JPH06153117A - Television system - Google Patents

Abstract

PURPOSE:To send plural audio signals and a background music at a narrow band. CONSTITUTION:A Japanese audio signal is limited to an audio band by a filter 12, an English audio signal is controlled to an audio band by a filter 14, left/ right background sound signals of the audio signals are modulated into a stereo signal by a modulation circuit 19, each output of the filters 12, 14 modulates modulation circuits 15, 16, and the modulation output and the stereo signal are set to have a highest frequency of a picture signal from a terminal 22 and synthesized by a multiplexer circuit 21, and the synthesized signal is transmitted to a receiver side. The receiver side separates the synthesized signal into a modulated Japanese signal, a modulated English signal, the stereo signal and the picture signal, demodulation circuits 26, 27 demodulate the Japanese audio signal and the English audio signal, either of them is selected by a selection circuit 29, the selected audio signal and reproduced left/rightbackground acoustic signals of the stereo signal are synthesized by a synthesis circuit 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television system for modulating an image signal and a sound signal at different frequency positions for transmission, and more particularly to a system for transmitting a plurality of audio signals.

[0002]

2. Description of the Related Art Conventionally, a television signal is frequency-multiplexed with one image signal and a sound signal consisting of one or two channels and is used for broadcasting or transmission. That is, as shown in FIG. 3A, the baseband signal of the sound signal used in the television system is, for example, only one main channel with a frequency of 15 kHz or less, or as shown in FIG. 3B, it is superimposed on a subcarrier in addition to the main channel. Two channels were used, a sub-channel for both sidebands that were generated. When two channels are used, when a stereo audio signal is transmitted, a signal is added to the sum of the left and right signals on the main channel and a difference signal of the left and right signals is transmitted on the sub channel. When bilingual voices of Japanese and English are transmitted, for example, Japanese voice is transmitted on the main channel and English voice is transmitted on the sub channel.

As a voice signal, its frequency bandwidth is 4 to
Sufficient sound quality can be obtained at about 7 kHz. However, the frequency band is 1 to faithfully reproduce an acoustic signal such as music.
A band of about 5 kHz, that is, a band of 2 to 3 times that of a voice signal or more is required. Therefore, in order to superimpose an audio signal such as a background audio on an audio signal, the transmission requires a frequency band of the audio signal. Conventionally, in order to transmit a sound signal in which a plurality of sound signals, for example, a sound signal in two languages and a sound signal are superimposed as a television signal together with an image signal, in FIG. 3B, the sound signal is transmitted through both the main channel and the sub-channel. And a relatively wide frequency band is required.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to transmit a plurality of audio signals and to superimpose an audio signal such as a background audio on them, and to combine with an image signal in a frequency band narrower than the conventional one. It is to provide a television system capable of transmitting.

[0005]

According to the present invention, one sound transmission system for transmitting sound signals and sound signals on the transmission side,
The audio signal is transmitted through a plurality of audio channels for transmission, and in the receiver, the acoustic signal demodulated by the acoustic transmission system and the audio signal demodulated by one of the audio channels are combined and output as a sound signal.

[0006]

Embodiment An embodiment of the present invention will now be described with reference to FIG.
Try. The first voice signal input from the voice input terminal 11.
No., for example, Japanese voice signal is voice band pass filter 12
Limits the transmission voice band of 5 kHz, for example.
It Similarly, the second voice input from the voice input terminal 13
A signal, for example, an English voice signal, is a voice bandpass filter 14
Is limited to the transmission voice band of 5 kHz by
It Band-limited first audio signal and band-limited first audio signal
The two audio signals are the first audio modulation circuit 15 and the second audio signal, respectively.
Subcarrier f in the modulation circuit 16₂, F₃To modulate.
Also, the left and right sounds input from the sound input terminals 17 and 18
The sound signal is combined with the conventional sum signal in the sound signal modulation circuit 19.
The difference signal is a stereo signal. Therefore, these modulation circuits
The outputs of 15, 16, and 19 are, for example, as shown in FIG. 2A.
The sum signal L + R of the reverberation signals of the frequency band below 15 kHz
Located in the main channel, the difference signal LR of the acoustic signal is the sub-carrier
Wave f ₁Side occupies a frequency band of 15 kHz on both sides of the
Located on the channel and above this subchannel, the subcarrier f₂
The first audio signal of ± 5kHz is located, and the sub signal is placed above it.
Carrier f₃The second audio signal of ± 5 kHz is located.

Further, in the television signal multiplexing circuit 21, with respect to the image signal from the image input terminal 22, a carrier having a frequency higher than the highest frequency thereof is supplied to the modulation circuits 15 and 16.
, And 19 are modulated, combined, and multiplexed to form a baseband television signal. This baseband television signal is delivered to the partner device via the transmission path 23. The received baseband television signal is first modulated by the television signal separation circuit 24.
The audio signal, the modulated second audio signal, the modulated acoustic signal, and the image signal are separated, and the image signal is directly applied to the terminal 25.
Output and displayed. The modulated first voice signal is demodulated in the first voice demodulation circuit 26 using the subcarrier f ₂ used in the first voice modulation circuit 15. The modulated second voice signal is demodulated in the second voice demodulation circuit 27 using the subcarrier f ₃ used in the second voice modulation circuit 16. The modulated stereo acoustic signal is demodulated in the acoustic signal demodulation circuit 28 using the subcarrier f ₁ used in the acoustic signal modulation circuit 19. For the demodulated first audio signal and the second audio signal, only the preset audio signal is selected in the selection circuit 29, and the selected audio signal and the demodulated stereo acoustic signal are combined in the sound signal combining circuit 31. Is output.

The voice signal bandwidth is 5 kHz =
ΔF and the acoustic signal bandwidth is 15 kHz =
If 3ΔF, the entire occupied frequency band is as shown in FIGS. 2 and 3. When transmitting the audio signal as monaural, only the main channel is required as shown in FIG. 2B. That is, the acoustic signal may be transmitted by one transmission system of the main channel or may be transmitted by one transmission system as a stereo of the main channel and the sub-channel. It should be noted that in the past, in the case of transmitting a voice signal and an acoustic signal (background sound), in the case of monaural, as shown in FIG. 2A, a combination of the first voice signal and the acoustic signal has a bandwidth of 3ΔF. The sub-channel having the bandwidth of 6ΔF is transmitted by transmitting the signal through the channel and superimposing the second audio signal and the acoustic signal. Therefore, as can be understood by comparing FIGS. 3A and 2B, according to the present invention, the entire occupied frequency band can be narrowed.

In the present invention, when the first and second audio signals are also stereo signals, for example, as shown in FIG. 2C,
A stereo first audio signal in which a sub-carrier is modulated by a sum signal and a difference signal of the first audio signal is respectively positioned above the stereo audio signals of the main channel and the sub-channel, and the sum of the second audio signal is further above the stereo first audio signal. It suffices to position the stereo second audio signal in which the subcarrier is modulated by the signal and the difference signal, respectively. On the other hand, in the conventional technique, as shown in FIG. 3C, the stereo signal of the superimposed signal of the first audio signal and the acoustic signal is located in the conventional main channel and the sub-channel, and the second audio signal and the acoustic signal are located above them. A stereo signal in which different subcarriers are respectively modulated by the sum signal and the difference signal of the superimposed signal of and is located. Therefore, while the former (FIG. 2C) has a total occupied band of 17ΔF, the latter (FIG. 3C) has a total occupied band of 27ΔF.
It becomes quite wide with F.

In the above description, the number of voice signals is two, but the number of voice signals may be three or more. Further, the audio signal and the acoustic signal may be transmitted in a digitally encoded state, and the present invention can be applied to that case as well. Further, the present invention can be applied not only to the television system but also to a case where a plurality of audio signals are transmitted together with the background sound in other broadcasting systems.

[0011]

As described above, according to the present invention, the acoustic signal is transmitted by only one transmission system, the audio signal is transmitted by a plurality of audio channels, and the receiver side selects one of the plurality of audio channels. By superimposing one demodulated sound signal on one demodulated sound signal of one sound transmission system, the transmission frequency band can be made narrower than in the conventional case.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing various examples of a baseband signal of a sound signal in the television transmission system according to the present invention.

FIG. 3 is a diagram showing various states of a baseband signal of a sound signal in a conventional television system.

Claims (1)

[Claims] 1. In a television system for modulating and transmitting an image signal and a sound signal at different frequency positions, one acoustic transmission system for transmitting the sound signal on the transmitting side, and a plurality of sound transmission systems for transmitting the sound signal. A television system characterized in that the signal is transmitted through an audio channel, and a signal demodulated by the acoustic transmission system in the receiver and an audio signal demodulated by one of the audio channels are combined and output as a sound signal. .