What it is

libass is a portable subtitle renderer for the ASS/SSA (Advanced Substation Alpha/Substation Alpha) subtitle format. It is mostly compatible with VSFilter.

Known issues and differences to VSFilter

Get it

See "Downloads" for the latest release 0.10.0 (released 2011-09-25). This is a major release that includes bidirectional layout and OpenType shaping support. FriBidi is now a mandatory dependency and required for basic bidirectional support. Full OpenType shaping support requires a recent snapshot of HarfBuzz-ng. See the changelog for a detailed list of changes.

For the latest code, check out the Git repository (see "Source").

Related Links

The following projects use libass:

• MPlayer
• mplayer2
• VLC
• GStreamer (assrender plugin)
• Aegisub
• XBMC
• avidemux
• PunkGraphicsStream (BD subtitle encoder)
• HandBrake
• Crunchyroll

Information about the ASS format:

• ASS specification (incomplete)
• ASS override tags (Aegisub wiki)
• VSFilter source code (guliverkli2)

Other ASS/SSA implementations:

• VSFilter
• asa (defunct)
• Perian