Character generator

A character generator is a computer whose main task is to convert texts set in a video signal. He finds in inserts in television shows such as belly bands or end credits application and is thus part of the On Air design of a television station.

Next, it is common for example in sports, to connect external data sources such as time measuring means to the character generator, which converts the data without operator intervention in on-screen graphics.

History

Even before the introduction of computer technology received movies and TV shows pre-or end credits in which the parties involved were listed. First and foremost were the painted by hand panels, which were filmed by a film or television camera and were cut into it until later in the finished product.

But gradually it came in the film Tricktechnik fashionable to copy the track using an optical bench in the animated motion picture. This was, however, a photographic effect that was very intricate use in the electronic medium of video.

After introduction of the keying technology, the titles have been painted on special cards or sheets and filmed by a camera. This camera was then mixed with the actual electronic image signal. Rolling or crawling titles have been realized by filming an applied on a roll text. An example of this is found in the popular television show Dinner for One. For more complex animations the cut-out animation was used, which had to be pre-produced.

The invention of a computerized system therefore represented a considerable simplification, as the title will now create cost-effective and time-saving, flexible and processed for future use could be stored relatively easily.

Technology

Character generators are often specially constructed computers, their hardware must meet special requirements of stability and signal quality. Often the character generator is supplied as a complete package of software and specialized hardware. There are, however, character generation, which are integrated as software in existing video editing programs, such as Adobe Premiere, Avid and Final Cut Pro.

With the hardware character generators, the texts are placed on the screen, passed as an analog or digital video signal to a video mixer and there, mixed with the main image, the background signal. This usually happens "live ", ie in direct temporal relation to a television broadcast or production.

Thus, the video signal of the character generator, the fill signal, the background image is not completely covered, it must be keyed, so be masked. Here, the signature signal is " cut " that only its relevant parts, ie letters and graphics, can be seen in the mixed signal. The technical facilities for the Key operation today are usually fully integrated into the video mixer.

For the display itself comes at the switchers often called the Downstream Key used. However, this does not denote a particular key technique, but a special component of the image mixer. The display is placed at the end of the signal chain within the image mixer on the picture, so after all other image editing operations have already been made. This makes it possible to tap the clean feed before this last processing step. This is an image signal, the insertions of the character generator missing.

Keying the various methods can be applied. Often this is done through a luminance key, in which the darkest parts of the character generator signal are transparent. However, this is only useful if the font is relatively bright and the font generator signal contains any games, the dark, but also opaque, so do not want to be transparent on the one hand. If the contour of a letter, for example, black to make the letters visible on bright backgrounds, the luma key would also represent this contour transparent.

It is common to use a so-called linear Key: where a further signal in addition to the actual video signal sent to the video mixer, the key signal which describes the transparent parts. This signal is similar to the alpha channel in the image processing.

The key signal must be thought of as full-resolution black / white television signal. The brightness of a given pixel of this signal is crucial for the transparency with which the corresponding pixel of the fill signal is superimposed on the background signal.

On a deeper level all character generators based on character generators that do the basic representation of ( individual ) character on a screen.

Development

With the development of technology since the early 1980s, it became possible to involve graphics in the set text to work with multiple layers or animate text and graphics. Today, the possibilities offered by a character generator, grown: So you can now also integrate video clips and create complex 3D animations. Thus, the application areas of a character generator combine with those of a digital video effects device.

The Commodore Amiga was a continuous tape from the outset to video applications computer system. Especially his genlock capability - along with the overscan support - made ​​him from the mid-1980s to an often used device in video studios. A dedicated genlock interface led to the Amiga it from outside the studio clock to synchronized while the whole computer to this clock so that its video output could be easily mixed with other studio signals, the latter often in genlock interface itself was the type of display case be varied from hard to soft overlay to fade-in. This allowed for the first time with a simple programming of a microcomputer ( a pinch in BASIC) effects such as insert text in any size, color and design and of other arbitrary graphics - all also animated on request - be realized with a simple tabletop device. A special application was for a long time using Amigas to generate the channel logos in one of the corners of the screen.

Today's PCs are to take over from its calculation capabilities quite capable, the work of a font generator. But this is true only under the condition that appropriate expansion cards are installed that provide a sufficient quality video signal. Typically it involves a SDI signal. The quality of the composite signal of a normal consumer graphics card is not sufficient. And the better quality signal components must have a sufficient bandwidth. If the font generator used in live broadcasts, so the demands on the stability and reliability of the software and hardware are also much higher.

In general, a transition from the pure special solutions can currently be seen at building on PC technology systems. An example of this are the Chyron systems that run under the Windows operating system, but continue to be sold as complete systems. However, PCI expansion cards are available with which you can upgrade a regular PC to a font generator.

Manufacturer

• Viz | Engine / Viz | Artist
• Pixel Power
• Chyron
• Inscriber / Leitch / Harris
• Aston Broadcast Systems
• Type of Pinnacle Deko
• XPression by Ross Video

• Video technology
• Computer
• Written Communication