I’ve used and recommended others to use Subtitle Workshop as a good open-source tool for producing subtitles or captions for video. A problem with the software is that it doesn’t export Timed Text DFXP XML caption files that are pretty standard for web video, both in Flash and for the jQuery-based caption handler that I’ve seen used for HTML5 video.
Not being able to export TTML isn’t really a problem for me, since years ago I wrote a suite of scripts to translate captions and subtitles between all the different formats I run into. I took a few minutes today to make a Custom Format Profile for TTML that you can download here, if you’re so inclined.
Save that to the CustomFormats directory where Subtitle Workshop installed (on a Windows machine, that’s in one of the Program Files directories, then under URUSoft/Subtitle Workshop/). When you got to save the captions you made, click on custom formats, hit the Load Project button, and pick the DFXP_XML.cfp profile that you saved there.
Maybe I’ll post again sometime this year. I’m a busy dude.

Thanks a lot, great job.
Thank you very much! I was looking all over the internet for something that could help me export XML subtitles in subtitleworkshop.
U rock!