Timecode offsets

[marsdeat]

This is a feature request, not a bug:

Especially when working with media files, my transcription files are often coded with the absolute time of day, (burned into video, for example) rather than the time into the file. An option to set the start of the file as, say, 15:06:34, rather than 00:00:00 (by adding 15h06m34s to the timecode throughout) would be massively helpful.