luim,
Subtitles can be a lot of work, but if done correctly, add a lot to the project.
I'll assume you want to add subtitles without regard to video choice. For example, you have "aliens" speaking "alienspeak" such that the subtitle will always be on screen.
First, make a list of all the subtitles you're going to need. It'll look like this:
SubTitle001: A cafe in Ricksmanworth, 1909
Subtitle002: Why did you come here, Laura?
SubTitle003: I had to -- you left your copy of the 1999 Guiness Book of World Records at my office.
SubTitle004: But Laura, that's not going to be published for ninety years!
SubTitle005: Yes my dear, and I adore your non-sequitur nature
and so on in that fashion until
SubTitle423: Now all of you go home.
If you have Photoshop, this next tedious job will be slightly easier. Make a single image, matching your project specs (say, 720 x 480). Make a layer a text file and pick your biggest SubTitle. Space everything out the way you want it at the bottom of the screen (be sure to keep in mind the video-safe regions, etc.). If you want to be kind to your viewers, give the text some kind of contrasting keyline (for example, white text, but with a thin black keyline will allow the subtitle to stand out, even with a white background).
Make an alpha channel to match the non-captioned image. I do this by keeping a layer of #888888 and doing a select-by-color, then increasing the size of the selection by a pixel. Export that frame as a file, named SubTitle004.pct. Exporting as pict format preserves the alpha channel.
Click back in history until you can modify the text of the caption, then build a new alpha channel and export the new PCT file.
This is a tedious step, but will produce all the subtitles, each with an alpha channel.
Import the files into your project.
Expand your dialogue audio files such that you can see the waveforms.
Place the various slides on their own unique layer (so you can turn it off or turn it on at will) such that each slide appears on top of the appropriate wave form.
When all 423 subtitles are placed accordingly, choose everything on that layer and set the transparency (by pressing CTRL+G) to "Alpha Channel".
There might be easier ways of doing this, but this is the way I use.
Good luck!
![[monkey] [monkey] [monkey]](/data/assets/smilies/monkey.gif)
Edward
"Cut a hole in the door. Hang a flap. Criminy, why didn't I think of this earlier?!" -- inventor of the cat door