JP3074800B2 - Digital radio telephone equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telephone device using a radio telephone line such as a car telephone and a portable telephone, and more particularly to a telephone device for a digital radio telephone line transmitting digital data.

[0002]

2. Description of the Related Art Various types of mobile phones and mobile phones have been developed as mobile phone devices using wireless telephone lines. In this case, as a communication system using this kind of wireless telephone device, a communication system using a digital wireless line in which communication is performed by wireless transmission of digital data has been developed.

[0003] On the other hand, various so-called answering machines incorporating a recorder capable of recording the contents of a call and the like have been developed. In the case of this answering machine, a tape recorder is generally incorporated as a recorder, and a message from the other party is recorded or a message to be conveyed to the other party is recorded in advance by using the tape recorder. The use of an answering machine improves the usability of the phone.

[0004]

Here, even in the case of the above-mentioned wireless telephone device such as a portable telephone, the convenience of use can be improved by configuring the telephone as an answering machine. When a tape recorder or the like is incorporated in the telephone device, the telephone device becomes larger and becomes unsuitable for carrying.

[0005] In this case, as an answering machine, a semiconductor memory is used in place of a tape recorder to record an audio signal (so-called solid-state recording), and there is a recorder in which a recording unit is downsized. Since the storage capacity is limited, messages up to several tens of seconds can be recorded at the maximum, and it cannot be said that the recording capacity is sufficient for an answering machine.

An object of the present invention is to provide a radio telephone device in which solid-state recording processing by a semiconductor memory is performed efficiently.

[0007]

SUMMARY OF THE INVENTION According to the present invention, an audio signal compressed into digital data by high-efficiency encoding is
In a digital wireless telephone device wirelessly transmitted to and from a base station, a digital data audio signal received from the base station is variable-length encoded, and the variable-length encoded audio signal is converted into a semiconductor signal. The sound is recorded in a memory and solid-state recording is performed.

The present invention also relates to a digital radio telephone apparatus in which a voice signal compressed and digitized by high-efficiency coding is wirelessly transmitted to and from a base station. When the information indicating the state is added, the time information in which the silent state of the received audio signal continues is detected, and the information indicating the received silent state is detected.
Instead of this, the detected time information is stored in a semiconductor memory to perform solid-state recording.

[0009]

The voice signal received from the base station is variable-length coded and stored in the semiconductor memory, so that the amount of stored data of the voice signal is reduced, and the voice data is efficiently stored in the semiconductor memory.

[0010] When information indicating a silent state is added to the audio signal received from the base station, the detected time information is stored in the semiconductor memory instead of the silent audio signal. The data amount of the stored audio data is saved corresponding to the length of the silent section, and the audio data is efficiently stored in the semiconductor memory.

[0011]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

In this embodiment, the present invention is applied to a digital radio telephone apparatus of a cellular system or the like in which communication is performed by a digital line, and a digital data-converted audio signal which is communicated between a base station and the radio telephone apparatus. Is compressed by high-efficiency coding in this example.

Here, the high-efficiency encoding of the audio data will be described. For example, an audio signal is divided into a plurality of channels on a time axis or a frequency axis, and bit allocation (bit allocation) for adaptively allocating the number of bits for each channel. Bit assignment). The coding technique based on the bit allocation of the voice signal includes band division coding (sub-band coding: SB) in which a voice signal on a time axis is divided into a plurality of frequency bands and encoded.
C), so-called adaptive predictive coding (AT) in which an audio signal on the time axis is converted into a signal on the frequency axis (orthogonal transform), divided into a plurality of frequency bands, and adaptively encoded for each band.
C) Or, a combination of band division coding and so-called adaptive prediction coding (APC) is performed, and a signal on the time axis is band-divided, and each band signal is converted into a base band (low band). There are coding techniques such as so-called adaptive bit allocation (APC-AB) for performing predictive coding.

[0014] In the high-efficiency coding, for example, in adaptive prediction coding, a speech signal on the time axis is converted into a fast Fourier transform (FFT) or a discrete cosine transform (DCT).
And the like, and transforms the axis into a frequency axis (frequency axis) orthogonal to the time axis, then divides the band into a plurality of bands, and quantizes the FFT coefficients, DCT coefficients, and the like in each of the divided bands by adaptive bit allocation. (Requantization). As an example of requantization in adaptive transform coding of fast Fourier transform, for example, F
The FT amplitude value and the like are divided into blocks, and additional information required when requantizing each block is calculated. Using the additional information, requantization is performed for each block, and the additional information is also quantized. There is a technique to do.

In the case of highly efficient encoding of a voice signal transmitted over a telephone line or the like, when the transmitted voice is in a silent state due to a temporary break in conversation or the like, the voice signal at this time is encoded. Instead of transmitting the data in a silence state, only the information indicating the silent state is transmitted to reduce the amount of transmitted information during silence. For example, as shown in FIG. 2A, when a silent portion is generated intermittently as an input audio signal, as shown in FIG. 2B, the input audio signal has a high level at a sound portion a and a low level at a silent portion b. On the sending side, a silence detection flag (DTX flag) which is a level is generated, and while the silence detection flag is at a low level, transmission of the encoded audio signal is stopped, and only the silence detection flag is added with additional information. Let it be transmitted.

The wireless telephone device of the present embodiment communicates with a base station by transmitting and receiving a signal which has been efficiently coded by various methods as described above. The telephone device is configured as shown in FIG. That is, in FIG. 1, reference numeral 1 denotes an antenna for receiving data transmitted from a base station and transmitting the data to the base station. This antenna 1 is connected to a reception processing circuit 2, and the reception processing circuit 2 A process for receiving a band signal is performed. Then, the signal received by the reception processing circuit 2 is supplied to the demodulation / equalization circuit 3 to perform demodulation processing and equalization processing. Then, the processed received signal is supplied to the link controller 4, and the link controller 4 extracts the voice information and the additional information of the highly efficient encoded received signal. Then, the extracted audio information and the additional information are supplied to the audio codec circuit 5, and the audio signal coded with high efficiency by the audio codec circuit 5 is returned to the original transmission rate digital data. Is supplied to a digital / analog converter 6 to be converted into an analog audio signal, and the converted analog audio signal is supplied to a speaker 7 for output.
In this case, the silence detection flag extracted from the received signal by the link controller 4 is supplied to the audio codec circuit 5, and when the received audio is in a silent state, the audio codec circuit 5 performs a corresponding process. The silence detection flag extracted from the received signal by the link controller 4 is also supplied to a recording control unit 22 of the solid-state recording unit 20 described later.

The audio picked up by the microphone 8 is supplied to an analog / digital converter 9 as an analog audio signal, and is converted into digital data by the analog / digital converter 9. Then, the converted digital data is supplied to the audio codec circuit 5, and the audio codec circuit 5 performs a high-efficiency encoding process. Then, the audio data and the additional information, which have been efficiently coded by the audio codec circuit 5, are supplied to the transmission processing circuit 10 via the link controller 4, and the transmission processing circuit 10 converts the transmission data into a predetermined frequency band transmission signal. A signal is transmitted from the antenna 1. At the time of this transmission, when the audio codec circuit 5 detects a silent state of the audio to be transmitted, a silent detection flag is set, and the silent detection flag is supplied to the transmission processing circuit 10 to be transmitted as additional information.

The received audio data obtained by the link controller 4 can be supplied to the solid-state recording unit 20 and recorded (stored). That is, the high-efficiency encoded audio data output from the link controller 4 is supplied to the variable-length encoding circuit 21, and the high-efficiency encoded audio data is directly converted into a variable-length code under the control of the recording control unit 22. And compress the amount of data. Then, the converted voice data as a variable length code is stored in the memory 23 which is a semiconductor memory. In addition, audio data obtained by highly efficiently encoding the audio picked up by the microphone 8 by the audio codec circuit 5 can be stored in the memory 23 through the variable-length encoding circuit 21 by the same processing.

In this case, in the present embodiment, the variable length encoding process in the variable length
The speech parameters of the coding are coded according to the probability of occurrence. Depending on the type of parameter,
df (probability density fu
nction), an entropy coder table is prepared for each parameter. Then, for example, entropy coding is performed on the residual data based on the frequency of occurrence of the index of the output of the quantizer.

Note that parameters for which entropy coding is performed and parameters for which entropy coding is not performed may be mixed. That is, if no word in the same table is a prefix of another word, it is completely decoded. That is, if there is information on the decoder side that "n data has been entropy coded by table m", even when different tables are used (bit allocation is different),
Even if the data is packed, it is completely decoded. Since this is information that can be held off-line, a mixture of a plurality of types of entropy coding is eventually allowed.

In the variable length coding by Huffman coding, there is no deterioration in sound quality due to the variable length coding.

In the present embodiment, when the silence detection flag added to the audio data supplied to the solid-state recording unit 20 is set, the recording control unit 22 detects the time when the silence detection flag is set. Instead of the audio data, the memory 23 stores information about the time during which the silence detection flag is set (the number of data frames).

When reproducing (reading) the audio data recorded (stored) in the memory 23 in this manner, the read output of the memory 23 is supplied to a variable length decoding circuit 24, and this variable length decoding circuit 24 is provided. The decoding circuit 24 decodes the original highly efficient encoded audio data. Then, the decoded audio data is supplied to the audio codec circuit 5, and the audio codec circuit 5 performs decoding from the high-efficiency code, and
Output from Alternatively, the decoded audio data is supplied to the link controller 4 and transmitted from the antenna 1 via the transmission processing circuit 10.

At the time of reproduction from the solid-state recording unit 20, where time-related information is stored in place of the variable-length-encoded audio data, the time information is stored in the link controller 4 or the link controller 4. It is supplied to the audio codec circuit 5 and is subjected to a corresponding process (creation of a silent section at a corresponding time).

By providing the solid-state recording unit 20 for performing recording / reproduction using the memory 23 in this manner, the recording of the voice received by the telephone device and the voice responding to the incoming call are recorded in advance. For example, the wireless telephone device can be used as an answering machine. In this case, the audio data which is transmitted after being highly efficient coded is further compressed and recorded (stored) by a variable length code, so that the audio data can be stored for a long time with a small storage capacity. 23 storage capacities are effectively utilized. Further, in the silent section, only the time information of the silent section is stored, so that there is no needless storage of data, and the storage capacity of the memory 23 is effectively utilized from this point. Therefore, it is possible to record voice for a long time by using the solid-state recording unit 20 using a semiconductor memory, and it is possible to incorporate a function of an answering machine into a small-sized wireless telephone device for portable use or the like.

Further, since the voice data which has been highly efficiently coded for transmission is subjected to variable length coding as it is, the circuit configuration for variable length coding is simplified, and the solid-state recording section 20 is simplified. .

In the above-described embodiment, the Huffman coding entropy coding is used as the variable length code to be stored in the memory. However, the variable length code which has been subjected to the variable length coding by another process may be stored.

[0028]

According to the present invention, high-efficiency-encoded audio data for transmission is subjected to variable-length encoding as it is for solid-state recording, so that the amount of stored audio signal data is reduced and the semiconductor memory Voice data is stored efficiently, and a small-sized wireless telephone device having a built-in recording function such as an answering machine can be easily realized.

Also, by storing the detected time information in the semiconductor memory instead of the silent audio signal, the data amount of the stored audio data can be reduced corresponding to the length of the silent section, and the semiconductor memory can be saved. In this case, the voice data is efficiently stored, and this also makes it possible to easily realize a small-sized wireless telephone device having a built-in recording function.

[Brief description of the drawings]

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

FIG. 2 is a timing chart for explaining one embodiment.

[Explanation of symbols]

 Reference Signs List 4 link controller 5 audio codec circuit 20 solid-state recording section 21 variable-length encoding circuit 22 recording control section 23 memory 24 variable-length decoding circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H04Q ^7/ 00-7/38 H04B ⁷ /24-7/26 102

Claims (2)

(57) [Claims] 1. A digital radio telephone device in which an audio signal compressed and digitized by high-efficiency encoding is wirelessly transmitted to and from a base station, wherein the digital data received from the base station is converted into a digital signal . The audio signal is variable-length coded, and the variable-length coded audio signal is stored in a semiconductor memory for solid-state recording.
Digital wireless telephone device. Wherein when the information indicating that to the digital data voice signals received from the above SL base station is a silent state is added to detect the time information silence of the received audio signal follows 2. The digital radio telephone apparatus according to claim 1 , wherein said detected time information is stored in said semiconductor memory in place of said received information indicating the silent state, and solid-state recording is performed.