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TDA9178
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.
In the demonstration mode all the features selected by the user are automatically toggled between on and off.
The TDA9178 concept has a maximum flexibility which can be controlled by the embedded I²C-bus. The supply voltage is 8 V. The device is mounted in a 24-lead SDIP package, or in a 24-lead SO package.
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).
Design support
Application Notes
AN99063_1;
TV Reference design GTV4000 update (02-Nov-99)
Support Documents
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