Luma Sharpness Enhancer (Lse); Dynamic Peaking; Luma Transient Improvement (Lti); Mixing Of Dynamic Peaking And Lti - Daewoo DTK-28 Service Manual

Chassis : cp-850/f

Table of Contents

CP-850/F Service Manual

5.3.2.5 Luma Sharpness Enhancer (LSE)

Sharpness is one of the most critical features for optimum picture quality. This important processing is performed in the

LSE circuitry of DDP 3315C. It consists of the dynamic peaking, the luma transient improvement (LTI) and an adaptive

mixer. The luma input signal is processed in the peaking and LTI block in parallel. Both output signals are combined in

the mixer depending on the selected LSE characteristic.

The dynamic peaking improves the details of a picture by contour emphasis. It adapts to the amplitude and the

frequency of the input signal. Small detail amplitudes are sharpened, while large detail amplitudes stay nearly

unmodified.

For small detail amplitudes the dynamic peaking is the most appropriate processing to improve the sharpness.

However, for large amplitudes even small over-and/ or undershoots of the peaking are too annoying. The luma transient

improvement enhances the slope of picture detail without these effects by a non-linear processing. The contour

correction signal calculated in this block, is limited to the adjacent extreme values to prevent over- and undershoots.

The LTI features an adjustable gain control and an adjustable coring threshold to prevent the enhancement of small

noise amplitudes.

The contour correction signals of the dynamic peaking and the LTI block are combined by the mixer. Controlled by the

amplitude of a picture edge, this circuitry fades between these two signals. Thus, small and medium picture detail is

enhanced by contour emphasis (peaking) and large picture detail is enhanced by step-improvement (LTI).

The intention of this block is to enhance the chroma resolution. A correction signal is calculated by differentiation of the

colour difference signals. The differentiation can be selected according to the signal bandwidth, e.g. for

PAL/NTSC/SECAM or digital component signals, respectively. The amplitude of the correction signal is adjustable.

Small noise amplitudes in the correction signal are suppressed by an adjustable coring circuit. To eliminate "wrong

colours", which are caused by over and undershoots at the chroma transition, the sharpened chroma signals are limited

to a proper value automatically.

-51-

Table of Contents

Dtk-29