KiiMix Subtitle formats and encoding guide
If a subtitle file will not open, looks garbled or fails to convert, check its format, character encoding and whether it contains text in the first place.
- Already have an SRT, VTT, ASS or SSA file? Convert its format
- Only need the dialogue? Save subtitles as TXT
These tools accept subtitle files, not MP4 or MKV videos. They do not extract video tracks or perform OCR. Saving a subtitle file as TXT is different from recognizing or extracting subtitles from a video.
Choosing SRT, VTT or ASS
SRT is a common choice for exchanging subtitles, VTT is designed for web video, and ASS is useful for detailed styling and effects. Check the receiving player or editor’s requirements before choosing.
| Format | Styling | Typical use | Conversion notes |
|---|---|---|---|
| SRT (.srt) | Plain text; some players support basic tags | Players, editors and subtitle exchange | Not suitable for preserving complex layouts |
| VTT (.vtt) | Styles and positioning; rendering depends on the player | Web video captions | Requires a WEBVTT header |
| ASS / SSA (.ass / .ssa) | Fonts, colors, positioning and effects | Subtitles with detailed typesetting | Conversion may discard styling |
A format’s capabilities are separate from what a converter preserves. KiiMix keeps dialogue and basic timing, removes inline formatting, and does not preserve the original positioning, effects or complete layout. ASS output uses a default style and 10 ms timing precision; converting to ASS does not create complex styles that were absent from the source.
Soft subtitles and burned-in subtitles
Soft subtitles are stored separately from the picture, either as a track inside a video or as an external file. They can contain text or images. Text tracks can be extracted or converted by tools that support their format; image subtitles need OCR to become text.
Burned-in subtitles are pixels in the video image, with no separate subtitle text to export. Rebuilding the displayed subtitles requires OCR and proofreading. Speech transcription can produce new dialogue captions, but it does not extract the original on-screen subtitles.
Being able to turn subtitles off usually indicates that they are separate from the picture. Being unable to turn them off is not conclusive: the player may not expose the controls. Check the media’s subtitle tracks and any external subtitle files loaded by the player.
Why image subtitles cannot be converted directly to text
PGS, commonly saved as .sup, and VobSub, typically an .idx file paired with .sub, contain subtitle images and display timing rather than copyable text. They can be extracted as soft subtitle tracks, but converting them to a text format such as SRT still requires OCR.
The current tools do not support PGS, VobSub or OCR. Use software that recognizes image subtitles to produce a text subtitle file, proofread it, then convert its format or save its dialogue as TXT.
Fixing garbled Chinese subtitles
Garbled text often means a file was opened with the wrong encoding. Choosing the correct encoding can usually recover the text if the original bytes are intact. If it was already saved with replacement characters such as � or question marks, changing the encoding cannot recover the lost content; obtain the original file again.
| Encoding | Common source | What to select |
|---|---|---|
| UTF-8 | Modern software and downloaded subtitles | Try first; also used for output |
| GBK / GB2312 | Older simplified Chinese subtitles | GB18030 (GBK) |
| Big5 | Older traditional Chinese subtitles | BIG5; check the preview |
KiiMix checks encoding markers, tries UTF-8, and estimates another encoding when needed. Detection can be wrong. Change Input encoding for the affected file and inspect the Chinese text; once it looks right, click Process all to generate a new result. Output uses UTF-8.
Open the converter to check encoding →Common questions
How do I fix subtitles that are out of sync?
A constant offset can be corrected by shifting all timestamps in a subtitle editor. Growing drift can result from a frame-rate, playback-speed or source-version mismatch; a sudden change may indicate different cuts or edits. The current tools do not shift timestamps or synchronize subtitles automatically.
Why can’t I extract subtitles from an MP4?
MP4 is a container, and visible on-screen subtitles do not prove it has a separate subtitle track. Check the media information: subtitles may be burned in or loaded from an external file. If a track exists but extraction fails, check its type, selected language and the extractor’s supported formats. KiiMix’s subtitle-to-text tool accepts subtitle files, not MP4.
What are the file and batch limits?
Each subtitle file can be up to 2 MB (2,000,000 bytes), with up to 10 files per batch. File contents stay in your browser. For larger files, use a local subtitle application that supports them.
Why did the styles disappear after conversion?
The target format may be unable to express the original styling, or the converter may not preserve that information. KiiMix focuses on dialogue and basic timing. To retain the original layout and effects, keep the source file and use a player or editor that supports its format.