Graphics PC

This is the machine used to render on-screen graphics which are then overlayed onto the live video output using a Coriogen Eclipse genlock. This replaced the Commodore Amiga which had formerly performed the same function, but had become top unreliable and hard to use.

Graphics PC is a Duron 1300 with an Nvidia MX2 graphics card, both of which were considered high spec when it was built by the station in 2002Unverified or incomplete information. It was used for a short time as a video edit system before moving to it's current role with the purchase of the genlock in Autumn 2003.

A custom built box attached to the parallel port provides switches to fade graphics in and out, and select the speed of fade. This is monitored by a visual basic application written by Ed Jellard which sends the appropriate commands out of the serial port to the genlock itself to control it. This application also sends a (somewhat ill-conceived) set of configuration commands to the unit when the application is started, which attempt to adjust the edge areas of the screen to match the visible bits of the TV picture.

The main problem with the Coriogen genlock is that isn't as good as it's marketing claims. As a straight luma-keyed overlay unit it works fine, but the added features like fades in / out and automatic scan adjustment don't really work. When the hardware fades in and out there is a noticeable change in the brightness of the whole picture, and the automatic scan area adjustment has a habit of not making circles round on screen. For this reason an increasing range of software has been developed to keep all the graphics manipulation on the software side, with the genlock providing just a hardware interface from the computer to the vision chain. The down side of this is more software to look after, especially when it is custom written.