JPS6333987A - Terminal equipment for videotex - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a sound noise at the interblock of a voice data by separating each information data into a character/graph information data and the voice information data and allowing a muting circuit to give a prescribed leading/trailing characteristic to an analog voice output at the interblock of the voice information data. CONSTITUTION:A muting pulse (on.off pulse) PA representing the interblock of the voice data DA is fed to a time constant circuit 32. The muting pulse PA is at '0' at the end timing of the data DA and at '1' in the start timing as an on/off pulse and its leading/trailing slows doen by the time constant circuit 32. Thus, the muting pulse P'A provided with the leading/trailing characteristic and the analog voice output SA are multiplied, then an analog voice output SA' with slow level change is outputted from the muting circuit 30. Thus, no sound noise is caused.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is a terminal device for Videotex (interactive character and graphic information system), and in particular, a videotex (interactive character and graphic information system) terminal device, in particular, a terminal device that transmits not only character and graphic information but also audio information corresponding to this character and graphic information. The present invention relates to a Videotex terminal device that is capable of encoding content.

[Conventional technology]

Videotex, as is well known, is a system that allows text and graphic information to be monitored by transmitting text and graphic information to telephone line subscribers using a telephone line, but it requires a dedicated line. If used for high-speed data transmission, this videotex will be able to transmit not only text and graphics information but also audio information related to this text and graphics information in real time, allowing the selected text and graphics information to be transmitted in real time. At the same time, audio information can be played back at the same time.

Therefore, on the leased line subscriber side, by using a terminal device αΦ as shown in FIG. 5, it is possible to receive voice information services in addition to image information. That is, the information center on the data sending side and the user are connected by a dedicated line, and as shown in FIG. 5, the dedicated line (2) is connected to the line control section (3).

The line control unit (LCU) (3) is composed of an S/P converter, modem, etc. that converts line data such as information data and command data into serial and parallel data, and a line clock CK (not shown) extracted from the line data. ) is the write clock formation circuit (6)
A write clock CK-W synchronized with this line clock CK is formed, and this write clock CK-W
Image, audio, and instruction data DV, DA, which are information data, are synchronized with the information data.

Da is written to the buffer memo January 4).

The buffer memo 4) is a FIFO-type shift register, and each data in the buffer memo 4) is read out in synchronization with a readout clock CK-R, which will be described later, and is sent to the subsequent image/audio processing unit (5). The image data Dv thus output is stored in the video RAM (71). When all the predetermined image data Dv are stored,
This is converted into an analog image signal by a D/A converter (8) and displayed on the screen of a monitor (television receiver) (9).

On the other hand, the audio data D^ supplied to the processing section (5) is D/
The A converter (11) converts the signal into an analog audio signal, which is supplied to the speaker (12) to reproduce audio information. Here, the audio system is not provided with a memory equivalent to the video RAM (7), but this is because the audio data D is processed in real time.

Further, this terminal device α is provided with a clock generator (20) having a PLL configuration in order to obtain various control clocks,
Write and read clock W/R that controls writing and reading of video RAM (7) and D/A converter (8)
, a sampling clock CK-S for executing the conversion process of (11) is formed, and the processing unit (5)
A control clock CK-C is generated for controlling the read timing of the audio data DA.

Read clock CK supplied to buffer memory (4)
-R is formed based on this control clock CK-C.

Note that since the line data transfer rate is constant and the bit length per l sample of audio data is also constant, the control clock CK-C also has a constant frequency. For example, if the line data transfer rate is 64K bPS and the bit length of one sample is 8 bits, the control clock C
The frequency of KC is 8k tlz.

[Problem that the invention seeks to solve]

By the way, in the conventional terminal equipment ROω configured as described above, the audio data D^ is immediately sent to the speaker (12
), so if there is a break in the audio data D, such as when the transmission of the audio data DA is finished, the audio data D that should be written to the D/A converter (11)
Since A becomes zero, the D/A analog audio output becomes zero.

For example, when the last audio data DAa is sent out at time ta as shown in FIG. 6A, there is no audio data at the next time tb, so it becomes zero. Therefore, the D/A converter (1
1) The analog audio output S^ output from the diagram changes from the state shown by the solid line to the state shown by the broken line, so when the last audio data DAa is large as shown in the diagram, the audio level suddenly suddenly changes. When the level changes, abnormal noise (shock noise) occurs.

This abnormal sound may also occur during data transmission. For example, as shown in FIG. 6B, when the first audio data DAd is supplied at time t, 1, and its level is high, the analog audio output SA between time tc%td
The level changes rapidly as shown by the broken line. Therefore, in this case as well, abnormal noise is generated.

As a means to reduce the abnormal sounds that occur at the breaks in the audio data DA, the curve shown in FIG. 7 can be used! ! As shown in FIG. 1, it is conceivable to configure the processing unit (5) to send out the last audio data DAa even after the end of sending out the audio data so as to maintain the same analog level as the last audio data DAa.

However, in the case of this method, if the first audio data DAd to be sent out of the next audio data D^ is significantly different from the previous audio data DA&,
Since the level difference between the audio data DAa and DAd is large, abnormal sounds occur as in the conventional case, and it is not always possible to reduce the abnormal sounds.

On the other hand, the D/A converter (11) and the speaker (12)
Between the figure 7 curve! Although it is conceivable to provide an analog filter having an attenuation characteristic as shown in FIG. 2, this is not very preferable since the frequency characteristics of the analog audio output SA of the audio data DA itself will deteriorate.

This invention solves these problems,
The present invention proposes a video test terminal device that has a simple configuration and can reduce the occurrence of abnormal sounds.

[Means for solving problems]

In order to solve the above-mentioned problems, in the present invention, as shown in FIG. 1, a muting circuit having predetermined rise and fall characteristics is provided between the D/A converter (11) and the speaker (12). (30) is provided.

The muting circuit (30) can be composed of a multiplier (31) and a time constant circuit (32), and the time constant circuit (32) includes a muting pulse representing a break in the audio data DA. (On, off pulse) P^ is supplied. On the other hand, the D/A converter (11) is supplied with, for example, the same audio data as the last audio data DA& until the next audio data DAd is sent out.

[Effect]

The muting pulse P^ (Fig. 3B) is an on/off pulse that becomes "0" at the end timing of the audio data DA and "1" at the start timing, but its rise and The fall is slow (Fig. 3C). Therefore, since the muting pulse P^' (C in the figure) to which falling and falling characteristics have been applied is multiplied by the analog audio output S^ (A in the figure), the muting pulse P^' (C in the figure) is multiplied by the analog audio output S^ (A in the figure). As shown in the diagram,
' is output to the analog audio output S whose level changes slowly. Therefore, no abnormal noise is generated.

〔Example〕

FIG. 1 shows a videotex terminal device 0I according to the present invention.
5 is a system diagram showing an example of FIG. 5, and parts corresponding to those in FIG. 5 are given the same reference numerals, and detailed explanation thereof will be omitted.

In this invention, a D/A converter (11) and a speaker (12) are provided.
) for audio output between the muting circuit (30
) is provided. In this example, the muting circuit (30) is composed of a multiplier (31) and a time constant circuit (32), and the analog audio output S^ output from the D/A converter (11) is Audio data D supplied to the multiplier (31) and sent out from the processing unit (5)
Of the ^, the bits indicating the start and end of data transmission are used as the muting pulse P^, which is supplied to the time constant circuit (32) and turned into a muting pulse P with predetermined rise and fall characteristics. ’ is the multiplier (3
1).

The image/audio processing section (5) is connected to C as shown in FIG.
The data acquisition timing from the buffer memory (4) is controlled by the command pulse obtained from the PU (33), and the timing of data acquisition from the buffer memory (4) is controlled.
, instruction data Dc, etc., and this CPU (33
) The audio data DA sent from the latch circuit (34)
After the signal is latched once, it is supplied to the D/A converter (11).

Now, in this embodiment, the last transmitted audio data DA
For a, the same audio data DAa is held until the next new audio data DAd is sent out (section Tx in FIG. 3). Therefore, the last audio data DAa is continuously supplied from the CPU (33) to the latch circuit (34) only during the interval Tx (as shown by the broken line in FIG. 3A).
.

However, in this case, since a bit indicating the start and end of data transmission (hereinafter referred to as a determination bit) of the audio data D^ is used as the muting pulse PΔ, this determination bit must be inverted in the interval Tx. Therefore, as shown in FIG. 3, at time t1, the last audio data DA
Assuming that a has been obtained, at the next time t2, the logic level of only the discrimination bit is inverted, and the latch circuit (34
), and thereafter the same bit contents are applied to the launch circuit (34) until new audio data DAd is transmitted.

As a result of such data processing, a muting pulse PA having the polarity shown in FIG. 3 is obtained.

This muting pulse PA is supplied to the time constant circuit (32), so that its steep rise and fall are controlled by the curve I! of FIG. 3C. As shown by OFF+'ON, it has slow rise and fall characteristics.

In this example, the rise and fall time constants are selected to be equal, and their values (times) are selected to be longer than a time that can prevent the occurrence of abnormal noise.

Waveform corrected muting pulse PA' (Fig. 3C
) is multiplied by the analog audio output SA, and as a result, as shown in the third diagram, the output level at the audio end timing (time t1) is gradually lowered until the audio output level reaches zero, and the audio output level at the audio start timing (time t1) is gradually lowered as shown in the third diagram. The output level of tx) gradually increases from zero, and at time t4, the analog audio output S is outputted at the audio output level of the audio data DA itself from the dedicated line (2). Therefore, even if there is a break in the audio data DA, no abnormal sound is generated.

Note that the audio data to be held in the section Tx does not have to be the same as the final transmitted audio data DAa, and may be data such that the audio data DAa decreases with time, for example. In this case, the time constant τ may be selected to be slightly smaller.

In addition, the final audio data DAa is not held over the entire section Tx where there is a break in the audio data DA, but the audio data DAa is D/A converted for a period that is approximately equal to or slightly longer than the time constant τ. It may be configured to supply the liquid to the container (11).

FIG. 4 is a flowchart showing an example of image/audio processing in the terminal device α shown in FIG. ), in
Initialization of the latch circuit (34) is executed, and the latch data of the latch circuit (34) when the power is turned on is reset to zero. Next, in step (42), instruction data pc is added to the information data read from the buffer memory (4).
It is checked whether or not the instruction data DC is included.
is included, the process moves to step (43), where it is checked whether the command data Dc is command data for the image data Dv or command data for the audio data D^, and it is determined that the command data Dc is the command data for the image data Dv. In this case, step (44
) image processing is performed.

Image processing means converting image data Dv to video RAM (71
In addition to the process of writing to the , it refers to a series of processes such as decoding the command data Da to display an image in a blinking manner, and by what means to display the image.

Then, in step (45), the sending state of the image data Dv is checked, and if it is during the sending period of the image data DV, the process moves to step (44) and image processing is continued. Once the period has passed, the step (
Return to 42).

On the other hand, if it is checked in step (43) that the command data is for audio data DA, step (
46), the above-mentioned control clock CK・C is transferred to the CPU (
33) accepts and takes in the audio data DA from the buffer memory (4), and also sets the discrimination bit in the audio data DA to "1" by setting a flag to obtain the muting pulse PA. The process to

Then, in step (47), the sending state of the audio data DA is checked, and if it is during the sending period of the audio data DA, the process moves to step (48), and the latch processing of the audio data D^ as shown in FIG. is executed. Audio data D^
When the transmission period has elapsed, the process moves to step (49) and the above-mentioned flag is reset so that a muting pulse P^ is obtained so that the fall of '' to the analog audio output S becomes as shown in the third figure. In addition, a process for prohibiting the control clock CK-C from being sent to the CPU (33) is executed.

〔Effect of the invention〕

As explained above, according to the configuration of the present invention, even if there is a break in the transmitted audio data DA, no abnormal sound is generated at the break, so that the audio output is significantly improved compared to the conventional one. Can be done.

Moreover, according to this configuration, it is possible to eliminate the occurrence of abnormal sounds at both the transmission start point and the transmission end point of the audio data DA, and the circuit configuration for obtaining such an effect is extremely simple. , it is very useful for practical use.

Therefore, the present invention is extremely suitable for application to a videotex terminal device capable of reproducing audio, such as a data transmission system using a dedicated line.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of the main parts showing an example of a videotex terminal device according to the present invention, FIG. 2 is a system diagram of the main parts of the image/audio processing section, and FIG. 3 is used to explain the operation of the invention. 4 is a flowchart showing an example of image/audio processing operation, FIG. 5 is a system diagram similar to FIG. 1 showing a conventional example of a videotex terminal device, and FIGS. FIG. 3 is a waveform diagram for explaining the operation. (2) is a dedicated line, (3) is a line control unit, (4) is a panzer memory (FIFO), +5+ is an image/audio processing unit, (11) is a D/A converter, (30) is muting circuit, (31) is a multiplier, (32) is a time constant circuit, D
^ is audio data, P^p A/ is a muting pulse, and SA and SA' are analog audio outputs. Figure 4

Claims (1)

[Claims] In the Videotex terminal device, character and graphic information data including audio information data is supplied to the line control unit via a dedicated line, each of the above information data is selected, and each of the selected information data is transferred to the image/sound processing unit. The audio information data is supplied to a muting circuit having predetermined rise and fall characteristics via a D/A converter, and the audio information data is separated into character/graphic information data and audio information data. A videotex terminal device configured to give predetermined rise and fall characteristics to analog audio output at breaks in information data.