[updated 2012-06-19]

capblaster logotypcapblaster is a Web app that adds live captioning (aka subtitling) features to VidBlaster (a live video production tool).

See below for screen shots and video demos.

This is a small project, that hopefully will do some big things when it comes to captioning/subtitling of livecasts.

An installation package is available as zip files containing the files to be installed in any web directory:


Read this carefully before you try the app!

The software is released “as is”. We take no responsability for its functioning or anything that might happen to the user’s computer. VidBlaster does not (yet as of v 1.21) support Web sockets, therefore the user must have Java installed, and bypass the security warnings (about insecure/unsigned certificates). Recommended browsers are Chrome, Safari and Firefox.

Ready to try?
Read the above, then go to

We appreciate all comments and feedback, please send them to

Features and limitations

capblaster is (currently):

  • free to use (with VidBlaster, note an edition with API support is required)
  • requires the captioner(s) to be located at the live production site
  • limited to open captions/subtitles (mixed into the video signal)
  • VidBlaster’s API functionality (documented in its wiki) has been changed several times since capblaster was originally developed. Therefore different versions of capblaster works only with the proper version of VidBlaster.
  • handles national characters (utf-8) only from VidBlaster v1.22 and upwards)
  • logs captions in the SubRip format only
  • released as open source

Known issues

  • after some time (around 10-15 minutes) the text buffer seems to be clogged, making a save/and restart of capblaster necessary. We are looking into this problem.

Some background information about the project can be found in LiveCaptionApp-spec2.pdf. See Wikipedia for more about Subtitles, closed/open captions and the SubRip format.

If you require closed captions, multi language support, and remote captioning, you might find SubPLY’s live captons services useful.


Screen shots

Screen shot of capblaster beta 0.80Example of output in the video (still)

Video demos

The first clip shows an actual live recording with captions generated with capblaster. The clip can also be downloaded (40 Mb):

The second clip shows the same material after some post production, where the recorded text (.srt) was re-synced to obtain a better fit with the audio and encoded into a format suitable for a wide range of viewing platforms (16:9 .mp4). The clip can also be downloaded (7 mb):