Cameron KS21TK305A, Руководство по обслуживанию

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SERVICE MANUAL
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•
Blue-stretch. This circuit is intended to shift colour near
‘
white
’
with sufficient contrast values
towards more blue to obtain a brighter impression of the picture.
•
Dynamic skin tone (flesh) control. This function is realised in the YUV domain by detecting the
colours near to the skin tone.
•
Scan-Velocity modulation output. Also the SVM function can be activated for all incoming CVBS,
Y/C and RGB/YPBPR signals. The delay between the RGB output signals and the SVM output
signal can be adjusted (by means of the SVM2-SVM0 bits in subaddress 48H) so that an optimum
picture performance can be obtained. Furthermore a coring function can be activated. It is possible
to generate Scan Velocity Modulation drive signals during the display of
‘
full screen
’
teletext (not in
mixed mode). Another feature is that the SVM output signal can be made dependent on the
horizontal position on the screen (parabola on the SVM output).
The effect of the various features can de demonstrated by means of the
‘
split-screen
’
mode.
When the TV receiver is switched to this mode the features are switched on in the left half of the
picture and switched off in the right half of the picture or vice versa. It is possible to add a signal
blanking in the middle of the screen. The features that are switched on and off are: peaking, scan
velocity modulation, black stretch, gamma control, DC transfer ratio, blue stretch, dynamic skin
tone control, tint on U/V and soft clipping.
1.8.10 Colour decoder
The ICs decode PAL, NTSC and SECAM signals. The PAL/NTSC decoder does not need
external reference crystals but has an internal clock generator which is stabilised to the required
frequency by using the clock signal from the reference oscillator of the TCG m-Controller.
Under bad-signal conditions (e.g. VCR-playback in feature mode), it may occur that the colour
killer is activated although the colour PLL is still in lock. When this killing action is not wanted it is
possible to overrule the colour killer by forcing the colour decoder to the required standard and to
activate the FCO-bit (Forced Colour On) in subaddress 3CH. The sensitivity of the colour decoder
for PAL and NTSC can be increased by means of the setting of the CHSE1/CHSE0 bits in
subaddress 3CH.
The Automatic Colour Limiting (ACL) circuit (switchable via the ACL bit in subaddress 3BH)
prevents that oversaturation occurs when signals with a high chroma-to-burst ratio are received. The
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