Subtitle Formats, Acronyms & AI Subtitle Studio Capabilities

This page provides an overview of common subtitle formats and terminology, and explains how AI Subtitle Studio handles each format. It is intended as a reference for understanding which subtitle tracks can be extracted, edited, and translated within the application.

Quick Capability Summary

AI Subtitle Studio supports the following workflows:

  • Extraction
    • Text-based subtitle tracks are extracted as text (usually converted to .srt, or preserved as .ass when styling should be retained).
    • Image-based subtitle tracks are extracted as bitmap files (.sup or .sub/.idx).
    • For MKV containers with image-based subtitles, the app prefers mkvextract for improved reliability.
  • Editing & Translation
    • Editing and translation require text-based subtitles.
    • Image-based subtitles must be converted to text using OCR before they can be edited or translated.
  • OCR Availability
    • If Subtitle Edit (OCR) is installed, image-based subtitles can be converted to .srt and then edited or translated.
    • If OCR is not available, image-based tracks are hidden from the Edit/Translate track selection views.

Subtitle File Formats

Subtitle formats are broadly classified as text-based (directly editable) or image-based (bitmap graphics; OCR required for text editing).

SRT (SubRip) — Text-based

Plain text subtitles with timestamps.

AI Subtitle Studio support

  • Extract: Yes
  • Edit: Yes
  • Translate: Yes

ASS / SSA (Advanced SubStation Alpha / SubStation Alpha) — Text-based

Styled text subtitles with advanced formatting.

AI Subtitle Studio support

  • Extract: Yes (preserved as .ass to retain styling)
  • Edit: Yes
  • Translate: Yes

WebVTT (VTT) — Text-based

Web-oriented subtitle format commonly used in HTML5 players.

AI Subtitle Studio support

  • Extract: Yes (converted to .srt when required)
  • Edit: Yes
  • Translate: Yes

TTML / DFXP / XML — Text-based

XML-based timed text subtitle formats.

AI Subtitle Studio support

  • Extract: Yes (converted to .srt when required)
  • Edit: Yes
  • Translate: Yes

SBV / SCC / STL / MCC / CAP / TXT / SMI / SMIL / USF / JSS / PSB / RT / LRC / QTX / QT / MPL2 / MicroDVD / SAMI / DKS / PJS / MPSub / VPlayer / SubViewer / SubViewer2 / RealText / TTXT / SBT — Text-based

Legacy and niche text subtitle formats.

AI Subtitle Studio support

  • Extract: Yes (converted to .srt when required)
  • Edit: Yes
  • Translate: Yes

PGS / SUP (Blu-ray) — Image-based

Bitmap subtitles stored as images.

AI Subtitle Studio support

  • Extract: Yes (.sup)
  • Edit: Only after OCR
  • Translate: Only after OCR

VobSub (SUB / IDX) — Image-based

DVD bitmap subtitles stored in paired files.

AI Subtitle Studio support

  • Extract: Yes (.sub + .idx)
  • Edit: Only after OCR
  • Translate: Only after OCR

DVB Subtitles — Image-based

Broadcast bitmap subtitles.

AI Subtitle Studio support

  • Extract: Yes (image output)
  • Edit: Only after OCR
  • Translate: Only after OCR

OCR Requirement for Image-Based Subtitles

Image-based subtitle formats are not directly editable as text. To enable editing or translation, AI Subtitle Studio converts these subtitles into .srt using Optical Character Recognition (OCR).

  • OCR tool used: Subtitle Edit (or seconv CLI when available)
  • Without OCR: Image-based subtitle tracks are hidden from the Edit and Translate selection views.

Common Subtitle Acronyms

SDH (Subtitles for the Deaf and Hard of Hearing)

Subtitles that include dialogue as well as descriptions of relevant sounds, music cues, and speaker information.

CC (Closed Captions)

Accessibility-focused captions that may include sound effects and speaker labels, typically toggleable in media players.

Subtitle Terminology

Forced Subtitles

Subtitles that appear only for foreign-language dialogue or on-screen text, while the primary spoken language remains unsubtitled.

Hardcoded (Burned-In) Subtitles

Subtitles that are permanently embedded into the video image and cannot be disabled or extracted as a separate subtitle track.

Standard Subtitles

Subtitles primarily intended for translation of dialogue. Inclusion of lyrics, on-screen text, or additional context varies by source.

Notes on Media Player and Container Behavior

Media players and container formats may label the same subtitle stream differently. AI Subtitle Studio determines subtitle capabilities based on the actual codec and stream type rather than player labels. This ensures consistent handling of extraction, editing, and translation regardless of how a subtitle track is presented in third-party players.

This documentation reflects the current capabilities of AI Subtitle Studio and may be updated as additional formats and tools are supported.