I can't embed this but I'll leave the link anyway - here (the link at the bottom of the message) is an mp4 file containing a section that involved some heavy compositing work that I'm extremely proud of. For context, the scene where Cassandra appears on Holly's monitor in the Time Wand scene acts as a segue from
Pete Part 1 back into
Cassandra. For this, I used shots of Geraldine from the deleted scenes that, as a blessing and a curse, hadn't been CSO'd onto that funky backdrop.
However, it wasn't merely a case of comping her in. Matching up the colours and creating a matte, while not as quick and easy as it probably ought to have been, had a simple enough solution. The big problem I had was Cassandra's dialogue. First, I had to edit the audio in such a way that it both made sense and said what I needed her to say (I believe some refer to this as sentence mixing), and then - the considerably more tricky part - find a way to make the movements of her mouth fit that.
Now, there are only two shots of Cassandra and one of them didn't even need tweaking - the original line was 'sorry to interrupt Arnold', so all I had to do there was to replace the t sound at the end to stop it running into the next word, and cut away to a repurposed reaction shot to disguise it. The second shot, however, would be more tricky as there weren't many more useable shots of the characters to work from.
Fortunately for me, the second line wasn't too big of a stretch. The mouth movements of Cassandra in the primary shot - 'Kryten, time to make your time bends speech' - didn't feature too much movement on Geraldine's part, and thus all it took to better match the mouth movements was to cut it at the point where the lip movements diverge, reverse the subsequent footage, and subtly fade between the two. It wasn't perfect though, so just for the finishing touch I also faded in and out an additional masked, transparent layer of just Geraldine's mouth when she says 'come in' from 'but Blood Drinker is about to come in', which, when all put together, results in a somewhat decent approximation of Cassandra saying the line 'Kryten, time to come in'. Not exactly Shakespeare, but under the circumstances I'd say it works out pretty good.