It was really useful to have one feature like this.

There would be an option somewhere on "Subtitles" called by "Quality Check” mode.

To illustrate the idea, I did this on Photoshop: http://img42.imageshack.us/img42/5653/aegisubqc.jpg

Features:
- When using this mode, the main text area will load the “Original” subtitles. If the text got modified, it will apply the modifications to the “Revised” box.
- Possibility to add a comment to the revision using the “Comments” box.
- Possibility to add timelines to report external problems (like video-audio sync, typesetting, etc.) or add non-translated lines. The added timelines would be saved with “Original” box empty.
- Add button to hide non-modified timelines (“Editor view”). This would hide all the timelines which has the “Revised” box empty.

Optional stuff:
- Auto-scroll could be the ultimate tool to make this work properly.
- Auto-load .ass files from .mkv videos.

Against issues:
- .ass files doesn’t, currently, have structure to save this kind of modifications on the files. The file must be exported with another format or that would require adapting the actual .ass format.
Probably, this add-on would need a massive modification on Aegisub coding. It would be a nice feature to introduce on a 3.0 version.

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I’ve managed to get one other idea that requires fewer modifications to the main Aegisub’s interface. Still, doesn’t minimize the current problems.

Another illustration: http://img132.imageshack.us/img132/5020/aegisubqc2.jpg

This was made based on Translation Assistant tool. We got rid of some major modifications. Still, we got more issues instead.

Features:
- The “Original” box will be a “read-only” box. The “Revised” box will be loaded like the original, but with the modify option.
- “Play” option will make video and audio run at the same time.

Against issues:
- Auto-scroll is a must-have feature to this option.
- How will act if there’s two simultaneous lines or how to report problems with other stuff (video-audio sync, external typesetting, etc.)
- .ass files doesn’t, currently, have structure to save this kind of modifications on the files. The file must be exported with another format or that would require adapting the actual .ass format.
The best option to save the quality checking on this tool could be generating a new .ass file with just the “Revised” and “Comments” lines (on {} bracket in the “Text” box).

My mom is taking a translation class, where she needs to follow rules o how many characters per second she can put in the screen to make her assignments, and can't use aegisub because the lack of this feature. She is then forced to use Subtitle Workshop (can you fell the pain?!?).

Usualy there is plenity of space to put it above the text area, besides time and formatation, on the right. The number of characters (with blank-spaces and punctuation) could fit very well there. This should be trivial to implement (I guess), and would let many people be blessed by aegisub.

Aditionaly, there could be the default maximum recomended number of characters for x seconds speech automaticaly calculated and displayed. Maybe between (), or just coloring the character number of green/orange/red as the limit is reached? This would be handy, obsoleting the paper table and calculations that otherwise would have to be made. But it is not essential.

Additional information:
http://www.literarytranslation.com/workshops/almodovar/
http://accurapid.com/journal/30subtitling.htm

The make adjacent subs continuous and keyframe snapping functions work by thresholds and it is unknown what lines they will affect until after being committed. If the user wants to review these changes he must compare the scripts through some diff tool and see what lines were changed afterwards.

Instead I think the TPP should record these changes and allow the user to view/revert/edit all changes done. I already have done an implementation of this though it is in no way complete.

My current idea of how it should be done is this:
- TPP should be modeless so the user can work on the subtitles it affected (bonus is to become transparent when unfocused so it is easier to work with the grid)
- It should record all changes in a user viewable/clickable list
- When the user clicks on an item in the list it should seek directly to it in the grid/video/audio/editbox
- A clicked item should be revertable and removable from the list
- When done the user should be able to commit whatever items are left or even revert the rest with a simple click of a button

Here's a pic of the last version I wrote:
http://i78.photobucket.com/albums/j81/SuzumiyaHarukalover/TPP_Demo_2710_v2.png

But I note that like I said it is unfinished and it may even be worser off then I believe it is (I haven't poked at it in a few weeks now, though I may work on it again if any interest for it exists)