U.S. patent application number 13/860625 was filed with the patent office on 2014-08-07 for progressive scan video processing.
This patent application is currently assigned to FAROUDJA ENTERPRISES INC.. The applicant listed for this patent is FAROUDJA ENTERPRISES INC.. Invention is credited to Yves Faroudja.
Application Number | 20140219362 13/860625 |
Document ID | / |
Family ID | 51259192 |
Filed Date | 2014-08-07 |
United States Patent
Application |
20140219362 |
Kind Code |
A1 |
Faroudja; Yves |
August 7, 2014 |
PROGRESSIVE SCAN VIDEO PROCESSING
Abstract
A method and system for separating even and odd lines in a
progressive video signal comprises generating from the even lines
simulated odd lines, comparing the simulated odd lines with the
original odd lines to obtain a support signal, and transmitting the
even lines and the support signal in order to reconstitute the full
picture. Alternatively, separating odd and even lines may be
replaced by separating high- and low-frequency vertical signal
components, generating from the low-frequency vertical signal
components simulated high-frequency vertical signal components,
comparing the simulated high-frequency vertical signal components
with the original high-frequency signal components to obtain a
support signal.
Inventors: |
Faroudja; Yves; (Los Altos,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FAROUDJA ENTERPRISES INC. |
Los Altos |
CA |
US |
|
|
Assignee: |
FAROUDJA ENTERPRISES INC.
Los Altos
CA
|
Family ID: |
51259192 |
Appl. No.: |
13/860625 |
Filed: |
April 11, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61760275 |
Feb 4, 2013 |
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Current U.S.
Class: |
375/240.26 |
Current CPC
Class: |
H04N 19/00854 20130101;
H04N 19/593 20141101; H04N 19/65 20141101 |
Class at
Publication: |
375/240.26 |
International
Class: |
H04N 7/26 20060101
H04N007/26 |
Claims
1. A method for processing a progressive scan video signal, the
video signal having scan lines in which one set of alternate
consecutive scan lines are designated as even scan lines and
another set of alternate consecutive scan lines, offset by one scan
line from the first set, are designated as odd scan lines,
comprising: separating the even and odd scan lines of the
progressive scan video signal and selecting the even scan lines,
deriving a simulation of the odd scan lines from the selected even
scan lines, subtracting the simulation of the odd scan lines from
the selected odd scan lines to obtain an error signal, and
transmitting or storing the selected even scan lines and the error
signal.
2. A method for processing a progressive scan video signal
according to claim 1 wherein said deriving includes an encoder and
a complementary decoder.
3. A method for processing a modified progressive scan video signal
comprising even scan lines of a progressive scan video signal and
an error signal, the error signal representing a difference between
the odd scan lines of the progressive scan video signal and a
simulation of the odd scan lines, wherein even scan lines are one
set of alternate consecutive scan lines in the progressive scan
video signal and odd scan lines are another set of alternate
consecutive scan lines in the progressive scan video signal, offset
by one scan line from the first set, the method comprising deriving
from the even scan lines in the modified progressive scan video
signal a simulation of the odd scan lines of the progressive scan
video signal, improving the reconstruction of the odd scan lines of
the progressive scan video signal by using the error signal, and
combining the even scan lines and the improved reconstruction of
the odd scan lines of the progressive scan video signal to provide
a complete line scan of said progressive scan video signal.
4. A method for processing a progressive scan video signal,
comprising: separating the low frequency vertical signal components
and the high frequency vertical signal components of the
progressive scan video signal, deriving a simulation of the high
frequency vertical signal components from the low frequency
vertical signal components of the progressive scan video signal,
subtracting said simulation from the high frequency vertical
components separated from the progressive scan video signal to
obtain an error signal, and transmitting or storing the low
frequency vertical signal components of the progressive scan video
signal and the error signal.
5. A method for processing a progressive scan video signal
according to claim 4 wherein said deriving includes an encoder and
a complementary decoder.
6. A method for processing a modified progressive scan video signal
comprising the low frequency vertical signal components of a
progressive scan video signal and an error signal, the error signal
representing a difference between the high frequency vertical
signal components of the progressive scan video signal and a
simulation of those signal components, the method comprising
deriving from the modified progressive scan video signal a
simulation of high frequency vertical signal components of said
progressive scan video signal, and improving the reconstitution of
the high frequency vertical signal components of said progressive
scan video signal by using the error signal, and combining the
improved reconstitution of the high frequency vertical signal
components of said progressive scan video signal and the low
frequency vertical components of said progressive scan video signal
to provide a full bandwidth of the progressive scan video
signal.
7. A method for processing a progressive scan video signal, the
video signal having scan lines in which one set of alternate
consecutive scan lines are designated as even scan lines and
another set of alternate consecutive scan lines, offset by one scan
line from the first set, are designated as odd scan lines,
comprising: separating the even and odd scan lines of the
progressive scan video signal and selecting the even scan lines,
deriving a simulation of the odd scan lines from the selected even
scan lines, subtracting the simulation of the odd scan lines from
the selected odd scan lines to obtain an error signal, deriving
from the even scan lines a simulation of the odd scan lines of the
progressive scan video signal, improving the reconstruction of the
odd scan lines of the progressive scan video signal by using the
error signal, and combining the even scan lines and the improved
reconstruction of the odd scan lines of the progressive scan video
signal to provide a complete line scan of said progressive scan
video signal.
8. A method for processing a progressive scan video signal,
comprising: separating the low vertical frequency and high
frequency vertical signal components of the progressive scan video
signal, deriving a simulation of the high frequency vertical signal
components of the progressive scan video signal from the low
frequency vertical signal components, subtracting said simulation
from the high frequency vertical signal components separated from
the progressive scan video signal to obtain an error signal,
deriving from the modified progressive scan video signal a
simulation of high frequency vertical signal components of said
progressive scan video signal, improving the reconstitution of the
high frequency vertical signal components of said progressive scan
video signal by using the error signal, and combining the improved
reconstitution of the high frequency vertical signal components of
said progressive scan video signal and the low frequency vertical
components of said progressive scan video signal to provide a full
bandwidth of the progressive scan video signal.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of provisional Patent
Application Ser. No. 61/760,275, filed Feb. 4, 2013, and is
assigned to the Assignee of the present application and
incorporated herein by reference.
BACKGROUND
[0002] In progressive video scanning, successive scanning lines are
vertically aligned from frame to frame. For example, in the
1080p/60 standard (1080 scanning lines per frame, 60 frames per
second), line 1 of frame 2 is scanned at the same vertical location
as is line 1 of frame 1, and so are lines 1 of frames 3, 4, etc.
For interlaced video, line 1 of field 2 is vertically located
between line 1 and line 2 of field 1, and so is line 1 of field 4,
while line 1 of field 3 is vertically coincident with line 1 of
field 1.
[0003] An interlaced signal is composed of a succession of even and
odd fields, two successive fields making a frame. For example, in
the 1080i/60 standard (1080 lines interlaced, 60 fields per
second), each field is composed of 540 lines, and there are 60
fields or 30 frames per second. A frame is composed of one even
field and one odd field in succession.
[0004] A progressive scan video signal is composed of horizontal
lines drawn consecutively in sequence. In describing aspects of the
present invention herein, reference is made to "even" and "odd"
lines of a progressive scan video signal, "even" lines being the
second line and every other consecutive line (i.e., lines 2, 4, 6,
etc.) and "odd" lines being the first line and every other
consecutive line (i.e., lines 1, 3, 5, etc.) or vice-versa (in the
case of a progressive scan video signal, the designations "even"
and "odd" are arbitrary). In cases in which a progressive scan
video signal is derived from an interlace scan video signal, "even"
lines are typically labeled as those derived from "even" fields and
"odd" lines are typically labeled as those derived from "odd"
fields.
[0005] Interlaced video has been used since the early days of
television, and has been slowly falling into disfavor, and replaced
by progressive scan for more and more applications, mostly because
of the specific needs of computer or computer-like displays. More
recent television displays such as LCDs or DLPs can only be driven
with a progressive scan. In these cases, interlaced signals have to
be de-interlaced, which is costly and difficult.
[0006] The main advantages of progressive scan (as compared to
interlace scan) are 1) absence of interlace artifacts, such as line
twitter, serrations, flicker, etc., 2) ease of processing, from a
camera to a display, and 3) ease of digital processing, such as
bandwidth or bit-rate compression. The main disadvantage of
progressive scan is an increase by a ratio of two of bandwidth
requirements, as compared to an interlaced standard having the same
field rate as the comparable progressive scan standard.
[0007] Digital compression systems require a high bit count
(equivalent to large bandwidth) to process the progressive scan
video signal with an acceptable quality. The requirements for
bandwidth are increasing daily, and the available bandwidth
provided by present communication channels is limited. For example,
more than 50% of the Internet traffic is occupied by video.
[0008] Broadcasters are no longer satisfied with present HDTV
standards (1080i and 720p) and would like to move to higher scan
rates (e.g., "4K", which is approximately 2000.times.4000 pixels)
or higher frame rates (120 Hz). Furthermore, interlace standards,
which in the past employed analog transmission, reduced the
bandwidth requirements by two at the cost of image quality
(artifacts). Interlacing does not present such an advantage in
compression systems, and is not computer-friendly.
[0009] Thus, increased bandwidth, or for a more efficient use of
the bandwidth available on different media are required.
[0010] Compression standards are slowly improving, getting more
efficient in packing an increasing data load into increasingly
over-worked channels, but an improvement by a ratio of two in the
bandwidth utilization (Mb/s for a constant channel) occurs only
every eight to ten years or so.
[0011] A need has arisen to reduce the bandwidth of progressive
scan video signals while maintaining a reasonable image
quality.
SUMMARY OF THE INVENTION
[0012] In a first aspect of the invention, a method for processing
a progressive scan video signal is disclosed, the video signal
having scan lines in which one set of alternate consecutive scan
lines are designated as even scan lines and another set of
alternate consecutive scan lines, offset by one scan line from the
first set, are designated as odd scan lines. The method comprises
separating the even and odd scan lines of the progressive scan
video signal and selecting the even scan lines, deriving a
simulation of the odd scan lines from the selected even scan lines,
subtracting the simulation of the odd scan lines from the selected
odd scan lines to obtain an error signal, and transmitting or
storing the selected even scan lines and the error signal.
Optionally, the deriving may include an encoder and a complementary
decoder.
[0013] In another aspect of the invention, a method for processing
a modified progressive scan video signal is disclosed, the video
signal comprising even scan lines of a progressive scan video
signal and an error signal, the error signal representing a
difference between the odd scan lines of the progressive scan video
signal and a simulation of the odd scan lines, wherein even scan
lines are one set of alternate consecutive scan lines in the
progressive scan video signal and odd scan lines are another set of
alternate consecutive scan lines in the progressive scan video
signal, offset by one scan line from the first set. The method
comprises deriving from the even scan lines in the modified
progressive scan video signal a simulation of the odd scan lines of
the progressive scan video signal, improving the reconstruction of
the odd scan lines of the progressive scan video signal by using
the error signal, and combining the even scan lines and the
improved reconstruction of the odd scan lines of the progressive
scan video signal to provide a complete line scan of the
progressive scan video signal.
[0014] In yet another aspect of the invention, a method for
processing a progressive scan video signal comprises separating the
low frequency vertical signal components and the high frequency
vertical signal components of the progressive scan video signal,
deriving a simulation of the high frequency vertical signal
components from the low frequency vertical signal components of the
progressive scan video signal, subtracting said simulation from the
high frequency vertical components separated from the progressive
scan video signal to obtain an error signal, and transmitting or
storing the low frequency vertical signal components of the
progressive scan video signal and the error signal (support out).
Optionally, the deriving may include an encoder and a complementary
decoder.
[0015] In another aspect of the present invention, a method for
processing a modified progressive scan video signal is disclosed,
in which the signal comprises the low frequency vertical signal
components of a progressive scan video signal and an error signal,
the error signal representing a difference between the high
frequency vertical signal components of the progressive scan video
signal and a simulation of those signal components, the method
comprises deriving from the modified progressive scan video signal
a simulation of high frequency vertical signal components of said
progressive scan video signal, improving the reconstitution of the
high frequency vertical signal components of said progressive scan
video signal by using the error signal, and combining the improved
reconstitution of the high frequency vertical signal components of
said progressive scan video signal and the low frequency vertical
components of said progressive scan video signal to provide a full
bandwidth of the progressive scan video signal.
[0016] In another aspect of the present invention, a method for
processing a progressive scan video signal is disclosed, the video
signal having scan lines in which one set of alternate consecutive
scan lines are designated as even scan lines and another set of
alternate consecutive scan lines, offset by one scan line from the
first set, are designated as odd scan lines, the method comprises
separating the even and odd scan lines of the progressive scan
video signal and selecting the even scan lines, deriving a
simulation of the odd scan lines from the selected even scan lines,
subtracting the simulation of the odd scan lines from the selected
odd scan lines to obtain an error signal, deriving from the even
scan lines a simulation of the odd scan lines of the progressive
scan video signal, improving the reconstruction of the odd scan
lines of the progressive scan video signal by using the error
signal, and combining the even scan lines and the improved
reconstruction of the odd scan lines of the progressive scan video
signal to provide a complete line scan of said progressive scan
video signal.
[0017] In yet a further aspect of the present invention, a method
for processing a progressive scan video signal comprises separating
the low vertical frequency and high frequency vertical signal
components of the progressive scan video signal, deriving a
simulation of the high frequency vertical signal components of the
progressive scan video signal from the low frequency vertical
signal components, subtracting said simulation from the high
frequency vertical signal components separated from the progressive
scan video signal to obtain an error signal, deriving from the
modified progressive scan video signal a simulation of high
frequency vertical signal components of said progressive scan video
signal, improving the reconstitution of the high frequency vertical
signal components of said progressive scan video signal by using
the error signal, and combining the improved reconstitution of the
high frequency vertical signal components of said progressive scan
video signal and the low frequency vertical components of said
progressive scan video signal to provide a full bandwidth of the
progressive scan video signal.
[0018] Exemplary embodiments provide methods and systems for
processing a progress scan video signal. Aspects of the exemplary
embodiments include separating the second line and every other line
consecutive line in the progress scan video signal (i.e., the
"even" lines) from the remaining lines (i.e., the "odd" lines), or
vice-versa (separating the "odd" lines from the remaining "even"
lines); generating from the even lines simulated odd lines (such
simulated lines may be referred to alternatively as "approximated",
"reconstituted" or "regenerated"); comparing the simulated odd
lines with original odd lines in the progress scan video signal to
obtain a support signal (a type of error signal); and transmitting
or storing the even lines and the support signal in order to
reconstitute a video signal that simulates the original progressive
scan video signal and has both even and odd lines.
[0019] In an alternative embodiment, separating odd and even lines
is replaced by a process that separates high- and low-frequency
vertical signal components of the progressive scan video signal in
every line and reduces or eliminates the high-frequency vertical
signal components, as by applying, for example, a
vertical-signal-component low-pass filter. This may be
accomplished, for example, by generating simulated high-frequency
vertical signal components from low-frequency vertical signal
components. By "high--frequency vertical signal components" is
meant image frequency components that contribute to resolution in
the vertical domain ("vertical-domain resolution"). Simulated
high-frequency vertical signal components are compared with the
original high-frequency vertical signal components to obtain a
support signal. The low-frequency vertical video signal components
may be enhanced in the vertical domain, for example, by a
non-linear process that generates high-frequency vertical video
signal components, such frequencies being similar in amplitude and
phase to those reduced or eliminated by a vertical low-pass
filter.
[0020] The support signal is the difference between the original
high-frequency vertical video signal components and simulated
high-frequency vertical video signal components obtained, for
example, by a non-linear process operating on the low-frequency
vertical video signal components. If the simulation is well done,
the support signal may be small such as close to zero or zero, and
may require that only a narrow bandwidth support signal be
transmitted or stored.
[0021] The various features of the present invention and its
preferred embodiments may be better understood by referring also to
the following discussion and the accompanying drawings in which
like reference numerals refer to like elements in the several
figures. The contents of the discussion and the drawings are set
forth as examples only and should not be understood to represent
limitations upon the scope of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a schematic block diagram embodying aspects of the
present invention, illustrating the processor generating from a
progressive scan video input signal having n progressively scanned
lines per frame, which may be designated "np", a modified
progressive scan video output signal having n/2 lines per frame,
which may be designated "np/2" and a support (error) signal. The
letter "p" indicates a progressive scan format. The letter "n"
indicates the number of scan lines (thus "np/2" indicates a
progressive scan video signal having n/2 scan lines.
[0023] FIG. 2 is a flow diagram, which may be compared to FIG. 1,
illustrating a process for processing a progressive scan video
signal in accordance with aspects of the present invention.
[0024] FIG. 3 is a schematic block diagram embodying aspects of the
present invention illustrating a processor similar to the FIG. 1
processor, but including a combination encoder-decoder in the
support path.
[0025] FIG. 4 is a flow diagram, which may be compared to FIG. 3,
illustrating a process for processing a progressive scan video
signal in accordance with aspects of the present invention.
[0026] FIG. 5 is a schematic block diagram embodying aspects of the
present invention illustrating a processor that follows
transmission or storage of the signals generated by the processor
of FIG. 1 or FIG. 3, and using the two signals generated by the
processor of FIG. 1 or FIG. 3 to reconstitute a full progressive
scan video signal having n progressively scanned lines per frame
that approximates the original progressive scan input signal
applied to the processor of FIG. 1 or FIG. 3.
[0027] FIG. 6 is a flow diagram, which may be compared to FIG. 5,
illustrating processing of the even lines and the support
signal.
[0028] FIGS. 7-9 are schematic block diagrams embodying aspects of
the present invention illustrating alternative implementations of
the structures and processes described in FIGS. 1-6, in which the
separation between even and odd lines is replaced by a separation
between high-frequency vertical signal components and low-frequency
vertical signal components.
DETAILED DESCRIPTION OF THE INVENTION
[0029] The exemplary embodiments relate to methods, devices and
systems for processing a progressive scan video signal and a
modified progressive scan video signal. The following description
is presented to enable one of ordinary skill in the art to make and
use the invention and is provided in the context of a patent
application and its requirements. Various modifications to the
exemplary embodiments and the generic principles and features
described herein are readily apparent. The exemplary embodiments
are mainly described in terms of particular methods and systems
provided in particular implementations. However, the methods and
systems will operate effectively in other implementations. Phrases
such as "exemplary embodiment", "one embodiment" and "another
embodiment" may refer to the same or different embodiments. The
embodiments are described with respect to systems and/or devices
having certain components. However, the systems and/or devices may
include more or fewer components than those shown, and variations
in the arrangement and type of the components may be made without
departing from the scope of the invention. The exemplary
embodiments will also be described in the context of particular
methods having certain steps. However, the method and system
operate effectively for other methods having different and/or
additional steps and steps in alternative time order that are not
inconsistent with the exemplary embodiments. Thus, the present
invention is not intended to be limited to the embodiments shown,
but is to be accorded the widest scope consistent with the
principles and features described herein.
[0030] FIG. 1 is a schematic block diagram of a processor in
accordance with aspects of the present invention that receives a
progressive scan input video signal 2 having n progressively
scanned lines per frame to generate a modified progressive scan
output video signal 4 having n/2 progressively scanned lines per
frame, and a support signal 6.
[0031] A progressive scan video input signal 2 having n
progressively scanned lines per frame, which may be designated
"np", may be applied first to a "Nyquist Vertical Low-Pass Filter"
device or function ("Nyquist Filter") 1 characterized in that its
frequency domain response in the vertical domain satisfies the
Nyquist criterion. It is possible, particularly with
computer-generated alphanumeric characters, or graphics, that the
progressive scan input signal contains vertical frequency signal
components in excess of the Nyquist frequency (half of the scanning
line frequency), and these frequencies may, later in the video
processing, generate undesirable artifacts.
[0032] A "Separate Odd/Even Lines" device or function ("Separator")
8 receives the Nyquist filter output, separates even lines from odd
lines of the input signal 2, and selects the even lines. It will be
appreciated that either the "even" lines or the "odd" lines may be
selected and Processed--the result is equivalent. The way in which
even and odd lines are separated from each other is easily
accomplished in many different ways and is not critical to the
invention.
[0033] A "Line Interpolator" device or function ("Interpolator") 10
receives the even lines from device or function 8, and performs an
interpolation process in order to generate simulated "odd" lines of
the input signal 4. Interpolators are well known in the art and the
selection of any particular interpolator is not critical to the
invention. In general, simple interpolators tend to be less
effective, have errors, and require a high transmission bandwidth
(such as simple averaging of the line before and the line after)
and have errors, therefore requiring a high transmission bandwidth.
Some are very sophisticated (see, for example, U.S. Pat. No.
6,133,357) and are very accurate.
[0034] A time expander device or function ("Time Expander") 12
receives the even lines from device or function 8 and expands by
two the time scale of the signal in order to deliver an output
signal 4 having n/2 progressively scanned lines per frame. The Time
Expander reads out the selected lines at half the rate they were
inputted. A subtractor device or function ("Subtractor") 14 (shown
schematically as a minus sign within a circle) is an arithmetic
subtractor that subtracts the separated out "odd" lines signal
outputted by Separator 8 from the simulated "odd" lines outputted
by Line Interpolator 10 in order to generate a "support" error
signal representative of the differences between "odd" lines and
simulated "odd" lines. Time expander ("Time Expander") 16 is a time
expander by two, identical in function to the Time Expander 12 time
expander. It receives the error signal from Subtractor 14 to
deliver the support signal output 6.
[0035] FIG. 2 is a flow diagram, based on FIG. 1, illustrating a
process for processing a progressive scan video signal. The process
may begin by receiving an input progressive scan video signal
having n progressively scanned lines per frame and vertical
low-pass filtering the signal so as to provide a signal that
respects (complies with) the Nyquist criterion in the vertical
domain (block 200). In an identical way from frame to frame, a
separator receives the filtered input signal and separates even and
odd lines and selects even lines (block 201). A time expander
expands in time the even lines by a ratio of two and outputs n/2
progressively scanned lines per frame (block 202) in a continuous
data flow. The line interpolator interpolates two or more
successive even lines to obtain simulated odd lines (block 204).
The odd lines are input to a subtractor along with the simulated
odd lines to generate an error signal (block 206). "Odd" lines are
subtracted from simulated (interpolated) odd lines. Processing in
blocks 201, 202, 204 and 206 may be performed in parallel. A time
expander expands the error signal in time by the ratio two and
outputs a support signal (block 208).
[0036] FIG. 3 is a schematic diagram embodying aspects of the
present invention illustrating a processor similar to the FIG. 1
processor, but further including a combination encoder-decoder,
which may be a bit-rate compression-decompression process or a
progressive scan to interlace scan conversion, for example. This
approach ideally requires tracking between the encoding process in
the support signal generation loop and the one used for
transmission-reception in the support path. The processor also
makes use of a progressive scan video signal having n progressively
scanned lines per frame to generate a progressive scan output
having n/2 progressively scanned lines per frame, and a support
signal. Blocks 1, 8, 10, 12, 14 and 16 are identical in structure
and functions to the corresponding devices and functions in FIG. 1.
Encoder function or device 18 is an encoder, simulating the effect
of an encoder that may be in the transmission or recording path,
and is followed by Decoder function or device 20. Decoder 20 is a
decoder complementary to encoder 18 and duplicating the structure
and function of a decoder that may be used at the receiving or
reproduction end of the transmission or storage path. Devices or
functions 18 and 20 are inserted between Separator 8 and Subtractor
14. They contribute to generating simulated odd lines that are
closer to ideal simulated "odd" lines than if they were not
employed.
[0037] FIG. 4 is a flow diagram, based on FIG. 3, illustrating a
process for processing a progressive scan video signal according to
aspects of the present invention. The process may begin by
receiving an input progressive scan video signal having n
progressively scanned lines per frame and vertical low-pass
filtering the signal so as to provide a signal that respects the
Nyquist criterion in the vertical domain (block 400). In an
identical way from frame to frame, a separator separates even and
odd lines in the input signal and selects even lines (block 401). A
time expander expands in time the even lines by a ratio of two and
outputs lines at n/2 progressively scanned lines per frame (block
402). The line interpolator interpolates successive even lines to
obtain simulated odd lines (block 404). An encoder encodes the
simulated odd lines and a decoder decodes the simulated odd lines
(block 406). The odd lines from the separator are subtracted from
the encoded/decoded simulated odd lines to generate an error signal
(block 408). A time expander expands the error signal in time by a
ratio of two and outputs a support signal (block 410).
[0038] FIG. 5 is the block diagram of a processor in accordance
with aspects of the present invention. It may receive after
transmission or storage and decoding (if the outputs of the
processor of FIG. 1 or FIG. 3 are encoded) the two signals,
originated as output 4 and output 6 of the processor of FIG. 1 or
FIG. 3. Line Interpolator device or function 22 receives even
lines, scanned having n/2 progressively scanned lines per frame,
from an optional decoder (decoder not shown), and generates
simulated odd lines through a line interpolation process. Delay
device or function 24 receives the support signal from an optional
decoder (decoder not shown), a signal that originates at output 6
of FIG. 1 or FIG. 3, and then is encoded and transmitted or stored
and decoded. In Delay 24, this signal is delayed in order to match
the delay of the Line Interpolator 22. A summing device or function
("Summer") 26 (shown schematically as a circle with a plus sign
inside) arithmetically adds the simulated odd lines from Line
Interpolator 22 and delayed support signal from Delay 24 and
delivers reconstituted odd lines having n/2 progressively scanned
lines per frame. Another Delay device or function 28 receives the
decoded even lines, and performs a delay in order to match the
delay in other paths. A further summing device or function
("Summer") 30 (shown schematically as a circle with a plus sign
inside) receives the delayed even lines from Delay 28 and the
reconstituted odd lines from Summer 26, and adds these two signals
in order to obtain an output having n progressively scanned lines
per frame.
[0039] If the support signal is not available (i.e., the simulated
odd lines from Interpolator 22 are the only input to Summer 26 and,
hence, are the reconstructed odd lines), the reconstructed
progressive scan output from Summer 30 may still be useful even
though it may not match the original signal as closely as if the
support signal were available. This is particularly true when the
unavailable support signal has a very low bandwidth.
[0040] FIG. 6 is a flow diagram illustrating processing of the even
lines and the support signal corresponding to FIG. 5. The process
may begin by receiving even lines output and support signal output
from an optional decoder and interpolating the even lines to
generate simulated odd lines (block 600). The support signal output
by the optional decoder is received by a delay, which delays the
support signal and generates a delayed support signal (block 602).
The simulated odd lines and the delayed support signal are added to
obtain reconstituted odd lines (block 604). The even lines output
from the decoder are received by a delay to generate delayed even
lines (block 606). The delayed even lines and reconstituted odd
lines are added to generate a full output video signal having n
progressively scanned lines per frame (block 608).
[0041] FIGS. 7-9 are schematic diagrams illustrating alternative
implementations of the devices and functions described in FIGS.
1-6, in which separation between even and odd lines is replaced by
separation between high-and low-vertical-frequency signal
components.
[0042] In these alternative aspects of the present invention, the
method for processing a video signal comprises receiving a
progressive scan video signal and separating high and low frequency
vertical signal components of the progressive scan video signal
into two paths; generating simulated high-frequency vertical signal
components from the low-frequency vertical signal components of the
progressive video signal; subtracting the simulated high-frequency
vertical signal components from the high-frequency vertical signal
components of the progressive video signal to obtain a support
signal; and transmitting low-frequency vertical signal components
of the input signal and the support signal.
[0043] FIG. 7 is a block diagram of an alternative implementation
of the aspects of the invention shown in FIG. 1. A "Separate
High-Low Vertical Frequencies" device or function ("Separator") 34
separates high-frequency vertical signal components from
low-frequency vertical signal components of the progressive scan
video input signal (32) having n progressively scanned lines per
frame. The way in which high-frequency vertical signal components
are separated from low-frequency vertical signal components is not
critical to the invention. One suitable way is to perform vertical
high-pass and low-pass frequency signal component filtering. This
may be accomplished by matrixing the outputs of successive one
scanning line delays to obtain a desired filtering in the vertical
domain. A "Simulate High Frequency Vertical Signal Components"
device or function ("Simulator") 36 receives the low-frequency
vertical signal components from device or function 34 and performs
a non-linear process in order to generate an approximation of the
high-frequency vertical signal components of the progressive scan
input signal. Such non-linear processes are well known and the use
of any particular one is not critical to the invention.
[0044] A Subtractor device or function 38 (shown schematically as a
minus sign within a circle) is an arithmetic subtractor that
subtracts the separated out original high-frequency vertical signal
components from the simulated high-frequency vertical signal
components from Simulator 36 in order to generate a "support" error
signal representative of the differences between the actual
progressive scan signal and the progressive scan signal having
simulated high-frequency vertical signal components.
[0045] FIG. 8 is a schematic block diagram of aspects of the
present invention relating to another embodiment of a processor
that makes use of a progressive scan video signal source having n
progressively scanned lines per frame to generate a progressive
scan video signal output having n progressively scanned lines per
frame and a support signal. Separator 34 separates high-frequency
vertical signal components from low-frequency vertical signal
components in the video signal. Separator 34 and Simulator 36 may
be the same as those devices and functions in the schematic diagram
of FIG. 5. Encoder 18 is an optional encoder, simulating the effect
of the encoder that is in the transmission path and is followed by
an optional decoder, Decoder 20. Decoder 20 may be a decoder
complementary to encoder 18 and duplicating the structure and
function of the decoder that is used at the receiving end of the
transmission or storage path. Encoder 18 and Decoder 20 may be
inserted between Separator 34 and Simulator 36. They contribute to
generating simulated high-frequency vertical signal components that
are closer to ideal simulated high-vertical-frequency signal
components than if they were not employed.
[0046] FIG. 9 is a schematic block diagram of an alternative
embodiment of a processor in accordance with aspects of the present
invention. It may receive after transmission or storage and
decoding (if the outputs of the pre-processor of FIG. 7 or FIG. 8
are encoded) the two signals, originated as output 40 and output 42
of the processor of FIG. 7 or FIG. 8.
[0047] "Simulate High Frequency Vertical Signal Components" device
or function ("Simulator") 44 receives low-frequency vertical signal
components, progressively scanned at n lines per frame, from the
decoder (decoder not shown), and generates simulated high-frequency
vertical signal components. The Simulator 44 receives the
low-frequency vertical signal components and performs a non-linear
process in order to generate an approximation of the high-frequency
vertical signal components of the progressive scan input signal.
Such non-linear processes are well known and the use of any
particular one is not critical to the invention.
[0048] Delay device or function 24 receives the support signal from
the decoder, a signal that originates at the separated out
low-frequency vertical signal components output signal of Separator
34 in FIGS. 7 and 8. After being encoded, transmitted or stored,
and decoded, it is delayed in Delay device or function ("Delay") 24
in order to match the delay of the simulated high-frequency
vertical signal components. Summing device or function 26 is an
arithmetic adder that, by adding the simulated high-frequency
vertical signal components from Simulator 44 and the delayed
support signal from Delay 24, delivers reconstituted high-frequency
vertical signal components. Delay 28 receives the decoded
low-frequency vertical signal components and performs a delay in
order to match the delay of the path of devices or functions in
other paths. Summing device or function 30 receives the delayed
low-frequency vertical signal components from Delay 28, and the
reconstituted high-frequency vertical signal components from Summer
26 and adds these two signals in order to obtain an output having n
progressively scanned lines per frame with substantially full
vertical bandwidth.
[0049] A method and system for pre-processing a progressively
scanned video signal has been disclosed. The present invention has
been described in accordance with the embodiments shown, and there
could be variations to the embodiments, and any variations would be
within the spirit and scope of the present invention. For example,
an exemplary embodiment may be implemented using hardware,
software, a computer readable medium containing program
instructions, or a combination thereof. Software written according
to the present invention may be either stored in some form of
computer-readable medium such as a memory, a hard disk, or a
CD/DVD-ROM and may be executed by a processor. Accordingly, many
modifications may be made by one of ordinary skill in the art
without departing from the spirit and scope of the appended
claims.
[0050] If the support signal is not available (i.e., the simulated
high-vertical-frequency signal components from Simulator 44 are the
only input to Summer 26 and, hence, are the reconstructed odd
lines), the reconstructed progressive scan output from Summer 30
may still be useful even though it may not match the original
signal as closely as if the support signal were available. This is
particularly true when the unavailable support signal has a very
low bandwidth.
[0051] The present invention and its various aspects may be
implemented in analog circuitry, or, for example, as software
functions performed in digital signal processors, programmed
general-purpose digital computers, and/or special purpose digital
computers. Interfaces between analog and digital signal streams may
be performed in appropriate hardware and/or as functions in
software and/or firmware. Although the present invention and its
various aspects may involve analog or digital signals, in practical
applications most or all processing functions are likely to be
performed in the digital domain on digital signal streams in which
video signals are represented by samples.
* * * * *