Interesting! Actually, there is a standard for this, although for a different use: subtitles. I'm an Anime addict, and not a speaker of Japanese, so I've become somewhat familiar with the art of subtitling; there's been an enormous amount of progress made in recent years managing the synchronization of short lines of text with a running video. And I've even seen it done with audio as well. Let me see if GStreamer has any built-in support for subtitling, and see if I can mess around with it...