Subtitle Edit

the subtitle editor :)

Command Line (seconv)

seconv is Subtitle Edit’s headless command-line converter. It reuses the same core libraries as the desktop app (libse, libuilogic), so it supports the same formats, operations, and OCR engines — without any GUI dependency. Useful for scripts, CI pipelines, server-side workflows, and bulk conversion.

seconv lives in the main Subtitle Edit repository and ships in lockstep with the desktop app — no separately maintained fork, no version drift.

Highlights

380+ subtitle formats — text, binary, and image-based.
Container input — Matroska (.mkv / .mks), MP4, MCC, transport stream teletext, Blu-Ray .sup.
OCR for image-based sources via five engines (Tesseract subprocess, nOCR built-in, BinaryOCR built-in, Ollama HTTP, PaddleOCR subprocess).
Auto-translate via local LLMs (llama.cpp with automatic server start, Ollama, LM Studio) or self-hosted services (LibreTranslate, NLLB).
Image-based output — Blu-Ray sup, BDN-XML, DOST, FCP (Final Cut Pro + image), D-Cinema interop / SMPTE 2014, images-with-time-code.
Operations pipeline — offset, fps change, change-speed, renumber, adjust-duration, fix-common-errors, merge/split, balance, redo casing, RTL fixes, multiple-replace, custom-text format, plain text.
Cross-platform — Windows, Linux, macOS. Only requires the .NET runtime; no display or GUI needed.

Installation

Pre-built binaries are distributed alongside Subtitle Edit. To build from source:

dotnet build src/seconv/SeConv.csproj -c Release

The executable is seconv (or seconv.exe on Windows).

Usage

seconv <pattern> <format> [options]
seconv <pattern> --format <name> [options]   # alternative syntax

The format may be passed as the second positional argument or via --format <name>. Multiple input patterns can be passed as separate quoted arguments or comma-separated:

seconv "file1.srt" "file2.srt" subrip --overwrite
seconv "*.srt,*.ass" subrip --input-folder:./in

Options accept either --option:value, --option=value, or --option value. The colon form is shown throughout this page.

Quick examples

seconv *.srt sami                                                  # SRT → SAMI
seconv movie.srt subrip --encoding:windows-1252                    # encoding override
seconv movie.srt subrip --encoding:source                          # keep input's encoding on output
seconv *.sub subrip --fps:25 --output-folder:./out                 # frame-based → time-based

seconv movie.mkv subrip --track-number:3                           # extract MKV text track #3
seconv movie.sup subrip --ocr-engine:tesseract --ocr-language:eng  # OCR a Blu-Ray .sup
seconv movie.sup subrip --ocr-engine:nocr --ocr-db:Latin.nocr      # OCR via nOCR
seconv movie.sup subrip --ocr-engine:binaryocr --ocr-db:Latin.db   # OCR via BinaryOCR
seconv movie.sup subrip --ocr-engine:ollama --ollama-model:llama3.2-vision

seconv subs.srt bluraysup --resolution:1920x1080                   # render text → Blu-Ray sup
seconv subs.srt bdnxml --resolution:1920x1080                      # render text → BDN-XML
seconv subs.srt bluraysup --background-color:"#B4000000"           # ... with a black background box

seconv subs.srt customtext --custom-format:my-template.xml         # custom template
seconv *.srt subrip --multiple-replace:rules.xml                   # search-and-replace pass

seconv subs.srt subrip --offset:-2000 --renumber:1 --overwrite     # offset 2s back, renumber from 1

Subcommands

seconv formats              # list all supported formats
seconv list-encodings       # list text encodings
seconv list-pac-codepages   # list PAC code pages
seconv list-ocr-engines     # list OCR engines + installation status
seconv list-fce-rules       # list FixCommonErrors rule IDs
seconv info <file>          # print format/encoding/duration/language for a file
seconv lint <pattern>       # validate subtitle(s); exit 1 if issues found
seconv --help               # show help
seconv --version            # print version and exit

Inspect & validate

seconv info movie.srt                # human-readable table
seconv info movie.srt --json         # machine-parseable

seconv lint *.srt                    # check overlaps, line lengths, tags, ...
seconv lint *.srt --json             # CI-friendly: exit 1 on any issue

Options

File / I/O

Option	Description
`--input-folder:<path>`	Input folder; relative patterns resolve against it
`--output-folder:<path>`	Output folder (default: input file’s directory)
`--output-filename:<name>`	Output file name (single input only)
`--overwrite`	Overwrite existing files (default: rotate to `name_2.ext`, `_3.ext`, …)
`--encoding:<name>`	Encoding name or codepage. Special values: `utf-8`, `utf-8-no-bom` (also `utf-8-nobom`, `utf8-nobom`), a code page number, or `source` to keep the input file’s detected encoding. Defaults: auto-detect on input, UTF-8 BOM on output

Time / frame

Option	Description
`--offset:hh:mm:ss:ms`	Shift all timecodes (also accepts plain ms, signed: `-1500`, `+1500`)
`--fps:<rate>`	Source frame rate (used for frame-based input formats)
`--target-fps:<rate>`	Target frame rate (with `--fps`, calls `Subtitle.ChangeFrameRate`)
`--adjust-duration:<ms>`	Add/subtract milliseconds to each paragraph’s duration
`--change-speed:<percent>`	Scale all times by 100/percent (e.g. `125` = 1.25× faster). Must be > 0
`--renumber:<n>`	Renumber paragraphs starting at `n`

Format-specific

Option	Applies to	Description
`--resolution:<WxH>`	ASSA, image-based	Sets `PlayResX`/`PlayResY` for ASSA; sets canvas for image outputs (default `1920x1080`)
`--assa-style-file:<file>`	ASSA	Apply `[V4+ Styles]` block from another ASSA file
`--pac-codepage:<page>`	PAC	Code page name (`Latin`, `Greek`, `Hebrew`, …) or numeric (0–12). See `seconv list-pac-codepages`
`--ebu-header-file:<file>`	EBU STL	Reuse the GSI header block from an existing `.stl` file
`--plaintext-merge`	Plain text (`txt`)	Merge all subtitles into one space-separated block (no blank lines). Takes precedence over the two options below
`--plaintext-unbreak`	Plain text (`txt`)	Unbreak each subtitle, joining its lines into one
`--plaintext-no-blank-line`	Plain text (`txt`)	Do not put a blank line between subtitles (default keeps it)

Image output styling

When rendering a text subtitle to an image-based target (Blu-Ray sup, VobSub, BDN-XML, DOST, FCP / Final Cut Pro + image, D-Cinema, images-with-time-code, WebVTT thumbnails), these options control how the text is drawn. <i>, <b>, and <font color=...> tags in the subtitle text are honored. The same values can be set in a --settings JSON file’s exportImages section (see Settings JSON); CLI flags win over the JSON.

Option	Description
`--font-name:<name>`	Font family (default: `Arial`)
`--font-size:<pt>`	Font size in points (default: `50`)
`--font-color:<color>`	Text colour (default: `white`)
`--font-bold`	Render text bold
`--outline-color:<color>`	Outline colour (default: `black`)
`--outline-width:<px>`	Outline width (default: `2.5`; `0` disables)
`--shadow-color:<color>`	Shadow colour (default: `black`)
`--shadow-width:<px>`	Shadow width (default: `0` = off)
`--background-color:<color>`	Background box colour, e.g. `black` or `#B4000000` (semi-transparent black). Implies `--box-type:one-box` unless `--box-type` is given
`--background-corner-radius:<px>`	Corner radius of the background box (default: `0`)
`--box-type:<type>`	`none` (default) \| `one-box` \| `box-per-line`
`--box-padding:<px>`	Box padding: one value for all sides, or `left,right,top,bottom` (default: `5,5,3,3`)
`--line-spacing:<percent>`	Extra gap between lines as percent of line height (default: `0`)
`--alignment:<pos>`	Screen position: `bottom-center` (default), `top-left`, `middle-right`, …
`--content-alignment:<align>`	Multi-line text justification: `left` \| `center` (default) \| `right`
`--bottom-top-margin:<px>`	Vertical screen-edge margin (default: 5% of height)
`--left-right-margin:<px>`	Horizontal screen-edge margin (default: 5% of width)

Colours accept hex (#AARRGGBB, #RRGGBB, with or without #) or a colour name (white, black, yellow, …).

# SRT → UHD Blu-Ray sup with a semi-transparent black background box (SE4-style)
seconv movie.srt bluraysup --resolution:3840x2160 --background-color:"#B4000000"

# Custom font, bold, box per line
seconv movie.srt bluraysup --font-name:Verdana --font-size:60 --font-bold --box-type:box-per-line

Containers / tracks

seconv automatically extracts subtitle tracks from container files:

Extension	Sources
`.mkv`, `.mks`	Matroska text tracks (S_TEXT/UTF8, SSA, ASS, HDMV/TEXTST) and image tracks (S_HDMV/PGS via OCR)
`.mp4`, `.m4v`, `.m4s`, `.3gp`	MP4 text tracks and WebVTT VTTC
`.mcc`	MacCaption 1.0
`.ts`, `.m2ts`, `.mts`	Transport stream — teletext (no OCR) and DVB-sub (via OCR)
`.sup`	Blu-Ray sup (via OCR)

When a container has multiple usable tracks, one output file is written per track with the track’s language code as a suffix:

movie.mkv → movie.eng.srt
            movie.deu.srt
            movie.fra.srt

If two tracks share a language, the track number is added: movie.#3.eng.srt.

Option	Description
`--track-number:<list>`	Comma-separated track numbers to keep
`--forced-only`	MKV: keep only forced tracks
`--teletext-only`	TS: skip DVB-sub OCR (teletext only)
`--teletext-only-page:<n>`	TS: extract only this teletext page

OCR

`--ocr-engine`	Type	Setup
`tesseract` (default)	Subprocess	Install Tesseract (`apt install tesseract-ocr`, `brew install tesseract`, or the Windows installer); ensure it is on `PATH`. Pass `--ocr-language` as ISO 639-2 (`eng`, `deu`, `spa`, …).
`nocr`	In-process	Built-in nOCR matcher. Required: `--ocr-db:<path-to-Latin.nocr>`.
`binaryocr` (alias: `binary`)	In-process	Built-in BinaryOCR matcher (different accuracy profile, similar speed). Required: `--ocr-db:<path-to-Latin.db>`.
`ollama`	HTTP	Local Ollama server with a vision-capable model (e.g. `llama3.2-vision`, `qwen2.5vl`). Configure via `--ollama-url` (default `http://localhost:11434/api/chat`) and `--ollama-model` (default `llama3.2-vision`). Pass `--ocr-language` as a human name like `English`.
`paddle` (alias: `paddleocr`)	Subprocess	Install via `pip install paddleocr`; ensure the `paddleocr` binary is on `PATH`. Pass `--ocr-language` as a short code (`en`, `de`, …).

Option	Description
`--ocr-engine:<engine>`	`tesseract` (default) \| `nocr` \| `binaryocr` \| `ollama` \| `paddle`
`--ocr-language:<lang>`	Tesseract: ISO 639-2 (`eng`, `deu`); Paddle: short (`en`); Ollama: human (`English`)
`--ocr-db:<path>`	OCR database file: `.nocr` for `nocr`, `.db` for `binaryocr` (required for both)
`--dictionary-folder:<path>`	Folder with Hunspell dictionaries + `*_OCRFixReplaceList.xml`; enables the “Fix common OCR errors” pass of `--fix-common-errors` (English is bundled, so this is only needed for other languages)
`--ollama-url:<url>`	Default `http://localhost:11434/api/chat`
`--ollama-model:<model>`	Default `llama3.2-vision`
`--time-codes-only`	Image sources (`.sup`, VobSub `.sub`/`.idx`, MKV PGS/VobSub, MP4 VobSub, TS DVB-sub) → text format with time codes only and empty text. Skips OCR entirely — no OCR engine required. Ignored for text inputs and image output targets.
`--no-vobsub-isolate-colors`	Disable VobSub OCR colour isolation, which is on by default. Isolation rebuilds each subpicture as a crisp black-on-white bitmap via histogram-based colour analysis — the most frequent opaque colour (the glyph fill) becomes black and the gray outline / anti-alias colours collapse into the white background, which helps on discs whose outlines otherwise melt adjacent characters together (`Yuri` → `Yurl`). Pass this flag to OCR the raw palette instead. Ignored for non-VobSub sources and with `--time-codes-only`.

OCR database files are not bundled with seconv. The nocr and binaryocr engines need a .nocr or .db file passed via --ocr-db. Sources:

If you have the desktop UI installed: %AppData%\Subtitle Edit\OCR\ (Windows) or ~/.config/Subtitle Edit/OCR/ (Linux/macOS).

From the repo: Ocr/Latin.nocr and Ocr/Latin.db.

Other languages: download from the SE UI (Tools → “OCR with nOCR” / BinaryOCR → download).

Run seconv list-ocr-engines for the per-engine installation-status table.

# Tesseract
seconv movie.sup subrip --ocr-engine:tesseract --ocr-language:eng

# nOCR (no external dependency)
seconv movie.sup subrip --ocr-engine:nocr --ocr-db:"C:\Users\me\AppData\Roaming\Subtitle Edit\Ocr\Latin.nocr"

# BinaryOCR
seconv movie.sup subrip --ocr-engine:binaryocr --ocr-db:"C:\Users\me\AppData\Roaming\Subtitle Edit\Ocr\Latin.db"

# MKV with image (PGS or VobSub) tracks — OCR runs automatically
seconv movie.mkv subrip --ocr-engine:tesseract --ocr-language:eng

# VobSub .sub + .idx pair — the .idx companion is auto-detected
seconv movie.sub subrip --ocr-engine:tesseract --ocr-language:eng

# Transport-stream teletext (no OCR needed)
seconv broadcast.ts subrip

# Time codes only — extract timing with no OCR (empty text); works for any image source
seconv movie.sup subrip --time-codes-only
seconv movie.sub subrip --time-codes-only

Auto-translate

--translate-to:<language> machine-translates each file as part of the conversion (after OCR for image sources, before the cleanup operations). Languages are given as a code or English name (de, German, da, Danish, …); the source language is auto-detected per file unless --translate-from is set.

Option	Description
`--translate-to:<lang>`	Target language — enables translation
`--translate-from:<lang>`	Source language (default: auto-detect per file)
`--translate-engine:<engine>`	`llamacpp` (default) \| `ollama` \| `lmstudio` \| `libretranslate` \| `nllb-serve` \| `nllb-api`
`--translate-url:<url>`	Endpoint of an already-running translate server. For `llamacpp` this skips the local server auto-start; a bare `host:port` is completed to `/v1/chat/completions`.
`--translate-model:<model>`	`ollama`/`lmstudio`: model name. `llamacpp`: a `.gguf` file name from the models folder or a full path (default: the first installed translate model).

llama.cpp (default engine). With no --translate-url, seconv runs a local llama-server for you: it looks for the binary in Subtitle Edit’s data folder (llama.cpp next to seconv, then %AppData%\Subtitle Edit\llama.cpp / ~/Library/Application Support/Subtitle Edit/llama.cpp / ~/.config/Subtitle Edit/llama.cpp) and falls back to llama-server on PATH. The server is started on a free localhost port with the model’s correct chat-template flags and stopped again when seconv exits. Models resolve against the data folder’s models subfolder.

seconv never downloads engines or models (same policy as Tesseract/PaddleOCR). Get llama.cpp + a translation model in one of these ways:

Run auto-translate with llama.cpp once in the Subtitle Edit UI (Tools → Auto-translate → llama.cpp) — it downloads both into the data folder that seconv probes.

Install llama.cpp yourself (brew install llama.cpp, winget install ggml.llamacpp, or a GitHub release) and drop a .gguf translation model (e.g. TranslateGemma) into the models folder, or pass it via --translate-model:<path.gguf>.

Point --translate-url at any llama-server you already have running.

# Translate to German via a local llama.cpp server (started and stopped automatically)
seconv movie.srt subrip --translate-to:de

# Specific source language and model
seconv movie.srt subrip --translate-from:en --translate-to:da --translate-model:translategemma-4b_Q4_K_M.gguf

# Already-running llama-server (local or remote)
seconv movie.srt subrip --translate-to:de --translate-url:http://192.168.1.10:8080

# Ollama
seconv movie.srt subrip --translate-to:da --translate-engine:ollama --translate-model:gemma2

# OCR a Blu-Ray sup and translate the result in one pass
seconv movie.sup subrip --ocr-engine:tesseract --ocr-language:eng --translate-to:de

Templates / replacements

Option	Description
`--multiple-replace:<path.xml>`	SE MultipleSearchAndReplaceGroups XML, applied per paragraph after operations. Supports `Normal` (case-insensitive), `CaseSensitive`, and `RegularExpression` rules
`--custom-format:<path.xml>`	SE CustomFormatItem XML (use with `--format customtext`)
`--settings:<path.json>`	JSON file overlaying `Configuration.Settings` (general / tools / removeTextForHearingImpaired) plus image-output styling (exportImages). Optional `profiles` map for named overlays
`--profile:<name>`	Selects a named overlay from the settings file’s `profiles` map. Requires `--settings`

Multiple-replace XML

<?xml version="1.0" encoding="utf-8"?>
<MultipleSearchAndReplaceGroups>
  <Group>
    <Name>Demo</Name>
    <IsActive>true</IsActive>
    <Rules>
      <Rule>
        <Active>true</Active>
        <FindWhat>colour</FindWhat>
        <ReplaceWith>color</ReplaceWith>
        <SearchType>Normal</SearchType>
      </Rule>
      <Rule>
        <Active>true</Active>
        <FindWhat>\bteh\b</FindWhat>
        <ReplaceWith>the</ReplaceWith>
        <SearchType>RegularExpression</SearchType>
      </Rule>
    </Rules>
  </Group>
</MultipleSearchAndReplaceGroups>

seconv *.srt subrip --multiple-replace:fixes.xml

Custom text format XML

<?xml version="1.0" encoding="utf-8"?>
<CustomFormatItem>
  <Name>JSON-ish</Name>
  <Extension>.json</Extension>
  <FormatHeader>{
  "lines": [</FormatHeader>
  <FormatParagraph>    {"start": "{start}", "end": "{end}", "text": "{text}"},</FormatParagraph>
  <FormatFooter>  ]
}</FormatFooter>
  <FormatTimeCode>hh:mm:ss.zzz</FormatTimeCode>
</CustomFormatItem>

seconv subs.srt customtext --custom-format:lines.xml

Available template tokens: {title}, {number}, {start}, {end}, {duration}, {gap}, {text}, {text-line-1}, {text-line-2}, {actor}, {cps-comma}, {cps-period}, {text-length}, {bookmark}, {media-file-name}, {media-file-name-full}, {#lines}, {#total-words}, {#total-characters}, {tab}. Time-code tokens accept hh/h, mm/m, ss/s, and zzz/zz/z for milliseconds (or zzzzzzz... for total milliseconds without breakdown).

Settings JSON

{
  "general": {
    "subtitleLineMaximumLength": 43,
    "subtitleMinimumDisplayMilliseconds": 1000,
    "subtitleMaximumDisplayMilliseconds": 8000,
    "currentFrameRate": 23.976,
    "defaultFrameRate": 23.976,
    "minimumMillisecondsBetweenLines": 24,
    "maxNumberOfLines": 2,
    "mergeLinesShorterThan": 33,
    "subtitleMaximumCharactersPerSeconds": 25.0,
    "subtitleOptimalCharactersPerSeconds": 15.0,
    "subtitleMaximumWordsPerMinute": 400.0,
    "dialogStyle": "DashBothLinesWithSpace",
    "continuationStyle": "None"
  },
  "removeTextForHearingImpaired": {
    "removeTextBeforeColon": true,
    "removeInterjections": false
  },
  "exportImages": {
    "fontName": "Arial",
    "fontSize": 50,
    "fontColor": "#FFFFFF",
    "isBold": false,
    "outlineColor": "black",
    "outlineWidth": 2.5,
    "shadowColor": "black",
    "shadowWidth": 0,
    "backgroundColor": "#B4000000",
    "backgroundCornerRadius": 0,
    "boxType": "one-box",
    "boxPaddingLeft": 5,
    "boxPaddingRight": 5,
    "boxPaddingTop": 3,
    "boxPaddingBottom": 3,
    "lineSpacingPercent": 0,
    "alignment": "bottom-center",
    "contentAlignment": "center",
    "bottomTopMargin": 54,
    "leftRightMargin": 96
  },
  "profiles": {
    "broadcast": {
      "general": { "subtitleMaximumDisplayMilliseconds": 6000 },
      "removeTextForHearingImpaired": { "removeInterjections": true }
    },
    "uhd": {
      "exportImages": { "fontSize": 100 }
    }
  }
}

The exportImages section styles text → image rendering (see Image output styling for the semantics); the equivalent CLI flags override it. The general section mirrors Configuration.Settings.General; any key left out keeps the libse default. The profile-shaping values (minimumMillisecondsBetweenLines, maxNumberOfLines, mergeLinesShorterThan, subtitleMaximumCharactersPerSeconds, subtitleOptimalCharactersPerSeconds, subtitleMaximumWordsPerMinute, dialogStyle, continuationStyle) feed Fix common errors and the split/merge operations, so set them to reproduce an SE4 profile. dialogStyle and continuationStyle take the enum names (case-insensitive): dialogStyle ∈ DashBothLinesWithSpace, DashBothLinesWithoutSpace, DashSecondLineWithSpace, DashSecondLineWithoutSpace; continuationStyle ∈ None, NoneTrailingDots, NoneTrailingEllipsis, OnlyTrailingDots, LeadingTrailingDots, LeadingTrailingEllipsis, LeadingTrailingDash, … (see the Fix common errors continuation styles).

seconv *.srt subrip --settings:my.json --profile:broadcast --remove-text-for-hi

Verbosity

Option	Description
`--quiet` / `-q`	Suppress per-file progress and the parameters table; only print the final summary
`--verbose` / `-v`	Print extra diagnostic information, including full exception details (stack traces) on errors
`--json`	Emit per-file results as JSON to stdout (suppresses Spectre output)

Operations

Operations run after the structural transforms (offset, fps, renumber, adjust-duration, change-speed) in a fixed, sensible order regardless of where they appear on the command line:

Option	Description
`--apply-duration-limits`	Apply duration limits
`--apply-min-gap:<ms>`	Enforce minimum gap of N ms between paragraphs
`--balance-lines`	Balance line lengths
`--beautify-time-codes`	Beautify time codes
`--bridge-gaps:<ms>`	Bridge gaps shorter than N ms (extends previous end time)
`--convert-colors-to-dialog`	Convert colors to dialog
`--delete-first:<n>`	Delete first N entries
`--delete-last:<n>`	Delete last N entries
`--delete-contains:<word>`	Delete entries containing the given word
`--fix-common-errors`	Fix common subtitle errors (all 39 rules)
`--fix-common-errors-rules:<list>`	Run a subset of FCE rules (CSV; supports `all,-RuleId`)
`--fix-rtl-via-unicode-chars`	Fix RTL via Unicode characters
`--merge-same-texts`	Merge entries with same text
`--merge-same-time-codes`	Merge entries with same time codes
`--merge-short-lines`	Merge short lines
`--redo-casing`	Redo text casing
`--remove-formatting`	Remove formatting tags
`--remove-line-breaks`	Remove line breaks
`--remove-text-for-hi`	Remove text for hearing impaired
`--remove-unicode-control-chars`	Remove Unicode control characters
`--reverse-rtl-start-end`	Reverse RTL start/end
`--split-long-lines`	Split long lines

# Common cleanup pass
seconv *.srt subrip --remove-text-for-hi --merge-same-texts --split-long-lines --overwrite

FixCommonErrors rule selection

--fix-common-errors (no value) runs all 39 rules. Pass --fix-common-errors-rules:<list> to pick a subset — supplying that option implies --fix-common-errors.

seconv movie.srt subrip --fix-common-errors                                  # all rules
seconv movie.srt subrip --fix-common-errors-rules:FixCommas,FixMissingSpaces
seconv movie.srt subrip --fix-common-errors-rules:all,-FixDanishLetterI      # all except one
seconv list-fce-rules                                                        # show rule IDs

FixCommonOcrErrors is intentionally excluded — it requires UI-side spell-check and OCR-engine setup that seconv doesn’t carry.

Output format aliases

Aliases	Format
`srt`, `subrip`	SubRip
`ass`, `assa`	Advanced Sub Station Alpha
`ssa`	Sub Station Alpha
`vtt`, `webvtt`	WebVTT
`smi`, `sami`	SAMI
`sbv`	YouTube SBV
`pac`	PAC (Screen Electronics) — binary
`unipac`, `pacunicode`	PAC Unicode
`ebu`, `ebustl`, `stl`	EBU STL — binary
`cavena`, `cavena890`	Cavena 890 — binary
`cheetahcaption`	CheetahCaption — binary
`capmakerplus`	CapMakerPlus — binary
`ayato`	Ayato — binary
`bluraysup`, `sup`	Blu-Ray sup — image
`vobsub`	VobSub — image
`bdnxml`, `bdn-xml`	BDN-XML — image (folder of PNGs + index.xml)
`dost`, `dostimage`	DOST/image
`fcpimage`, `fcp`	FCP/image
`dcinemainterop`	D-Cinema interop/png
`dcinemasmpte2014`	D-Cinema SMPTE 2014/png
`imageswithtimecode`	Images with time codes in file name
`plaintext`, `text`, `txt`	Plain text (HTML stripped)
`customtext`, `customtextformat`	Custom-templated text (requires `--custom-format`)

Run seconv formats for the full catalog (380+ entries, including input-only formats like Matroska, MP4, and MCC).

Exit codes

Code	Meaning
`0`	Conversion succeeded for all matched files
`1`	Any error: validation failure, parse error, OCR engine missing, invalid `--settings` file, or one or more files failed to convert

Legacy syntax

Old SE 4.x /parameter:value syntax is auto-translated to --parameter:value.
Older smashed-together long options (--inputfolder, --ocrengine, --FixCommonErrors, …) are kept as hidden aliases for the new POSIX-style names (--input-folder, --ocr-engine, --fix-common-errors, …), so existing scripts keep working.

More examples

Bulk format conversion

seconv "*.srt" assa --input-folder:./input --output-folder:./output --overwrite

MKV → SRT extraction

seconv movie.mkv subrip --overwrite                       # one SRT per language
seconv movie.mkv subrip --track-number:3 --overwrite      # only track 3
seconv movie.mkv subrip --forced-only --overwrite         # forced only

Blu-Ray sup OCR with cleanup

seconv subs.sup subrip \
  --ocr-engine:tesseract \
  --ocr-language:eng \
  --remove-text-for-hi \
  --split-long-lines \
  --overwrite

Round-trip via image-based output

seconv subs.srt bluraysup --resolution:1920x1080 --overwrite
seconv subs.srt bdnxml --overwrite

Styled Blu-Ray sup (SE4 `/convert` parity)

# SE4: SubtitleEdit.exe /convert movie.srt blu-raysup /Resolution:3840x2160 (+ styling from Settings.xml)
seconv movie.srt bluraysup \
  --resolution:3840x2160 \
  --font-name:Arial --font-size:100 \
  --background-color:"#B4000000" \
  --overwrite

EBU STL with reused header

seconv new.srt ebustl --ebu-header-file:original.stl --overwrite

Time shift + frame-rate conversion

seconv subs.srt subrip --fps:24 --target-fps:25 --offset:500 --overwrite

Plain text export

seconv movie.srt plaintext --overwrite

Custom JSON output via template

seconv movie.srt customtext --custom-format:lines-template.xml --output-filename:movie.json --overwrite

Architecture

seconv depends only on Subtitle Edit’s core libraries — no Avalonia / GUI runtime:

src/
├── libse/        Core subtitle library (NuGet-shippable, netstandard2.1)
├── libuilogic/   Shared headless logic (BatchConverter pipeline, OCR matchers, image renderer)
├── seconv/       This CLI
└── ui/           Avalonia desktop UI (not referenced by seconv)

This means seconv can run on systems without a display (CI, headless servers, Docker) without bundling Avalonia or any X server.