Originally posted by: daveytod
I've just downloaded AVISynth but it's a jibberish to me so if someone could talk me through?

Assuming you have installed AviSynth, there are a couple of other plugins you will also need:
VSFilter
DGMPGDec

First get the video into AviSynth. Start DGIndex from the DGMPGDec package, open your mpeg video file, and save a d2v project file.

Open Notepad, and write a script like this:

LoadPlugin("C:\Program Files\DGMPGDec\dgdecode.dll")
mpeg2source("project.d2v")

(Obviously the path in the first line depends on where you extracted the DGMPGDec package to). Save this text file with the extension avs. Now open the avs file with VirtualDubMod or AvsP and check your video is displayed.

Now, the actual subtitling step may have changed since I last used it, but the premise is that you create a text file with the extension srt (see this thread for the format). Then you amend your avs file to look like this:

LoadPlugin("C:\Program Files\DGMPGDec\dgdecode.dll")
LoadPlugin("C:\Program Files\VSFilter\vsfilter.dll")
mpeg2source("project.d2v")
TextSub("subtitles.srt")

When you are happy with your timings, just open the avs file in your MPEG encoder (TMPGEnc/CCE/whatever) and encode a new MPEG stream; the encoded file will have the subs permanently "burnt" into the video.