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Friday, February 19, 2010

The old and present: VSFilter

A short while ago, yet another fork of the VSFilter subtitle renderer has surfaced, introducing more extensions. Let it be clear immediately: Aegisub will not support any new extensions to the ASS subtitle format. We strongly urge you to not use any extensions, and as for why, please read on.

Let's start with the history of the ASS subtitle format: In 2004, Gabest made the Guliverkli project open source under the GPL license. This corresponds to the version 2.23 of VSFilter, or VobSub as it was better known as then. By this time, the ASS format was essentially already in its final form, no real extensions ever came up then. That's more than 5 years ago. Around 2006-2007, the Guliverkli project mostly died off, almost no more development happened. However, a few patches started to crop up. In 2008, we made a fork for Aegisub, and ended up applying those existing patches, fixing a bunch of bugs and, unfortunately, also adding some new features. Very soon the Guliverkli2 project is forked off the Guliverkli project, and includes patches for all parts of it. The Aegisub patches are ported to Guliverkli2. Some more development happens, the Aegisub fork is abandoned in favour of Guliverkli2. The MPC-HC (Media Player Classic Home Cinema) project pops up, as a second fork of Guliverkli. They import most all the Guliverkli2 patches too, as well as add many major new features to Media Player Classic. Now, a new, fourth fork of VSFilter appears, and it has several new extensions.

The important part of the history is in the very beginning: The ASS subtitle format was essentially finalised in 2004. In retrospect, it was wrong to ever extend it, because it creates fragmentation. We regularly receive support requests from people who can't make VirtualDub render their subtitles correctly. The reason? They use TextSub 2.23, the version from 2004, which is clearly still in distribution from some sites. This only shows that changing and extending a standard after it has been finalised is a really poor idea, because old software will always be around.

We, as developers of Aegisub, have discussed the situation with the MPC-HC developers and the main libass developer, and all agree that extending the ASS format, or supporting any new extensions, is a bad idea, for the reasons of fragmentation of standards and backwards compatibility, and we strongly recommend staying away from any extensions to the ASS format. This in fact also includes the extensions introduced in 2008, namely: \blur, \be with parameter over 1, \fax, \fay, \iclip, \xbord, \ybord, \xshad, \yshad. — None of those tags are compatible with the 2004 versions of VSFilter, and if you use them, you have a great risk that your subtitles will just look wrong for some viewers.

Another thing we agree on is that the ASS subtitle format is in general bad and has many problems, and that the only solution is to draft and implement a new subtitle format, using our experience with subtitles and knowledge of how other projects for new subtitle formats have failed, to make a good subtitle format that supports what subtitlers want and need, is usable and editable and is supported across all relevant platforms.

For now, we have just one request: Please do not use any extensions to the ASS subtitle format.


Saturday, January 30, 2010

Aegisub 2.1.8 released

It finally happened. About 6 weeks later than planned.
We have released Aegisub version 2.1.8.

Download it from

So what's new? Not a whole lot, actually. The major news would be that we now have versions for Mac OS X, Linux and other Unix systems. Do note that especially the Mac version is unstable and has several known problems, we consider it alpha quality software.

For the Windows version, the major highlights are:

  • Video should now work on almost all systems, the display code has been made much more robust.
  • The "Could not lock buffer for filling" audio bug has been fixed.
  • We have an Upgrade installer, which is much less to download. If you already have 2.1.7 release installed, this is the fastest way to get up-to-date. (But it only works on exactly 2.1.7 release. Not on older versions. Not on pre-release versions.)
  • The Portable version is now feature-complete, save for ASSDraw3, which we can't easily make portable. But you do get all dictionaries and translations in the portable versions now.
You can see everything in the full changelog.

Update: There is a mistake in the installer causing the Russian and Vietnamese program translations to be mixed up. We have uploaded updated installers for Windows. If you downloaded 2.1.8 early and have problems with Russian or Vietnamese, download the Upgrade installer, it can correct the problem.


Wednesday, January 6, 2010

Linking to Aegisub

Okay, since Aegisub has had a lot of different websites and lots of different URLs throughout the years, I thought it'd be time to clear up things a bit.

These are the correct addresses to link to:

Two things happened last night: We set up a new, temporary website at, this site will be replaced with a more complete website at a later point. When that happens, the purpose of this blog will change back to the original one: A developer blog, not a general news site.
Also, the old Mediawiki installation at was deleted last night, and set up to redirect to the new website. Please do not make direct links to addresses, they will become invalid at some point.

We will of course try to keep old URLs valid as long as possible, but please try to update all existing links you reasonably can.

The network problems previously mentioned in this post have been resolved.