JP2002006888A - System for discriminating codec system and automatic selection circuit for codec system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple circuit which selects a CODEC system without requiring a private data line or complicated sound decoding processing for automatic selection of the CODEC system. SOLUTION: The circuit is composed of a frame signal period measuring circuit 11 which takes a frame signal 21 as the input and measures the period of this frame signal to output the result, a counter circuit which takes a slot signal 24 or the frame signal 21 as a gate signal input and counts a serial clock signal 22 to output the counted value, a CODEC system discrimination part 13 which takes the frame period measurement result and the counted value 27 as the input to discriminate a CODEC system, and a sound CODEC 14 which inputs sound encoded data and the discrimination result outputted from the CODEC system discrimination part 13 and performs sound decoding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a codec type determination method and an automatic codec type selection circuit, and more particularly to a codec type used in a digital type mobile telephone system (PDC). The present invention relates to an automatic selection circuit of a codec system for selecting a system.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a conventional audio codec circuit corresponding to a plurality of codec systems.
Voice code data input by a frame signal 12 as a time unit for performing voice coding, a serial clock signal 13 for data transmission, and a serial data signal 14 transmitted in synchronization with the serial clock signal 13; An audio codec 11 receives a system selection signal 15 and outputs an analog audio 16. The audio codec 11 determines the codec system based on the codec system selection signal 15 and decodes the encoded audio data in a format conforming to the codec system to generate analog audio. Note that the above-mentioned codec method selection signal 15 is a dedicated data line signal created outside regardless of the frame signal 12, serial clock signal 13, and serial data signal 14.

FIG. 3 is a block diagram showing a conventional audio codec circuit corresponding to a plurality of codec systems. A codec which receives as input a voice coded data input by a frame signal 13 which is a time unit for performing voice coding, a serial clock signal 14 for data transmission, and a serial data signal 14 transmitted in synchronization with the serial clock. Codec system determination unit 11 that outputs system setting signal 16
And an audio codec 1 that receives the same encoded audio data as described above and a codec scheme setting signal 16 output from the codec scheme determining unit 11 and outputs analog audio 17.
It consists of two. The codec method determination unit 11 has a decoding function of a plurality of codec methods and an analog sound determination function, and outputs a frame signal 13, a serial clock 14, a frame signal 13 input in a format conforming to an unknown codec method.
A codec that can be converted into analog audio is searched for from the result of decoding the serial data 15 by all of the plurality of codecs that can be decoded by the codec determining unit, and the codec is output as a codec setting signal 16. . The audio codec 12 determines a codec system based on the codec system setting signal 16 from the codec determination unit 11, decodes the encoded audio data input in a format conforming to the codec system, and generates analog audio.

[0004]

In the conventional selection of a codec system, there is a method of selecting a codec system using a dedicated data line for designating the codec system. For this purpose, another transmission line is used. Required. Also,
There is also a method of judging the contents by using the difference in the audio coding method and selecting the codec method. However, in this case, complicated processing is involved and it is not suitable for easily and accurately performing the judgment.

[0005]

A codec system determination method according to the present invention comprises the following steps: 1: counting a frame period of a frame signal, which is a time unit for transmitting voice encoded data, by using a clock pulse;
The codec method is determined based on the count value. 2: The serial clock signal 22 and a frame signal, which is a unit of time for transmitting encoded audio data, are gated to a gate signal
A codec system determination method comprising: inputting a counter circuit as input; counting the number of serial clocks in a gate signal; and determining a codec system based on the count value. 3: The frame period is 20 ms and the count value is 22
In the case of 4, it is characterized that it is determined that the codec system is the VSELP system. 4: The frame period is 20 ms and the count value is 16
In the case of 0, it is determined that the codec system is the CS-ACELP system. 5: When the frame period is 40 ms and the count value is 224, it is determined that the codec system is the PSI-CELP system.

In the present invention, indispensable for speech encoding,
A frame signal, a slot signal indicating the timing of desired data among voice encoded data, a serial clock signal for transmitting voice encoded data, and a serial data signal transmitted in synchronization with the serial clock signal are input. The above object can be achieved by configuring an automatic selection circuit of the following codec system. 6: A frame signal is input, a frame signal cycle measuring circuit for measuring the cycle of the frame signal and outputting the result, a slot signal or a frame signal as a gate signal input, counting a serial clock signal, and counting the count value. A counter circuit to be output, a codec method determining unit that determines a codec method by using the frame period measurement result and the counter value as input, and a determination result that is an output of the voice encoded data and the codec method determining unit, It is composed of an audio codec that performs audio decoding. 7: The frame cycle measuring circuit measures the cycle of the input frame signal by using a monomulti having different pulse width outputs determined by the frame signal cycle and comparing the cycle of the input frame signal with the pulse pulse width of the monomulti. I do. 8: The counter circuit counts the number of serial clock signals in one frame signal and counts the number of serial data signals in one frame signal. 9: The codec scheme determination unit determines the codec scheme based on a combination of the above-described frame cycle measurement result and count value. 10: The audio codec receives the encoded audio data and the determination result output from the codec type determination unit to obtain an analog audio output.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on examples.

An embodiment of the present invention in a Japanese PDC system will be described with reference to FIG. Japanese PDC systems sometimes use three codec systems, VSELP, PSI-CELP, and CS-ACELP, as codec systems. FIG. 4 shows the data formats of these codec systems.
In FIG. 4, for the sake of explanation, the serial clock signal is shown by extracting only a serial clock signal of a desired data portion from a continuous serial clock signal by a slot signal. The configuration shown in FIG. 5 corresponds to the case of claim 3, in which the serial clock signal is generated only at the timing of a desired serial data signal, and the gate signal of the counter circuit 13 is a frame signal. Used. The frame signal, serial clock signal, and serial data signal of FIG. 4 are applied as the frame signal 21, serial clock signal 22, and serial data signal 23 of FIG. 5, respectively.

A frame period measuring circuit 11 receives a frame signal 21 as an input and has a frame period of 20 ms or 40 m.
s is determined, and the result is output as a frame period measurement result signal 24. The counter circuit 13 receives the serial clock signal 22 and the frame signal 21 as a gate signal 25, counts the number of serial clocks in the gate signal, and outputs a count value 26. The codec method determination unit 12 determines the codec method from the frame period measurement result signal 24 determined by the frame period measurement circuit 11 and the count value 26 counted by the counter circuit 13 as follows, and outputs the codec method as a codec method setting signal 27. .

1: The frame period measurement result signal 14 is 20
If the count value 26 is 224 in ms, the codec system setting signal 27 is output as the VSELP system. 2: When the frame cycle measurement result signal 24 is 20 ms and the count value 26 is 160, the codec scheme setting signal 27
Is output as the CS-ACELP method. 3: If the frame cycle measurement result signal 24 is 40 ms and the count value 26 is 224, the codec scheme setting signal 27
Is output as the PSI-CELP method.

The audio codec 14 determines the codec system based on the codec system setting signal 17, and inputs a frame signal 21, a serial clock 22, and serial data 2 input in a format conforming to the codec system.
3 to generate analog audio. The codec display 16 receives the codec setting signal 27 and displays the codec currently used.

An example using a mono-multi as an embodiment of the frame signal period measuring circuit will be described with reference to FIG. In the case where there are two types of frame signals as in this embodiment and the difference between the periods is large, the present method is simple and effective. 1: The frame signal 21 is input to the first mono multi 31,
This output is input to the second mono-multi 32, and the output of the second mono-multi 32 is used as the frame signal cycle measurement result 24 used in the codec type determination unit 12 in FIG. 2: The operating conditions of the mono-multi are as follows.・ Pulse width 1st monomulti: Short frame signal cycle <pulse width <long frame signal cycle 2nd monomulti: pulse width> long frame signal cycle ・ Operation 1st monomulti: Output pulse of logic H at input rise Then, retrigger is possible. 2nd mono-multi: A pulse whose logic is H is output at the falling edge of the input, and retrigger is possible. 3: An output signal as shown in FIG. 4: The frame signal cycle measurement result signal 24 is changed as follows according to the output state of the second mono-multi. If the output logic state of the second mono-multi is L, the frame cycle measurement result signal 24 is 20 ms. If the output logic state of the second mono-multi is H, the frame cycle measurement result signal 24 is 40 ms.

[0013]

The present invention has been described above, but the present invention has the following effects. 1. Audio codec data line can decode audio even if codec format is unknown. 2. Recognition of currently used voice codec method is possible. 3. Since the codec method is determined based on the combination of the frame period and the number of data in the frame according to the codec method, it is possible to determine the codec method that cannot be determined only by the frame period.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an automatic selection circuit of a codec system according to the present invention.

FIG. 2 is a configuration diagram of an audio codec circuit corresponding to a plurality of conventional codec systems.

FIG. 3 is a configuration diagram of an audio codec circuit corresponding to a plurality of conventional codec systems.

FIG. 4 is a data format diagram according to a codec method of a PDC system.

FIG. 5 is a configuration diagram of an embodiment of an automatic selection circuit of a codec system according to the present invention.

FIG. 6 is a configuration diagram of an embodiment of a frame signal period measurement circuit of the present invention.

FIG. 7 is a timing chart of the embodiment of the frame signal period measuring circuit of the present invention.

Claims (10)

[Claims] 1. A codec method determination method, wherein a frame period of a frame signal, which is a time unit for transmitting voice encoded data, is counted by a clock pulse, and a codec method is determined based on the count value. 2. A counter circuit receives a serial clock signal 22 and a frame signal, which is a time unit for transmitting encoded audio data, as a gate signal 25, counts the number of serial clocks in the gate signal, and uses the count value as a codec. A codec method determination method, wherein the method is determined. 3. The codec method determination method according to claim 1, wherein when the frame period is 20 ms and the count value is 224, the codec method is determined to be the VSELP method. 4. The method according to claim 1, wherein when the frame period is 20 ms and the count value is 160, it is determined that the codec system is the CS-ACELP system.
The described codec method determination method. 5. The codec method determination method according to claim 1, wherein when the frame period is 40 ms and the count value is 224, the codec method is determined to be the PSI-CELP method. 6. A frame signal which is a time unit for transmitting encoded audio data, a slot signal indicating a timing of desired data among encoded audio data, and a serial clock signal for transmitting encoded audio data. In a device having an audio codec for outputting analog audio from audio encoded data with a serial data signal transmitted in synchronization with a serial clock signal as an input, a frame signal for inputting a frame signal and outputting a frame period measurement result A period measurement circuit, a counter circuit that receives the slot signal or the frame signal as a gate signal input, counts a serial clock signal, and outputs a count value, and a codec that determines a codec method using the frame period measurement result and the counter value as inputs A method determination unit; And an audio codec for obtaining an analog audio output by inputting a determination result output from the codec type determination unit, and a codec type display unit for displaying a codec type in which the audio codec is operating. Automatic selection circuit of codec system to be used. 7. The codec system automatic selection circuit according to claim 6, wherein the codec system display unit performs display by using a determination result output from the codec system determination unit as an input. 8. The gate circuit according to claim 6, wherein in the counter circuit, when a serial clock signal is generated only at a timing of a desired serial data signal, a frame signal is used as an input gate signal. Automatic codec selection circuit. 9. The codec according to claim 6, wherein said frame signal period measurement circuit uses a monostable multivibrator having a different pulse width output determined by a frame signal period. Automatic method selection circuit. 10. The automatic codec system selection circuit according to claim 6, wherein said codec system determination unit determines a codec system based on a combination of the frame period measurement result and the count value.