Monday, June 13, 2011

Chroma Kee

I’ve always found that I learn far more about a piece of software through playing rather than working and that’s certainly been the case with the offline video editing program Kdenlive. I’ve also found that when you have a definite goal in mind then “the software doesn’t do that” no longer becomes an option and you use the software far more inventively in order to achieve it.

And so it proved when I decided, using Flash 8 and Kdenlive, I’d try and recreate the title sequence for ITN’s News At One. I first saw this title sequence back when the programme was called First Report – that was before the soporific Aussie soap The Sullivans pushed the programme to its more familiar one o’clock slot.

Here are the original News At One titles that someone culled from TV Ark:

As you can see, it’s quite a complicated title sequence and people who know far more about this sort of thing than me have noted how hard it would have been to achieve in the 70s. They’ve always been very, very good technically at ITN.

Although I haven’t got a clue how ITN did it, I decided on the basic approach of having two layers of video in Kdenlive for my version.

The bottom layer would be the typing hands (or paws in my case – thanks Lionel!). These were shot on my little Canon Ixus camera and then put through the Kdenlive “Threshold” filter and coloured with, of all things, the MSU Old Cinema filter.

Lionel touch-typing

The top layer of video would consist of the zoom out of the Houses of Parliament’s clock tower (replaced by the block of flats where I live) which fades out, and the photo montage of odd people and drab places (replaced by pictures of my daughters, their toys and things in the square outside).

Creating the montage for the top layer was straight forward. I loved the fact that, on the original, the outlines around the images were all different widths, and some of them were even bent out of true. Even the top of the News at One logo was at an angle!

Creating the montage in Flash

The problem I faced was how to merge these two layers. My first thought was to use a Chroma key, but this gave me all sorts of problems and some rather nasty digital fringing that looked like anything but 70s television.

Click to enlarge

What I really needed was to be able to export transparency from Flash into Kdenlive – and it turned out that I could. The first step was to export the sequence out of Flash 8 as a PNG sequence at 24 bits per pixel with alpha channel, like this:

Getting transparency from Flash to Kdenlive

Then I could import the PNG sequence into Kdenlive, and use a Composition transition to knit the two layers together.

Click to enlarge

PNG sequences are the best thing ever invented for my work – everything can use them perfectly and they mean that I can transfer work between packages without losing quality or suffering odd effects.

So, here’s the finished sequence:

Now I understand keying properly I can do loads of things I thought I simply couldn’t do before. And all because I thought I’d do a little sequence to make my daughters laugh.


Tim said...

I am SO jealous - I would barely know where to begin recreating that sequence! (I'd never thought before how ITN could've assembled it with late-70s technology. THAT would be interesting to find out.)

Nice work as ever :-)

Kecske said...

Thanks Tim. I remember reading an online conversation where television producer Gareth Randall and others discussed just how they ITN have done it in the 70s. Trouble is, I can't remember where I read it now!