Genlock

As a genlock (generator locking device) the ability of video signal sources is referred to can be synchronized in frequency and phase of the image change from the outside, so that for example two signal sources can be mixed uninterrupted and fault- free or can be switched between them. In studio environments, the synchronization is usually done by an externally generated clock studio, video signals from computers are synchronized to the external video signal to be processed.

For this, a PLL is often employed. Those obtained from the most low-frequency clock signal (e.g., the television sync signal ) a higher-frequency signal (for example, pixel clock ), which is then used in place of its own free running oscillator signal.

If the video signal at the output is not always clean enough, a Time Base Corrector (TBC ) is used for security often connected behind it.

In the IT Genlocks often also contain small video mixer, with which it is possible to combine the generated by the computer image with an image provided by an external source.

PC Genlock

In the PC area a Genlock for synchronizing the PC is used on a studio clock. Mind you, the entire video portion of the PC on these external clock is then synchronized and is therefore dependent on its correctness. ( In particular, provisions for the event must be taken that the external clock fails, . Then the PC should not remain, of course ) the same is set ( in the PAL region ) is the vertical refresh rate to 50 Hz in order at a standard resolution of 720 × 576 points to allow a smooth output of animation, video, ticker, etc.. ( Instead 720 × 480 points are used at 59.94 Hz for NTSC ).

Dignity among PAL refresh rates continue to run with for example 60 or 70 Hz, would be applicable no clean animation because the computer would then calculate the animation with 60 or 70 Hz. Inevitably, then 10 or 20 pictures too much, and the animation is lagging. This can also be observed at various scan converters that simply take a VGA signal at 60 or 70 Hz and 50 Hz on this umkonvertieren: For still images, this works well, but moving images stutter very strong.

When real genlock the image is also not interpolated or changed in size. This maintains the quality of the PC image with 720 × 576 points in full.

In addition Genlocks offer often an overlay function (defined as a transparent mask, usually simply by choosing a particular color) by Key to punch the PC graphics into a video signal. This can be much more, for example for logo, ticker, PIP display be used.

Amiga Genlock

The Amiga computer by Commodore was the pioneer of this technology in the field of personal computers. Here not only the video part, but contains the entire computer to the external clock source is synchronized, a tribute to the optimized resolutions on television design of this platform. The Amiga was with this feature for about 10 years for the standard equipment for home and professional video studios. Some broadcasters used this technique a long time to display their station logo in a corner of the current program.

  • Video technology
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