JPS6027230B2 - Still image signal receiving device - Google Patents

Description

[Detailed Description of the Invention] This invention provides a still image signal (including a character signal) that is transmitted during a part of the vertical retrace period of a television signal.
A still image signal receiving device that selectively records images, reads out the signals, and reproduces the images on the screen of a television receiver, is free from defects and is not subject to restrictions on the timing of turning on a stop switch. The reproduced image is configured to be displayed on a screen.

Attempts have been made to multiplex transmit a still image signal separate from the television signal into a portion of the vertical line period of the television signal, and the NHKC system is an example of this.

In order to facilitate understanding of this invention, an overview of the NHKC system will first be explained. In this system, the IH period is equivalent to 20 days from the beginning of the vertical retrace period, and the NHKC system is equivalent to the 289th day. A still image signal is superimposed on the IH period.

Now, if one character in a still image is composed of 18 dots vertically and 15 dots horizontally, and one line is 14 characters, and the spaces between characters and the spaces at the beginning and end of the line are 2 dots each, then the horizontal direction of one line is The number of dots is 240, and the number of vertical dots is 18. Furthermore, if one screen is made up of seven lines and the space between the lines is made 12 dots, then the number of vertical dots on one screen is 198. in fact,
Since one dot in the vertical direction is displayed with one horizontal scanning line, the screen is displayed with 198 lines. Such an image signal is "IH in one field".
Since the image is inserted by address, it takes 30 fields, or 0.5 seconds, to transmit one line of still images (3 plates including spaces between lines). In addition, the system sequentially transmits three types of signals at a rate of one line every 0.5 seconds, taking into account the reading speed of humans.

That is, as shown in Fig. 1A, each of the first line signals A-1, B-1...1-1 of nine programs A-1 is divided into units of 30 fields (0.5 seconds). After sending the same program A
~1, each two-line self-number A-2, B-2...
...・Transmit 1-2 sequentially. Therefore, when you select a certain program, the maximum waiting time is 4 seconds (however, 0.5 seconds x 8).
The program is extracted and the first line is recorded and read over a period of 0.9 seconds or less. Then, four seconds after the end of the recording, the next first line of the same program is recorded for 0.5 seconds and read out, and this is repeated sequentially thereafter. On the other hand, the signal that appears in the second frame of the vertical women's line period is a binary signal that indicates the type of program at the beginning of the line signal a corresponding to one horizontal scanning line of characters, as shown in Figure 2 The 4-bit program code, the binary 8-bit line code a3 that indicates which line of one screen displayed in that program the signal corresponds to, and the signal that serves as the standard for reading these signals. STX is added.

Note that HP indicates a horizontal synchronizing pulse signal, and T indicates a color bust signal. When a television signal containing still image signal components as described above is captured by a receiving antenna, it is applied to a signal extraction circuit through a tuner and a waveform shaping circuit. The second signal component extracted here is then applied to a program code detection circuit 2 comprising a buffer memory 1 and a shift register, as shown in FIG. The program code detection circuit 2 detects a 4-bit program code signal using a code determination pulse and a sampling pulse, and this program code signal is a 4-bit selected program code signal extracted from a program selection switch 3 through a decoder 4. The bits of the program code signal are held until the 2qH signal of the next field is taken out, so that the bits of the program code signal match the selected program code signal. , and when the second extraction pulse appears, an output signal is sent from the AND gate circuit 6. As a result, the write transfer control circuit T opens the gate of the rewrite gate circuit 8, so that the buffer The IH recorded content of the memory 1 is transferred to the main memory 9, and the main memory 9 records the IH portion of the selected program.
When a certain program is selected in advance, the IH signal components of the program are sequentially extracted from the still image signals transmitted within the vertical line period, and are sequentially recorded in the main memory 9. The still image signals recorded in the main memory 9 are updated and read out one row (three rows) at a time, and are sequentially displayed on the screen of the television receiver. By the way, right now there may be a situation where you would like to continue viewing a certain image displayed on the screen.

In such a case, the image stop switch is turned on to close the gate of the transfer gate circuit 8. In this way, the input signal transferred from the buffer memory 1 to the main memory 9 is The screen will be cut off and the same screen will continue to be displayed. However, if the nail switch is turned on at an inappropriate time, an unreadable missing portion will appear in the reproduced image. In other words, it is OK to turn on the stop plow switch after recording a character signal on a certain line, but if you turn on the stop plow switch while recording a character signal on a certain line, for example, the third line, As shown in FIG. 4, the characters in the third line of the image displayed on the screen are missing at the bottom, making it difficult to read them. Moreover, the entire screen becomes very unsightly. The present invention eliminates the above-mentioned conventional disadvantages, and the still picture signal receiving apparatus of the present invention will be described in detail together with the embodiments shown in the drawings from FIG. 5 onwards.

In FIG. 5, the program code of the 20th day signal (A in FIG. 6) sent to the program code detection circuit 2 is detected using the same code determination pulse and sampling as in the prior art.

Then, the 4-bit program code signal A', 8, 〇, 〇 generated here is held until the second signal appears in the next field `, as shown in Figure 6-2. On the other hand, when these program code signals A', B', C', and ○ are input, the 4-bit latch circuit 10 operates using the 24th day sampling pulse (FIG. 6 C) as a latch clock pulse. At the rising edge of , a 4-bit inverted code signal A'', B'', 0', 0' corresponding to the content of the program code signal is output. This code signal is held until the next field day when the second cape extraction pulse is generated, as shown in FIG. 6(e).
Output code signal A'' of comparison circuit 11' and latch circuit 10
, B'', C'', D'' and program code signals A', B', C
′, 〇.

That is, the signal A' and the signal A', the signal B' and the signal
EXCLUSIVE-OR gate circuits 12, 13, 14 respectively
, 15, and its output signal is connected to 4-input NAND
The voltage is applied to the gate circuit 16. Now, taking as an example the second line signal FA29 and the third line signal FA30 of program A shown in FIG.
The program code signal (0001) of A29 is latched by the double peak removal pulse P29 in the same field.

That is, the program code detection circuit 2 converts the code signal (0001) of the program A into the third expense line signal F of the next field.
The latch circuit 1 is held until the occurrence of A30.
The code signal (1110) obtained by inverting the code signal (0001) is output and held until the generation of the second cape extraction pulse P3o in the next field.During this period, the comparator circuit 11 The output signal of
”.Output signals A', B' of the program code detection circuit 2
, C', 0 is switched to the program B code signal (0010) in the field of the first line signal FBI of program B, but the output signals A'', B of the latch circuit 10 are ″, C″, D″ are program B
Until the first line signal FBI appears, the signal becomes the inverted code signal (1110).

Therefore, the output signal of the comparison circuit 11 during this period becomes "1" as shown in FIG. in this way,
The output signal of the comparison circuit 11 becomes "1" only when the still image signal transmitted from the broadcasting station switches its program code, and becomes "0" during the period when the same program is sent over 30 fields. .

Then, from the AND gate circuit 17 which inputs the output signal of the comparator circuit 11 and the pulse 2 (b in FIG. 6), a program mismatch pulse as shown in g in FIG. 6 is taken out. Become. Now, when program B is selected and the second line signal of the same program is written in buffer memory 1, the stop plow switch is turned on to generate a stop signal as shown in Figure 6. Assume that the voltage is applied to the flip-flop circuit 18.

In this case, the output terminal QsT of the flip-flop circuit 18
, QsT are taken out as shown in FIG. 6, and the gate of the transfer gate circuit 8 is thereby closed. In other words, the 30 lines (1 line) of program B will not be transferred to the main memory 9.
This eliminates the unsightly appearance of images caused by incomplete image reproduction of this line.

[Brief explanation of the drawing]

FIG. 1 is a diagram chronologically showing an example of a still picture signal selectively reproduced by a conventional still picture signal receiving device, and FIG. 2 is a schematic diagram showing signal components in the IH period of the still picture signal.
FIG. 3 is a block diagram mainly of a program selection control section of a conventional still picture signal receiving device, FIG. 4 is a plan view of an image projected on the screen of the same device, and FIG. 5 is a still picture signal according to the present invention. FIG. 6 is a block diagram of the main parts of one embodiment of the receiving apparatus, and is an electrical waveform diagram of each part of the receiving apparatus. 2...Program code detection circuit, 5...Selected program code match detection circuit, 9...Main memory, 10
・・・・・・Flip circuit, 18・・・Flip flop circuit. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1 The program code of the still image signal sent superimposed on a part of the vertical retrace period of the television signal and the selected program code selected by the program selection switch are added to the selected program code coincidence detection circuit, and In the still image signal receiving device, the still image signal is selectively recorded in a main memory by an output signal of a circuit, and the still image signal is read out to reproduce an image of a selected program on the screen of a television receiver. Utilizing the fact that the program code of the signal changes when the program of the still image signal is switched, a program mismatch pulse is generated in the latch circuit, and this pulse and the image stop signal are applied to the flip-flop circuit to send the signal to the main memory. A still image signal receiving device characterized in that a gate of a transfer gate circuit that performs transfer control is controlled by an output signal of the flip-flop circuit, and a time point at which the image stop signal is applied to the transfer gate circuit during an image stop operation is delayed. .