Video-lock and the reason it is important

Sometimes the solution to a display noise issue can be elusive. For example it may look like a cable or system noise issue or a firmware related panel signal mismatch. Or it may be simply a signal timing issue resolved by turning off video-lock.

So what is video-lock? 

Video-lock is when the timing of the output signal to the LCD panel is locked to the timing of the input signal. So input a signal of 50Hz and the result will be an output signal to the LCD panel of 50Hz.

Conversely if video-lock is turned off, as is possible on Digital View’s fully memory buffered boards such as the SVX family, then the LCD controller can provide an output timing different from the input timing. This output timing can then be matched to within the tolerance of the panel’s input signal.

How might this be important?

As in the example above if an LCD panel has a timing range that doesn’t match the input signal the LCD controller it will be necessary to turn off video-lock so the LCD controller can deliver the correct timing to the panel irrespective of the input signal timing. In some cases this might be obvious such as in the case of a 50Hz input signal where the panel has only narrow tolerance around 60Hz, however we have seen other cases where both input signal and LCD panel specification may be noted as the same but for some reason don’t match but turning video-lock off resolves the issue.

When would you want video-lock on?

In most case having video-lock on is appropriate as it will ensure the LCD display scans at the same rate as the input signal which will prevent shearing artifacts in panning video.

Related considerations…

An LCD controller with full memory buffer offers other benefits such as the ability to manage and enhance the image, motion compensation and better de-interlacing as well as support for a wider range of input frame rates.

The full frame memory buffer such as in the Digital View SVX family of LCD controllers does introduce additional latency as the image has to be loaded into memory for processing, approx 16~20ms. If near zero latency is required then LCD controllers like the Digital View ALR-1920 and ALR-1400 are suitable with approx <0.3ms.

For more information on the SVX and ALR families of LCD controllers click here.