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. You can open and edit them immediately.

  • Native Support (Fast Copy): SRT (SubRip), ASS (Advanced SubStation Alpha), SSA, MicroDVD, SAMI, MPL2.
  • 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.

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 generic 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 green “External” badge.

Step 3: Extract

  • Single Track: Click the Extract button next to the specific language you want.
  • Batch Extraction: If you have multiple videos, check the box next to the files you want to process and click the Batch Extract button in the top header. This will automatically extract the first available subtitle track from every selected video.

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

  1. FFmpeg: This is the default tool used for almost all text subtitles and standard image-based extraction. It allows for “Stream Copying,” which is incredibly fast because it doesn’t re-encode the video.
  2. MKVExtract Fallback: If you are extracting PGS subtitles from an MKV file, FFmpeg can sometimes fail due to corrupt data streams. The application detects these specific error patterns (e.g., “Error submitting a packet”) and automatically switches to mkvextract, a specialized tool that is more tolerant of errors.

Automatic Conversion

If you extract a format that isn’t widely supported (like mov_text inside an MP4), the application automatically converts it to a standard .srt file during the extraction process so you can use it immediately.

Handling Image Formats

If you extract an image-based format (like PGS), the application saves it as a .sup file. Upon completion, the dashboard will alert you that this is an image file and recommend OCR tools (like SubtitleEdit or PgsToSrt) if you need to convert it to editable text.

4. Troubleshooting Extraction

If an extraction fails, check the dashboard status icons:

  • Yellow Spinner: The file is currently being processed. Large image-based subtitles may take a moment.
  • Red Error Icon: The extraction failed.
    • Common Fix: If extracting from an MKV fails, ensure you have the mkvextract tool installed, as the system may be trying to use the fallback method.
    • Permission Denied: If the application cannot write to the video’s folder, it will prompt you to select a different save location (e.g., your Documents folder).