Note: Descriptions are shown in the official language in which they were submitted.
3~8~S
COMPATIBILITY OF WIDESCREEN AND
NON-WIDESCREEN TELEVISION TRANSMISSION
BAC~GROUND OF THE INVENTION
Technical Field
This invention relates to the transmission of
widescreen television signals for reception and display
on both widescreen televisions and non-widescreen
televisions. The term "widescreen television" refers to
a television having a display whose ratio of width to
height (the aspect ratio) is greater than a
predetermined reference value.
One aspect of this invention allows the
widescreen transmission to be displayed either in its
entirety on a widescreen display or in a contiguous
portion on a non-widescreen receiver. Another aspect of
this invention relates to the inverse operation of
allowing a non-wide-screen transmission to be displayed
on a widescreen display wherein the aspect ratio of the
displayed picture is that of a non-widescreen display.
As reference now will have to be made to the
drawings, these will first be briefly described as
follows:
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an amplitude-vs.-frequency
diagram illustrating in simplified form a typical NTSC
color television signal.
Figure 2 is an amplitude-vs.-time diagram of a
typical NTSC color television signal.
Figure 3 is an amplitude-vs.-time diagram of a
single video line of a typical MAC color television
signal.
Figure 4 is a simplified block diagram of the
decoder of the present invention wherein a MAC
widescreen color television signal is transmitted for
display on both widescreen and standard screen displays.
Figure 5 is a simplified block diagram of the
clock frequency generator circuitry required by the
decoder of Figure 4.
Figure 6 is a simplified block diagram of the
decoder of the present invention wherein an NTSC
widescreen television signal is transmitted for display
on both widescreen and standard screen displays.
Figure 7 is a simplified block diagram of the
decoder of the present invention wherein a conventional
NTSC television signal is displayable on a widescreen
display.
Background Information
The current standard of all television
broadcasts has an aspect ratio (the ratio of the
display width to the display height) of 4:3, or 1.3333.
This aspect ratio was based on the motion picture
practice at the time of standardization.
In the United States, Canada and Japan, color
broadcasts are made according to the National Television
System Committee (NTSC) composite standards. Color
video signals broadcast under the NTSC standard require
that picture information be separated into two compo-
nents: luminance, or brightness, and chrominance, or
color. Figure l is an amplitude-vs.-frequency diagram
illustrating, in simplified form, a
~8~5
-- 2 --
typic~l NTSC composite color television signsl 50 comprising ~
luminance signal 52 and a chrominance signal 54. (A composite televi-
sion sign~l is one in which chrominance information is csrried on
subcarrier.) The sign~l occupies a nominal bandwidth of 6 M~z with
the picture c~rrier 56 being 1.25 MHz above the lower end of the
band. Luminance information is modulated directly onto picture
carrier 56, while chrominance information is modulated onto color
subcarrier 58 which is in turn used to modulate picture carrier 56.
Color subc~rrier 58 has a frequency of 3.579545 MHz, 8 standsrd
established by the NTSC. (Audio information is carried on another
subcarrier 40 Iying near the upper edge of the band.)
Television signals &re produced and displayed as ~ result of
line scsnning process. The picture information is scsnned using a pro-
gressive series of horizontal lines which are transmitted sequentiallv in
time. The transmitted signal is a continuous analogue of the
brightness intensity corresponding to each point of the line. Such 8
signal is shown in Figure 2 from which it may be seen that in a
series of standard lines, any two adj~cent active line periods (periods
during which video inform~tion is trsnsmitted) ~re separated by a
period in which no video information is trsnsmitted. This latter period
is known as the line blanking interval and is introduced to allow the
scanning device in the receiver to reset to the line-start position.
In the NTS C st~ndard, the active line period includes one signal
which simultaneously represents the inst&ntaneous values of three inde-
pendent color components. Other composite signals, SECAM, which is
used in France, and PAL, which predominates the rest of Europe, hs ve
the sa m e basic format as the NTSC standard, including a line-blanking
interval and an active line period in each scfln.
The region labeled A in Figure 1 is of particular importance for
it represents overlap between the luminsnce 52 and chrominance 54
sign~ls. Since sepsration of luminance and chrominance is accomplished
by filtering a frequency-division multiplexed signal, overlaps such a5 A
s
between the two signAls lead to several problems. If, upon reception,
complete separation between luminance and chrominance is desired, the
necessary filtering will cause the loss of some of the information in
both signals. On the other hsnd, if no loss of inform~tion csn be
tolerated, then one must accept interference between the luminance
and chrominance signals. Moreover, since the various parts of the
NTSC television signals are transmitted at different frequencies, phase
shifts occurring during transmission will affect them differently, causing
the signal to deteriorate. Also, the available color information is
severely limited by the small color b~ndwidth permitted.
Other types of analogue video signals which are particulsrly
sdapted to transmission by satellite Qnd cable, and which lead to
improved picture quality in comparison with existing standards, are
presently being studied. These sign~ls are based on a time multiplex
of the three independent color components during the active line period
of the scan line. Instead of coding the three components into one
signal using the NTSC, PAL or SECAM standard, the components are
sent sequentially using a time-compression technique. One version of
this type of signal is know as MAC (Multiplexed Analogue Components).
Signals gener~ted by a t~me compression technique also adhere to the
same b~sic format ~s the NTSC, PAL and SECAM standards, including
the presence of ~ line-blanking interval and an ective line period in
each scan line. It should be noted that when a MAC signal is
employed, digital data may also be transmitted during the line-blanking
interval.
A MAC color television signAl is illustrated in Figure 3, which is
an amplitude-vs.-time diagram of a single ~rideo line of 63.56 us
duration. The first l0.9 us is in the horizontal blanking intervsl
(HBI) 62, in which no picture information is transmitted. Following
HBI 62 are chrominance signal 64 Qnd lumin~nce signal 66, either of
which mhy be time-compressed. Between chrominanee signal 64 and
lumin~nce signal 66 is a 0.28 us guard band 68, to assist in preventing
interference between the two signals.
~8~S
The MAC color television signal of Figure 3 is obt~ined by
generating conventional luminance and chrominance signals (as would be
done to obtain a conventional NTSC or other composite color television
signal) snd then sampling and storing them separately. Luminance is
sampled at Q luminance sampling frequency and stored in a luminance
store, while chrominance is sampled at a chrominance sampling
frequency and stored in a chrominance store. The luminance or
chrominflnce samp2es may then be compressed in time by writing them
into the store st their individual sampling frequency and reading them
from the store at a higher frequency. A multiplexer selects either
the luminance store or the chrominance store, at the appropriate time
during the active line period, for reading, thus creating the MAC
signal of Figure 3. If desired, audio samples may be transmitted
during the HBI; these are multiplexed (and may be compressed) in the
same manner as the video samples. The sample rate at which all
samples occur in the multiplexed MAC signal is c~lled the MAC sam-
pling frequency.
With the adoption of a new transmission standard, a new and
improved television service should offer a wider aspect ratio for,
among other ressons, motion pictures h~ve adopted wider aspect ratios.
For example, motion pictures are commonly filmed with sspect ratios
of 1.85:1. The Society of Motion Plcture and Television Engineers
tSMPTE) ~avors an ~spect ratio for a television production standard of
16:9, which is the square of the standard 4:3 television aspect ratio.
Another aspect ratio under consideration for new television systems is
5:3.
With the introduction of a widescreen television receiver, more
samples per line of active video will occur in order to display the
picture on the wider screen. Thus, the sampling rate of the picture
elements will be higher if more samples are to be transmitted during
the same active video line time. Correspondingly, the sample rate at
the widescreen receiver would have to be higher.
~3~ S
-- 5 --
One problem with the introd~lction of any new television system
is its compatibility with the standard 4:3 ~spect ratio receivers
presently in use by the public.
One way to ~chieve compatibility is to transmit two television
signals, one having the widescreen ~spect ratio for receivers having a
widescreen and the other having the standard aspect ratio for receivers
having the standard screen. The standard aspect ratio television
picture could be generated by selecting a portion of the widescreen
picture. Both could be transmitted simultaneously for the simultsneous
receipt at both aspect r~tio televisions. The method of selecting a
portion of the widescreen picture is known in the prior art. For
example, U.S. Patent No. 4,476,493, issued to Poetsch et ~l., and U.S.
Patent No. 4,223,343, issued to Belmares-Sarabia et al. both discuss
this method of selecting d portion of H widescreen picture for displfly
on standard televisions. This method, however, is costly for it requires
dual storage and transmission of every picture.
Another possibility is to transmit the entire widescreen television
sign~l and let the standard ~spect ratio television skip alternate sam-
ples, allowing the widescreen picture to fit on the standard display.
Such a method is described in U.S. Patent No. 4,134,128, issued to
Hurst. However, this method causes geometric distortion of the
picture on the stAndard display.
Another posslble method is to display the widescreen picture on
the standard displ~y, c~using the widescreen picture width to be
squeezed into the st~ndard display and the height to be disp~ayed by
only 8 portion of the stsndard display height so as to affect a
simulated widescreen aspect ratio. This method is contemplated in
U.S. Patent No. 4,394,690, issued to Kobsyashi. This method, however,
~Iso geometrically distorts the picture, in addition to r~ot making full
use of the display screen.
Another problem with the introduction of any new television
system is that the broadcasts or home recorded versions of 4:3 aspect
~;~ 3!8~5
ratio television signals would not be compatible with
the new widescreen television receivers.
SUMMARY OF THE INVENTION
It is therefore an object of an aspect of the
present invention to transmit a widescreen television
signal for display on both a widescreen receiver and a
non-widescreen receiver without introducing geometric
distortion.
It is an object of an aspect of the present
invention to transmit a widescreen television signal for
display on a non-widescreen receiver wherein a
contiguous portion of the widescreen signal is
displayed.
It is an object of an aspect of the present
invention to transmit a widescreen television signal for
reception at both widescreen and non-widescreen
receivers in either NTSC or MAC format, and to do so in
the same time used to transmit NTSC signals currently in
use for non-wide~creen receivers.
It is an object of an aspect of the present
invention to display non-widescreen television pictures
on widescreen displays, and to do so without introducing
geometric distortion.
Various aspects of this invention are as follows:
A method of transmitting a widescreen television
signal so as to display a portion of the widescreen
television signal without geometric distortion on a non-
widescreen television, the method comprising the steps
of:
~36:18~5
6a
selecting the portion of the widescreen television
signal;
developing a selection signal representative of the
selected portion; and
transmitting the entire widescreen television
signal together with the selection signal.
A method of displaying a line of a widescreen line-
and-field scanned television signal so as to display the
entire line on a widescreen receiver's display and a
portion of the entire line on a non-widescreen
receiver's display, the method comprising the steps of:
selecting the portion of the line;
developing a selection signal representative of the
selected portion;
transmitting the entire line;
transmitting the selection signal;
receiving the entire line at the widescreen
receiver;
displaying the entire line on the widescreen
receiver's display;
receiving the entire line and the selection signal
at the non-widescreen receiver; and
displaying the portion of the line on the non-
widescreen receiver's display according to the selection
signal.
6b
An apparatus for transmitting a widescreen
television signal so as to display a portion of the
widescreen television signal without geometric
distortion on a non~widescreen television, said
apparatus comprising:
selection means for selecting the portion of the
widescreen television signal;
signal generating means for developing a selection
signal representative of the selected portion; and
transmitter means for transmitting the entire
widescreen television signal together with the selection
signal.
By way of added explanation, the foregoing and
other objects of the present invention are accomplished
by sampling a widescreen television picture at a higher
sampling rate so as to fit all of the information in the
current 52.5 us active video line time. A selection
signal is also incorporated with the widescreen picture
signal, allowing non-widescreen television receivers to
display a contiguous portion of the widescreen picture
without geometric distortion. The widescreen
television signal is transmitted either in MAC or
widescreen NTSC format, and is received by a decoder.
The dscoder allows the entire widescreen picture to be
displayed on a widescreen receiver, and makes use of the
selection signal to display the selected portion of the
picture on a standard receiver without geometric
distortion. In another embodiment, a decoder allows
television signals having the standard aspect ratio to
be displayed on receivers having widescreen aspect
ratios without geometric distortionO
In this way, both wldescreen and non-
widescreen television signals are fully compatible on
either widescreen or non-widescreen receivers.
The spirit of this invention is to transmit a
S widescreen television signal in such a manner that it
can be displayed on either a widescreen receiver or a
non-widescreen receiver, without producing geometric
distortion at the display of either receiver. The
television signal can be transmitted in either an NTSC
or MAC format. If NTSC format is employed, a higher
color subcarrier frequency is used in order to make the
wider television picture fit in the same active video
line time (52.5 us~. If MAC format is employed, the
signal may be transmitted at the standard frequency of 6
Fsc or at a higher frequency. Regardless of the method
employed for transmitting the widescreen television
signal, the invention also provides a device for
receiving the transmission and time-compressing the
signal for display on either a widescreen or
non-widescreen display.
~L3~ 75
DESCRIPTTON OF THE PREFERRED EMBODIMENTS
Turning now to Figure 4, the decoder 400 for receiving a MAC
transmission of the widescreen color television signal will now be
discussed. The MAC trsnsmission is received by sn antenna (not
shown) and sent to switch 410, controlled by controller 415. Con-
troller 415 controls switch 410 to direct MAC luminance to switch
412, chrominance to switch 414, and the remainder of the received
signal to controller 415. A user-controlled switch 422 informs the
controller as to the size of the displsy attached to decoder 400.
The MAC signal is transmitted serially flS analog components
and, therefore, ~ sample-~nd-hold and sn A/D converter (not shown)
are required in order to receive the MAC transmission. The sampling
frequency will be the frequency to which s~mples were originally com-
pressed before transmission. (In the event sufficient bandwidth is
available so that the time compressed components may be transmitted
digitally, the sample-and-hold and A/D converter would not be neces-
sary.)
Luminance data is written into luminance line store 402 at the
sampling frequency and is read out st a lower frequency, explained
below. Simil~rly, chrominance data is written into chromin~nce line
store 406 at the sampling frequency and is read out at a lower
frequency, 81so explained below. Because the luminance snd
chrominance d~ta must be decompressed, two line stores are provided
for each component. One line store (402 or 406) is written into while
the other line store (404 or 108) is re6d. Switches 412 and 414 con-
trol read/write while switches 416 and 418 control write/read, respec-
tively, and ere themsellres controlled by controller 415 to alternate
every active line period.
The line stores are preferably rAndomly sccessable, such as
RA M, but can be of the first-in, first-out (FIF O) type, ~uch as
charg~coupled devices tCCD).
s
Switch 422, user-selected at the time that the
decoder is first installed at the television receiver,
informs controller 415 of the aspect ratio of the
television display. If switch 422 is set at the
~^~IDESCRE~N position, all of the memory locations in the
line stores are used by the display to display the
widescreen picture. These time decompressed components
are sent to a converter (not shown) for display on a
widescreen display. The converter is well-knowr. to
those skilled in the art, and either converts the
luminance and chrominance to PAL, SECAM, or ~TSC format
for a PAL, S~CAM, or NTSC type widescreen receiver,
respectively, or matrixes the luminance and chrominance
to ~ed, Green and Blue color components for an RGB
]5 widescreen receiver.
If switch 422 is set to the STANDARD position, all
of the luminance and chrominance components in the line
stores will not fit on the display. Preferably, a
selection siynal, sent with the widescreen television
2(j signal, informs the controller which memory locations to
use for ultimate display.
- The widescreen television signal is monitored
before transmission, and an operator manually selects
the center of interest and causes a signal to be
generated which is transmitted with the picture.
Methods of selecting the center of interest and
generating the selection signal are well-known to those
skilled in the art, as shown, for example, by U.S.
Patent Nos. 4,476,493 and 4,223,343 (discussed above).
The selection signal could represent, for example, the
offset between the centers of the 16:9 and 4:3 displays
or the first or last memory location where the selected
portion is stored in memory (offset between right edges
or left edges). In the preferred embodiment, this
selection signal is sent during the vertical blanking
interval. If no selection signal is transmitted with
the widescreen television signal, the decoder will
generate a default selection signal.
~ 3 ~ 75
Controller 415 receives the data, including the
selection signal, from switch 410, recapturinq the
selection signal and passing the rest of the data to the
television receiver (not shown). The selection signal
is decoded by controller 415 and used to generate the
star and end addresses for reading out the luminance
and chrominance components from the line stores. The
chrominance and luminance address signals represent a
display enable signal.
Althouch the above description has assumed the use
of random access memory as the line stores, the
preferred embodiment alternatively contemplates the use
of first-in-first-out (FIFO) memories. Each of the four
line stores (two luminance and two chrominance) must
have enough memory locations to store an entire
widescreen active video line of the respective samples
(752 for luminance and 376 for chrominance). ~he
selection signal may then be used to control either the
writing of samples into the line stores, or the reading
2(j of samples from them.
If the selection signal controls the writing of
samples, it is used to switch the input of the FIFO
between actual samples of the video line and a zero
signal. For example, if the leftmost portion of the
widescreen picture is to be displayed on a
non-widescreen display, the selection signal will first
cause actual picture signals to be written into the
FIFO. When enough picture signals (564) have been
written to fill a non-widescreen line, the selection
signal will cause zero signals to fill the remainder of
the FIFO. Upon reading, the zero signals are simply
discarded.
I r the selection signal is to control the reading
of samples, first the entire widescreen line is written
into the FIFO. Then the selection signal either
connects the FIFO's output to the display, or it does
not. Once again, assuming that the leftmost portion of
a widescreen active video line is to be displayed on a
non-widescreen display, the selection signal would cause
lOa
~L3~ 7S
the FIFO to be connected to the display during the
reading of the first 564 samples and disconnected from
the display durlng the reading of the remainder (which
would again be discarded).
s
2(j
7~
The rate st which the luminance and chrominance components
are written into and read from their respective line stores in order to
achieve time decompression will now be discussed. The write clock
rate will be the ssmpling frequency. In the preferred embodiment,
this is six times the color subcarrier frequency (6 Fsc). The
luminance read clock rate will prefer~bly be two-thirds of the sampling
frequency (4 Fsc), and the chrominance re~d clock rate will ordinarily
be half the luminance read clock value (2 Fsc). To decompress the
components so that they cQn be displayed on the standard sspect ratio
display, the standard screen resd clock rates are determined by the
following equations:
RCSL = STANDARD ASPECT RAT~O ~ RCWL
WIDESCREEN ASP-ECT RATIO
RCSC = RCSL/2
wherein RCSL = luminance read clock for standard screen
RCWL = luminance resd clock for wide screen
RCSC = chromin~nce read clock for standsrd screen
E XA MP LE
Samples of a 1.85:1 aspect ratio widescreen television signsl will
be transmitted st 6 Fsc. Accordingly, the luminAnce ~nd chrominance
write clocks at the receivers will also be 6 Fsc. For display on
1.85:1 sspect rstio, the luminQnce read clock will be ~ Fsc, and the
chrominance read clock will be 2 Fsc. For display on standsrd (4/3)
Aspect ratio teleYisions, the luminance resd clock will be:
~/3 ~ 4 Fsc = 2.88 Fsc
1.~5
and the chrominance read clock will be 1.44 Fsc.
~3Q~4~5
- 12 -
EXAMPLE 2
Samples of ~ 16:9 aspect ratio widescreen television signfll will
be transmitted flt 6 Fsc. Accordingly, the luminance and chrominflnce
write clocks flt the receivers will also be 6 Fsc. For display on 16:9
sspect ratio televisions, the luminance read clock will be 4 Fsc, flnd
the chrominance re~d clock will be 2 Fsc. For display on standard
(4:3) flspect ratio televisions, the lumin~nce read clock will be:
4/3 ~ 4 Fsc- 3 Fsc
1 6/9
~nd the chrominance read clock will be 1.5 Fsc.
By the above two examples, it can be seen that the rQtiO of
the receiver's sspect ratio to thflt o~ the transmitted signal determines
the proper write clock rates. This holds true regflrdless of the
frequency at which samples are transmitted. For exflmple, if s~mples
of 16:9 aspect ratio Sigllfll were MAC formfltted ~nd transmitted ~t 8
Fsc, the lumin~nce read clock would be 4 Fsc, and the chromin~nce
read clock would be 2 Fsc for display on a 16:9 sspect r~tio display;
the luminance resd clock would be ((4/3)t(16/9~) x 4Fsc = 3Fsc, with
the chromin~nce read clock being 1.5 Fsc, for display on a st~ndard
(4:3) aspect ratio display.
Figure 5 shows a simplified block diagram of the clock
frequency generQtor circuitry used by the decoder of Figure 4. As in
st~nd~rd B-MAC, a voltage controlled oscill~tor 510 operates at
12 Fsc, and is frequency locked to the B-MA C burst which follows
data and precedes chrominsnce in eech line. Oscillstor 510 drives two
frequency dividers 512 end 514, producing the 6 Fsc write clock and
the 4 Fsc widescreen lurnin~nce read clock, respectively. I)ivider 512
drives frequency divider 516, producing the 3 Fsc non-widescreen
luminance read clock. Frequency divider 518 divides the luminance
read clock by two, producing the chrominance read clock. Both refld
clock frequencies are controlle(i by switch 422, which is the s~me
switch ~s shown in Figure 4.
It is also possible to transmit an NTSC-like sigr.al
carryina all o~ the widescreen television slgnal
informa~ion. However, in order to get all of the
information in the came active video line of 52.5 us,
the siqnal must be time-compressed. As the NTSC and
similar composite signals are analog, time-compressior
is achieved by modulating the widescreen color
information onto a higher subcarrier frequency. The new
suhcarrier frequency (P'sc) will be determined according
l to the following equation:
WIDESCREEN A~PECT RATIO * NON-WIDESCRE~N SUBCARRIER = ~'cc
NON-WIDE SCREEN ASPECT RATIO
where NON~WIDESCREEN ASPECT RATIO= 4.3
NON-WIDESCREEN SUBCARRIER= 3.579545 MHz
Therefore, if the widescreen aspect ratio is chosen as
1.85:1, the widescreen signal's color subcarrier will be
approximately 4.9667 MHz. Similarly, for an aspect
ratio of 16:9, the new color subcarrier will be
2() approximately 4.7727 MHz, and for an aspect ratio of
5:3, the modulating subcarrier will be approximately
4.4'44 MHz.
As these frequencies are not prime numbers, the
design of a new generator may be simplified.
Additionally, other odd integers near these values could
be used with very minor changes in the actual aspect
ratio of the signal transmitted. It is known that small
differences in the aspect ratio are not noticed by the
observer.
Turning now to Figure 6, a description of the
decoder of the present invention wherein a composite
widescreen signal is transmitted for display on both
widescreen and standard (NTSC) displays will now be
discussed. The baseband signal is received from a
television receiver front end (not shown) which includes
a demodulator for demodulating the received signal to
baseband, and processed by decoder 1010 as follows.
Switch 1012 is set by the user, informing decoder 1010
of the display aspect ratio to which the decoder is
connected. If switch 1012 is set at WIDESCREEN, the
decoder simply passes the entire widescreen sian~1 to
composite television 10~5.
ln
2()
- 14 -
If switch 1012 is set at STANDARD, the anRlog signal is con-
verted to digital by sample-an~hold circuit 1020 ~nd A/D converter
1025. This digital signal is written into a memory at a first clock
rste ~nd read out at a second ~slower) clock r~te. A portion of the
samples read out are selected for display by time decompressor and
selector 1030. The time decompressor requires two memories, one of
which is written into while the other is read fromO The portion of
the samples read out (if random access memories) or written in (if
FIFO memory devices) are selected according to the selection signAl
previously described with reference to Figure 4. If no selection signal
is present, a default position is generated by the decoder. The control
of the rnemories and the selection is identic~l to the description of
Figure 4. The selected portion of the widescreen signal is converted
back to analog by digit~l-to-~n~log converter 1035, snd the selected
portion is then passed to composite television 1045. The decompressed
signal will contain ~ color subcarrier of 3.579545 MHz, if the non-
widescreen television is designed to receive NTSC signals.
Decoders have been described for sllowing widescreen transmi~
sions to be comp~tible with non-widescreen receivers. Given the vsst
amount of non-widescreen pictures, either transmitted by television
StAtions or stored ~t home on video tape, there is a need for wide-
screen receivers to be compatible with these non-widescreen signals.
Turning now to Figute 7, ~ decoder for displaying standard television
signals on widescreen displ~ys having an ~spect ratio of 16:9 will now
be discussed.
The NTSC composite baseb~nd video signal is input at the
decoder At input port 1105, where it is optionally low pass filtered
1110 ~nd con~verted to ~ digital sign~l by sarnple-~nd-hold ~nd A/D
eonverter 1115. The digital samples need to be tim~compressed to fit
on the widescteen display without distortion. To do this,
demultiplexers 1125 ~nd 1130, along with multiplexers 1135 and 1140,
time compress the samples through line stores 1145-1160. The
~8~5
com~ressed picture will not fill up the entire
widescreen display. The non-widescreen signal,
compressed for displaying without distortion on a
widescreen display, is therefore delayed hy counter 1165
and read enable gate 1170 by a delay pre~erably caUcing
the displayed picture to be centered on the widescreen
display. During the delay, no picture elements are
output from the line stores. Additionally, no picture
elements are output after the line stores have read out
the entire non-widescreen video line. The absence of
picture elements creates null components which are used
to produce a border for bordering the non-widescreen
signal on the widescreen display. It is noted that
luminance and chrominance are ~Iritten into their
respective line stores at 3 Fsc and read out at 4 Fsc.
This time-compressor ratio (4:3) is the ratio of the
widescreen aspect ratio (16:9) to the standard screen
aspect ratio (4:3). Other read/write rates could be
chosen, and will also be dependant upon the widescreen
2(j aspect ratio.
The compressed chrominance components are separated
into their R-Y and B-Y components by demultiplexer 1175.
The luminance and R-Y and B-Y chrominance components are
converted to analog by digital-to-analog converters
1180, 1185 and 1190, respectively, where they are
lowpass filtered by filters 1195a, b, and c,
respectively, and converted into displayable signals by
converter 1200. Converter 1200 either converts the
signals for NTSC, PAL or SECAM, or matrixes the signals
for display on an RGB display.
Although illustrative embodiments of the present
invention have been described in detail with reference
to the accompanying drawings, it is to be understood
that the invention is not limited to those precise
embodiments and that various changes or modifications
may be effected therein by one skilled in the art
without departing from the scope or spirit of the
invention.
