JPS6032438A - Voice suppressing device of satellite broadcast receiver - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a sound suppression device in a satellite broadcast receiver configured to directly receive satellite broadcasts.

Conventional configurations and their problems In television broadcasting using direct broadcasting satellites or dedicated audio broadcasting, four-screen systems that attempt to convert audio into PCM are being considered in various countries. In Japan, it has already been stipulated that the PCM system be used for audio in television satellite broadcasts scheduled to begin in 1986.

In the PCM audio transmission scheduled to be implemented in Japan, the transmission side will be able to select either two high-quality audio channels or four medium-quality audio channels depending on the program content. has been adopted. In this switching method, a mode identification code indicating which of the above two modes is being transmitted is transmitted in the broadcast signal, and the receiver automatically selects the demodulation method corresponding to the transmission mode based on this identification code. The PGM code can be selectively restored to analog audio. However, since it usually takes a certain amount of time to determine this identification code, there is a difference between the timing at which the PGM code mode switches and the timing at which the receiver responds to the mode switching. This will generate a lot of noise. Therefore, in order to prevent the occurrence of this noise, an audio suppression instruction code is further transmitted in the broadcast signal. That is, prior to the timing of mode switching, the transmitting side can send out a voice suppression instruction code in advance to forcibly suppress the voice of the receiver. Here, if the suppression instruction period is set to sufficiently include the above-mentioned transient noise generation timing, noise generation can be prevented.

However, such a sound suppression configuration alone is insufficient for actual satellite broadcasting. This is because the local transmitting station that transmits the signal may change depending on the broadcast balance. In this switching of transmitting stations,
The radio waves will be temporarily interrupted, and during that time, the receiver will be unable to detect the voice suppression indicator. This situation is shown in FIG.

In FIG. 1, it is assumed that the audio output is suppressed when the detected audio suppression instruction code is at a high level.

In Figure 1, the timing of the occurrence of transient noise is sufficiently included.
: Even if the suppression instruction period T is set, when the terrestrial transmitting station AB is switched, there is a portion C where the suppression instruction signal is insufficient, and the next transmitting station B is not received in this insufficient portion C. Within the time delay t before starting normal demodulation,
There is a possibility that noise may be generated, and if the period of voice suppression is short when the next transmitting station B is received, there is a possibility that noise may be generated after that. The problem is that the suppression indicator sent out is actually useless.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a sound suppression device for a satellite broadcasting receiver that can perform appropriate sound suppression operations on the receiver even in the above-mentioned transmitting station switching λ.

Structure of the Invention In order to achieve the above-mentioned object, the present invention uses a frame synchronization detection signal obtained inside the receiver for voice suppression in addition to a voice suppression code, and also uses an appropriate time constant to control the suppression. This system is designed to prevent noise from occurring when switching between transmitting stations.

DESCRIPTION OF EMBODIMENTS FIG. 2 shows the configuration of a voice suppression device according to the present invention. Second
In the figure, 1 is a voice suppression instruction code detection means, and 2 is a frame synchronization detection means. Typically, a paM signal is transmitted with a specific frame structure. On the receiving side, frame synchronization is detected to synchronize the frames, but if there is no input signal or it is not the desired signal, frame synchronization is not detected. 3 is an OR circuit, 4 is a timing control means It is. The timing control means 4 has a function of outputting a signal that maintains the suppressed state for a predetermined period of time even if the output signal of the OR circuit 3 changes from the speech suppressed state to the suppressed state, for example.

The charging time is sufficiently short, and the predetermined discharge time constant 4/ζ charging/discharging 71 can be realized by the circuit. Reference numeral 5 denotes a voice suppressing means, which generates 9'1 corresponding to zero level in the digital signal domain. In addition, in the case of the analog/J signal area, it is simply a means of opening and closing the red signal.

FIG. 3 is an explanatory diagram of the operation for switching transmitting stations when the configuration of FIG. 2 is used. As shown in FIG. 3, when the output of the frame synchronization detection means 2 is used, the majority of the period T in which the audio should be suppressed can be controlled by the output of the OR circuit 3, and furthermore, the output of the timing control means 4 can be used to control the audio Yanagawa period. Since the signal can be extended over time t, it is possible to obtain a complete signal 41 and perform reliable speech suppression.

By the way, in FIG. 2, suppression instruction code detection means 1.
Frame 1/- frame synchronization detection means 2. Since the voice suppression means 6 is originally included in the receiver, only the OR circuit 3 and the timing control means 4 are necessary to realize this embodiment. In the embodiment, the OR circuit 3 is powered by two people, but it is possible to increase the number of people and make it possible to cope with audio suppression during channel switching operations on the receiver side, for example. be.

Effects of the Invention As is clear from the above explanation, the present invention achieves reliable noise prevention not only at the time of switching the P'CM mote but also at the time of switching the ground transmitting station. It is something that can be done.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an operating object in a conventional voice suppression method, FIG. 2 is a block diagram showing an embodiment of the voice suppression device according to the present invention, and FIG. 3 is an explanation of the operation of the voice suppression method according to the present invention. It is a diagram. 1... Voice suppression instruction code detection means, 2...
Frame synchronization detection means, 4. Timing control means, 5
...Voice suppression means. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure 2/

Claims (1)

[Claims] An audio suppression control signal is obtained by the audio suppression instruction signal in the PCM audio broadcast signal and the frame synchronization detection signal of the receiver, and even if the content of this control signal changes from the audio suppression state to the suppression release state, the predetermined A sound suppression device for a satellite broadcasting receiver, characterized in that the sound suppression device is configured to maintain a sound suppression state for a certain period of time.