Page turning effect generating apparatus

A page turning effect generating apparatus for video signals is provided with a memory for storing a video signal, an output switch for switching incoming video signal and a memory output video signal in accordance with a switching control signal, and a control signal generator including a circuit for generating the switching control signal and a circuit for generating a read address to be supplied to the memory, wherein the read address generating circuit includes a convertor for non-linearly converting a first vector which represents one of the vector components of a vector expressing a scanning point of a display image from an origin of a modification, and a generator for generating a final vector by synthesizing the non-linearly converted first vector and a second vector which represents another of the vector components of the vector, the final vector indicating the read address to be supplied to the memory.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a page turning effect generating apparatus 
for video signals. 
2. Description of the Prior Art 
As methods of changing over a video image (video screen) from an image A to 
an image B, there are generally known dissolve, cut-out and cut-in, wipe 
and so on, while a page turning method is used as a special image 
change-over method. 
The page turning method is performed such that an image A is first 
displayed, as shown in FIG. 1A, the image A is then gradually replaced by 
an image B as if a page of a book is being turned over, as shown in FIGS. 
1B to 1D, and finally the image B is displayed as shown in FIG. 1E. In 
this event, a portion out of the image A being turned over which is 
outside the screen shown in FIG. 1D (shown by a phantom line) is not 
naturally displayed. Further, as shown in FIGS. 1B to 1D, a turned portion 
of the image A is displayed in reverse, and a bent portion formed by the 
page turning is displayed as being deformed into a cylindrical shape 
(non-linear). 
In the explanation below, respective portions will be designated by the 
following names which are also shown in FIG. 2, as occasions arise: 
Display screen D: An overall image displayed on a screen of a display; 
Previous image A: An image which is to be erased by a page turn-over; 
Remaining portion Z: A portion of the previous image A which is not yet 
erased; 
Next image B: An image which is to appear by a page turn-over. 
Reverse portion R: A portion of the previous image A which is being 
reversely displayed by a page turn-over; 
Edge L: An edge for turning the previous image A (a border between the next 
image B and the reverse portion R); 
Nonlinear portion N: A portion of the remaining portion Z and the reverse 
portion R which is deformed as being nonlinear or cylindrical in the 
vicinity of the edge L (a portion indicated by hatching); and 
Hidden portion S: A portion of the previous image A which is hidden by the 
reverse portion R. 
Incidentally, in order to obtain page turning effects as mentioned above, 
image data of the remaining portion Z, image data of the reverse portion R 
and the image data of the next image B are necessary. Among the image 
data, as to the next image B, when a scanning position on the displayed 
screen D arrives at the next image B, image data at that position is 
merely outputted as it is as image data on the next image B. Such 
processing may be performed likewise for the remaining portion Z except 
for the nonlinear portion N. 
However, in the nonlinear portion N, it is necessary to modify the order of 
the image data of the previous image A to a nonlinear or cylindrical form. 
Also, in the reverse portion R except for the nonlinear portion N, it is 
necessary to modify the order of the image data of the previous image A, 
though in a linear form. 
For this reason, image data necessary for the nonlinear portion N has been 
conventionally derived by linearly writing image data of the previous 
image A into a video memory as well as generating nonlinearly changing 
read address signals by a cylindrical address generating circuit. 
The above configuration for deriving nonlinear image data, nevertheless, 
requires a very complicated and expensive cylindrical address generating 
circuit. Also, the configuration allows little freedom relative to the 
shape (apparent shape in cross-section) of the nonlinear portion N when 
the reverse portion R is turned over. Therefore, the hardware 
configuration must be modified for producing the nonlinear portion N in a 
shape other than a cylindrical shape, for example an involved shape. 
Further, since read addresses are generated separately for the portions N 
and R and the portion Z, the address generating method is complicated, 
which results in reduced freedom relative to the image changing 
processing. The configuration becomes further complicated when performing 
other page turning effects, for example, transferring the edge L in a fan 
shape simultaneously with a page turn-over. 
Furthermore, there is little compatibility of hardware with other page 
turning effect generating circuits, for example, a three dimensional 
rotation effect generating circuit. 
OBJECTS AND SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide an 
improved page turning effect generating apparatus which can eliminate the 
aforenoted shortcomings and disadvantages of the prior art. 
More specifically, it is an object of the present invention to provide a 
page turning effect generating apparatus which is capable of eliminating 
the above-mentioned problems inherent to conventional apparatus, i.e., a 
complicated configuration, little freedom, little compatibility and so on. 
As an aspect of the present invention, a page turning effect generating 
apparatus for video signals comprises a memory for storing video signals, 
an output switch for switching incoming video signals and memory output 
video signals in accordance with a switching control signal, a control 
signal generating circuit including a device for generating the switching 
control signal, and a device for generating a read address to be supplied 
to the memory. The read address generating circuit includes a device for 
non-linearly converting a first vector which represents one of the vector 
components of a vector expressing a scanning point of a display image from 
an origin of a modification, and a device for generating a final vector by 
synthesizing the non-linearly converted first vector and a second vector 
which represents another of the vector components of the vector, the final 
vector indicating the read address to be supplied to the memory.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Now, an embodiment of the present invention will hereinafter be described 
with reference to the accompanying drawings. 
FIG. 3 shows the whole circuit arrangement of a first embodiment of the 
page turning effect generating apparatus according to the present 
invention. In FIG. 3, vertical and horizontal synchronizing pulses serving 
as references, a burst signal and a clock signal are supplied through a 
terminal 11 to a timing generator 12 which generates a variety of signals 
in synchronism with the supplied signals and supplies the same to 
respective circuits constituting the apparatus described later. 
A microcomputer 15 sets a page turning speed and so on and starts page 
turning processing upon receiving a start signal from a terminal 16. 
In the page turning process, first a color video signal Sa of a previous 
image A is supplied through a terminal 1 to a decoder 2 where three 
primary color signals Er, Eg, and Eb respectively representing red, green 
and blue are decoded, and the signal Er is supplied to a processing 
circuit 3R. 
In the processing circuit 3R, the signal Er is supplied to an A/D 
(analog-to-digital) converter 31 to be converted to a digital red signal 
Er which is alternately supplied to field memories 331, 332 through a 
switching circuit 32 in every field period. A write address generating 
circuit 13 receives a signal from the timing generator 12 and then 
generates a write address signal WRAD for each sample of the signal Er 
which is supplied to one of the memories 331, 332. The write address 
signal WRAD is then supplied with the signal Er alternately in every field 
period. 
The memories 331, 332 in this embodiment are composed of so-called V-RAMs 
wherein a scanning position of the signal Sa corresponds to an address. 
More specifically, assuming that horizontal and vertical coordinates of a 
scanning position are represented by (xm, ym), the write address WRAD 
indicates a write address (xm, ym) corresponding to the scan position 
coordinates (xm, ym). 
Thus, the signal Er is written into the memories 331, 332 alternately in 
every field period, and sequentially in a one sample by one sample manner 
in a dot image. 
A read address generating circuit 14 generates a read address signal RDAD 
which is changed in a manner later referred to. The signal RDAD is 
supplied to one of the memories 331 or 332 in which a write is not being 
performed alternately in every field period. Thus, the signals Er 
representing a remaining portion Z and a reverse portion R are alternately 
read out of the memories 331, 332 in every field period. These signals are 
then supplied through a switch circuit 34 to a D/A (digital-to-analog) 
converter 35 to be converted to analog signals, and then delivered to an 
encoder 4. 
Processing circuits 3G, 3B, constructed in a manner similar to the 
processing circuit 3R, are respectively supplied with the signals Eg, Eb 
which are processed in a manner similar to the signal Er and supplied to 
the encoder 4. 
In the encoder 4, the signals Er, Eg, Eb are encoded to generate a color 
video signal Sp representing the remaining portion Z and the reverse 
portion R which in turn is supplied to a switch circuit 5. 
Also, a color video signal Sb representing a next image B is supplied to 
the switch circuit 5 through a terminal 7, while a signal Sc which becomes 
"1" during a displayed period of the next image B is supplied from the 
generating circuit 14 to the switch circuit 5 as a control signal thereof. 
The signals Sp and Sb are then selectively derived from the switch circuit 
5 in accordance with the signal Sc, and a color video signal for the page 
turning process is delivered to a terminal 6. 
Next, a read method or procedure for the memories 331 and 332 will be 
explained with reference to FIGS. 4 to 7. 
(1) Upon turning over a page, the position of the edge L may be changed in 
every field period or every integer-time period thereof and may not be 
changed within one field period. 
Assuming, as shown in FIG. 4, that: 
P: an arbitrary point (a scanning point or a pixel) on the displayed screen 
D in an arbitrary field period; 
O: an arbitrary point which is the origin of a page turning over; and 
OP: a vector from the origin O toward the point P; the following vectors 
are calculated: 
OU: a component vector of the vector OP in a direction parallel to the edge 
L; and 
OV: a component vector of the vector OP in a direction perpendicular to the 
edge L or a page turning over direction. 
As shown in FIGS. 5A to 5C, a scanning position or a position of the point 
P is located in either the remaining portion Z (FIG. 5A), the reversed 
image R (FIG. 5B) or the next image B (FIG. 5C) in a field period in which 
a page is being turned. It should be noted, however, that in this event 
the position of origin O is not changed regardless of the position of the 
point P in the same field period. 
However, as shown in FIGS. 6A to 6C, if the field periods are different 
even with the point P remaining at the same position, the position of the 
origin O is changed once in every predetermined field period in the 
direction of the vector OV corresponding to a page turning speed. In other 
words, the length between the origin 0 and the edge L in the direction of 
the vector OV is constant. 
(2) Next, with a magnitude or length OV of the vector OV being an input, 
the magnitude OV is converted to a predetermined value OW, for example, 
with reference to a look-up table memory. 
In this event, when the point P is located on the remaining portion Z 
(except for the case where the point P is located on the nonlinear portion 
N) as shown in FIG. 5A, OW=OV stands. 
However, when the point P is located on the reverse portion R or the 
nonlinear portion N as shown in FIG. 4; the value OW (FIG. 7B) is a value 
corresponding to the transformation. More specifically, a v axis is 
assumed to be a coordinate axis provided by projecting the vector OV in 
parallel, as shown in FIG. 7. Also, supposing that the reverse portion R 
is solid, the cross-section of the reverse portion R taken along the 
v-axis direction is as shown in FIG. 7B. It should be noted, however, that 
values in FIG. 7B are included as comparisons for facilitating 
understanding and therefore are not correct. 
Then, conversions are performed as follows: 
when OV=200, OW=90; 
when OV=180, OW=115; 
when OV=173, OW=140 (with L); 
when OV=178, OW=160; 
when OV=198, OW=190 
Note, the values OW in the upper half belong to the reverse portion R, 
while those in the lower half belong to the hidden portion S. 
Stated another way, when the coordinate (=OV) of the point V on the v-axis 
is converted to the coordinate (=OW) on the v-axis before the reverse 
portion R is turned over, this converted value is equal to the value OW. 
Incidentaly, the values OW include one converted from the magnitude OV of 
the reverse portion R and one converted from the magnitude OV of the 
hidden portion S. To distinguish these two values from each other, the 
former, that is, the value OW converted from the magnitude of the reverse 
portion R is designated OWUP while the latter, that is, the value OW 
converted from the magnitude OV of the hidden portion S is designated 
OWDN. 
(3) The values OWUP, OWDN calculated in Paragraph (2) are regarded as 
vectors in the direction of the vector OV, and the following vector 
composing is carried out: 
I. The vector OU is vector synthesized with the value OWUP to obtain the 
coordinate of a point Pu based on the origin O as the origin; and 
II. The vector OU is vector synthesized with the value OWDN to obtain the 
coordinate of a point Pd based on the origin O as the origin. 
In the above vector synthesis, if the original point P is located on the 
remaining portion Z (except for the nonlinear portion N), OWUP (=OW)=OV 
stands, so that the position of the point Pu is coincident with the 
position of point P. 
Alternatively, if the point P is located on the reverse portion R, the 
point Pu, is positioned within the display screen D. 
Further, if the point P is located on the next image B, the points Pu, Pd 
are positioned outside the display screen D. 
Then, the processing of the following paragraph (4) is carried out on the 
basis of the positions of the points Pu, Pd. 
(4) Read addresses for the memories 331, 332 are generated by performing 
the following processing from the coordinates of the points Pu, Pd: 
I. When the point Pd is located within the display screen D, the 
coordinates of the point Pd are designated as a read address irrespective 
of the position of the point Pu; 
II. When the point Pd is located outside the display screen D, and the 
point Pu is located on the display screen D, the coordinate of the point 
Pu is designated as a read address; and 
III. When the point Pd is located outside the display screen D, and the 
point Pu is also located outside the display screen D, read outs from the 
memories 331, 332 are not performed. Instead, the video signal Sb 
representing the next image B is fetched. 
The above-mentioned reading method for the memories 331, 332 can be 
explained by using equations in the following manner. 
Assuming that (xs, ys) designate the coordinates of the point P on the 
display screen D, (x.sub.0, y.sub.0) designate the coordinate of the 
origin O, N(Nx, Ny) is a unit vector in the direction of the vector OU, 
and T(Tx, Ty) is a unit vector in the direction of the vector OV, the 
magnitude n of the vector OU (=OU) and the magnitude t of the vector OV 
(=OV) are given by the following equations: 
EQU n=Nx(xs-x.sub.0)+Ny(ys-y.sub.0) (i) 
EQU t=Tx(xs-x.sub.0)+Ty(ys-y.sub.0) (ii) 
Then, further assuming that reference characters t.sub.1, t.sub.2 designate 
results of nonlinearly transforming the magnitude t, where t.sub.1 =OWUP 
and T.sub.2 =OWDN, then horizontal and vertical read addresses xm, ym 
(constituting a read address signal RDAD) for the point P in the memories 
331, 332 are given by the following equations: 
EQU xm=x.sub.0 +Txt.sub.1 +Nxn (iii) 
EQU ym=y.sub.0 +Tyt.sub.1 +Nyn (iv) 
Next, substituting the equation (i) for the equations (iii), (iv), xm and 
ym are given by the following equations: 
EQU xm=Txt.sub.1 +Nx.sup.2 xs+NxNyys+Ny.sup.2 x.sub.0 -NxNyy.sub.0(v) 
EQU ym=Tyt.sub.1 +NxNyys+Ny.sup.2 ys-NxNyx.sub.0 +Nx.sup.2 y.sub.0(vi) 
Further assuming: 
EQU X=Nx.sup.2 xs+NxNyys+Ny.sup.2 X.sub.0 -NxNyy.sub.0 (vii) 
EQU Y=NxNyxs+Ny.sup.2 Ys-NxNyx.sub.0 +Nx.sup.2 y.sub.0 (viii) 
the above equations (v), (vi) are expressed as follows: 
EQU xm=Txt.sub.1 +X (ix) 
EQU ym=Tyt.sub.1 +Y (x) 
The above procedure is likewise applied to the value t.sub.2. 
For providing a simple page turning effect or a page turning effect for 
moving the edge L at a constant speed in the same direction, the values 
Nx, Ny, Tx, Ty in the above equations (vii) to (x) are constant. The 
values x.sub.0, y.sub.0, on the other hand, vary corresponding to a page 
turning speed in every field period or every integer multiple period 
thereof. 
While the values xs, ys vary corresponding to the horizontal and vertical 
scans, they may be incremented by one corresponding to the scans, or they 
may be accummulatively added. 
FIG. 8 shows an example of the read address generating circuit 14 
implementing the above-mentioned algorithm. 
Specifically, signals Tx, Ty representing the above-mentioned values Tx, Ty 
are fetched from the microcomputer 15 through buffer registers 41, 42. 
Signals representing the values Nx, Ny, x.sub.0, y.sub.0 are also supplied 
from the microcomputer 15 to operating circuits 43 to 45, while a clock 
signal and so on are supplied from the timing generator 12 to the 
operating circuits 43, 44 and 45 to generate signals X, Y, t respectively 
representing the values X, Y, t. 
Then, the signal t is supplied to look-up tables 51, 52 to be converted to 
signals t.sub.1, t.sub.2 representing the values t.sub.1, t.sub.2, 
respectively. These signals t.sub.1, t.sub.2 are supplied to multiplier 
circuits 61, 62 which are also supplied with the signals Tx, Ty 
respectively from the registers 41, 42, whereby signals representing the 
values Txt.sub.1, Tyt.sub.1, Txt.sub.2, Tyt.sub.2 appearing in the 
foregoing equations (ix), (x) are generated from the multiplier circuits 
61, 62. The signals Txt.sub.1, Tyt.sub.1, Txt.sub.2, Tyt.sub.2 are then 
supplied to adder circuits 71, 72 which are also supplied with the signals 
X, Y from the operating circuits 43 and 44, whereby address signals xm, ym 
corresponding to the value OWUP and address signals xm, ym corresponding 
to the value OWDN are generated and supplied to a selector circuit 81. 
In the selector circuit 81, the addresses xm, ym corresponding to the value 
OWUP or OWDN are selected in accordance with sections I to III of the 
foregoing Paragraph (4) and supplied by the selector circuit 81 to the 
memories 331, 332 as read addresses. Further, the control signal Sc is 
fetched from the selector circuit 81 in accordance with sections I to III 
of Paragraph (4) and supplied to the switch circuit 5. Thus, from the 
terminal 6 coupled to the switch 5 emanates a color video signal for a 
page turning effect. 
It is appreciated that the apparatus of the present embodiment is capable 
of generating color video signals for page turning effects without the 
necessity of a complicated and expensive cylindrical address generating 
circuit which has been needed for conventional apparatus. 
Also, for modifying the shape (apparent shape in cross-section) of the 
nonlinear portion N for turning up the reverse portion R, data in the 
tables 51, 52 may be simply modified, which results in providing great 
freedom in the shape of the nonlinear portion N. 
Further, the read addresses can be generated separately for the portions N, 
R and the portion Z, so that great freedom is also provided for image 
change-over processing. For example, if it is desired to move the edge L 
in a fan shape at the same time a page is turned over, it is sufficient to 
modify the values X, Y in every field period or every integer-multiple 
period thereof. In alternative examples, if a reduced image is to be 
superimposed on a page which is being turned over, a reduced next page B, 
which is being turned over, can be superimposed on the display screen D 
without difficulty. 
The apparatus of the present embodiment further provides a high 
compatibility with other special effect generating circuits such as a 
three-dimensional rotation effect generating circuit. 
Next, a second embodiment of the present invention will be explained with 
reference to FIG. 9. 
FIG. 9 shows an example of the circuit 14 which is used in a case where, 
when a previous image A is turned over, its reverse portion R is displayed 
so as to look as if it is involved, for example as the cross-section shown 
in FIG. 10. Explaining more specifically with reference to FIG. 10, when a 
point P is located on an involved portion, three values t.sub.1, t.sub.2 
and t.sub.3 are necessary for generating such a page turning effect. For 
this reason, a third look-up table memory 53 as well as a multiplier 
circuit 63 and an adder circuit 73 are provided for generating signals 
representing the foregoing equations (ix), (x) for the value t.sub.3 which 
are supplied to the selector circuit 81. 
The cross-section shape of the "turning page" can be made more complicated 
and effective by adding an operating circuit corresponding to a series 
circuit of the look-up table memory 53, the multiplier circuit 63 and the 
adder circuit 73, shown in FIG. 10. The look-up table memories 51, 52 may 
only contain data on the nonlinear portion N such that data on linear 
portions are calculated. 
It should be further noted that for the previous image A, which is a still 
image, only one of the field memories 331, 332 is needed. 
According to the present invention as described above, the page turning 
effect generating apparatus does not need a cylindrical address generating 
circuit, which results in avoiding a complicated configuration and high 
cost of the apparatus. 
Also, for modifying the shape (apparent shape in cross-section) of the 
nonlinear portion N for turning over the reverse portion R, data in the 
tables 51, 52 may be simply modified, which is simple and results in 
providing great freedom in designing the shape of the nonlinear portion N. 
Further, the read addresses can be generated separately for the portions N, 
R and the portion Z, so that great freedom is also provided for image 
change-over processing. For example, if it is desired to move the edge L 
in a fan shape at the same time a page is turned over, it is sufficient to 
modify the values X, Y in every field period or every integer-multiple 
period thereof. In alternative examples, if a reduced image is to be 
superimposed on a page which is being turned over, a reduced next page B, 
which is being turned over, can be superimposed on the display screen D 
without difficulty. 
The apparatus of the invention further provides a high compatibility with 
other special effect generating circuits such as a three-dimensional 
rotation effect generating circuit. 
Having described the preferred embodiments of the invention 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 and 
modifications thereof could be effected by one skilled in the art without 
departing from the spirit or scope of the invention defined in the 
appended claims.