WO2000077775A1

WO2000077775A1 - Sound switching device

Info

Publication number: WO2000077775A1
Application number: PCT/JP2000/003230
Authority: WO
Inventors: Toshiyuki Nomura
Original assignee: Nec Corporation
Priority date: 1999-06-11
Filing date: 2000-05-19
Publication date: 2000-12-21
Also published as: EP1204095A1; JP2000352999A; AU773996B2; CA2376816A1; AU4778900A; EP1204095A4

Abstract

A sound switching device is provided with a sampling frequency converting circuit (1) for converting the sampling frequency of an input signal, a delay adjusting circuit (2) for adjusting and outputting the phases of the signal whose sampling frequency is converted and the other input signal, a switching circuit (3) for selecting a signal from the output signals of the delay adjusting circuit according to a control signal. This makes it possible to reduce noise in switching the reproduction of one of different sound signals to that of another signal.

Description

Description Audio switching device Technical field

The present invention relates to an audio encoding / decoding device, and more particularly, to an audio switching device that switches any one of a plurality of audio signals. Background art

Conventionally, when transmitting audio over a transmission line where the bit rate changes, the bandwidth of the audio signal is increased or decreased according to the transmission line bit rate, so that the encoding bit rate is adapted to the transmission line bit rate and played back. An encoding method for adjusting the quality of the audio signal is used. For example, the inventor of the present application has already disclosed in Japanese Patent Application Laid-Open No. 9-202475 that when an audio signal is hierarchically encoded, N + 1 signals obtained by changing the sampling frequency of the input audio signal are used. A linear prediction coefficient, a pitch, a multipath signal, and an index representing a gain obtained by encoding an input audio signal and a signal obtained by changing the sampling frequency in order from a signal having a lower sampling frequency, for N layers. As an audio encoding device that performs multiplexing by means of a multiplexing, and an audio decoding device in which the sampling frequency of a reproduced signal changes hierarchically according to the bit rate to be decoded, CELP

(Code-excited linear prediction) The encoding circuit outputs the encoded output to the second CELP encoding circuit, and the second CELP encoding circuit encodes the input signal based on the encoded output of the first CELP encoding circuit. The multiplexer outputs the encoded output of the first and second CELP encoding circuits to the bit stream, and the demultiplexer encodes the first CELP encoding circuit from the bit stream when the control signal is at a low bit rate. Output the output to the CELP decoding circuit. At a high bit rate, extract a part of the output of the CELP encoding circuit and the output of the second CELP encoding circuit from the bit stream and output it to the second CELP decoding circuit. Speech encoding / decoding device for outputting and outputting via a switching circuit Has been proposed.

On the decoding side, the bandwidth of the reproduced audio signal, that is, the sampling frequency of the decoded audio signal changes according to the bit rate at the time of reception. On the other hand, when listening to sampled audio signals, it is necessary to set the sampling frequency for the conversion process from digital signals to analog signals. At this time, in order to switch and reproduce the audio signals having different sampling frequencies, the sampling frequency setting change processing is required, and during the sampling frequency setting change processing, the reproduced sound is often interrupted.

The operation of the conventional voice switching device will be described with reference to FIG. The audio switching device uses two types of sampled audio signals (for example, 8 kHz and 16 kHz) and two standardized audio signals (first digital audio signal and second digital audio signal, respectively). Audio signal) and a control signal, and switch between the first and second audio signals according to the control signal for playback.

Here, the control signal is a signal for instructing which of the two types of audio signals is to be reproduced.

The switching circuit 103 receives the first audio signal, the second audio signal, and the control signal, and switches between the two types of audio signals at the timing when the switching is instructed by the control signal. The DZA conversion circuit 1 1 2 Output to

The DZA conversion circuit 112 sets the sampling frequency of the audio signal specified by the control signal, converts the input digital signal to an analog signal, and outputs the analog signal.

In the above-described conventional audio switching device, when switching and reproducing an audio signal having a different sampling frequency, it is necessary to change the sampling frequency setting in the DZA conversion circuit. The problem is that the sound is interrupted.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide an audio switching device capable of reducing abnormal noise when switching reproduction of a plurality of different audio signals. . Disclosure of the invention To achieve the above object, an audio switching device according to the present invention comprises a plurality of input signals sampled at a plurality of different sampling frequencies and a control signal for designating a signal to be reproduced from the plurality of input signals. And an audio switching device for selecting one of the plurality of input signals according to a control signal and outputting the selected signal, wherein at least one of the plurality of input signals converts a sampling frequency of at least one of the input signals. A sampling frequency conversion circuit, a delay adjustment circuit that adjusts the phase of a signal whose sampling frequency has been converted by the sampling frequency conversion circuit with respect to a plurality of input signals, and outputs the remaining input signals, and a plurality of outputs of the delay adjustment circuit And a switching circuit for selecting one signal from the signals according to the control signal.

Here, the delay adjustment circuit may adjust the phase of the signal whose sampling frequency has been converted and the phase of the remaining input signal to be the same.

Further, the switching circuit may switch the output from a timing at which the switching is instructed by the control signal at a timing in consideration of a delay time in the delay adjustment circuit. Also, the audio switching device of the present invention receives a plurality of input signals sampled at a plurality of different sampling frequencies and a control signal for designating a signal to be reproduced from the plurality of input signals, and receives a plurality of signals according to the control signal. An audio switching device for selecting and outputting one signal from a plurality of input signals, comprising: a plurality of sampling frequency conversion circuits for converting sampling frequencies of a plurality of input signals into predetermined frequencies; and a plurality of sampling frequencies. It is characterized by including a delay adjustment circuit that adjusts and outputs a phase between output signals of the conversion circuit, and a switching circuit that selects one signal from a plurality of output signals of the delay adjustment circuit according to a control signal.

Further, the switching circuit may switch the output from a timing at which the switching is instructed by the control signal at a timing in consideration of a delay time in the delay adjustment circuit. Also, the audio switching device of the present invention receives a plurality of input signals sampled at a plurality of different sampling frequencies and a control signal for designating a signal to be reproduced from the plurality of input signals, and receives a plurality of signals according to the control signal. An audio switching device for selecting and outputting one signal from input signals of at least one of a plurality of input signals. At least one sampling frequency conversion circuit for converting the pulling frequency, a delay adjustment circuit for adjusting the phase of a signal whose sampling frequency has been converted by the sampling frequency conversion circuit for a plurality of input signals, and outputting the remaining input signals, and An adder circuit that selects two signals from a plurality of output signals of the delay adjustment circuit according to a control signal and performs weighting and addition, and one signal from the plurality of output signals of the delay adjustment circuit and the output signal of the adder circuit according to the control signal. And a switching circuit for selecting.

Here, the switching circuit switches from the signal before switching the output signal from the delay adjustment circuit to the output signal of the addition circuit from the timing at which the switching is instructed by the control signal to the timing considering the delay time of the delay adjustment circuit. After outputting the output signal of the adding circuit for a predetermined interval, the signal after switching may be output.

Also, the audio switching device of the present invention receives a plurality of input signals sampled at a plurality of different sampling frequencies and a control signal for designating a signal to be reproduced from the plurality of input signals, and receives a plurality of signals according to the control signal. A plurality of sampling frequency conversion circuits for converting a sampling frequency of each of a plurality of input signals into a predetermined frequency, and a sampling frequency conversion circuit. A delay adjustment circuit that adjusts the phase between the output signals of the delay adjustment circuit, outputs two signals from a plurality of output signals of the delay adjustment circuit, selects and weights and adds two signals according to a control signal, and a plurality of output signals of the delay adjustment circuit And a switching circuit for selecting one signal from the output signal of the adding circuit according to the control signal. Here, the switching circuit switches from the signal before switching the output signal from the delay adjustment circuit to the output signal of the addition circuit from the timing at which the switching is instructed by the control signal to the timing considering the delay time of the delay adjustment circuit. After outputting the output signal of the adding circuit for a predetermined interval, the signal after switching may be output.

Further, the above audio switching device is an audio decoding circuit that decodes a plurality of signals sampled from one bit stream at different sampling frequencies and outputs the decoded signals as a plurality of input signals to a sampling frequency conversion circuit or a delay adjustment circuit. It may be arranged such that one signal is selected from a plurality of output decoded signals of the audio decoding circuit by a control signal in accordance with a bit rate at the time of reception and output. In addition, the above audio switching device inputs a bit stream obtained by multiplexing a plurality of bit streams obtained by compressing a plurality of types of signals having different sampling frequencies, and switches to a plurality of output terminals according to the type of the bit stream. A bit stream switching circuit for outputting, and a plurality of audio decoding circuits for respectively decoding the bit stream output from the bit stream switching circuit and outputting as a plurality of input signals to a sampling frequency conversion circuit or a delay adjustment circuit. One of the decoded signals output from the audio decoding circuit may be selected and output according to the control signal. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram showing the configuration of the first exemplary embodiment of the present invention.

FIG. 2 is a diagram showing the configuration of the second exemplary embodiment of the present invention.

FIG. 3 is a diagram showing the configuration of the third exemplary embodiment of the present invention.

FIG. 4 is a diagram showing the configuration of the fourth exemplary embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of the fifth exemplary embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of the sixth exemplary embodiment of the present invention.

FIG. 7 is a diagram illustrating an example of a configuration of a conventional voice switching device. BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described below. The present invention converts a plurality of digital audio signals having different sampling frequencies to the same sampling frequency in order to eliminate the interruption of the reproduced sound caused by setting the sampling frequency when switching the reproduction of digital audio signals having different sampling frequencies. It is designed to adjust the phase generated thereby and reproduce.

More specifically, a sampling frequency conversion circuit (1 in Fig. 1) that converts the sampling frequency of a digital audio signal, and a delay adjustment circuit (Figure 1) that adjusts the phase shift caused by the sampling frequency conversion between a plurality of digital audio signals. 1) 2) and.

Furthermore, in order to eliminate discontinuities between samples that occur when playing back digital audio signals with the same sampling frequency but different signal bandwidths, switching is performed. The digital audio signals before and after are weighted and added at fixed intervals, and then switched and played. More specifically, a sampling frequency conversion circuit (1 in Fig. 3), a delay adjustment circuit (2 in Fig. 3), and an addition circuit (Fig. 3) for weighting and adding the output signal of the delay adjustment circuit to a predetermined interval. 3-6), and a switching circuit (7 in FIG. 3) that performs switching after outputting the output signal of the adder circuit at the interval when switching the output signal according to the control signal.

In the present invention, by setting the sampling frequency conversion circuit and the delay adjustment circuit to have the same phase as the sampling frequency of the digital signal before and after the switching, the sampling frequency setting in the DZA circuit is not required, and the reproduced sound is interrupted. It becomes difficult to repel.

Further, in the present invention, the addition circuit weights and adds the digital signal before and after the switching, so that the discontinuity between the last sample of the audio signal before the switching and the starting sample of the interval is compared with the case where no weighting addition is performed. Less. In the switching circuit, by performing switching after outputting the output signal of the adding circuit at a predetermined interval, discontinuity between samples at the beginning and end of the interval is reduced, so that abnormal noise is less likely to occur in reproduced sound. Become.

Embodiments of the present invention will be described with reference to the drawings in order to describe the above embodiments in more detail.

FIG. 1 is a block diagram showing a configuration of the first exemplary embodiment of the present invention. Referring to FIG. 1, a first embodiment of the present invention provides two different sampling frequencies (eg, 8 kHz and 16 kHz) of audio signals (a first audio signal and a second audio signal, respectively). 2) and a control signal for instructing which of the two types of audio signals to reproduce, and switch the audio signal according to the control signal for reproduction.

Sampling frequency conversion circuit 1 converts the sampling frequency of the first audio signal a second equal as the sampling frequency conversion with the sampling frequency of the audio signal (e.g., a Sanpurigu frequency from 8 k H _Z in 1 6 k H _Z ) And outputs it to the delay adjustment circuit 2. Here, the sampling frequency conversion circuit 1 performs frequency conversion by performing a frequency multiplication or frequency division circuit, or an interpolation or decimation process, and a known circuit is used for this frequency conversion. For example, reference is made to the description in Section 4.1.1 (Figure 4-1-8) of the document entitled "Multirate Systems and Filter Banks J" by PP Vaidyanathan.

The processing of the sampling frequency conversion circuit 1 causes a phase delay of the output signal with respect to the input signal. Let D be the delay time that occurs at this time.

The delay adjustment circuit 2 outputs to the switching circuit 3 a signal obtained by delaying the input second audio signal by a delay circuit (not shown) by a delay time D and an output signal of the sampling frequency circuit 1. As the delay circuit, an arbitrary one such as an inverter train or a delay line is used.

The switching circuit 3 inputs the first audio signal whose sampling frequency has been converted and the second audio signal whose delay has been adjusted from the delay adjustment circuit 2, and takes the delay time D into account, and in accordance with the control signal, Switch between two types of audio signals and output to DZA conversion circuit 4.

The DZΑ conversion circuit 4 converts the input digital audio signal into an analog signal and outputs it. The analog signal is provided to a user via a speaker, headphones, or the like.

FIG. 2 is a block diagram showing the configuration of the second exemplary embodiment of the present invention. Referring to FIG. 2, the second embodiment of the present invention is different from the first embodiment in that a sampling frequency circuit 5 for converting a sampling frequency of a second audio signal is further added. The sampling frequency conversion circuit 1 converts the sampling frequency of the first audio signal into a predetermined sampling frequency and outputs the same to the delay adjustment circuit 2. Similarly, the sampling frequency conversion circuit 5 converts the sampling frequency of the second audio signal into the predetermined sampling frequency and outputs the same to the delay adjustment circuit 2. Note that the delay time generated by the sampling frequency conversion circuit 1 is D1, and the delay time generated by the sampling frequency conversion circuit 5 is D2.

The delay adjustment circuit 2 adjusts the delay so that the phases of the first audio signal and the second audio signal that have been subjected to the sampling frequency conversion are the same, and outputs the same to the switching circuit 3.

As a delay adjustment method, the longer one of the delay times D1 and D2 is set to D, and both signals are delayed by the same time, that is, the delay time D by a delay circuit (not shown).

The switching circuit 3 receives the first audio signal and the second audio signal that have been subjected to the sampling frequency conversion and the delay adjustment from the delay adjustment circuit 2, and takes the delay time D into consideration. The two types of audio signals are switched according to the control signal and output to the DZA conversion circuit 4.

The D / A conversion circuit 4 converts the input digital audio signal into an analog signal and outputs it. The analog signal is provided to a user via a speaker, headphones, or the like.

In the present embodiment, for example, when the sampling frequencies of the first and second audio signals are 8 kHz and 12 kHz, respectively, the first and second audio signals are sampled by the sampling frequency circuit. Is converted to 24 kHz, so that the processing amount of the sampling frequency conversion can be reduced as compared with the first embodiment in which only the first audio signal is converted to the sampling frequency of 12 kHz.

FIG. 3 is a block diagram showing a configuration of the third exemplary embodiment of the present invention. Referring to FIG. 3, the third embodiment of the present invention further includes an adder circuit 6 and differs from the first embodiment in the operation of the switching circuit 7.

The sampling frequency conversion circuit 1 converts the sampling frequency of the first audio signal to be equal to the sampling frequency of the second audio signal, and outputs it to the delay adjustment circuit 2. The delay time generated by the sampling frequency conversion circuit 1 is D. The delay adjustment circuit 2 outputs a signal obtained by delaying the input second audio signal by the delay time D and an output signal of the sampling frequency circuit 1 to the addition circuit 6 and the switching circuit 7.

The adding circuit 6 weights and adds the sampling frequency-converted first audio signal and the delay-adjusted second audio signal, and outputs the result to the switching circuit 7.

For example, as an example of weighted addition, the signals before and after switching are

Sl (n), S2 (n), n = 0, 1, .. ·, T-1

The output signal of the adder circuit 5 is S 3 (n),

S3 (n) = (n / (T-l)) S2 (n) + ((T- 1-n) / (T-l)) Sl (n),

n = 0, Ι,.,., Τ-1,

Becomes Here, Τ is the number of samples representing the interval at which the output signal of the adder circuit is used, and is determined for each sampling frequency of the input audio signal.

One of a first audio signal whose sampling frequency has been converted and a second audio signal whose delay has been adjusted are assigned to the signals before and after the switching. y The switching circuit 7 receives the sampling frequency-converted first audio signal, the delay-adjusted second audio signal, the output signal of the adding circuit 6, and the control signal, and the switching signal is instructed by the control signal. The output signal is switched from the signal SI (n) before switching to the output signal S 3 (n) of the adder circuit 6 at a timing that takes the delay time D into consideration from the output timing, and S 3 (n ), And outputs the switched signal S 1 (n) to the D / A conversion circuit.

The DZA conversion circuit 4 converts the input digital audio signal into an analog signal and outputs it. The analog signal is provided to a user via a speaker, headphones, or the like.

FIG. 4 is a block diagram showing a configuration of the fourth exemplary embodiment of the present invention. Referring to FIG. 4, the fourth embodiment of the present invention further includes an adder circuit 6 and differs from the second embodiment in the operation of the switching circuit 7.

In the fourth embodiment of the present invention, the operations of the adder circuit 6 and the switching circuit 7 are the same as those described in the third embodiment.

The sampling frequency conversion circuit 1 converts the sampling frequency of the first audio signal to a predetermined sampling frequency (for example, 24 kHz) and outputs the same to the delay adjustment circuit 2. Similarly, the sampling frequency conversion circuit 5 converts the sampling frequency of the second audio signal into a predetermined sampling frequency, and outputs it to the delay adjustment circuit 2. Note that the delay time generated by the sampling frequency conversion circuit 1 is D1, and the delay time generated by the sampling frequency conversion circuit 5 is D2. The delay adjustment circuit 2 adjusts the delay so that the phases of the first audio signal and the second audio signal subjected to the sampling frequency conversion become the same, and outputs the same to the addition circuit 6 and the switching circuit 7. Here, as an example of the delay adjustment, the longer one of the delay times D 1 and D 2 is set to D, and both signals are delayed by the delay time D.

The adder 6 weights and adds the first audio signal and the second audio signal whose sampling frequency has been converted and the delay has been adjusted, and outputs the result to the switching circuit 7.

For example, the above equation (1) is used as an example of weighted addition. Here, as the signals SI (n) and S2 (n) before and after the switching, one of the first audio signal and the second audio signal subjected to the sampling frequency conversion and the delay adjustment is assigned. The switching circuit 7 receives the first audio signal, the second audio signal, which has been subjected to the sampling frequency conversion and the delay adjustment, the output signal of the adding circuit 6, and the control signal, and starts from the timing at which the switching is instructed by the control signal. At the timing considering the delay time D, the output signal is switched from the signal SI (n) before switching to the output signal S3 (n) of the adder circuit 5, and S3 (n) for a predetermined interval. After that, the switched signal SI (n) is output to the DZA conversion circuit.

The D / A conversion circuit 4 converts the input digital audio signal into an analog signal and outputs it. The analog signal is provided to a user via a speaker, a headphone, or the like.

FIG. 5 is a block diagram showing, as a fifth embodiment of the present invention, a configuration of a voice decoding circuit 8 based on bandwidth hierarchical voice coding and a voice switching device in which the configuration of the third embodiment is combined. It is. Referring to FIG. 5, in a fifth embodiment of the present invention, a bandwidth hierarchical audio decoding circuit 8 converts a digital audio signal obtained by decoding an input bit stream into a sampling frequency conversion circuit. 1. Output to the delay circuit 2 as a first digital audio signal or a second digital audio signal, respectively.

Bandwidth hierarchical audio decoding circuit 8 outputs a control signal for instructing which of the two types of audio signals to reproduce, to addition circuit 6 and switching circuit 7.

Here, the bit stream is divided into a basic part essential for decoding the compressed audio signal information and an extended part for improving the quality by expanding the bandwidth of the audio signal.

Therefore, when only the basic part is received, the bandwidth hierarchical speech decoding circuit 8 decodes a speech signal having a narrow bandwidth (for example, a digital signal having a sampling frequency of 8 kHz) and performs sampling. Output to frequency conversion circuit 1.

If the extension is also received, it decodes an audio signal with a wider bandwidth (for example, a digital signal with a sampling frequency of 16 kHz) and outputs it to the delay adjustment circuit 2.

Here, as for the decoding operation of the bandwidth hierarchical audio decoding circuit 8, for example, the description in Japanese Patent Application Laid-Open No. 11-30997 is referred to.

The bandwidth-layered speech decoding circuit 8 is an extension In the case where only the basic part is used and the extended part is used, a plurality of decoded signals can be simultaneously decoded.

In the present embodiment, it is assumed that a decoded signal using only the basic part of the bit stream is always decoded and output to the delay adjustment circuit 2.

The description of the operation of the sampling frequency conversion circuit 1, the delay adjustment circuit 2, the addition circuit 6, the switching circuit 7, and the D / A conversion circuit 4 is the same as that described in the second embodiment. Omitted.

FIG. 6 is a block diagram showing a configuration of a voice switching device in which a plurality of voice decoding circuits and the first embodiment are combined as a sixth embodiment of the present invention. Referring to FIG. 6, in a sixth embodiment of the present invention, bit stream switching circuit 11 receives a bit stream obtained by multiplexing a plurality of bit streams obtained by compressing signals of different sampling frequencies, and The input bit stream is output to the first audio decoding circuit 9 or the second audio decoding circuit 10 according to the type of the input bit stream.

Here, as the bit stream multiplexing method, a plurality of bit streams may be multiplexed simultaneously or may be switched and multiplexed. In the former case, two types of audio signals are decoded simultaneously from the two types of bit streams, while in the latter case, the audio signal is decoded from only one of the bit streams. In this embodiment, it is assumed that a bit stream multiplexed by switching a plurality of bit streams is input.

Further, the bit stream switching circuit 11 outputs to the switching circuit 3 a control signal for instructing which of the two types of audio signals to reproduce.

The first speech decoding circuit 9 decodes a bit stream having a lower bit rate (for example, 8 kbit / s) than the second speech decoding circuit 10 (for example, a sampling frequency Is output to the sampling frequency conversion circuit 1 as a first digital audio signal.

The second audio decoding circuit 10 decodes a bit stream having a higher bit rate (for example, 16 kbit / s) than the first audio decoding circuit 9 (for example, if the sampling frequency is 16 kHz digital signal) to the second digital It is output to the delay adjustment circuit 2 as an audio signal.

Here, as for the first speech decoding circuit 9 and the second speech decoding circuit 10, reference is made to, for example, the description of Japanese Patent Application Laid-Open No. H10-2007496.

The operations of the sampling frequency conversion circuit 1, the delay adjustment circuit 2, the switching circuit 3, and the DZA conversion circuit 4 are the same as those of the first embodiment, and the description thereof will be omitted.

FIG. 5 shows a combination of the bandwidth hierarchical speech decoding circuit and the configuration of the third embodiment. FIG. 6 shows a plurality of speech decoding circuits and the configuration of the first embodiment. Is shown, but it goes without saying that any combination of the above embodiments may be used.

However, in the third and fourth embodiments, since a plurality of signals are required at the same time in the adder circuit, both signals overlap when switching between the first audio signal and the second audio signal. Need to be.

Therefore, in the third and fourth embodiments to be combined with the audio decoding circuit, the combination with the bandwidth hierarchical audio decoding circuit, or when a plurality of audio decoding circuits are used, a plurality of input bit streams are required. Must be multiplexed simultaneously.

In each of the above embodiments, the case where there are two types of input audio signals has been described. However, when the input audio signal has three or more types, a sampling frequency conversion circuit and input / output lines connected to the sampling frequency conversion circuit are required. Is realized by adding as many as necessary.

As described above, according to the present invention, it is possible to reduce an abnormal sound at the time of switching the reproduction of a plurality of different audio signals.

The reason is that, in the present invention, by changing the sampling frequency and the phase of the signals before and after switching of a plurality of audio signals to be the same, it is not necessary to change the sampling frequency setting.

Also, by adding a predetermined interval weight to the audio signals before and after the switching, it is possible to reduce the discontinuity between samples at the beginning and end of the interval, thereby producing a reed effect.

Claims

The scope of the claims

1. A plurality of input signals sampled at a plurality of different sampling frequencies, and a control signal specifying a signal to be reproduced from the plurality of input signals are input, and the plurality of input signals are input according to the control signal. An audio switching device for selecting and outputting one signal from signals,

At least one sampling frequency conversion circuit for converting a sampling frequency of at least one input signal of the plurality of input signals;

A delay adjustment circuit that adjusts the phase of a signal whose sampling frequency is converted by the sampling frequency conversion circuit with respect to the plurality of input signals, and outputs the remaining input signals;

A switching circuit for selecting one signal from a plurality of output signals of the delay adjustment circuit in accordance with the control signal.

2. In the audio switching device according to claim 1,

The delay adjusting circuit adjusts the phase of the signal obtained by converting the sampling frequency so that the phase of the remaining input signal is the same as the phase of the signal.

3. The voice switching device according to claim 1,

The audio switching device, wherein the switching circuit switches an output from a timing at which the switching is instructed by the control signal, at a timing considering a delay time in the delay adjustment circuit.

4. Inputting a plurality of input signals sampled at a plurality of different sampling frequencies and a control signal designating a signal to be reproduced from the plurality of input signals, and inputting the plurality of input signals in accordance with the control signal An audio switching device for selecting and outputting one signal from signals,

A plurality of sampling frequency conversion circuits for respectively converting the sampling frequencies of the plurality of input signals into predetermined frequencies;

Adjusting and outputting the phase between the output signals of the plurality of sampling frequency conversion circuits; Delay adjustment circuit,

5. The voice switching device according to claim 4,

6. The voice switching device according to claim 4,

7. A plurality of input signals sampled at a plurality of different sampling frequencies, and a control signal specifying a signal to be reproduced from the plurality of input signals are input, and the plurality of input signals are input according to the control signal. An audio switching device for selecting and outputting one signal from signals,

At least one sampling frequency conversion circuit for converting a sampling frequency of at least one signal of the plurality of input signals;

An addition circuit that selects two signals from a plurality of output signals of the delay adjustment circuit according to the control signal and performs weighted addition;

An audio switching device, comprising: a switching circuit that selects one signal from a plurality of output signals of the delay adjustment circuit and an output signal of the addition circuit according to the control signal.

8. The voice switching device according to claim 7,

The switching circuit outputs the output signal of the addition circuit from the signal before switching of the output signal from the delay adjustment circuit at a timing in consideration of the delay time of the delay adjustment circuit from the timing when the switching is instructed by the control signal. Switch to signal and add the above for a predetermined interval A voice cut-off characterized by outputting a signal after switching after outputting an output signal of a circuit.

9. A plurality of input signals sampled at a plurality of different sampling frequencies, and a control signal specifying a signal to be reproduced from the plurality of input signals are input, and the plurality of input signals are input according to the control signal. An audio switching device for selecting and outputting one signal from signals,

A delay adjustment circuit that adjusts and outputs the phase between the output signals of the sampling frequency conversion circuit,

An addition circuit that selects two signals from a plurality of output signals of the delay adjustment circuit according to the control signal and weights and adds;

10. The audio switching device according to claim 9, wherein

The switching circuit outputs the output signal of the addition circuit from the signal before switching of the output signal from the delay adjustment circuit at a timing in consideration of the delay time of the delay adjustment circuit from the timing when the switching is instructed by the control signal. Switching to a signal, outputting an output signal of the adding circuit for a predetermined interval, and then outputting a signal after the switching.

1 1. The audio switching device according to claim 1,

An audio decoding circuit that decodes a plurality of signals sampled at different sampling frequencies from one bit stream and outputs the plurality of signals as the plurality of input signals to the sampling frequency conversion circuit or the delay adjustment circuit;

An audio switching device, wherein one signal is selected from the plurality of output decoded signals of the audio decoding circuit according to the control signal in accordance with a bit rate at the time of reception and is output.

1 2. In the voice switching device according to claim 4,

Multiple samples sampled at different sampling frequencies from a single bitstream An audio decoding circuit that decodes a signal and outputs the plurality of input signals to the plurality of sampling frequency conversion circuits,

1 3. The audio switching device according to claim 1,

A bit stream switching circuit that inputs a bit stream obtained by multiplexing a plurality of bit streams obtained by compressing a plurality of types of signals having different sampling frequencies, and switches and outputs the output to a plurality of output terminals according to the type of the bit stream;

And a plurality of audio decoding circuits for decoding the bit stream output from the bit stream switching circuit and outputting the decoded signal as the plurality of input signals to the sampling frequency conversion circuit or the delay adjustment circuit. And

An audio switching device, wherein one of the decoded signals output from the plurality of audio decoding circuits is selected and output according to the control signal.

14. The voice switching device according to claim 4,

A plurality of audio decoding circuits for decoding the bit streams output from the bit stream switching circuit, respectively, and outputting the decoded signals as the plurality of input signals to the plurality of sampling frequency conversion circuits;

An audio switching device, wherein one of the decoded signals output from the plurality of audio decoding circuits is selected and output in accordance with the control signal.