US 3891792 A
A method and apparatus for superimposing printed characters of any such nature as may be transmitted upon a received television image, at the will of the viewer at the receiver. The character information is incrementally transmitted during the vertical blanking interval of the television scanning format. The receiver is especially constructed to have a dynamic shift register, also means to manually select one or none of plural character programs; such as news, stock market, or weather. The characters may be made to crawl horizontally to present an extended message, which crawl may be halted by the viewer. The mandatory display of emergency messages is possible by a control located at the transmitter.
Description (OCR text may contain errors)
United States Paten 1 Kimura i 1 TELEVISION CHARACTER CRAWL DISPLAY METHOD AND APPARATUS I75] Inventor:
(73] Assignee: Asahi Broadcasting Corporation,
Osaka. Japan 1221 Filed: June 25,1974
Hisao Kimura, Kyoto. Japan June 24, 1975 4/1974 Coombe 340/324 AD Miyata et a]. 340/324 AD 57 ABSTRACT A method and apparatus for superimposing printed characters of any such nature as may be transmitted upon a received television image, at the will of the viewer at the receiver. The character information is incrementally transmitted during the vertical blanking interval of the television scanning format. The receiver is especially constructed to have a dynamic shift register, also means to manually select one or none of plural character programs; such as news, stock market, or weather. The characters may be made to crawl horizontally to present an extended message, which crawl may be halted by the viewer. The mandatory display of emergency messages is possible by a control located at the transmitter.
17 Claims, 18 Drawing Figures SHEET PATENTEDJUN 24 ms mmbwmqm COO --OOO CO0 v-v-OOO N OI COO
PATENTED JUN 24 I975 SHEET w OE mum 2:2 hzmzomm TELEVISION CHARACTER CRAWL DISPLAY METHOD AND APPARATUS BACKGROUND OF THE INVENTION This invention relates to multiple images upon a television display tube.
At times the prior art has provided multiple images on a television display tube, usually a traveling line of alpha-numeric type at the bottom ofa television image. The purpose has been to present news flashes without interrupting the television program in progress. Such a line of characters has been transmitted as an integral part of the video signal forming the image and has been displayed upon all receivers without choice or recourse by the viewer.
In such systems the receivers are not modified. Additional required apparatus is provided wholly at the transmitter.
In other systems where a choice has been possible by the viewer. the prior art has required a memory at the receiver in which alphanumeric characters are usually stored, to be called-out for display by a code signal received from the transmitter. Oriental languages contain about 2,500 characters instead of the about 60 alphanumeric characters of the western languages. Thus, the code-memory at the receiver system is impractical for anything other than the storage of under I characters.
Certain other apparatus has been provided by the prior art for displaying plural stock market tapes, but without the combination with a television image. This is a simple technique, in that exact correlation between the timing of the television image scanning and the process for superimposing a message is not required.
Still other apparatus has employed delay lines for temporary storage. A code was used to key-out characters from a receiver memory.
SUMMARY OF THE INVENTION This invention provides a selected one of a plurality of elongated area character messages, or none, superimposed upon the image of a television receiver, at the option of the viewer at the receiver. This is accomplished by providing additional apparatus and manual controls at the television receiver. A mandatory display of emergency messages is also possible and this is under the exclusive control of the transmitter.
At the transmitter, digital logic, including a clock generator, plural registers and memories for each character pattern, memories for message, counters, and decoders from the character signals. These are incrementally transmitted during successive vertical blanking intervals of the known television image signal (video). The character signal itself directly provides the information required for the display at the receiver.
At the receiver, in addition to the known television circuits, there is provided digital logic, including a character signal data extractor, buffer registers, character element counters, and a large dynamic shift register. These are interconnected by suitable gates and flipflops. A video data mixer reinserts the characters signal into the video channel, this signal having been read-out of the shift register at a time to be displayed at a selectable vertical position on the television image display device to be seen by the viewer.
Manual controls at the receiver allow one of a plurality of character messages, or none, to be selected for viewing, also to stop the horizontal crawl of the message, if desired.
The characters displayed are formed by low "high" electrical bit pulses supplied to the television image reproducing device. These are suitably timed to form the characters in synchronism with television scanning. These may be alpha-numeric in any language, Japanese or Chinese characters, or any suitable diagrams or representations.
A flag identifies the initiation of character data transmission and promotes simplified apparatus at the receiver.
Typically, all character data are transmitted, incrementally and successively, upon one line of horizontal television scanning during the vertical blanking interval.
A dynamic shift register temporarily stores thousands of bits that have been incrementally transmitted from the transmitter. These form in themselves the character display at the receiver.
Accordingly, permanent memory storage apparatus is not required at the receiver and the information required for the display is not drawn therefrom by merely a transmitted code. The method of operation of the system is thus widely removed from the conventional mode of operation.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. I shows the face of a display tube with a representative display thereon and indications of other positions which the display of the line of characters may occupy.
FIG. 2 shows how the letter E is formed on the television raster by appropriately timed bit signals.
FIG. 3 shows the entire transmitter system block diagram.
FIG. 4 shows a segment diagram of a 9l bit shift register, as a simplified example.
FIG. 5A shows related shift pulse trains to the shift register.
FIG. 5B shows display element addresses on the television raster.
FIG. 6 shows the contents of the shift register shifted by I bit.
FIG. 7 shows the horizontal crawl sequence of sample letters A B C.
FIG. 8 is a waveform and channel allocation diagram for the 21st horizontal line.
FIG. 9 is a schematic diagram of the transmitter character-signal forming logic.
FIG. 10 shows a detailed schematic diagram of u, w and W counters.
FIG. 11 is a block diagram of the receiver charactersignal forming logic.
FIG. 12 shows a functional block diagram of a portion of the receiver system.
FIG. 13 shows a raster representation of the receiver functioning.
FIG. 14 is a representation of receiver system timing.
FIG. 15 is a further portion of the functional block diagram of the receiver system.
FIG. 16 is a schematic logic diagram of the receiver character-signal forming logic.
FIG. I7 is a schematic logic diagram of the apparatus for accomplishing mandatory control".
GENERAL FIG. 1 shows the television display for this system, including the timing relationship for the known television scanning from left to right and top to bottom, respectively, Numeral 1 shows a field started with a vertical drive signal and completed just before the vertical drive signal of the next field. Numeral 2 shows the frame of the raster and 3 indicates a significant part of the normal televised picture. Numeral 4 indicates a typical sub-raster, dimensioned as 16 lines per field, or a total of 32 lines for the full frame of the display system of this invention. Numeral 5 shows a typical superimposed font of this display system; i.e., the message "Electronic Display is popular.
Other positions, such as 7 and 7', are selectable for positions of the sub-raster.
The display normally crawls in the direction indicated by arrow 6. The letter E of the message starts to crawl from the right end of sub-raster 4 and travels to the left, where it is now shown.
The television image may be reproduced in color by the known television process. No interference between the display waveforms and the waveforms required for color television is experienced.
Numeral 8 shows the transmitted data signal, superimposed on the 2 Ist horizontal line, just above the top of the raster frame 2. The exact nature and composition of this signal varies with the details of the message.
In FIG. 2, the capital E of the above illustrated message is identified by numeral 9. It is divided into a number of vertical columns, such as ten, as shown. Pattern data bits (PD bits) in the first (left) column 10 are l, I, l, l, l, to a total of l2, from the top down to the bottom of this letter. Thereafter, 0, 0, 0, 0. This is sent in the first television scanning field.
In the same manner, the second column, ll, becomes 1,0, 0, 0, 0, l, 1,0, 0, 0, 0, l, 0,0,0, 0, and this is sent on the second field. Continuing, the third column, 12, is sent on the third field, and so on; to the tenth column identified by numeral 13. These columns of PD bits are an important aspect of the system of this invention.
it will be noted that there are four 0 spaces at the bottom of each column on the E. This sets the bottom of that letter and others like it sufficiently far up in the sub-raster so that lower stems of certain small letters such as the p and y can be executed.
TRANSMITTER MODE The block diagram of FIG. 3 gives the method and apparatus involved in adding the character display to known television transmitting apparatus.
Character coder I4 is the input originating device for coding a large number of characters, such as 2,500 Chinese characters. By pointing with a known light pen each character can be coded as a 6 bit X two frame, or a 12 bits code. The operator selects the character according to the sentence he is forming for transmission.
Sentence memory 15 is connected to character coder 14, for the storage of the coded data output from coder [4. These data are stored in address sequence. For the sending sequence the stored data in sentence memory 15 is read out in address sequence according to the time lapse for each letter covering the entire sentence.
At the end of the sentence memory 15 is programmed to address back to the beginning of the sentence.
The output of sentence memory I5 enters character pattern memory 16. The latter is a magnetic core memory. having a capacity of 131 K bytes. A total of 2,500 character patterns are stored therein, in a l6 X 16 array for each character. The core memory is segmented as 1,024 lines for the X axis. 64 lines for the Y axis, and 16 bits for the Z axis.
X address register 17 is connected to character pattern memory 16 as is x address counter 18. These select the 1,024 lines having to do with the X axis.
Y address register 19 is also connected to character pattern memory 16. This register selects 64 lines having to do with the Y axis, subsequent to the selection for the X axis.
Six bits two frames of a character are assigned for the X and Y address registers, and its l6 columns for the x address counter 18.
Sixteen bits for the Z axis correspond to the vertical PD bit of each column.
In the address of the core memory that corresponds to the code of each character, the pattern for the character is previously stored.
Buffer register 20 is connected to the output of character pattern memory 16. The display is normally a horizontally crawling format and the coded characters from the sentence memory are converted into vertical column PD bits, 16 bits, and sent out for every field, V. Accordingly, x address counter 18 is set to zero at the beginning of the character and the PD bits in the left end of the character are read from the Z axis and temporarily stored in the 16 bits capacity buffer register 20. This register holds the data until a selected line, typically in the vertical blanking period of the television raster, such as the 21st television scanning line, 21H, occurs, and then the data are sent out serially on that line. At the same time x counter 18 is stepped up one, and the second vertical column PD bit is read out to be ready to be sent out on the followingV 2lst line. In the same manner, one character is completed with 16 vertical PD bits upon 16 V periods having occurred.
The following two V intervals do not have an output from character memory 16, but sentence memory 15 is addressed out one step and the next letter code set in the X and Y registers. This two V interval becomes the space between characters. The above operation is then repeated in order to send out the entire sentence.
Encoder 21 is connected to the output of buffer register 20, and the encoder accomplishes the above process. The output of the encoder is connected to mixer 22.
Mixer 22 also receives an input from program-line 23, upon which typically a full color video signal flows. The output of the mixer is taken by the on-air-line 24 and thence to a television video transmitter, pay television cable, or other apparatus that conveys the full transmitter signal to receivers for viewing.
RECEIVER MODE The previously mentioned column PD bits are extracted in the receiver, stored for accumulating a certain amount of data, processed for display and then displayed.
In order to simply explain the mode of receiver operation, a display area of l3 X 7 bits is chosen. A stored capacity of 91 bits is thus required. This is accomplished by shift register 30, shown in FIG. 4.
The input 3l of shift register 30 is switched to either new pattern data 33, or the output 34 of the shift register through recirculation line 35 by means of appropriate actuation of transfer switch 32.
The various segments 36 of shift register 30 begins at number 0, number I, etc. from the upper-left output side of the register. They progress to number 90 at the lower-right input side of the register.
The output of the shift register 34 is fed to display means 37, which is shown as the known television cathoderay tube. When the output of the register is high; i.e.. a digital I, then a white (bright) dot appears on the television screen and an elemental part of the character display is formed. When the output of the register is low; i.e., a digital 0, there is no contribution to the image television signal.
In FIG. 4 the data bits are given a designation corresponding to their position in the shift register. These start at the upper-left, output, end of the register with Al, then Bl, Cl etc. to M1 in the top row in the illustrative example of this figure. Similarly, the second row starts with A2 and ends with M2; and so on, until the end of the last row is M7. Each of these designations may be a l or a 0, according to the data required to reproduce the characters of the message.
Going further, in FIG. 5A pulse train 38 is generated for the duration of one horizontal line, say the Kth line; kth H. It is fed into the clock pulse input of shift register 30 as the shift pulse.
In the recirculation mode, Al is seen at the beginning of the kth H line. Shift pulse SI is then added and B1 is shifted into the No. segment of shift register 30. At the same time BI is seen on display tube 37. Also, previous data bit Al is fed back into the No. 90 segment via recirculation line 35 and data transfer switch 32. With the next shift pulse S2, Cl is seen on display tube 37.
In this manner, as shown in FIG. 58, Al through Ml are displayed on the kth H line, identified by numeral 39 in that figure, by the train of shift pulses SI through SI3. This occurs in synchronism with television scanning.
Then A2 is shifted with Sl3 and MI is stored in segment No. 90, at the lower right in FIG. 4.
On the (k I) the H line, identified by numeral 40 in FIG. B, the same shift pulse train 38 of FIG. 5A is applied to shift register 30, and the same result occurs as has been explained for the k the H line. Similarly, this result occurs again for each of the lines shown in FIG. 58, as the (k 2) th H line to the (k 6) th H line, in this simplified example.
The contents of the shift register are displayed on the picture tube screen 41 of FIG. 58. They appear as the desired characters in accordance with the initial data.
Shift register 30 in the recirculation mode can hold back the data to the same location as long as the number of shift pulses equals the shift register length.
In other words, data are displayed once in the scanning duration of the k th H through (k 6) th H lines on screen 41 of the display device. As long as the data a recirculated back to the original segment location in the shift register 30 itself, the display is seen as a still display, having the formation of data Al through M7 in FIG. 4.
Normally, when the chain of display of data Al through M7 has been completed (hereinafter designated as the end of an event") one additional shift pulse designated q is applied to shift register 30.
The content of data in the shift register shown in FIG. 4 becomes that shown in FIG. 6. It is seen that each datum has been shifted one segment location to the left, except the data segmented on No. [2. No. 25, No. 38. No. 90. With one more pulse operation of the above these data will be displayed.
In the process heretofore outlined the previously displayed datum Al is recirculated into No. 9() segment through data transfer switch 32, but now, at that particular moment switch 32 is turned to accept a new datum A7 (not AI). In the same manner. new datum Al is an input by the time 13 shift pulses have occurred. In this way the last datum is replaced and written by new datum A6. As a result, the whole display is shifted 1 column bit to the left and the extreme right column of the display is refreshed with new data. By the continuation of this operation the character message is made to crawl from right to left.
Recapitulating, the sequence to accomplish the crawl operation is as follows:
I. display of the event,
2. insertion of the q pulse for each television field.
3. write new data for each field.
The order of the sequence does not affect the operation as a whole.
If the input to display tube 37 is gated off from the output 34 of the shift register the display disappears. However, the process of writing in new data can be accomplished independently of any display of it.
Crawl of the characters can be inhibited at the television transmitter by sending out the control signal of the q pulse insertion, because the q pulse is generated in the receiver. The speed of the crawl can also be decreased by controlling for less frequent insertion of the q pulse than normal. The display may also be frozen; i.e., the crawl stopped, by not inserting the q pulse to the shift register at the receiver.
A representation of how the crawl operation appears is given in FIG. 7. It shows a portion of the message characters ABC in the English alphabet. The top row 42 shows the data bits Al, Bl, Cl, to M7 for all of the A and B and the first stroke ofC. In the second row, 43, data bits Al, A2, A3 A7 have been added and the display has moved one data position to the left of what is shown in the first row. The same process is repeated for the successively lower rows, 44, 45 and 46, and it is seen that the A has been reduced to a line and the C is now complete.
CHARACTERISTICS OF AN ACTUAL EMBODIMENT The illustrative simple embodiment heretofore employed to set forth the method and the major aspects of the apparatus is modified in ways as follows in order to become a full-scale device.
For characters of the Chinese type an area of 16 X 16 bits is typically employed. For English and other alphabet letters an area of 10 X 16 bits with a 2 bit spacing is considered proper for the display, in view of the size of the characters and the number of characters in one line.
Typical crawl speeds then become as follows. For Chinese characters the width of the area plus a spacing of 2 bits is a total of I8 bits. With television fields per second and a l bit shift per field, as indicated in FIG. 7 the crawl speed for Chinese characters becomes 60/18 333 characters per second, and for alphabet characters becomes 60/12 characters per second.
A desirable vertical extent of pattern data bits includes 32 horizontal scanning lines over one frame; l6 in each field. Considering the aspect ratio of the character and the speed of television scanning, the clock frequency of the shift pulses may be altered to be twice that of the color sub-carrier, 3.58 megahertz (MHz), thus to be THE; MHz.
The formation of the sub-raster may typically require 16 X 250 bits =4096 bits storage capacity in the receiver. This provides the capability of displaying 14 Chinese characters or several words in English on one line.
There are numerous different vertical positions on the television viewing screen for the sub-raster which carries the character message. A net viewing raster typically contains 525 lines minus 2 X 2l lines for the vertical blanking. The sub-raster is 32 lines high in each frame. There are thus (525 21 X 2)/32 15 bands available.
However, since it is common television practice to mask off all around the edge of the raster from the view of the observer. and since all possible positions for the sub-raster are not aesthetically desirable, about six positions are considered proper.
As will become further evident later, more than one message can be transmitted and utilized at the will of the viewer at the receiver. All messages are available at the receiver, and any one, or none, is selected by the viewer by manual control.
A typical number of separate messages is five; such as weather reports, stock market quotations, news, etc. These are all transceived over the 21st horizontal. H, line. A suitable clock frequency for this transceiving is half the color television sub-carrier frequency, or 1.76 megahertz. This allows a sufficient margin for the television video band-width.
In the widely used manner of regenerating synchronizing signals in a television receiver, often known as a.f.c. horizontal synchronization, these synchronizing signals are not precisely in phase with the synchronizing signals that are transmitted. Thus. the television picture reproduced at the receiver may shift slightly with respect to the cathode ray tube reproducer. It is not; however, distorted.
For transceiving character data, critical accuracy of phasing in this aspect is required. According to this invention an additional pulse known as the initial flag" (pulse) is generated. It is timed to be, and is, inserted ahead of the series of character data transmission signals. It achieves the critial accuracy required at the receiver, so that the characters of the messages will be clearly formed. The complexity, and so the cost, of the receiver character handling apparatus is considerably simplified through the use of this pulse.
TIMING RELATIONSHIPS OF TRANSCEIVING The timing relationships for accomplishing transmis sion of character data and the scheme involved are shown in FIGS. 8, 9, 10.
In FIG. 8, numeral 50in a row, indicates the channel assignment of the various messages, such as weather, news, etc. This is on the 21st horizontal line. This is a preferred line, being at the end of the vertical blanking period and thus devoid of the video signal forming the television image. In general, another horizontal line. or even lines, in the vicinity may be used. with understandable adjustment or minor modification of the apparatus involved in handling this part of the process.
As will be seen, line is divided into seven channels; 0W, 1W, 6W. All have 18 divisions at the period of 0.5587 microseconds, corresponding to the frequency of 1.79 megahertz, except channel 6W. The latter is of residual nature.
Channel OW starts at the leading edge of the horizontal (H) syncronizing signal and holds until slightly over the termination of the horizontal blanking signal. Therefore, no character data signal can be assigned to channel OW. However, the last portion of it, identified by numeral 51, is used as the initial flag pulse for the synchronization of the character data signal in the receiver.
Channels IW through 5W are used for the allocation of the A, B, C, D and E roll character message data.
Channel 6W contains only 5.75 divisions instead of 18. It terminates at the leading edge of the next H syn chronizing pulse, and this channel is not used for data transmission.
The diagram identified by numeral 52 shows the control bit region lWo, 2W0, etc., which is formed of 2 bits, and the character data bit region 1W 2W etc., which is formed of l6 bits.
The diagram identified by numeral 53 gives the detail of one channel. Therein, S4 is a spare (unused) bit, 55 is a freeze bit, and the inclusive 56 numeral indicates the pattern data bits.
If the freeze bit 55 is in the I state, the insertion of the q pulse on that field is inhibited in the receiver and the character display is frozen (not allowed to crawl) for that scanning field for that channel. When that is the case, data are not to be transmitted in that channel. Both the space bit and the freeze bit may be programmed to control additional modes of operation, besides the basic mode mentioned.
The waveform identified by numeral 57 in FIG. 8 gives details for the line 21st H. Initial flag pulse 58 is the detail of the indication 51 on the numeral 50 row. The variations inclusively indicated at 59 comprise the data of the No. l channel. These waveform variations are accomplished in buffer register 20 and encoder 21 of FIG. 3.
TRANSMITTER APPARATUS FIG. 9 shows the transmitter character-forming logic, notably buffer register 20 and encoder 21.
For simplification of explanation FIG. 9 has been drawn for positive logic, regardless of the conventional integrated circuit (IC) system of logic. That is, flipflops and counters are enabled or cleared by the positive-going edge of the clock pulse or clear pulse. The outputs of gates are not inverted.
For reducing the influence of the frequency interleaving of the NTSC standards, the color sub-carrier frequency fs is frequency-doubled to 2fs=7.l6 megahertz.
This frequency, at 60 in FIG. 9, is fed into u-counter 61, where it id divided 4 times, to fs2,=l .79 MHz. This frequency, which is the clock frequency for the data transmission, is fed into following w-counter 62 and subsequently W-counter 63. These counters generate various timing pulses, shown at the top of each. as to the outputs.