Aegisub is the result of a few months of work in a project designed to completely replace Medusa for typesetting, as well as add a large number of useful and/or vital features that Medusa lacks.
Features:
Unicode in UTF-7, UTF-8, UTF-16LE and UTF-16BE encodings
Importing non-Unicode subtitles from over 30 different character encodings, including Shift_JIS, allowing you to resume work on any subtitles regardless of your system locale settings
Loading advanced Substation Alpha (.ass), Substation Alpha (.ssa), Subrip (.srt) and Plain-Text (.txt) (with actor data) subtitle formats
Full tag conversion from SRT to ASS
Multiple Undo levels
Powerful Automation module using the Lua scripting language to create advanced karaoke effects (including per-syllable effects, similar to AssCalc) - or any other kind of subtitles manipulation
Syntax highlighting
Fonts collector to collect all fonts used in a script into a folder
Opening of videos via Avisynth for true preview of subtitles using VSFilter, in any format supported by DirectShow
Aspect ratio overriding for anamorphic videos
Variable Frame Rate videos via timecodes file (v1 and v2), including exporting processed times for hardsubbing
Display of video coordinates under mouse and simple auto positioning support
Audio mode which allows you to open files in any format that your DirectShow can decode, including Wave, mp3, Ogg Vorbis, AAC, AC3 and others
Powerful audio timing and playback mode, including full support for karaoke manipulation
Functions and hotkeys easily synchronizing audio/video and subtitles
Time shifting and manipulation by timestamps or frame numbers (once video or timecodes are loaded)
Advanced find and replace with support for Regular Expressions
Cut/Copy/Paste subtitles via plain-text format, so it can be pasted in any plain-text editor
Translation assistant to easily translate subtitles to another language
Styling assistant to quickly pick styles for each line in subtitles
Styles manager that allows you to categorize subtitles styles, to make working on several projects painless
Keyframe navigation for fast seeking to scene boundaries
Several subtitles manipulation macros, such as making timing continuous or recombining double lines after OCR
Highlighting of subtitles that are visible on current video frame, and a button to select those
Preview subtitle changes imediately by pressing Ctrl+Enter
Shortcut buttons to set text as bold, italic, underline, strikeout, change font or any of the 4 colors
Extensive manual with detailed instructions and tutorials for typesetting and program usage
DirectSound audio player has been completely rewritten (again) - this should give much better stability of audio playback. Note that the old DirectSound player is still available, you can change to it in Options. If you're using Windows 7, the old one seems to be more reliable.
PCM WAV audio provider actually works again, and with files of any size. (No more crashing with files bigger than 256 MB.)
Tip of the Day has been removed.
Loads of changes to FFmpegSource2 (FFMS2) giving better support for almost everything, making it more stable and so on.
Lots of memory leaks have been fixed, Aegisub should use less memory now.
Bug fixes in many file format readers and writers. Loading and saving subtitles to foreign formats should be more reliable now. Problems with frame-based/SMPTE timecode-based formats fixed.
The Kanji Timer function has been almost completely rewritten, squashing all known bugs and giving a prettier GUI. The use is the same.
OpenGL errors in the video display are no longer fatal. You will get an error message, and video won't open if Aegisub doesn't support your graphics card/driver, but it shouldn't crash. See below for a workaround if video doesn't work for you.
Some additions to Karaoke Templater, you can now create loops with variable iteration counts (including infinite!) making a lot of effects more feasible.
The "Local configuration" option was removed from Options. If you want a "portable" version of Aegisub (as it was intended for making) we now have a separate download package for that. It also actually works as advertised now. See the download page for details.
An innumerable amount of other minor, cosmetic changes that just makes everyday use more convenient and smoother.
