What is ASS?

Advanced SubStation Alpha (ASS) is a script for more advanced subtitles than SSA. It is technically SSA v4+. It is able to produce anything from simple texts to manual graphic editing used in karaoke. There are few programs designed to create these scripts. The main feature of ASS is it has more specifications than normal SSA, like in styles programming. For example, the above script changed into ASS:

[Script Info]
; Script generated by Aegisub
; http://www.aegisub.net
Title: Neon Genesis Evangelion - Episode 26 (neutral Spanish)
Original Script: RoRo
Script Updated By: version 2.8.01
ScriptType: v4.00+
Collisions: Normal
PlayResY: 600
PlayDepth: 0
Timer: 100,0000
Video Aspect Ratio: 0
Video Zoom: 6
Video Position: 0

[V4+ Styles]
Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding
Style: DefaultVCD, Arial,28,&H00B4FCFC,&H00B4FCFC,&H00000008,&H80000008,-1,0,0,0,100,100,0.00,0.00,1,1.00,2.00,2,30,30,30,0

[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:01.18,0:00:06.85,DefaultVCD, NTP,0000,0000,0000,,{\pos(400,570)}Like an Angel with pity on nobody\NThe second line in subtitle

Related Software:

Macgo Mac Blu-ray Player: Display ASS format on your Mac.
Macgo Windows Blu-ray Player: Display ASS on Windows platforms.
Macgo Free Mac Media Player: Display ASS for Mac OS X.

Related Source:

How to add and set Subtitles to a Blu-ray movie?
How to sync audio, video, subtitle by Mac Blu-ray Player?

Further Reading:

See Advanced SubStation Alpha on Wikipedia.
"SSA/ASS Subtitles". Matroska.org. CoreCodec, Inc. Retrieved 12 July 2010.
"ASS Tags". Aegisub Manual. aegisub.org. Retrieved 25 March 2014.