SPT2110 查看數據表（PDF） - Signal Processing Technologies

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SPT2110

NTSC/PAL VIDEO DECODER

Signal Processing Technologies 

LUMINANCE PROCESSING

LUMINANCE SEPARATION

For composite video the luminance needs to be separated

from chrominance in the baseband video. Each is processed

separately. Selection of the separation method is determined

by register 3H. Separation of the luminance from the chromi-

nance is performed by a 2H comb, 1H comb or trap filter.

Comb filtering is available for NTSC signal processing only.

The comb is the best filter method for composite video. The

trap filter method of separation reduces the dynamic perfor-

mance of the luminance signal above 2.3 MHz due to the filter

transfer function.

This separation is not necessary for component (Y/C, S-Video).

The comb filtering is inhibited, and the digitized data is sent

on to the luma processing circuitry.

SYNC SEPARATOR

The sync signals are separated from the luminance compo-

nent and sent to the timing control circuit. The sync pulses are

used to synchronize the timing of the number of pixels per

line, number of lines, and odd field identification.

LUMINANCE MUX

A 2:1 mux is used to multiplex the digital luminance compo-

nent data to either the trap filter or comb filter.

AGC

Automatic Gain Control (AGC) for the luminance signal is

derived from the amplitude of the sync signal. The video

luminance is scaled by the value derived from the sync signal

value. This is a very important feature for nonstandard video

signal values. In addition, the sync is removed from the

luminance signal at this stage before further luminance

processing.

PICTURE QUALITY FUNCTIONS

signal levels. With the pass-band and the coring levels set,

the peaking compensation value is applied to those lumi-

nance signals that fit in the selected profile. Peaking is a

multiplicative factor that gains up the selected frequencies.

The higher the peaking factor the more gain provided for

those selected frequencies. Peaking is controlled by register

8H.

Brightness is controlled by register 12H. This puts an additive

value to the luminance signal. This additive value is plus or

minus 32 LSBs of the luminance signal. It is a DC value for the

luminance signal. Brightness is applied after luminance sig-

nal correction is performed.

Contrast is controlled by register 11H. This setting applies a

multiplying factor to the luminance signal. The coefficient

multiplies the luminance value after it has been corrected.

SYNC REINSERTION

The sync signals are reinserted into the luminance signal

after all luminance signal processing is performed.

LUMINANCE SAMPLE ALIGNMENT

Sample alignment circuitry ensures the same number of

pixels per line and field/frame. Counting registers control this

process based on the mode of operation. They determine the

number of pixels per line and the number of lines per field.

LUMINANCE COLOR SPACE CONVERSION

The color space conversion block uses the luminance signal’s

value to transform from the NTSC or PAL system format that

was originally digitized to either RGB of YCrCb. This process

requires the values of both luminance and chrominance be

synchronized in time to make this conversion correctly. The

transformation to RGB or YCrCb is performed using the

luminance and color difference signal data.

CHROMINANCE PROCESSING

LUMINANCE SIGNAL CORRECTION

Luminance signal correction is composed of three luminance

digital signal processing functions. These functions include

selecting a frequency pass band that will be further en-

hanced, a coring function and a peaking function. The peak-

ing function must be set to a compensation value (other than

zero, default) for either of the other two functions to be

enabled. The Pass-Band (PBAND) Filter is controlled by

register 6H. It sets the lower limit of the pass band filter. These

frequencies will be peaked further downstream. The coring

function provides a hysteresis effect on pixel-to-pixel data

value changes based on a threshold coring level set by the

core register 7H. Coring is performed on the pre-peaked

COLOR SEPARATION

For composite video, the chrominance needs to be separated

from luminance in the baseband video. Each is processed

separately. Selection of the separation method is determined

by register 3H. Separation of the chrominance from the

luminance is performed by a 2H or 1H comb filter or the trap

filter. The comb separation is the best separation method for

composite video. Comb filtering is available for NTSC signal

processing only.

For component (Y/C, S-Video), this separation is not neces-

sary. The comb filter is inhibited and the digitized chromi-

nance data is sent on for chroma processing.

SPT

6

SPT2110

3/27/98

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