OCR (Optical Character Recognition)

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

• Menu: File → Import image subtitle for edit (OCR)...

Supported Image Formats

• Blu-ray SUP (.sup)
• VobSub (.sub/.idx)
• DVD subtitles
• BDN XML
• Transport stream (DVB) subtitles
• Matroska embedded image subtitles (PGS, VobSub, DVB)
• MP4 embedded VobSub
• WebVTT with embedded images

OCR Engines

Tesseract

Open-source OCR engine with language packs.

• Download language packs via the OCR window
• Good general-purpose accuracy

nOCR (Nikse OCR)

Built-in trainable OCR engine.

• Train character databases for specific fonts
• Very accurate once trained
• Best for consistent fonts (like DVD/Blu-ray subtitles)

Binary OCR

Binary image comparison engine.

• Compares against a database of known character images
• Fast and accurate for known fonts

Google Lens OCR

Cloud-based OCR using Google Lens.

• Requires internet connection

Google Vision OCR

Cloud-based OCR using Google Cloud Vision API.

• Requires API key

Ollama OCR

Local LLM-based OCR using Ollama.

• Requires Ollama installation

Mistral OCR

Cloud-based OCR using Mistral API.

PaddleOCR

Local OCR engine.

• Download required

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

Keyboard Shortcuts

General

Subtitle Grid

Unknown Words List

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:

• Crop
• Binarize (convert to black/white)
• Invert colors
• Resize

Unknown Words

When the OCR engine encounters uncertain characters, you can:

• Choose from suggested alternatives
• Type the correct text
• Add to the OCR fix dictionary for automatic correction

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:

• Common character misrecognitions (e.g., 0 → o, l → I)
• Typical OCR errors for specific words
• Common misspellings that OCR produces

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:

• Fixing specific character combinations that are always wrong
• Removing special characters that OCR incorrectly inserted

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:

• Fixing common sound effect text
• Correcting specific phrases that always appear incorrectly

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:

• Fixing common spacing issues
• Correcting punctuation errors
• Fixing common word fragments

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:

• find: The regex pattern to match
• spellCheck: The text to check against the dictionary (use $1, $2 for capture groups)
• replaceWith: The replacement text if spell check passes
• replaceAllFrom / replaceAllTo: Optional character replacement before spell checking

Use cases:

• Fixing lowercase l to uppercase I (e.g., lTEM → ITEM)
• Correcting apostrophes in possessive forms
• Fixing missing spaces after common words
• Pattern-based corrections that should only apply if the result is a valid word

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:

• Use WholeWords for simple word replacements
• Use RegularExpressionsIfSpelledCorrectly for pattern-based fixes where you want to verify the result is a real word
• Test your regex patterns carefully to avoid unintended replacements
• The replacements are applied in the order they appear in the file