SubStation Alpha subtitles (SSA)
SSA is a styled subtitle script format whose v4 sections describe reusable styles and timed dialogue events.
SubStation Alpha, or SSA, is a text subtitle script format with reusable styles and timed events. It can describe font choice, colours, margins and alignment in addition to the words.
The commonly encountered SSA v4 script has three main sections:
| Section | Contents |
|---|---|
[Script Info] |
Script identification and rendering-related information |
[V4 Styles] |
Named styles with font and presentation fields |
[Events] |
Timed dialogue and comment records |
A dialogue event selects a style by name. Changing that style can alter all events using it without rewriting their text.
An SSA event is a structured record
Format: Marked, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: Marked=0,0:00:12.50,0:00:15.00,Default,,0,0,0,,The platform is empty.
This is an event-section excerpt, not a complete script. It assumes a Default style exists. The final field is text and can contain commas; the preceding commas separate defined fields. The start and end use hundredths of a second here.
The Marked field comes from the SSA record model. It is not a declaration that the event is forced, is a translation, or must always be displayed.
SSA v4 and ASS v4+ are related formats
SSA uses ScriptType: v4.00 and [V4 Styles]. ASS uses v4.00+ and [V4+ Styles]. Their style records differ; ASS also uses Layer where the SSA dialogue record has Marked. The legacy SSA alignment values are not the same overall numbering scheme as ASS's keypad-style alignment.
Renaming a file from .ssa to .ass leaves those declarations and records unchanged. A proper conversion interprets them and writes the target model.
For an Emby collection containing older styled subtitles, the useful identification is the script's declared format and the renderer handling it. A route using a compatible renderer can retain its styles; a conversion to plain text keeps a more limited description.
Matroska's SSA mapping retains script/style information as track configuration and stores timed event payloads separately. Associated font attachments are another resource. Preserving the dialogue words alone does not preserve the named styles or provide the requested font.