STV3550 datasheet(28/144 Pages) STMICROELECTRONICS

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STV3550

3.3.4

Brightness Estimator

The Brightness Estimator provides the value of the average field brightness of the picture. It can be

used to hardware tune the two brightness correction functions (spectral processing and contrast

enhancer).

Otherwise, a manual mode enables the CPU to force the average brightness value of the image.

3.3.5

Histogram

A high-resolution, non-linear histogram that uses 16 levels to characterize the image luminance is

included.

The accumulation of the histogram is done through an entire field and is ready to be used at the

next V sync signal. A window for histogram calculation can be selected for reducing the image size

which will be used for histogram processing.

3.3.6

Contrast Enhancer

The luminance processing block works only on the low pass spectrum of the input signal.

All these algorithms are based on the same model (Figure 15) that uses three different segments

for contrast modification: the high limit (Yhl), the low limit (Yll) and the middle segment (Ym).

Figure 14: Image Improvement Block Diagram

Contrast Enhancer

Chrominance Processing

Spectral Processing

Input Stage

Yin

Low pass

High pass

Mix

Yout

Adaptive Peaking

& Coring

Black Stretch

White Stretch

Grey Stretch

B&W Shrink

Average

Brightness

Filtering

Brightness

Estimator

Cbin, Crin

Cbout, Crout

Color Transient

Improvement

Histogram

Autoformat

Detection

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