About SUB Files
MicroDVD Subtitle
SUB (MicroDVD) is a subtitle format that uses frame numbers for timing instead of timestamps.
Family
Documents & Text
Extension
.sub
MIME Type
text/x-microdvd
Can Use As
53 55 42 46 00 01 00 00 4B 41 49 4A
ASCII: SUBF....KAIJ
📈 Target Minimum File Size (Guaranteed ≥ KB)
Lossless JPEG Q100 + standard COM segment padding for government & exam portals
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HOW SUB CAME TO BE.
The .sub extension covers two distinct subtitle formats that happened to share the same filename. The older, MicroDVD .sub (1998), is a plain-text format with each line formatted as `{startframe}{endframe}subtitle text`. DVD ripping communities in the early 2000s loved it because timing references were frames, not timestamps — easy to resync when framerate changed.
The newer .sub — VobSub, paired with an .idx index file — stores bitmap images of subtitles ripped straight from DVDs. Each subtitle is a pre-rendered PNG-like image with transparency. This avoids OCR and the mistakes that come with it, but loses the ability to edit the subtitle text. Every DVD ripper from 2002-2010 produced VobSub .sub+.idx pairs. Modern subtitle workflows prefer SRT or ASS, but VobSub lingers in archive quality.
Technical Specifications
- MIME type
- text/x-microdvd (MicroDVD); image/vnd.dvb.subtitle (VobSub)
- Extension
- .sub (paired with .idx for VobSub)
- Variants
- MicroDVD (text), VobSub (bitmap)
- Common conversion
- OCR VobSub → SRT
Typical Sizes & Weights
MicroDVD .sub for 2-hour movie
50-100 KB
VobSub .sub (2-hour movie)
1-10 MB
VobSub .idx metadata
50-200 KB
STRENGTHS & LIMITATIONS.
Strengths
- VobSub preserves DVD subtitle appearance exactly.
- MicroDVD is trivially editable text.
- Universal player support (VLC, mpv, MPC).
- Historical format for DVD-era subtitle preservation.
Limitations
- Bitmap subtitles (VobSub) cannot be edited as text.
- MicroDVD frame-based timing breaks on framerate changes.
- Two incompatible formats sharing one extension causes confusion.
- Superseded by SRT and ASS for editing and modern streaming.
CURIOSITIES & TRIVIA.
The .sub extension refers to two incompatible formats — MicroDVD text-based and VobSub image-based — context tells you which.
VobSub .sub files are always paired with a .idx metadata file; without the .idx, the .sub is useless.
MicroDVD timing is frame-based ({123}{456}) rather than time-based — which is why it syncs poorly when you change framerate.
VobSub subtitles are bitmap images pre-rendered in the DVD's colors — editing them requires OCR or redrawing.
Modern workflows OCR VobSub into SRT using tools like SubRip (the app after which the .srt format was named).
Specialized Utilities for .SUB Files
Subtitle Converter (SRT, VTT, ASS, TXT)
Convert subtitle and caption files between SRT, WebVTT (.vtt), ASS/SSA, SUB, SBV, SAMI, LRC, TTML, and plain text (.txt) transcripts with frame-accurate timecodes.
Compress Files to ZIP
Compress multiple files and folders into a single ZIP archive. Reduce total size for faster transfers and organized storage.
CONVERT FROM SUB
Common Use Cases
Video subtitles, legacy media players
Related Formats
Popular comparisons
SUB vs PDF
Differences, file size, and when to choose each format.
SUB vs DOCX
Differences, file size, and when to choose each format.
SUB vs ODT
Differences, file size, and when to choose each format.
SUB vs TXT
Differences, file size, and when to choose each format.
SUB vs MD
Differences, file size, and when to choose each format.
SUB vs HTML
Differences, file size, and when to choose each format.
Popular SUB conversions
The most-requested destinations when starting from SUB.
Frequently Asked Questions
SUB (MicroDVD Subtitle) is a document format used to store paginated text, with optional formatting, tables, images, hyperlinks, headers and footers. It sits in the documents & text family and is typically associated with a specific office suite or publishing pipeline that defined the format and ships the canonical reader.
Modern office suites — Microsoft Word, Google Docs, LibreOffice Writer, Apple Pages — open most SUB files with reasonable fidelity. If your installed software does not support SUB, convert to DOCX or PDF first using KaijuConverter; both open in virtually every reader, including free online viewers.
Upload the SUB to KaijuConverter and pick DOCX, PDF, ODT, RTF, HTML, Markdown, or plain text. Our pipeline runs LibreOffice headlessly plus pandoc for text formats — the same engines behind professional document pipelines. Styles, tables, images, and hyperlinks survive the conversion intact.
Yes, to a high degree. Standard fonts, headings, lists, tables, images, hyperlinks and page structure transfer cleanly. Custom fonts substitute to the closest match if not embedded; obscure layout features unique to SUB (frames, legacy macros) may flatten to static content in the target format.
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