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BACKGROUND OF THE INVENTION
The invention relates to the field of televisions capable of displaying
side by side pictures of substantially equal size from different sources,
and in particular, to such televisions having a wide display format ratio
screen. Most televisions today have a format display ratio, horizontal
width to vertical height, of 4:3. A wide format display ratio corresponds
more closely to the display format ratio of movies, for example 16:9. The
invention is applicable to both direct view televisions and projection
televisions.
Televisions having a format display ratio of 4:3, often referred to as
4.times.3, are limited in the ways that single and multiple video signal
sources can be displayed. Television signal transmissions of commercial
broadcasters, except for experimental material, are broadcast with a
4.times.3 format display ratio. Many viewers find the 4.times.3 display
format less pleasing than the wider format display ratio associated with
the movies. Televisions with a wide format display ratio provide not only
a more pleasing display, but are capable of displaying wide display format
signal sources in a corresponding wide display format. Movies "look" like
movies, not cropped or distorted versions thereof. The video source need
not be cropped, either when convened from film to video, for example with
a telecine device, or by processors in the television.
Televisions with a wide display format ratio are also suited to a wide
variety of displays for both conventional and wide display format signals,
as well as combinations thereof in multiple picture displays. However, the
use of a wide display ratio screen entails numerous problems. Changing the
display format ratios of multiple signal sources, developing consistent
timing signals from asynchronous but simultaneously displayed sources,
switching between multiple sources to generate multiple picture displays,
and providing high resolution pictures from compressed data signals are
general categories of such problems. Such problems are solved in a wide
screen television according to this invention. A wide screen television
according to various inventive arrangements is capable of providing high
resolution, single and multiple picture displays, from single and multiple
sources having similar or different format ratios, and with selectable
display format ratios.
Televisions with a wide display format ratio can be implemented in
television systems displaying video signals both at basic or standard
horizontal scanning rates and multiples thereof, as well as by both
interlaced and noninterlaced scanning. Standard NTSC video signals, for
example, are displayed by interlacing the successive fields of each video
frame, each field being generated by a raster scanning operation at a
basic or standard horizontal scanning rate of approximately 15,734 Hz. The
basic scanning rate for video signals is variously referred to as f.sub.H,
1f.sub.H, and 1H. The actual frequency of a 1f.sub.H signal will vary
according to different video standards. In accordance with efforts to
improve the picture quality of television apparatus, systems have been
developed for displaying video signals progressively, in a noninterlaced
fashion. Progressive scanning requires that each displayed frame must be
scanned in the same time period allotted for scanning one of the two
fields of the interlaced format. Flicker free AA--BB displays require that
each field be scanned twice, consecutively. In each case, the horizontal
scanning frequency must be twice that of the standard horizontal
frequency. The scanning rate for such progressively scanned or flicker
free displays is variously referred to as 2f.sub.H and 2H. A 2f.sub.H
scanning frequency according to standards in the United States, for
example, is approximately 31,468 Hz.
Television apparatus with conventional format display ratios can be
equipped for displaying multiple pictures, for example from two video
sources. The video sources may be the tuner in the television, a tuner in
a video cassette recorder, a video camera, and others. In a mode often
referred to as picture-in-picture (PIP), the tuner in the television
provides a picture filling most of the screen, or display area, and an
auxiliary video source provides a small inset picture generally within the
boundaries of the larger picture. A PIP display mode in a wide screen
television apparatus is shown in FIG. 1 (c). In many instances, the inset
picture can be positioned in a number of different locations. Another
display mode is often referred to as channel scan, wherein a large number
of small pictures, each from a different channel source, fill the screen
in a freeze frame montage. There is no main picture, at least in terms
size. A channel scan display mode in a wide screen television apparatus is
shown in FIG. 1(i). In wide screen television apparatus, other display
modes are possible. One is referred to as picture-outside-picture (POP).
In this mode, several inset auxiliary pictures can share a common boundary
with a main picture. A POP display mode in a wide screen television
apparatus is shown in FIG. 1(f). Another mode particularly suited for a
wide screen television is side by side pictures of substantially the same
size, from different video sources, for example two different channels.
This mode is illustrated for a wide screen television in FIG. 1(d) for two
4:3 video sources. It will be appreciated that this mode can be considered
a special case of the POP mode.
Horizontal scanning is accomplished in the same amount of time in a wide
screen television apparatus as in a conventional television apparatus.
However, the distance of the horizontal scan is greater in the wide screen
television. This will stretch the picture horizontally, creating
significant aspect ratio distortion of the images in the displayed
picture. Accordingly, problems can be encountered when displaying a video
signal having a conventional 4:3 display format ratio on a wide screen
television apparatus, for example one having a 16:9 format display ratio.
These particular format display ratios would result in a horizontal
stretching or expansion by a factor of 4/3. This is a problem for
displaying pictures having a 4:3 display format ratio as a main picture
and as an auxiliary picture, such as a PIP or POP. This is also a problem
for PIP and POP modes even if the main picture originates from a video
source having a 16:9 format display ratio which matches the display means
of the television apparatus.
Certain digital circuits, sometimes referred to generally as
picture-in-picture processors, are available which can implement PIP and
channel scan modes in a conventional television apparatus. One such
picture-in-picture processor is designated as a CPIP chip and is available
from Thomson Consumer Electronics, Inc. The CPIP chip is described more
fully in a publication entitled The CTC 140 Picture in Picture (CPIP)
Technical Training Manual, available from Thomson Consumer Electronics,
Inc., Indianapolis, Ind. Such picture-in-picture processors are not
suitable for implementing special display modes, such as PIP, POP and
channel scan, in wide screen television apparatus. If an auxiliary picture
developed by such a picture-in-picture processor from an auxiliary video
source were displayed on a wide screen television apparatus without an
external speedup circuit, the auxiliary picture, or pictures, would be
geometrically distorted as described above. The auxiliary picture would
exhibit a horizontal expansion by a factor of 4/3 due to the wider
horizontal scanning of the wider picture tube, whether direct view or
projection. If an external speedup circuit were used, the auxiliary
picture would appear without aspect ratio distortion, but would not fill
the screen or fill the portion of the screen otherwise allotted for the
auxiliary display.
A wide screen television can be provided with a signal processor for
distorting a video signal, for example an auxiliary video signal, such
that upon subsequent display the auxiliary picture will exhibit no image
aspect ratio distortion. The distortion can be implemented as an
asymmetric compression. The compression factors will depend upon the
relative display format ratios of the auxiliary video signal and the wide
screen television apparatus. In order to display an auxiliary video signal
having a 4:3 display format ratio on a television apparatus having a 16:9
format display ratio, The auxiliary picture will be horizontally
compressed by a factor of 4:1 and vertically compressed by a factor of
3:1. In a television apparatus having a different display format ratio,
for example 2:1, the horizontal compression factor would be 1.5 times
greater than the vertical compression factor. The asymmetric compression
produces geometrically distorted pictures which can then be stored in a
video memory associated with a picture-in-picture processor. When the
asymmetrically compressed auxiliary picture is read out of memory, in
accordance with the normal operation the picture-in-picture processor, the
resulting auxiliary display exhibits no aspect ratio distortion and is
proper size for its intended purpose, whether PIP, POP, channel scan or
otherwise. The horizontal expansion realized lay scanning in the wider
television tube exactly cancels the extra compression, that is the
asymmetric part, done prior to storage in the video memory.
SUMMARY OF THE INVENTION
A video display system for side by side pictures according to an inventive
arrangement comprises analog to digital converters for quantizing first
and second video signals, representing first and second pictures
respectively, at higher and lower levels of quantization resolution
relative to one another. The analog to digital converters can operate at
different sampling rates. The picture represented in the lower sampling
rate signal can have the appearance of being subsampled, relative to the
other picture. A video display is synchronized with the first video
signal. The second video signal is synchronized with the first video
signal. A signal processing circuit modifies the first and second video
signals to represent the first and second pictures respectively in sizes
smaller than the video display. A multiplexing circuit combines the
processed video signals for side-by-side display of said pictures. A
quantization resolution enhancing circuit improves the perceived quality
of the video signal having the lower level of quantization resolution. The
side by side pictures can displayed substantially without image aspect
ratio distortion, as well as with different relative amounts of cropping
and image aspect ratio distortion.
A video display system for synchronizing side by side pictures according to
an inventive arrangement comprises a first video signal source of a first
picture and a second video signal source of a second picture. A first
signal processor speeds up the first video signal. A video display is
synchronized with the first video signal. The second video signal is
vertically synchronized with the first video signal and the video display.
The second video signal is delayed by a fraction of a field period in a
field memory. A second signal processor speeds up the synchronized second
video signal. The first and second video signals are combined for side by
side display of the pictures. The first and second video signals have
first and second display format ratios respectively and the video display
has a third display format ratio greater than each of the first and second
display format ratios. If the first and second display format ratios are
each approximately 4:3 and the third display format ratio is approximately
16:9, each of the the side-by-side pictures can be displayed in a format
display ratio of approximately 8:9. If each of the video signals is
speeded up by a factor of approximately 4/3 and cropped horizontally by a
factor of approximately 1/3, each of the side by side pictures is
displayed substantially without aspect ratio distortion.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1(a)-1(i) are useful for explaining different display formats of a
wide screen television.
FIG. 2 is a block diagram of a wide screen television in accordance with
aspects of this invention and adapted for operation at 2f.sub.H horizontal
scanning.
FIGS. 3 is a block diagram of the wide screen processor shown in FIG. 2.
FIG. 4 is a block diagram of a wide screen television in accordance with
aspects of this invention and adapted for operation at 1f.sub.H horizontal
scanning.
FIG. 5 is a block diagram of the wide screen processor shown in FIG. 4.
FIG. 6 is a block diagram showing further details of the wide screen
processor common to FIGS. 3 and 5.
FIG. 7 is a block diagram of the picture-in-picture processor shown in FIG.
6.
FIG. 8 is a block diagram of the gate array shown in FIG. 6 and
illustrating the main, auxiliary and output signal paths.
FIGS. 9 and 10 are timing diagrams useful for explaining the generation of
the display format shown in FIG. 1(d), using fully cropped signals.
FIG. 11 is a block diagram showing the main signal path of FIG. 8 in more
detail.
FIG. 12 is a block diagram showing the auxiliary signal path of FIG. 8 in
more detail.
FIG. 13 is a block diagram of the the timing and control section of the
picture-in-picture processor of FIG. 7.
FIG. 14 is a block diagram of a circuit for generating the internal
2f.sub.H signal in the 1f.sub.H to 2f.sub.H conversion.
FIG. 15 is a combination block and circuit diagram for the deflection
circuit shown in FIG. 2.
FIG. 16 is a block diagram of the RGB interface shown in FIG. 2.
DETAILED DESCRIPTION OF THE INVENTION
The various parts of FIG. 1 illustrate some, but not all of the various
combinations of single and multiple picture display formats which can be
implemented according to different inventive arrangements. Those selected
for illustration are intended to facilitate the description of particular
circuits comprising wide screen televisions according to the inventive
arrangements. For purposes of convenience in illustration and discussion
herein, a conventional display format ratio of width to height for a video
source or signal is generally deemed to be 4.times.3, whereas a wide
screen display format ratio of width to height for a video source or
signal is generally deemed to be 16.times.9. The inventive arrangements
are not limited by these definitions.
FIG. 1(a) illustrates a television, direct view or projection, having a
conventional format display ratio of 4.times.3. When a 16.times.9 format
display ratio picture is transmitted, as a 4.times.3 format display ratio
signal, black bars appear at the top and at the bottom. This is commonly
referred to as letterbox format. In this instance, the viewed picture is
rather small with respect to the entire available display area.
Alternatively, the 16.times.9 format display ratio source is converted
prior to transmission, so that it will fill the vertical extent of a
viewing surface of 4.times.3 format display. However, much information
will be cropped from the left and/or right sides. As a further
alternative, the letterbox picture can be expanded vertically but not
horizontally, whereby the resulting picture will evidence distortion by
vertical elongation. None of the three alternatives is particularly
appealing.
FIG. 1(b) shows a 16.times.9 screen. A 16.times.9 format display ratio
video source would be fully displayed, without cropping and without
distortion. A 16.times.9 format display ratio letterbox picture, which is
itself in a 4.times.3 format display ratio signal, can be progressively
scanned by fine doubling or line addition, so as to provide a larger
display with sufficient vertical resolution. A wide screen television in
accordance with this invention can display such a 16.times.9 format
display ratio signal whether the main source, the auxiliary source or an
external RGB source.
FIG. 1(c) illustrates a 16.times.9 format display ratio main signal in
which a 4.times.3 format display ratio inset picture is displayed. If both
the main and auxiliary video signals are 16.times.9 format display ratio
sources, the inset picture can also have a 16.times.9 format display
ratio. The inset picture can be displayed in many different positions.
FIG. 1(d) illustrates a display format, wherein the main and auxiliary
video signals are displayed with the same size picture. Each display area
has an format display ratio of 8.times.9, which is of course different
from both 16.times.9 and 4.times.3. In order to show a 4.times.3 format
display ratio source in such a display area, without horizontal or
vertical distortion, the signal must be cropped on the left and/or right
sides. More of the picture can be shown, with less cropping, if some
aspect ratio distortion by horizontal squeezing of the picture is
tolerated. Horizontal squeezing results in vertical elongation of objects
in the picture. The wide screen television according to this invention can
provide any mix of cropping and aspect ratio distortion from maximum
cropping with no aspect ratio distortion to no cropping with maximum
aspect ratio distortion.
Data sampling limitations in the auxiliary video signal processing path
complicate the generation of a high resolution picture which is as large
in size as the display from the main video signal. Various methods can be
developed for overcoming these complications.
FIG. 1(e) is a display format wherein a 4.times.3 format display ratio
picture is displayed in the center of a 16.times.9 format display ratio
screen. Dark bars are evident on the right and left sides.
FIG. 1(f) illustrates a display format wherein one large 4.times.3 format
display ratio picture and three smaller 4.times.3 format display ratio
pictures are displayed simultaneously. A smaller picture outside the
perimeter of the large picture is sometimes referred to as a POP, that is
a picture-outside-picture, rather than a PIP, a picture-in-picture. The
terms PIP or picture-in-picture are used herein for both display formats.
In those circumstances where the wide screen television is provided with
two tuners, either both internal or one internal and one external, for
example in a video cassette recorder, two of the displayed pictures can
display movement in real time in accordance with the source. The remaining
pictures can be displayed in freeze frame format. It will be appreciated
that the addition of further tuners and additional auxiliary signal
processing paths can provide for more than two moving pictures. It will
also be appreciated that the large picture on the one hand, and the three
small pictures on the other hand, can be switched in position, as shown in
FIG. 1(g).
FIG. 1(h) illustrates an alternative wherein the 4.times.3 format display
ratio picture is centered, and six smaller 4.times.3 format display ratio
pictures are displayed in vertical columns on either side. As in the
previously described format, a wide screen television provided with two
tuners can provide two moving pictures. The remaining eleven pictures will
be in freeze frame format.
FIG. 1(i) shows a display format having a grid of twelve 4.times.3 format
display ratio pictures. Such a display format is particularly appropriate
for a channel selection guide, wherein each picture is at least a freeze
frame from a different channel. As before, the number of moving pictures
will depend upon the number of available tuners and signal processing
paths.
The various formats shown in FIG. 1 are illustrative, and not limiting, and
can be implemented by wide screen televisions shown in the remaining
drawings and described in detail below.
An overall block diagram for a wide screen television in accordance with
inventive arrangements, and adapted to operate with 2f.sub.H horizontal
scanning, is shown in FIG. 2 and generally designated 10. The television
10 generally comprises a video signals input section 20, a chassis or TV
microprocessor 216, a wide screen processor 30, a 1f.sub.H to 2f.sub.H
converter 40, a deflection circuit 50, an RGB interface 60, a YUV to RGB
converter 240, kine drivers 242, direct view or projection tubes 244 and a
power supply 70. The grouping of various circuits into different
functional blocks is made for purposes of convenience in description, and
is not intended as limiting the physical position of such circuits
relative to one another.
The video signals input section 20 is adapted for receiving a plurality of
composite video signals from different video sources. The video signals
may be selectively switched for display as main and auxiliary video
signals. An RF switch 204 has two antenna inputs ANT1 and ANT2. These
represent inputs for both off-air antenna reception and cable reception.
The RF switch 204 controls which antenna input is supplied to a first
tuner 206 and to a second tuner 208. The output of first tuner 206 is an
input to a one-chip, 202, which performs a number of functions related to
tuning, horizontal and vertical deflection and video controls. The
particular one-chip shown is industry designated type TA7730. The baseband
video signal VIDEO OUT developed in the one-chip and resulting from the
signal from first tuner 206 is an input to both video switch 200 and the
TV1 input of wide screen processor 30. Other baseband video inputs to
video switch 200 are designated AUX1 and AUX2. These might be used for
video cameras, laser disc players, video tape players, video games and the
like. The output of the video switch 200, which is controlled by the
chassis or TV microprocessor 216 is designated SWITCHED VIDEO. The
SWITCHED VIDEO is another input to wide screen processor 30.
With further reference to FIG. 3, a switch SW1 wide screen processor
selects between the TV1 and SWITCHED VIDEO signals as a SEL COMP OUT video
signal which is an input to a Y/C decoder 210. The Y/C decoder 210 may be
implemented as an adaptive line comb filter. Two further video sources S1
and S2 are also inputs to the Y/C decoder 210. Each of S1 and S2 represent
different S-VHS sources, and each consists of separate luminarice and
chrominance signals. A switch, which may be incorporated as part of the
Y/C decoder, as in some adaptive line comb filters, or which may be
implemented as a separate switch, is responsive to the TV microprocessor
216 for selecting one pair of luminarice and chrominance signals as
outputs designated Y.sub.-- M and C.sub.-- IN respectively. The selected
pair of luminance and chrominance signals is thereafter considered the
main signal and is processed along a main signal path. Signal designations
including .sub.-- M or .sub.-- MN refer to the main signal path. The
chrominance signal C.sub.-- IN is redirected by the wide screen processor
back to the one-chip, for developing color difference signals U.sub.-- M
and V.sub.-- M. In this regard, U is an equivalent designation for (R--Y)
and V is an equivalent designation for (B--Y). The Y.sub.-- M, U.sub.-- M,
and V.sub.-- M signals are converted to digital form in the wide screen
processor for further signal processing.
The second tuner 208, functionally defined as part of the wide screen
processor 30, develops a baseband video signal TV2. A switch SW2 selects
between the TV2 and SWITCHED VIDEO signals as an input to a Y/C decoder
220. The Y/C decoder 220 may be implemented as an adaptive line comb
filter. Switches SW3 and SW4 select between the luminarice and chrominance
outputs of Y/C decoder 220 and the luminarice and chrominance signals of
an external video source, designated Y.sub.-- EXT and C.sub.-- EXT
respectively. The Y.sub.-- EXT and C.sub.-- EXT signals correspond to the
S-VHS input S1. The Y/C decoder 220 and switches SW3 and SW4 may be
combined, as in some adaptive line comb filters. The output of switches
SW3 and SW4 is thereafter considered the auxiliary signal and is processed
along an auxiliary signal path. The selected luminance output is
designated Y.sub.-- A. Signal designations including .sub.-- A, .sub.-- AX
and .sub.-- AUX refer to the auxiliary signal path. The selected
chrominance is converted to color difference signals U.sub.-- A and
V.sub.-- A. The Y.sub.-- A, U.sub.-- A and V.sub.-- A signals are
converted to digital form for further signal processing. The arrangement
of video signal source switching in the main and auxiliary signal paths
maximizes flexibility in managing the source selection for the different
parts of the different picture display formats.
A composite synchronizing signal COMP SYNC, corresponding to Y.sub.-- M is
provided by the wide screen processor to a sync separator 212. The
horizontal and vertical synchronizing components H and V respectively are
inputs to a vertical countdown circuit 214. The vertical countdown circuit
develops a VERTICAL RESET signal which is directed into the wide screen
processor 30. The wide screen processor generates an internal vertical
reset output signal INT VERT RST OUT directed to the RGB interface 60. A
switch in the RGB interface 60 selects between the internal vertical reset
output signal and the vertical synchronizing component of the external RGB
source. The output of this switch is a selected vertical synchronizing
component SEL.sub.-- VERT.sub.-- SYNC directed to the deflection circuit
50. Horizontal and vertical synchronizing signals of the auxiliary video
signal are developed by sync separator 250 in the wide screen processor.
The 1 f.sub.H to 2f.sub.H converter 40 is responsible for converting
interlaced video signals to progressively scanned noninterlaced signals,
for example one wherein each horizontal line is displayed twice, or an
additional set of horizontal lines is generated by interpolating adjacent
horizontal lines of the same field. In some instances, the use of a
previous line or the use of an interpolated line will depend upon the
level of movement which is detected between adjacent fields or frames. The
converter circuit 40 operates in conjunction with a video RAM 420. The
video RAM may be used to store one or more fields of a frame, to enable
the progressive display. The converted video data as Y.sub.-- 2f.sub.H,
U.sub.-- 2f.sub.H and V.sub.-- 2f.sub.H signals is supplied to the RGB
interface 60.
The RGB interface 60, shown in more detail in FIG. 16, enables selection of
the converted video data or external RGB video data for display by the
video signals input section. The external RGB signal is deemed to be a
wide format display ratio signal adapted for 2f.sub.H scanning. The
vertical synchronizing component of the main signal is supplied to the RGB
interface by the wide screen processor as INT VERT RST OUT, enabling a
selected vertical sync (f.sub.Vm or f.sub.Vext) to be available to the
deflection circuit 50. Operation of the wide screen television enables
user selection of an external RGB signal, by generating an
internal/external control signal INT/EXT. However, the selection of an
external RGB signal input, in the absence of such a signal, can result in
vertical collapse of the raster, and damage to the cathode ray tube or
projection tubes. Accordingly, the RGB interface circuit detects an
external synchronizing signal, in order to override the selection of a
non-existent external RGB input. The WSP microprocessor 340 also supplies
color and tint controls for the external RGB signal.
The wide screen processor 30 comprises a picture in picture processor 320
for special signal processing of the auxiliary video signal. The term
picture-in-picture is sometimes abbreviated as PIP or pix-in-pix. A gate
array 300 combines the main and auxiliary video signal data in a wide
variety of display formats, as shown by the examples of FIGS. 1(b) through
1(i). The picture-in-picture processor 320 and gate array 300 are under
the control of a wide screen microprocessor (WSP .mu.P) 340.
Microprocessor 340 is responsive to the TV microprocessor 216 over a
serial bus. The serial bus includes four signal lines, for data, clock
signals, enable signals and reset signals. The wide screen processor 30
also generates a composite vertical blanking/reset signal, as a three
level sandcastle signal. Alternatively, the vertical blanking and reset
signals can be generated as separate signals. A composite blanking signal
is supplied by the video signal input section to the RGB interface.
The deflection circuit 50, shown in more detail in FIG. 15, receives a
vertical reset signal from the wide screen processor, a selected 2f.sub.H
horizontal synchronizing signal from the RGB interface 60 and additional
control signals from the wide screen processor. These additional control
signals relate to horizontal phasing, vertical size adjustment and
east-west pin adjustment. The deflection circuit 50 supplies 2f.sub.H
flyback pulses to the wide screen processor 30, the 1f.sub.H to 2f.sub.H
converter 40 and the YUV to RGB converter 240.
Operating voltages for the entire wide screen television are generated by a
power supply 70 which can be energized by an AC mains supply.
The wide screen processor 30 is shown in more detail in FIG. 3. The
principal components of the wide screen processor are a gate array 300, a
picture-in-picture circuit 301, analog to digital and digital to analog
converters, the second tuner 208, a wide screen processor microprocessor
340 and a wide screen output encoder 227. Further details of the wide
screen processor, which are in common with both the 1f.sub.H and the
2f.sub.H chassis, for example the PIP circuit, are shown in FIG. 6. A
picture-in-picture processor 320, which forms a significant part of the
PIP circuit 301, is shown in more detail in FIG. 7. The gate array 300 is
shown in more detail in FIG. 8. A number of the components shown in FIG.
3, forming parts of the main and auxiliary signal paths, have already been
described in detail.
The second tuner 208 has associated therewith an IF stage 224 and an audio
stage 226. The second tuner 208 also operates in conjunction with the WSP
.mu.P 340. The WSP .mu.P 340 comprises an input output I/O section 340A
and an analog output section 340B. The I/O section 340A provides tint and
color control signals, the INT/EXT signal for selecting the external RGB
video source and control signals for the switches SW1 through SW6. The I/O
section also monitors the EXT SYNC BET signal from the RGB interface to
protect the deflection circuit and cathode ray tube(s). The analog output
section 340B provides control signals for vertical size, east-west adjust
and horizontal phase, through respective interface circuits 254, 256 and
258.
The gate array 300 is responsible for combining video information from the
main and auxiliary signal paths to implement a composite wide screen
display, for example one of those shown in the different parts of FIG. 1.
Clock information for the gate array is provided by phase locked loop 374,
which operates in conjunction with low pass filter 376. The main video
signal is supplied to the wide screen processor in analog form, and Y U V
format, as signals designated Y.sub.-- M, U.sub.-- M and V.sub.-- M. These
main signals are converted from analog to digital form by analog to
digital converters 342 and 346, shown in more detail in FIG. 4.
The color component signals are referred to by the generic designations U
and V, which may be assigned to either R-Y or B-Y signals, or I and Q
signals. The sampled luminarice bandwidth is limited to 8 MHz because the
system clock rate is 1024f.sub.H, which is approximately 16 MHz. A single
analog to digital converter and an analog switch can be used to sample the
color component data because the U and V signals are limited to 500 KHz,
or 1.5 MHz for wide I. The select line UV.sub.- MUX for the analog switch,
or multiplexer 344, is an 8 MHz signal derived by dividing the system
clock by 2. A one clock wide start of line SOL pulse synchronously resets
this signal to zero at the beginning of each | | |
