JPH07297941A - Received signal switching control circuit - Google Patents

Abstract

PURPOSE:To transmit a high-quality PB signal at a voice codec. CONSTITUTION:When received data (a) are voice data, they are decoded by a voice decoder 2 and a voice signal (c) is outputted through a switch 6. When the received data are PB data, they are separated by a PB separator 4, inputted to a PB generator 3, decoded and outputted through the switch 6. At the time of switching from the PB data to the voice data, a silence circuit 1 is activated before that, and a silence signal is inputted to the voice decoder 2. Thus, even when the switch 6 is instantaneously changed over, an adverse-quality signal passing the PB data through the voice decoder 2 caused by the processing delay of the voice decoder 2 is not outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a received signal switching control circuit, and more particularly to a coded voice signal and a coded PB (push button) signal in a high-efficiency voice coding / decoding system for compressing and transmitting voice information. The present invention relates to a reception signal switching control circuit that receives a superimposed transmission signal and switches between the two signals.

[0002]

2. Description of the Related Art There is a method of compressing voice information for high efficiency coding, superimposing it on a coded PB signal, and multiplexing and transmitting it. In a receiving device that receives such a multiplexed signal,
The audio signal needs to be decoded and output via the audio decoder (CODEC), and the PB signal needs to be decoded and output via the PB generator. Therefore, the output of the audio decoder and the PB signal are output according to the signal content of the received data. It is necessary to switch and derive the output of the generator.

In this case, when the received data is switched from the PB signal to the audio signal, if the output of the PB generator is immediately switched to the output of the audio decoder, the audio decoder takes a long processing time, so that the output signal contains audio. The PB signal via the decoder will be derived. Since the PB signal via the audio decoder is of poor quality which does not satisfy the standard as the PB signal, the poor quality PB signal via the audio decoder is received at the moment when the received data is switched from the PB signal to the audio signal. You need to prevent it from being output.

The technique is proposed in Japanese Patent Laid-Open No. 2-246535, the receiving side block is shown in FIG. 2, and the format example of the transmission multiplexed signal is shown in FIG.

Referring to FIG. 3, the data is divided for each frame period, and each frame data has a 1-bit determination bit S. When S = 0, the audio signal data is given, and when S = 1, the decision signal S is given. Indicates PB signal data.

The transmission data having such a format is transmitted by the switch 61 and the FF constituting the separator 10 of FIG.
It is input to the (flip-flop) 62. The FF 62 operating by the S-bit latch clock generates and derives a switcher reset signal or a switcher set signal at its Q output according to whether it receives a voice coded signal or a PB signal from the transmission line.

The delay device 14 has a function of delaying the switching device reset signal by at least about the total processing delay time of the audio decoder (CODEC) 11 (T). Inverter 13
Is an inverter provided in association with the configuration of the switch 71 and the FF 72 of the switch 15.

The switches 61 and 71 are switched as shown in the figure when the switch reset signal is received, and are opposite to those shown in the figure when the switch set signal is received.

If the received data a transmitted is PB character data (S = 1), the PB generator 12
When it is decoded into a PB signal by derivation as an output signal h and is switched to voice coded data (S = 0), the voice decoder 1
It is decoded into an audio signal at 1 and is derived as an output signal h after a lapse of time T.

As described above, when the received data is switched from the PB signal to the voice signal, the switching of the switch 71 is delayed by the delay device 14 by about T time or more.
As the output h, P of poor quality that has passed through the audio decoder 11 is used.
The B signal is not derived.

[0011]

In the voice / PB switching control circuit described above, the received coded data is converted from the voice signal into the PB.
When changing to a signal, the output of the audio decoder and PB generator is switched immediately, but when changing from a PB signal to an audio signal, the output of the audio decoder and PB generator is delayed by the processing delay time of the audio decoder. Switching of is delayed. Therefore, there is a drawback in that a switching signal delay device and a switching switch control circuit are required.

An object of the present invention is to provide a reception signal control circuit capable of suppressing an increase in scale in terms of hardware.

[0013]

According to the present invention, there is provided a received signal switching control circuit for receiving a superimposed signal of an encoded voice signal and an encoded push button signal and controlling switching of these signals. Means for detecting the coded push button signal from a signal to generate a detection signal; means for separating the coded push button signal from the received signal to generate a decoded push button signal; and the coded speech signal. A sound decoding means for decoding a sound signal, a sound signal generating means for deriving a sound signal to the sound decoding means during a generation period of the detection signal, and a decoding push button signal for the generation period of the detection signal And a selecting means for selecting and deriving the output of the speech decoding means during the period of.

[0014]

A silencer circuit is inserted and provided in the input stage of the audio decoder, and the silencer circuit supplies the silencer signal to the audio decoder while the received data is the PB signal, and the received data is the PB signal. The output of the PB signal generator is immediately switched to the output of the audio decoder when the signal changes from to the audio signal. Even if switching is performed immediately in this manner, since the silence signal is applied to the audio decoder by the silence circuit immediately before the switching, the silence signal is output during the processing delay time of the audio decoder, resulting in poor quality PB. No signal will be output.

[0015]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention. The reception coded data a is input to the audio decoder 2 via the reception data silencer circuit 1 and is input to the switch 6 after being decoded.

On the other hand, the received encoded data a is the PB separator 4
To the PB detector circuit 5, the PB signal d is separated by the PB separator 4 and applied to the PB generator 3, and the decoded PB signal e becomes the other input of the switch 6.

When the PB detection circuit 5 detects the PB signal (detection by S bit in FIG. 3), it generates, for example, a low level detection signal during the data period of the PB signal. The reception data silencer circuit 1 applies the silence signal to the audio decoder 2 during the existence period of this low level detection signal, and P
The B generator 3 decodes the PB signal d.

Usually, the received coded data a is a voice signal, the detection signal f is in a high level state, and the PB generator 3 is in a reset state. At this time, the reception data silencer circuit 1 is not working, the reception encoded data a is being output to the audio decoder 2 as it is, and the switch 6
Selects the decoded audio signal c.

Now, when the reception coded data a is changed from the voice signal to the PB signal, the PB separator 4 separates the PB signal from the reception coded data a and outputs the PB character data d.
Is output to the PB generator 3. Then P
The B detection circuit 5 sets the detection signal f to the low level state,
Release the reset of the generator 3.

At the same time, the reception data silencer circuit 1 outputs silence sound data in which the decoded sound signal c becomes silent. The switch 6 also selects the decoded PB signal e. The reception data silencer circuit 1 can be realized by, for example, one AND gate.

After that, the PB detection circuit 5 outputs the PB
A latch signal g for latching the character data d is generated, and the PB generator 3 outputs the decoded PB signal e. Since the switch 6 has already selected the decoded PB signal e, the PB signal is output as the received decoded data h.

Next, when the received coded data a changes from the PB signal to the voice signal, the PB separator 4 stops the output of the PB character data d, and the PB detection circuit 5 changes the detection signal f to the high level state. , PB generator 3 is reset.

At the same time, the reception data silencer circuit 1 outputs the reception encoded data again to the audio decoder 2, and the switch 6 selects the encoded audio signal c. However, since the audio decoder 2 has a processing delay, the received decoded data becomes silent during the processing delay time of the audio decoder 2 from the switching of the switch 6 and then becomes an audio signal.

[0025]

According to the present invention, a reception data silencer circuit is added to the input of a voice decoder and the PB detection signal is used to control the reception data silencer circuit and the voice / PB changeover switch. Compared with the technology, it is possible to prevent the output of the low-quality PB signal from the audio decoder with a smaller circuit.

[Brief description of drawings]

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

FIG. 2 is a block diagram of a conventional received signal switching control circuit.

FIG. 3 is a diagram showing an example of a format of received data.

[Explanation of symbols]

 1 reception data silencer circuit 2 voice decoder 3 PB generator 4 PB separator 5 PB detection circuit 6 switch

Claims (2)

[Claims] 1. A reception signal switching control circuit for receiving a superimposed signal of an encoded voice signal and an encoded push button signal and controlling switching of these signals, wherein the encoded push button signal is detected from the received signal. Means for generating a detection signal, a means for separating the encoded push button signal from the received signal to generate a decoded push button signal, and a speech decoding means for decoding the encoded speech signal, During the generation period of the detection signal, a silence signal generating means for deriving a silence signal to the voice decoding means, and during the generation period of the detection signal the decoding push button signal is selected, and the output of the voice decoding means during the other period is selected. A received signal switching control circuit, comprising: selecting means for selecting and deriving. 2. The reception signal switching control circuit according to claim 1, wherein the silence signal generation means has a prohibition means for prohibiting an input to the voice decoding means during a generation period of the detection signal.