Convert ASS to SUB

Advanced SubStation Alpha appeared in 2002 and was designed by people whose entire concern was how subtitles look: a style table, per-line overrides, positioning on a numeric grid, animation, karaoke. MicroDVD dates from 1998, is documented rather than standardised, and describes a line of text and the frames it occupies.

Every other conversion in this bundle moves information between formats that measure roughly the same things. This one moves from the richest to the poorest across four years that happen to sit on opposite sides of what a subtitle file was for. The registry marks any conversion out of ASS as approximate; for this target the word is doing more work than usual.

Override tags in curly braces are stripped, so colours, fades, moves, rotations and karaoke timing leave nothing behind. The style table is not read at all, so fonts, sizes, outline widths and alignments never enter the conversion. What reaches the intermediate representation is a start, an end and plain text — the same three things a caption from any other format reduces to.

That is the correct behaviour, because MicroDVD has nowhere to put any of it. Its inline codes cover italic, bold, colour, font and size, applied inconsistently by players for the format’s entire life, and there is no positioning at all. A converter that tried to map an ASS style onto them would be guessing, and would guess differently for every file.

Once the text is plain, the second loss begins. MicroDVD records which frame a line appears on, so the timings have to be multiplied by a frame rate and rounded to whole frames. This page offers no way to set that rate; the site asks for one only where MicroDVD is the source, because reading such a file is impossible without knowing it, and writing it here uses the fallback of 25.

If your video runs at 25 frames per second, that is exact to the frame. If it runs at 23.976, which is what most film transfers run at, the subtitles drift steadily later — 4.3 per cent, close to four minutes over a ninety-minute film. A player that lets you declare the subtitle frame rate can correct it in one step; a player that does not cannot, and those are exactly the players this conversion is aimed at.

The material this pair usually involves makes the odds worse rather than better. A typeset ASS track most often accompanies an anime episode or a film, and both are commonly distributed at 23.976 — so the frame rate you have is likely to be the one that drifts. Check what the video actually is before assuming the output will line up, and if it is not 25, plan on either a player setting or the burn-in route described further down rather than on the subtitle file happening to work.

The text of every dialogue line, with its hard line breaks turned into real breaks and then into the pipe character MicroDVD uses for the same purpose. The start and end of each line, translated into frames. Commented-out lines in the ASS are skipped, which is almost always what was wanted.

That is a complete list, and it is worth reading as a positive rather than only as a loss. If the track is a straightforward dialogue translation with no typesetting — plenty of them are — then nothing that mattered has gone, and the conversion delivers exactly the file the device needs. Check whether that describes yours before reading the rest of this page as a warning.

A translated sign in an ASS file is a dialogue line positioned over the thing it translates, in a style chosen to match it. Strip the position and the style and it becomes an ordinary caption, and MicroDVD puts every caption at the bottom of the frame because it has no way to express anything else.

On a release with much typesetting the effect is a running commentary appearing under the picture: shop signs, text messages, chapter cards and on-screen titles, all in the same place as the speech. It is not wrong, exactly — the information is there — but it is unlike what the file was designed to show, and removing the sign entries is often a better outcome than keeping them.

ASS routinely puts several lines on screen at once, on separate layers. MicroDVD has no layers, so a sign and a line of dialogue occupying the same seconds become two entries covering the same frames.

Players from this era differ on what they do with that. Some stack the two lines, some show only the first, and a few show the second on top of the first in the same place. None of the three is what the typesetter intended, and the file gives the player nothing to decide with. Where two entries genuinely overlap, choosing one and deleting the other before copying the file to a device is the only reliable outcome.

ASS files in circulation are essentially always UTF-8, and the SUB written here is UTF-8 as well. That is the correct modern choice and it preserves accented characters, non-Latin scripts and typographic punctuation exactly as the typesetter wrote them.

Hardware from the MicroDVD era frequently cannot read it. Those players expect a regional single-byte encoding and render UTF-8 as boxes or pairs of stray symbols, which looks like a corrupted file and is not one. Re-saving the output in the encoding the device expects is a text-editor job and the one step of this process that cannot happen here — and it will lose any character that encoding cannot represent, which for a track containing Japanese names is most of them.

This is the answer that fits the situation, and it is worth taking seriously before converting. If the styling was the point and the destination cannot render it, render it yourself: the subtitles become pixels in the video, and every player on earth shows them identically because they are no longer subtitles.

The cost is real and should be stated. The video has to be decoded and encoded again, which is the one part of the process that genuinely costs picture quality. The subtitles become permanent — unremovable, unswitchable, untranslatable — and a second language means a second copy of the file. For a track destined for one old player in one house, that is usually a trade worth making. For anything being archived, it is not.

A forced line break in ASS is a backslash and a capital N, because a dialogue line has to fit in one comma-separated field. MicroDVD has the same constraint for the same reason and solves it with a vertical bar. So the break survives the whole journey: it is read as a real newline, held as one, and written back out as a pipe that the player splits on.

The edge case is the pipe that was already there. Nothing escapes it in MicroDVD, so a caption containing a vertical bar — a transliteration convention, a table, dialogue quoting a command line — arrives split into two lines on screen. It is rare in a translated dialogue track and less rare in anything technical. Searching the ASS for the character before converting costs a second and is the only defence the format allows.

Before converting to MicroDVD, establish that the player actually wants it. SubRip is read by considerably more hardware, states times rather than frames so it cannot drift, and loses exactly the same styling — so if plain subtitles are the outcome either way, SubRip is the better plain file by every measure.

The usual reason a device shows nothing is not the format. It is the filename not matching the video exactly, the subtitle file being on a different partition or stick, or the character encoding being misread. Work through those three with an SRT first. If the device then genuinely reads MicroDVD and nothing else, this conversion is the right tool, the frame rate is the thing to check, and the ASS stays where it is as the only copy of the work.