JP2000244791A - Image and sound transmission system, transmitter, receiver and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sound quality in the case of low-speed transfer in a spread spectrum system. SOLUTION: In the transmission mode of a low transfer rate, a transmission control circuit 32 reads out the images stored in an image buffer memory 16 to a synthesis circuit 26 for 1/4 field and transmits them by 1/4 each in a one- field period. Sound is stored in a sound buffer memory 24 for four fields, read out to the synthesis circuit 26 altogether in an one-field period and transmitted. Thus, even when an obstacle is present between a transmitter and a receiver, the omission of sound data is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video / audio transmission system, a transmission device, a reception device, and a method thereof. And a receiving device and a method thereof.

[0002]

2. Description of the Related Art In recent years, digital still cameras, digital video cameras, and electronic cameras without an image recording medium have attracted attention as general-purpose image input devices. These are basically designed to reduce the weight and size by separately providing the imaging unit or the photoelectric conversion unit and the finder or the image display device as separate units. As a means for transmitting an image (and audio) from an imaging unit to a display unit, a configuration employing a spread spectrum transmission method has been proposed.

[0003] A spread spectrum transmission system will be briefly described. In general, in a spread spectrum system using a direct spread system, a baseband signal of a digital signal to be transmitted is extremely compared with original data on the transmitting side by using a spread code sequence such as a pseudo-noise code (PN code). Spread into a baseband signal with a wide bandwidth. Thereafter, the signal is modulated by a digital modulation method such as PSK (phase shift keying) and FSK (frequency shift keying), converted into an RF (radio frequency) signal, and transmitted to the air. On the receiving side, despreading is performed using the same spreading code as the transmitting side to correlate with the received signal, and the received signal is converted into a narrow-band signal having a bandwidth corresponding to the original data. The original data is reproduced by demodulating the data.

As described above, in the spread spectrum system,
Since the transmission bandwidth is extremely wide with respect to the information bandwidth, only a very low transmission rate can be realized under the condition that the transmission bandwidth is constant as compared with the normal narrowband modulation method.

When a large amount of data such as image data is wirelessly transmitted, a code division multiple access (CDMA) system capable of increasing a substantial transmission rate is used. In this method, an information signal is converted into a plurality of parallel data strings, each data string is spread-modulated with a different spreading code sequence, added, and then converted into an RF signal and transmitted in the air. As a result, high-speed data transmission can be realized under a constant transmission bandwidth without lowering the spreading factor of the spread modulation. When the number of multiplexes is increased, the data transfer rate per unit time increases, and when the number of multiplexes is set small, the data transfer rate decreases.

[0006]

However, the conventional example of the spread spectrum system using the code division multiple access system has the following problems. That is, when there is a radio obstacle between the transmitter and the receiver, the level of the composite wave decreases due to the difference in the phase between the direct wave and the reflected wave as the number of code division multiplexes increases. Phenomena (multipath fading) increase, and data transmission tends to be unstable. Conversely, if the number of code division multiplexes is reduced, the influence of multipath fading is small, but some random loss occurs when there is a radio obstacle or a large noise source.

Conventionally, in such a situation, the received data is interrupted on the receiving side, so that the immediately preceding image is held. As a result, although the received image sometimes appears to stop, it is possible to recognize rough information. However, if the received signal is output as it is, the audio is interrupted, and the interrupted portion becomes a large noise source, and the quality of the output audio is greatly reduced.

An object of the present invention is to provide a video / audio transmission system, a transmitting apparatus, a receiving apparatus, and a method for preventing such a decrease in received signal quality.

Another object of the present invention is to provide a video / audio transmission system, a transmission device, a reception device, and a method thereof, which can transmit images and images with higher quality.

[0010]

According to the present invention, there is provided an image and sound transmission system comprising: a transmitting device for transmitting an image and a sound to a transmission line; and a receiving device for receiving the image and the sound via the transmission line. An audio transmission system, comprising: a transmission image buffer memory for temporarily storing image information to be transmitted, a transmission audio buffer memory for temporarily storing audio information to be transmitted, and the transmission image buffer memory. Transmitting means for transmitting the information read from the transmission audio buffer memory to the transmission path, and reading the image information of one screen from the transmission image buffer memory into the transmission means in a plurality of periods, The transmission image buffer is configured to read out audio information of a plurality of screens from the transmission audio buffer memory into the transmission unit in one period. And a transmitter control unit for controlling the memory and the transmission voice buffer memory, the reception apparatus includes receiving means for receiving the information to be transmitted to the transmission path,
A receiving image buffer memory for temporarily storing the image information received by the receiving means, a receiving audio buffer memory for temporarily storing the audio information received by the receiving means, Screen image information is collectively read from the receiving image buffer memory in one period, and audio information of a plurality of screens received in one period is read from the receiving audio buffer memory in a plurality of periods. As described above, the image processing apparatus further includes a reception control unit that controls the reception image buffer memory and the reception audio buffer memory.

An image / audio transmission method according to the present invention is an image / audio transmission method for transmitting an image and a sound, wherein an image and a sound within a predetermined period are transmitted at the same period at a high transfer rate, and at a low transfer rate. A feature is that an image of one screen is transmitted in a plurality of periods and audio of a plurality of screens is transmitted in a single period.

A transmitting apparatus according to the present invention includes a transmitting image buffer memory for temporarily storing image information to be transmitted, a transmitting audio buffer memory for temporarily storing audio information to be transmitted, the transmitting image buffer memory, Transmitting means for transmitting the information read from the transmission audio buffer memory to the transmission path; and reading image information of one screen from the transmission image buffer memory into the transmission means in a plurality of periods. A transmission control unit for controlling the transmission image buffer memory and the transmission audio buffer memory so as to collectively read out the audio information of the screen from the transmission audio buffer memory in one period to the transmission unit; It is characterized by.

[0013] A receiving apparatus according to the present invention comprises: a receiving means for receiving information transmitted on a transmission path; a receiving image buffer memory for temporarily storing image information received by the receiving means; A receiving audio buffer memory for temporarily storing the received audio information, and a screen for reading out image information of one screen received in a plurality of periods from the receiving image buffer memory.
Reception control means for controlling the image buffer memory for reception and the audio buffer memory for reception so as to read out audio information of a plurality of screens received in one period from the audio buffer memory for reception in a plurality of periods. And characterized in that:

[0014] An image and sound transmission apparatus according to the present invention comprises: a transmission means for transmitting an image and a sound; an image and a sound within a predetermined period are transmitted at the same period at a high transfer rate; It is characterized by comprising control means for controlling the transmission means such that the image is transmitted in a plurality of periods and the sound of the plurality of screens is transmitted collectively in one period.

In the transmission method according to the present invention, image information to be transmitted is temporarily stored in a transmission image buffer memory, audio information to be transmitted is temporarily stored in a transmission audio buffer memory, and image information of one screen is stored. The transmission image buffer memory and the transmission audio buffer so that the transmission image buffer memory is read out in a plurality of periods and the audio information of a plurality of screens is collectively read out of the transmission audio buffer memory in one period. It is characterized by controlling a memory.

According to the receiving method of the present invention, image information received via a transmission path is temporarily stored in a reception image buffer memory, and audio information received via the transmission path is stored in a reception audio buffer memory. While temporarily storing and reading out the image information of one screen received in a plurality of periods from the image buffer memory for reception in one period,
Controlling the reception image buffer memory and the reception audio buffer memory so that the audio information of a plurality of screens received in one period is read out from the reception audio buffer memory in a plurality of periods. And

With such a configuration, audio data is transmitted and received at intervals. As a result, even when a random loss occurs due to a radio obstacle or a large noise source, the sound data is lost due to a collision with the noise source as compared with the conventional case where voice data is transmitted and received in a fine cycle. The probability can be reduced. As a result, even in a spread spectrum communication system in which the number of multiplexed code divisions is reduced and the transfer rate is reduced, it is possible to prevent voice data from being lost more than ever.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic block diagram of a transmitting side according to an embodiment of the present invention, and FIG. 2 is a schematic block diagram of a receiving side.

The configuration of FIG. 1 will be described. Reference numeral 10 denotes a camera unit for photographing a subject, 12 denotes an image input circuit that digitizes a video signal output from the camera unit 10 and converts the digital signal into components of luminance data and color difference data, and 14 denotes a luminance output from the image input circuit 12. An image compression circuit for image compression of data and color difference data;
4 is an image buffer memory for temporarily storing the compressed image data output from the image buffer 4.

Reference numeral 18 denotes a microphone, reference numeral 20 denotes a voice input circuit for digitizing a voice signal output from the microphone 18, reference numeral 22 denotes a voice compression circuit for compression-coding voice data output from the voice input circuit 20, and reference numeral 24 denotes a voice compression circuit 2.
2 is an audio buffer memory for temporarily storing the compressed audio data output from the audio buffer 2.

26, a synthesizing circuit for synthesizing the compressed image data from the image buffer memory 16 and the compressed audio data from the audio buffer memory 24 into packets of a predetermined size;
Reference numeral 8 denotes a spread spectrum transmission circuit which spreads the packet from the combining circuit 26, converts the packet into an RF signal, and supplies the RF signal to the antenna 30.

A transmission control circuit 32 controls the entire system.
Is a transfer rate setting switch for setting the transfer rate in the transmission control circuit 32, and 36 is an operation key for the user to input various instructions to the transmission control circuit 32.

The configuration of FIG. 2 will be described. 40 is an antenna,
42 is a spread spectrum receiving circuit for despreading the RF signal received by the antenna 40, 44 is a separating circuit for separating compressed image data and compressed audio data from the packet output from the spread spectrum receiving circuit 42, 46
Is an image buffer memory for temporarily storing the compressed image data from the separation circuit 44 until it becomes one screen, 48 is an image expansion circuit for expanding the compressed image data from the image buffer memory 46 and restoring the image data, 50 Is an image output circuit that converts the image data restored by the image decompression circuit 48 into an analog image signal in a standard television format (for example, NTSC system) and outputs the analog image signal. 52 denotes an analog image signal output from the image output circuit 50. This is an image display device that displays an image.

Reference numeral 54 denotes an audio buffer memory for temporarily storing the compressed audio data from the separation circuit 44; 56, an audio expansion circuit for expanding the compressed audio data from the audio buffer memory 54 to restore the audio data; An audio output circuit that converts the audio data restored by the audio expansion circuit 56 into an analog audio signal and outputs the analog audio signal, and a speaker 60 that outputs the audio signal output from the audio output circuit 50 as sound.

Reference numeral 62 denotes a reception control circuit for controlling the whole, 64
Is a transfer rate setting switch for setting the reception rate in the reception control circuit 62 in accordance with the multiplexing number on the transmission side, and 66 is an operation key for the user to input various instructions to the reception control circuit 62.

The basic flow of an image signal and an audio signal in this embodiment will be described. On the transmitting side, the image input circuit 1
2 digitizes a video signal output from the camera unit 10 and converts it into components of luminance data and color difference data. The image compression circuit 14 performs image compression on the luminance data and the color difference data output from the image input circuit 12. The output of the image compression circuit 14 is supplied to the synthesis circuit 26 via the image buffer memory 16. On the other hand, audio input circuit 2
0 digitizes the output audio signal of the microphone 18, and the audio compression circuit 22 compression-encodes the output of the audio input circuit 20. The output of the audio compression circuit 22 is supplied to the synthesis circuit 26 via the audio buffer memory 24.

The synthesizing circuit 26 includes the image buffer memory 16
And the compressed audio data from the audio buffer memory 24 into a packet of a predetermined size.
The spread spectrum transmitting circuit 28 spreads the spectrum of the packet from the combining circuit 26, converts the packet into an RF signal, and supplies the RF signal to the antenna 30. Thereby, the camera unit 1
The image signal of the object photographed by 0 and the audio signal input by the microphone 18 are wirelessly transmitted.

In the receiver shown in FIG. 2, the received signal is processed as follows. That is, the spread spectrum receiving circuit 42 despreads the RF signal received by the antenna 40. The separating circuit 44 separates the compressed image data and the compressed audio data from the packet output from the spread spectrum receiving circuit 42 and supplies them to the image buffer memory 46 and the audio buffer memory 54, respectively. The image buffer memory 46 stores the compressed image data from the separation circuit 44 until the data for one screen is stored.
8 is output. The image expansion circuit 48 expands the compressed image data from the image buffer memory 46 to restore the image data. The image output circuit 50 converts the image data restored by the image decompression circuit 48 into an analog image signal in a standard television format, and outputs the analog image signal to the image display device 52.
As a result, the received image is displayed on the screen of the image display device 52.

On the other hand, the audio buffer memory 54 temporarily stores the compressed audio data from the separation circuit 44. The audio expansion circuit 56 expands the compressed audio data from the audio buffer memory 54 to restore the audio data. The audio output circuit 58 converts the audio data restored by the audio expansion circuit 56 into an analog audio signal and supplies the analog audio signal to the speaker 60. As a result, the received audio signal is output as sound.

The timing of combining and separating image data and audio data will be described. FIG. 3 shows a transmission timing chart when the number of multiplexed spreading codes (ie, code division multiplexing number) is increased and the transfer rate is increased, and FIG. 4 shows a corresponding reception timing chart. On the sending side,
The input image and sound are compressed at a fixed sampling period (in this example, 1/60 second unit).
Compressed image data and compressed audio data within the same period are combined into the same packet, spread spectrum modulated, and transmitted wirelessly. On the receiving side, as shown in FIG. 4, the received packet is separated into image information and audio information, decompressed, and output at a predetermined data rate in real time.

Next, the characteristic operation of this embodiment when the number of multiplexed spreading codes is small and the transfer rate is low will be described. FIG. 5 shows an operation flowchart of the transmission control circuit 32, and FIG. 6 shows an operation flowchart of the reception control circuit 62. FIG. 7 shows an example of a transmission timing chart, and FIG. 8 shows a reception timing chart corresponding to FIG.

First, the transmission control circuit 32 initializes each part and itself (S1), and waits for an edge of the vertical synchronizing signal of the camera unit 10 in order to take a timing of 1/60 second of the basic transmission cycle (S2). The transmission control circuit 32 checks whether or not the transmission mode is set to a high-speed transmission mode with a high transfer rate in which the number of code division multiplexes is increased (S).
3).

When the high-speed transmission mode is set (S
3) Write the compressed image data for one field into the image buffer memory 16 (S4) and output it to the synthesizing circuit 26 (S5). At the same time, the compressed audio data in the same one field is written into the audio buffer memory 24 (S
6), and outputs the result to the combining circuit 26 (S7). That is, in the high-speed transmission mode, at the same timing as shown in FIG.
The compressed image data and the compressed audio data in the same field are combined into one packet in the next field, and transmitted in the air by the spread spectrum transmitting circuit 28 and the antenna 30. Other processes are executed (S8), and the process returns to S2.

If the high-speed transmission mode is not set,
That is, in the case of the low transfer rate transmission mode (hereinafter, low-speed transmission mode) (S3), it is confirmed whether or not all the data stored in the image buffer memory 16 has been transmitted (S3).
9). If all data has been transmitted (S9), the new compressed image data for one field is written to the image buffer memory 16 (S10). If not all have been sent (S9),
Alternatively, after writing new one-field compressed image data in the image buffer memory 16 (S10), the compressed image data stored in the image buffer memory 16 is read out to the synthesizing circuit 26 by 1/4 (S11).

Regarding the audio data, it is confirmed whether or not there are four fields of compressed audio data in the audio buffer memory 24 (S12), and if four fields of compressed audio data have been written (S12), All data stored in the audio buffer memory 24 is read out to the synthesis circuit 26 (S13). When the compressed audio data for four fields has not been written (S12), or after all the data stored in the audio buffer memory 24 has been read out to the synthesizing circuit 26 (S13), new compressed audio data is stored in the audio buffer memory 24. Write (S14). Other processes are executed (S8), and the process returns to S2.

As described above, in the low-speed transmission mode, as shown in FIG. 7, the image data is transmitted one quarter of one field at a time in one field period, and the audio data is transmitted once every four fields and four fields. The minutes are sent together.

The operation on the receiving side will be described. Reception control circuit 6
2 initializes each part and itself (S21), waits for new data reception (S22), and checks whether the reception mode is set to the high-speed reception mode (S23).

When the high-speed reception mode is set (S
23) The received image data (compressed image data) for one field included in the received packet is stored in the image buffer memory 4.
6 (S24) and output to the image decompression circuit 48 (S25). At the same time, 1
The received audio data (compressed audio data) for the field is written into the audio buffer memory 54 (S26) and output to the audio decompression circuit 56 (S27). That is, in the high-speed reception mode, the received image data and the received audio data in the same field are output in the next field period at the same timing as shown in FIG. Other processes are executed (S28), and the process returns to S22.

If the high-speed reception mode is not set,
That is, in the case of the low transfer rate reception mode (S23),
The received image data for / 4 fields are sequentially written into the image buffer memory 46 (S29). Then, it is checked whether or not one field of compressed image data is stored in the image buffer memory 46 (S30). If it is, the stored data of the image buffer memory 46 is read out to the image decompression circuit 48 and the received image data is read. Is decompressed and restored (S31). Thereby, the received image is displayed on the image display device 52.
Will be displayed on the screen.

The reception control circuit 62 checks whether or not new audio data has been received (S32). If new audio data has been received, the received audio data (compressed audio data for four fields) is stored in the audio buffer. Writing to the memory 54 (S33). When new voice data is not received (S
32) Or, after the received audio data (compressed audio data for 4 fields) is written to the audio buffer memory 54 (S33), the compressed audio data for 1 field in the data stored in the audio buffer memory 54 Is read out to the audio decompression circuit 58 (S34). Thereby, as shown in FIG. 8, sound of the same field as the image displayed on the screen of the image display device 52 is output from the speaker 60.
Other processes are executed (S28), and the process returns to S22.

Thus, in the case of a low transfer rate,
Since the number of times of transmitting voice data is reduced and voice transmission with a longer interval than before is possible, it is possible to reduce the probability of collision with a wireless communication noise source that occurs randomly.

In this embodiment, in the case of low-speed transmission / reception, the image of one field is divided into four and transmitted. However, it is clear that the number of divisional transmission of the image is not limited to four. What is necessary is just to determine together. Similarly, it is apparent that audio data of a larger number of fields can be collectively transmitted and received depending on the capacity and the like of the audio buffer memories 24 and 54 even if audio data is not collected every four fields.

[0044]

As can be easily understood from the above description, according to the present invention, even if a random drop occurs due to a radio obstacle or a large noise source, the timing of the audio data and the noise is one. As a result, it is possible to reduce the probability of missing data, and it is possible to prevent audio data from being lost and output in small increments. For example, even in a spread spectrum system in which the number of code division multiplexes is reduced and the transfer rate is reduced, it is possible to prevent the loss of audio data more than ever.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a transmitting side according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram of a receiving side of the embodiment.

FIG. 3 is an example of a timing chart on the transmission side at the time of a high transfer rate.

FIG. 4 is a timing chart example on the receiving side corresponding to FIG. 3;

FIG. 5 is an operation flowchart of the transmission control circuit 32 of the embodiment.

FIG. 6 is an operation flowchart of the reception control circuit 62 of the present embodiment.

FIG. 7 is a timing chart showing an operation example according to the embodiment at a low transfer rate.

FIG. 8 is a timing chart example on the receiving side corresponding to FIG. 7;

[Explanation of symbols]

 10: Camera unit 12: Image input circuit 14: Image compression circuit 16: Image buffer memory 18: Microphone 20: Audio input circuit 22: Audio compression circuit 24: Audio buffer memory 26: Synthesis circuit 28: Spread spectrum transmission circuit 30: Antenna 32: Transmission control circuit 34: Transfer rate setting switch 36: Operation key 40: Antenna 42: Spread spectrum reception circuit 44: Separation circuit 46: Image buffer memory 48: Image expansion circuit 50: Image output circuit 52: Image display device 54: Audio buffer memory 56: Audio expansion circuit 58: Audio output circuit 60: Speaker 62: Reception control circuit 64: Transfer rate setting switch 66: Operation key

Claims (24)

[Claims] An image / audio transmission system comprising: a transmission device for transmitting an image and an audio to a transmission path; and a reception device for receiving the image and the audio via the transmission line. A transmission image buffer memory for temporarily storing image information to be transmitted, a transmission audio buffer memory for temporarily storing audio information to be transmitted, and information read from the transmission image buffer memory and the transmission audio buffer memory. Sending means for sending to the transmission path,
The image information of one screen is read out from the transmission image buffer memory into the transmission unit in a plurality of periods, and the audio information of a plurality of screens is read out from the transmission audio buffer memory into the transmission unit in one period. like,
A transmission control unit that controls the transmission image buffer memory and the transmission audio buffer memory; the reception device receives information transmitted on the transmission path; and the reception unit receives the information. A receiving image buffer memory for temporarily storing image information, a receiving audio buffer memory for temporarily storing audio information received by the receiving means, and receiving one screen of image information received in a plurality of periods; The receiving image buffer memory is read out from the receiving image buffer memory in one period, and the plurality of screens of audio information received in one period are read out from the receiving audio buffer memory in a plurality of periods. A video / audio transmission system comprising: a buffer memory; and a reception control means for controlling the reception audio buffer memory. Stem. 2. The receiving apparatus further comprises: an image reconstructing means for reconstructing image information of one screen read from the receiving image buffer memory; and one screen read from the receiving audio buffer memory. 2. The image / audio transmission system according to claim 1, further comprising audio output means for outputting the audio information. 3. The image and sound transmission system according to claim 1, wherein the transmission path is a space, and the image and the sound are wirelessly transmitted from the transmission device to the reception device. 4. The video / audio transmission system according to claim 3, wherein said transmitting means comprises spread spectrum transmitting means, and said receiving means comprises spread spectrum receiving means. 5. The transmission unit according to claim 1, wherein the transmission unit collects the audio information of the plurality of screens read from the transmission audio buffer memory into one packet and transmits the packet to the transmission path. 3. The image and sound transmission system according to claim 1. 6. The image and sound transmission system according to claim 1, wherein the image information and the sound information are compression-encoded. 7. An image / audio transmission method for transmitting an image and an audio, wherein at a high transfer rate, an image and an audio within a predetermined period are transmitted at the same cycle, and at a low transfer rate, a plurality of images of one screen are transferred to a plurality of images. A video / audio transmission method, wherein the video / audio transmission method is performed in such a manner that the audio data of a plurality of screens are transmitted in one period while being transmitted in a period. 8. The image and sound transmission method according to claim 7, wherein the image and the sound are wirelessly transmitted. 9. The image and sound transmission method according to claim 8, wherein said image and sound are transmitted by a spread spectrum method. 10. At the high transfer rate, the image and sound within the predetermined period are transmitted in one packet, and at the low transfer rate, the image of one screen is transmitted in a plurality of packets and the plurality of screens are transmitted. The image / audio transmission method according to claim 7, wherein the audio is transmitted in one packet. 11. The image and sound transmission method according to claim 7, wherein the image and the sound are compression-encoded. 12. A transmission image buffer memory for temporarily storing image information to be transmitted, a transmission audio buffer memory for temporarily storing audio information to be transmitted, the transmission image buffer memory, and the transmission audio buffer memory. Transmitting means for transmitting the information read out from the transmission line to the transmission path; reading out the image information of one screen from the transmission image buffer memory into a plurality of periods to the transmitting means; In order to collectively read out from the transmission audio buffer memory to the transmission unit in one period,
A transmission apparatus comprising: the transmission image buffer memory; and transmission control means for controlling the transmission audio buffer memory. 13. The transmitting apparatus according to claim 12, wherein the transmission path is a space, and the image and the sound are wirelessly transmitted. 14. The transmitting apparatus according to claim 13, wherein said transmitting means comprises a spread spectrum transmitting means. 15. The transmission means converts the image information of the one screen read from the transmission image buffer memory into a plurality of packets and transmits the packets to the transmission path.
15. The transmission device according to claim 12, wherein the audio information of the plurality of screens read from the transmission audio buffer memory is converted into one packet and transmitted to the transmission path. 16. The transmission device according to claim 12, wherein the image information and the audio information are compression-coded. 17. A receiving means for receiving information transmitted through a transmission path, a receiving image buffer memory for temporarily storing image information received by the receiving means, and a temporary storage for audio information received by the receiving means. A receiving audio buffer memory, and a plurality of screens received in one period while image information of one screen received in a plurality of periods is collectively read out from the receiving image buffer memory. Receiving means for controlling the receiving image buffer memory and the receiving audio buffer memory so as to read out the audio information from the receiving audio buffer memory in a plurality of periods. apparatus. 18. An image reconstructing means for reconstructing image information of one screen read from the image buffer memory for reception, and audio information of one screen read from the audio buffer memory for reception. 18. The receiving device according to claim 17, further comprising an audio output unit for outputting. 19. The receiving apparatus according to claim 17, wherein the transmission path is a space, and the information is wirelessly transmitted. 20. The receiving device according to claim 19, wherein said receiving means comprises spread spectrum receiving means. 21. The receiving apparatus according to claim 17, wherein said image information and said audio information are compression-encoded. 22. A transmission means for transmitting an image and a sound, wherein at a high transfer rate, an image and a sound within a predetermined period are transmitted at the same period, and at a low transfer rate, an image of one screen is divided into a plurality of periods. A video / audio transmission apparatus, comprising: a control unit that controls the transmission unit so as to transmit and simultaneously transmit audio of a plurality of screens in one period. 23. Temporarily storing image information to be transmitted in a transmission image buffer memory, temporarily storing audio information to be transmitted in a transmission audio buffer memory, and transferring image information of one screen from the transmission image buffer memory. Controlling the transmission image buffer memory and the transmission audio buffer memory so that the audio information is read out in a plurality of periods and the audio information of a plurality of screens is collectively read from the transmission audio buffer memory in one period. Characteristic transmission method. 24. Temporarily storing image information received via a transmission path in a reception image buffer memory, temporarily storing audio information received via the transmission path in a reception audio buffer memory, The image information of one screen received in divided periods is collectively read from the image buffer memory for reception in one period, and the audio information of a plurality of screens received in one period is collectively read in the audio buffer memory for reception. A receiving image buffer memory and a receiving audio buffer memory so as to read the received image data in a plurality of periods.