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TDA9178T

YUV one chip picture improvement based on luminance vector-, colour vector- and spectral processor

Philips Electronics 

Philips Semiconductors

Preliminary specification

YUV one chip picture improvement based on luminance

vector-, colour vector- and spectral processor

TDA9178

FEATURES

• Picture content dependent non-linear Y, U and V

processing by luminance histogram analysis

• Variable gamma control

• Adaptive black and white stretch control

• Skin tone correction

• Green enhancement

• Blue stretch

• Luminance Transient Improvement (LTI)

• Smart peaking for detail enhancement

• Colour Transient Improvement (CTI)

• SCAn VElocity Modulation (SCAVEM) output

• Line Width Control (LWC)

• Video Dependent Coring (VDC)

• Colour Dependent Sharpness (CDS)

• Noise measurement

• Feature Mode (FM) detector

• Cue Flash (CF) detector

• Three additional pins for access to 6-bit ADC and

I2C-bus

• Adjustable chrominance delay

• TV standard independent

• I2C-bus controlled

• 1fH and 2fH

• DEmonstration MOde (DEMO).

GENERAL DESCRIPTION

The TDA9178 is a transparent analog video processor

with YUV input and output interfaces. It offers three main

functions: luminance vector processing, colour vector

processing and spectral processing. Beside these three

main functions, there are some additional functions.

In the luminance vector processor, the luminance transfer

function is controlled in a non-linear way by the

distribution, in 5 discrete histogram sections, of the

luminance values measured in a picture. As a result, the

contrast ratio of the most important parts of the scene will

be improved. Black restoration is available in the event of

a set-up in the luminance signal.

A variable gamma function, after the histogram

conversion, offers the possibilities of alternative brightness

control or factory adjustment of the picture tube.

The adaptive black stretch function of the TDA9178 offers

the possibility of having a larger ‘weight’ for the black parts

of the video signal; the white stretch function offers an

additional overall gain for increased light production.

To maintain a proper colour reproduction, the saturation of

the U- and V-colour difference signals is also controlled as

a function of the actual non-linearity in the luminance

channel.

In the colour vector processor, the dynamic skin tone

correction locally changes the hue of colours that match

skin tones to the correct hue. The green enhancement

circuit activates medium saturated green towards to more

saturated green. The blue stretch circuit can be activated

which shifts colours near white towards blue.

The spectral processor provides 1D luminance transient

improvement, luminance detail enhancement by smart

peaking and a 1 D colour transient improvement.

The TDA9178 can be used as a cost effective alternative

to (but also in combination with) scan velocity modulation.

In the spectral processor line width control (or aperture

control) can be user defined. The TDA9178 is capable of

adjusting the amount of coring according to the video level

with the video dependent coring. The TDA9178 is also

capable to give extra sharpness in the cases of saturated

red and magenta parts of the screen using the colour

dependent sharpness feature.

An embedded noise detector measures noise during the

field retrace in parts which are expected to be free from

video or text information. With the noise detector a variety

of ‘smart noise control’ architectures can be set up.

A feature mode detector is available for detecting signal

sources like VCR (in still picture mode) that re-insert the

levels of the retrace part. For this kind of signals the noise

measurement of the TDA9178 is not reliable.

An output signal (on the I2C-bus and on a separate pin) is

available that detects when the picture content has been

changed significantly, called cue flash.

An embedded 6-bit ADC can be used for interfacing three

analog low frequency voltage signals (e.g. ambient light

control or beam current voltage level) to the I2C-bus.

1999 Sep 24

2

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