Z][a-z]+)\b" spellCheck="$1" replaceWith="of $1" />
    <RegEx find="\bin([A-Z][a-z]+)\b" spellCheck="$1" replaceWith="in $1" />

    <!-- Fix 'l' in brackets: [GRlNDlNG] → [GRINDING] -->
    <RegEx find="\[([A-Z ]*)l([A-Z ]*)\]" spellCheck="[$1I$2]" replaceWith="[$1I$2]" />
</RegularExpressionsIfSpelledCorrectly>

Attributes:

Use cases:

Creating Custom Rules

To add your own OCR fix rules:

  1. Open the appropriate language file: Dictionaries/{language}_OCRFixReplaceList.xml
  2. Add entries to the relevant section based on the type of error
  3. Save the file
  4. Restart Subtitle Edit for changes to take effect

Tips: