Convert SUB to SBV Online

Converting a MicroDVD SUB File to SBV: What This Covers

SBV is SubViewer — the plain, no-markup caption format YouTube's own caption editor writes and accepts on upload. MicroDVD .sub is a much older text format whose timings are frame numbers rather than clock times. Moving between them is mostly a timing job, and this tutorial walks the whole thing: reading the frame rate out of your file, running the conversion in the browser, and fixing the handful of things that commonly go wrong before a YouTube upload.

How to Convert SUB to SBV

1. Load Your MicroDVD File: Click "📂 Upload .sub" to pick the file, or paste its {start}{end}text lines into the Input (SUB) box. The character count beside the label confirms it was read; one file at a time.
2. Read the Frame Rate Out of the File First: Open the .sub in a text editor and look at line one. A first line of {1}{1}23.976 is the frame-rate hint; note the number and delete the line. This converter reads every MicroDVD file at 25 fps and has no frame-rate control.
3. Check the Two Selectors: "From format" must read SUB, "To format" must read SBV. The output panel header should say "Output (SBV)" once you convert.
4. Convert, Download and Spot-Check: Press "Convert →", then "⬇ Download .sbv" — it saves as subtitles.sbv, UTF-8 encoded — or "📋 Copy" to paste into YouTube Studio's caption editor. Check the first and last cue against the video before you publish.

Walk-through: The Frame Rate Is Not in the File

A MicroDVD line like {25}{100}Hello says "show this from frame 25 to frame 100". Turning that into 00:00:01.000,00:00:04.000 needs the frame rate of the encode the subtitles were cut against, and MicroDVD's syntax has no field for it. By convention the rate is smuggled into the first cue as {1}{1}23.976 — FFmpeg's MicroDVD demuxer scans the opening lines for that shape, and the reference Python library pysubs2 raises UnknownFPSError and refuses the file rather than guess when it is missing.

This converter does neither. It does not read the hint line, it renders no frame-rate control, and it parses every MicroDVD file at 25 fps. So delete the hint line before converting — otherwise it becomes a caption reading 23.976 — and treat the timings in the output as provisional until you have checked them against the video. On YouTube that check costs nothing: upload the track, scrub to the end of the video, and see whether the last caption still lands on the right line.

The underlying arithmetic is simple, which makes it easy to sanity-check by hand — frame number divided by frame rate is the time in seconds:

Frame number	at 23.976 fps	at 24 fps	at 25 fps	at 29.97 fps	at 30 fps
24	0:00:01.001	0:00:01.000	0:00:00.960	0:00:00.801	0:00:00.800
1,500	0:01:02.563	0:01:02.500	0:01:00.000	0:00:50.050	0:00:50.000
90,000	1:02:33.754	1:02:30.000	1:00:00.000	0:50:03.003	0:50:00.000

Drift from a wrong frame rate compounds, which is exactly the failure mode viewers complain about: fine over the intro, unwatchable by the end.

Source authored at	Read at 25 fps, captions land	After 1 minute	After 10 minutes	After 1 hour
23.976 fps	early	2.5 s early	24.6 s early	2 min 28 s early
24 fps	early	2.4 s early	24.0 s early	2 min 24 s early
29.97 fps	late	11.9 s late	1 min 59 s late	11 min 56 s late
30 fps	late	12.0 s late	2 min 0 s late	12 min 0 s late

SUB and SBV Side by Side

Property	MicroDVD (.sub)	SubViewer (.sbv)
Timing	Frame numbers, {25}{100}	Clock time, 00:00:01.000,00:00:04.000
Precision	One frame — 40 ms at 25 fps	One millisecond
Cue separator	One line per cue	Timing line, text lines, then a blank line
Line breaks in a cue	Pipe character `	`
Styling	Inline {y:i}, {c:$BBGGRR}, {f:}, {s:} codes	None — YouTube recognises no markup in SBV
Speaker labels	No convention	>> Name: prefixes are common
Encoding	Unspecified; legacy files are often Windows-125x	YouTube requires plain UTF-8
YouTube upload	Accepted, listed as an alternate SubViewer extension	Accepted as a basic format

The practical read: SBV throws away nothing you can keep. MicroDVD's styling codes have no SBV equivalent and YouTube would ignore them anyway, so the only information that has to survive is text, order and timing.

Common Errors and How to Fix Them

• "No cues parsed from input. Check the format." — the parser accepts exactly one shape of line, {digits}{digits} followed by text. You get this message when the .sub is really VobSub (a binary bitmap track paired with an .idx), a SubViewer .sub that already uses timestamps, or a file whose curly braces were mangled in transit. Nothing was uploaded and nothing was lost; change "From format" to what the file actually is.
• A first caption that just says 23.976 — that is the frame-rate hint, {1}{1}23.976. It is not special-cased here, so it becomes a real cue. Note the number, then delete the line from the input.
• The captions are in sync early on and adrift later — the source was not authored at 25 fps. See the drift table in the walk-through.
• The first cue is missing entirely — a UTF-8 byte-order mark at the start of the file makes line one unmatchable, because the cue pattern is anchored to an opening {. Windows-authored .sub files often carry one; re-save without the BOM, or paste the text into the input box instead of uploading.
• A cue written {1234}{} never appears — an empty end-frame is accepted by some MicroDVD readers but not by this parser, which requires digits in both braces. Give the cue a real end frame.
• Accented characters upload as question marks or boxes — YouTube requires SBV files to be plain UTF-8, and this page reads your input as UTF-8 and writes UTF-8 out. If the source .sub was saved in Windows-1250, Windows-1251 or Big5, the damage happens on the way in: re-save the .sub as UTF-8 in a text editor first, then convert.
• Text vanishes mid-line — anything between a < and a > on the same line is treated as markup and removed, so 5 < 6 but 7 > 2 becomes 5 2. Reword or use typographic angle characters before converting.

When This Doesn't Work

If the .sub came with an .idx file, it is VobSub and there is no text inside it to convert — the subtitles are pictures lifted off a DVD, and getting them into SBV requires OCR rather than a format converter. Separately, if you are captioning for YouTube and have any choice in the matter, SRT is the safer upload: it is accepted everywhere, survives a round trip through more editors, and carries the same information SBV does. SUB to SRT covers that route, and SUB to VTT is the one to use for a self-hosted HTML5 player.

Frequently Asked Questions

Does YouTube still accept SBV uploads?

Yes. YouTube lists SubViewer among the basic caption formats it accepts, with the extension given as .sbv or .sub, alongside SubRip, MPsub, LRC and Videotron Lambda. The documented caveat is that only basic versions of these files are supported, no style markup is recognised, and the file must be plain UTF-8 — which suits a converted MicroDVD file, since none of MicroDVD's styling codes survive the conversion anyway.

Why does YouTube list .sub as a SubViewer extension when my .sub is MicroDVD?

Because three unrelated formats have claimed the extension. SubViewer files sometimes use .sub; MicroDVD files use .sub; and VobSub DVD rips use .sub for a binary bitmap stream paired with an .idx. Open the file in a text editor to tell them apart — curly-brace frame numbers mean MicroDVD, hh:mm:ss timestamps with a comma between them mean SubViewer, and unreadable binary means VobSub.

What timing precision does the SBV output carry?

Milliseconds, written as hh:mm:ss.mmm on both sides of the comma. That is finer than the source can justify: a MicroDVD frame at 25 fps is a 40 ms bucket, so the converted timings are precise to the millisecond but only accurate to the frame boundary the original author set. Cues past the hour mark are written with a real hours field, so a cue at 61 minutes reads 01:01:40.000.

Will the speaker labels in my subtitles be handled?

Not automatically. SubViewer files often mark speaker changes with a >> Name: prefix — the SBV reader on this page recognises that convention and strips those prefixes when it parses an .sbv file back in. Nothing in this conversion adds them, because MicroDVD has no speaker-label convention to translate from. If you want them, add them by hand after converting; they are plain text at the start of the cue.

Can I convert several .sub files in one pass?

No — the file picker takes a single file and the input box holds one document, so multi-episode batches are one conversion each. That is a consequence of how the tool works rather than a limit imposed on you: because the conversion runs inside the page, each run is only as slow as parsing a text file, and repeating it for a season of episodes is a matter of seconds per file.

Is my subtitle file uploaded to YouTube or to xconvert during the conversion?

Neither. This converter reads the file with the browser's FileReader API and builds the output with JavaScript that arrived with the page, so no request carries your subtitle text anywhere and there is no server-side copy to expire. Uploading to YouTube is a separate step you take afterwards with the downloaded .sbv.

What did the conversion actually produce in testing?

We ran a three-cue MicroDVD file, including one cue using the pipe separator, through this exact pipeline. The output was a well-formed SubViewer file: a timing line, the caption text on the following lines with the piped cue split across two real lines, and a blank line between blocks, using CRLF line endings throughout. Text, ordering and line breaks came through unchanged. The timings are the part to check against your video, for the frame-rate reasons in the walk-through.

What happens to an empty cue?

It is written out as a timing line followed by an empty text line. MicroDVD files occasionally carry cues whose text was deleted but whose frame markers remain, and nothing in the conversion drops them, so those come through as blank blocks. Scan the output before uploading and delete any block with no text — an empty caption is harmless in a desktop player but there is no reason to ship one.