Extract subtitles

AI Subtitle Studio acts as a powerful “ripper,” allowing you to pull embedded subtitles out of video containers (like MKV, MP4, or AVI) and save them as standalone files. It supports a wide range of formats, handling simple text conversion and complex image-based extraction automatically.

1. Supported Formats

The application categorizes subtitles into three main types, handling each differently to ensure the best output.

Text-Based Subtitles (Editable)

These are extracted directly as text (or converted to text). You can open and edit them immediately.

  • Native support (fast copy): SRT (SubRip), ASS (Advanced SubStation Alpha), SSA, MicroDVD, SAMI, MPL2, RealText, SubViewer, PJS, JacoSub, TTML, STL.
  • Auto-converted: Some formats are automatically converted to standard .srt for better compatibility, including:
    • MOV_TEXT (common in MP4/M4V files)
    • WebVTT (common in web videos)
    • EIA-608 / EIA-708 (Closed Captions)
    • Teletext

Image-Based Subtitles (Read-Only)

These are “pictures of text” (common on DVDs and Blu-rays). The studio extracts them as binary files. You cannot edit these in a text editor without performing OCR (Optical Character Recognition) first.

  • PGS (.sup): High-definition subtitles from Blu-rays (hdmv_pgs_subtitle).
  • VobSub / DVD (.sub + .idx): Standard definition subtitles from DVDs (dvd_subtitle, vobsub).
  • DVB Subtitles: From digital TV broadcasts (dvb_subtitle).

2. How to Extract Subtitles (Step-by-Step)

The Dashboard provides a visual interface to manage your video files and their internal streams.

Step 1: Import Video

Drag and drop your video files into the dashboard. The application will scan the file and display the number of Video, Audio, and Subtitle tracks found.

Step 2: Select a Track

Click on a video card to expand it. You will see a list of available subtitle tracks on the right side:

  • Embedded tracks: Marked with a video file icon and a blue Embedded badge. These are hidden inside the video file.
  • External files: If you already have subtitle files in the same folder, they will appear here with a description icon and a green External badge.

Step 3: Extract

  • Single track: Click the Extract button next to the specific track you want.
  • Batch extraction: Check the box next to the files you want to process and click Batch Extract in the top header. This extracts the first subtitle track in the list from every selected video (one track per file).

3. How It Works Under the Hood

The application uses a smart detection system to choose the best extraction tool for the job.

Smart Tool Selection

  • Image-based subtitles from MKV: For PGS, VobSub, or other image formats inside an MKV file, the app tries mkvextract first (most reliable for MKV), then falls back to FFmpeg if mkvextract is not installed or fails.
  • All other extractions: FFmpeg is used first. It supports stream copying for text subtitles (very fast, no re-encoding) and standard image-based extraction.
  • FFmpeg fallback to mkvextract: If FFmpeg fails when extracting image subtitles from MKV with certain error patterns (e.g. “Error submitting a packet to the muxer”, “Invalid data found when processing input”, “Error muxing a packet”, “Not enough data, skipping”), the app automatically retries with mkvextract when it is available.

Automatic Conversion

If you extract a format that isn’t widely supported (e.g. MOV_TEXT inside an MP4), the application converts it to standard .srt during extraction so you can use it immediately.

Handling Image Formats

If you extract an image-based format (e.g. PGS), the application saves it as a .sup file (or .sub for VobSub). For PGS, the app may attempt built-in OCR and return an SRT when possible; otherwise, upon completion the dashboard will alert you that the output is an image file and recommend OCR tools (e.g. SubtitleEdit, PgsToSrt, BDSup2Sub) if you need to convert it to editable text.

4. Troubleshooting Extraction

If an extraction fails, check the dashboard status:

  • Yellow / “Extracting…”: The file is currently being processed. Large image-based subtitles may take a moment.
  • Red / “Error”: The extraction failed.

Common fixes:

  • MKV extraction fails: Ensure mkvextract is installed (Settings → Dependencies). The app uses it first for image tracks from MKV and as a fallback when FFmpeg hits packet/mux errors.
  • Permission denied: If the application cannot write to the video’s folder, it will prompt you to choose a different save location (e.g. your Documents folder).