JP3078672B2 - Digital audio signal generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital audio device for generating a signal for measuring characteristics of a digital audio device.
The present invention relates to an audio signal generation device, and particularly to one that is capable of generating a measurement signal quickly.

[0002]

2. Description of the Related Art In recent years, consumer digital audio devices such as CDs (compact disks) and DATs (digital audio tapes) have become widespread, and digitalization of audio devices for broadcast studios has been further advanced. In response to these movements, standards for connecting digital audio equipment (digital audio interface standards) have been established by local industrial associations and international standardization organizations. In Japan, EIAJ (Japan Electronics Industry Association)
Was established in July 1987 as CP-340.

In the CP-340, the format of a digital audio signal is defined as shown in FIG. That is, one block includes 192 frames, and
One frame is composed of two subframes. Each sub-frame consists of an array of 31 bits, with a synchronization preamble from bits 0 to 3, audio sample data from bits 4 to 27, and V, U, and C bits from bits 28 to 30 respectively. , And P bits are arranged in bit 31.

[0004] Of these, bits 4 to 31 are:
In order to suppress the DC component of the transmission line, the signal is modulated by the bi-phase mark method.

[0005] The V bit (validity bit) is a bit indicating the validity of audio sample data. The U bit (user bit) is a bit for transmitting information individually defined for each medium (CD, DAT, etc.), and the block length of this information and the meaning of the bit are defined for each medium. It is determined respectively. The C bit (channel status
Bit) is the word length of the audio sample data,
It indicates the nature or source of information in the data portion, such as the presence or absence of pre-emphasis or the sampling frequency, and 192 bits of C bits included in each subframe constitute one information block. Further, the P bit (parity bit) is a bit for detecting a transmission error or a failure of the device. Bits are appended.

The digital audio signal generator is C
A digital audio signal having a predetermined format is generated for use in a characteristic test of a digital audio device such as D or DAT. This apparatus is configured so that the frequency and amplitude of audio sample data can be set to various values so that characteristics can be tested under various conditions.

As shown in FIG. 4, a conventional digital audio signal generator has a CPU 11, a ROM 12, and a RAM which constitute a general microcomputer basic system.
13, a display circuit 14, a display device 15, an input device 16 such as a keyboard and a mouse, and a CPU bus 17 connecting them, and audio sample data of a frequency or amplitude specified by an operator are generated under the control of the CPU 11. audio·
The sample data generation circuit 1 and the operator
A V / U / C bit output data storage memory 2 for storing additional information consisting of V, U, and C bits input in step 1, a parity addition circuit 3 for adding a parity bit to an input signal, A preamble addition / biphase modulation circuit 4 for modulating the input signal into a channel coding signal superior in transmission performance according to a rule of a biphase method, and adding a preamble of a synchronization pattern to the input signal. An output physical level conversion circuit 5 for converting from an ordinary TTL level to an output electrical level or optical level, and a timing generation circuit 6 for generating various timing signals necessary for the operation of each block are provided.

In this digital audio signal generating apparatus, an audio sample data generating circuit 1 generates audio sample data of a signal having a frequency and an amplitude designated by an operator through an input device 16, and generates the generated data. The digital audio signal is output at the timing of bit 4 to bit 27 of the subframe.

The V / U / C bit output data storage memory 2 stores V bit, U bit and C bit data created by the operator using the input device 16 as bit data. Data is output at the timing of bits 28, 29, and 30 of the digital audio signal subframe.

A source signal composed of a multiplexed bit string of these audio sample data and V, U, and C bit data is input to a parity addition circuit 3, where the bit of the digital audio signal subframe is input. The P bit is added so that the number of logic “1” of the bit value from 4 to bit 31 is even. The addition of the P bit is performed at the timing of bit 31 of the digital audio signal subframe.

The source signal to which the parity bit is added (the signal from bit 4 to bit 31 in FIG. 3E) is
Next, it is input to a preamble addition / biphase modulation circuit 4. This circuit 4 has a function of adding a preamble and converting a source signal into a channel coded signal having excellent transmission performance (FIG. 3 (d)). Outputs a synchronous preamble channel coding pattern, modulates the source signal after parity addition in accordance with the rules of the biphase mark system, and outputs bits 4 of the digital audio signal subframe.
Is output at the timing of bit 31 from FIG.
(D)).

The channel coded signal output from the preamble addition / biphase modulation circuit 4 is converted to a predetermined electric level or optical level by an output physical level conversion circuit 5 and sent to a digital audio interface.

As described above, in the conventional digital audio signal generating device, the audio signal generated inside the device is generated.
Sample data and V previously created by the operator,
A source signal is created from the U and C bit data, which is converted into a channel coding signal and output.

A digital audio signal measuring device is known as a device for analyzing characteristics of a received digital audio signal.

As shown in FIG. 5, this apparatus has a CPU constituting a general microcomputer basic system.
11, ROM 12, RAM 13, display circuit 14, display device 15, input device (keyboard and mouse) 16 and CPU bus 17 for connecting them, and digital audio signals input from a digital audio interface to internal signals of the device. An input physical level conversion circuit 10 for converting the input channel coding signal into a level (usually TTL level) and transmitting it as an input channel coding signal, and demodulating the input channel coding signal to obtain audio sample data, C-bit data and U-bit data. A reception separation circuit 9 for generating various timing signals and supplying the generated signals to other blocks, and an audio sample for measuring various characteristics of audio sample data received from the reception separation circuit 9 under the control of the CPU 11. The analysis circuit 8 and the C bit transmitted by the reception separation circuit 9 And a U-C-bit receive data capture circuit 7 for taking in over data and U bit data.

In this digital audio signal measuring device, an input digital audio signal having a predetermined electric level or light level input from a digital audio interface is converted by an input physical level conversion circuit 10 into a signal level inside the device. Then, it is input to the reception separation circuit 9 as an input channel coding signal.

The receiving / separating circuit 9 demodulates an input channel coding signal in which audio sample data and V bits, U bits, C bits, and P bits are time-division multiplexed and biphase mark modulated, and demodulated. The sample data is separated into U-bit data and C-bit data, and output to the audio sample analysis circuit 8 or the U / C-bit reception data acquisition circuit 7 at the timing shown in FIG. At the same time, the reception separation circuit 9
Synchronizes with the synchronization preamble of the input channel coding signal, generates timing signals such as a block head timing, a frame timing, and a bit timing, and outputs the timing signals to each block.

The U / C bit reception data acquisition circuit 7 receives the C bit data or U bit data separated by the reception separation circuit 9.
Bit data is sequentially recorded in the built-in RAM. The information represented by these bit strings is read and processed by the CPU 11 and displayed on the display device 15 in a binary or hexadecimal format.

The audio sample analysis circuit 8 measures various characteristics of the received audio sample data, which are quantized audio signals, such as a voltage value, a distortion rate, a frequency, and a voltage ratio between channels, in accordance with an operator's instruction. . The operation of the audio sample analysis circuit 8 is controlled by the CPU 11 having U-bit and C-bit information, and the obtained measurement results are processed by the CPU 11 and displayed on the display device 15.

[0020]

However, in the conventional digital audio signal generator, the operator has to operate the digital audio signal.
Since the C and U bits of the audio signal are created on the device as bit-wise data,
It takes a lot of time and effort to generate an audio signal.

The present invention solves such a conventional problem, and solves the above-mentioned problems.
It is an object of the present invention to provide a digital audio signal generating apparatus which is configured so that bits and U bits can be easily created in a short time, thereby shortening the time required to generate a digital audio signal.

[0022]

Therefore, in the present invention, C
In a digital audio signal generator for outputting a digital audio signal including bit data and U bit data, a digital audio signal is received, and C bit data and U bit data included in the signal are separated. And the specified frequency
Generate audio sample data with amplitude
And Dio sample data generating circuit, the C-bit data or U bit data and <br/> separated by the separating means, for inclusion as a C-bit data or U bit data of the output digital audio signal Said e
Multiplexing means for multiplexing with audio sample data .

[0023]

Therefore, the C-bit data or U-bit data separated from the existing received digital audio signal can be used as it is as the C-bit data or U-bit data of the output digital audio signal.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a digital audio signal generating apparatus according to an embodiment of the present invention has a configuration of a conventional digital audio signal generating apparatus (FIG. 4) and a digital audio signal measuring apparatus (FIG. 5). ), The CPU 11, the ROM 12, the RAM 13, the display circuit 1
4. For a microcomputer basic system consisting of a display device 15, an input device 16 and a CPU bus 17, an audio sample data generation circuit 1, a VUC bit output data storage memory 2, a parity addition circuit 3, a preamble The constituent blocks of the signal generation device including the addition / biphase modulation circuit 4, the output physical level conversion circuit 5, and the timing generation circuit 6 are connected, and the input physical level conversion circuit 10, the reception separation circuit 9, the audio sample analysis circuit 8 and a U / C bit reception data acquisition circuit 7 are connected.

This device can function not only as a digital audio signal generating device but also as a digital audio signal measuring device.

The latter function is performed by the building blocks 7, 8, 9, 10 relating to signal measurement in this device,
The input physical level conversion circuit 10 converts the reception signal level, and the reception separation circuit 9 demodulates the reception signal and separates it into audio sample data, U-bit data, and C-bit data. If the data capture circuit 7 is C
RA incorporating bit data and U bit data
M, and the audio sample analysis circuit 8 measures various characteristics of the received audio sample data under the control of the CPU 11.

On the other hand, when this device functions as a digital audio signal generating device, the constituent blocks 1, 2, 3, 4, 5, and 6 relating to signal generation operate and
The building blocks involved in signal measurement work together.

In generating a signal, the audio sample data generating circuit 1 generates audio sample data of a signal having a frequency and an amplitude designated by an operator, and outputs the signal at a predetermined timing.

When the operator creates V-bit, U-bit and C-bit data using the input device 16, the V / U / C bit output data storage memory 2 stores the data. Is output at a predetermined timing.

However, when the operator uses the input device 16,
Bit and C bit data transfer,
The configuration blocks 7, 8, 9, and 10 relating to signal measurement start operating, and the U / C bit reception data acquisition circuit 7 stores the U bit data and the C bit data. The C bit is transferred to the VUC bit output data storage memory 2 under the control of the CPU 11. Then, the V / U / C bit output data storage memory 2 outputs the transferred data as U bits and C bits.

The parity adding circuit 3 adds P bits to a multiplexed source signal of audio sample data and V, U, C bit data, and adds a preamble
The biphase modulation circuit 4 performs addition of a synchronization preamble to a source signal and modulation by a biphase mark method. Then, the output physical level conversion circuit 5 converts the level of the channel coding signal output from the preamble addition / bi-phase modulation circuit 4 and sends it out to the digital audio interface.

As described above, in the apparatus of the embodiment, the U bit and the C bit separated from the existing received digital audio signal can be incorporated in the generated signal as their own signal.

The CPU 11 executes the data transfer from the U / C bit reception data acquisition circuit 7 to the V / U / C bit output data storage memory 2 according to the procedure shown in FIG.

Step 1: When the operator operates the input device 16 to start the measurement operation as a stage prior to the data transfer, Step 2: the CPU 11 controls the input physical level conversion circuit 10, which is a component block related to signal measurement, Reception separation circuit 9,
It instructs the audio sample analysis circuit 8 and the UC bit reception data acquisition circuit 7 to start the operation, and waits for an instruction of data transfer from the operator.

Step 3: When the operator instructs the transfer of the C-bit data with the input device 16, Step 6;
The PU 11 converts the C bit data stored in the U / C bit reception data acquisition circuit 7 into the V / U /
The data is transferred to the C-bit output data storage memory 2. As a result, the digital audio signal C
The bit data is the C of the received digital audio signal.
Replaced by bit data.

Step 4: If the transfer of C-bit data is not instructed in step 3, the operator
It is determined whether or not the transfer of bit data is instructed by the input device 16, and if so, step 5; the CPU 11 transfers the U bit data of the U / C bit received data acquisition circuit 7 to the CPU path. V via 17
The data is transferred to the U / C bit output data storage memory 2. As a result, the U-bit data of the digital audio signal output from the device is replaced with the U-bit data of the received digital audio signal.

Step 7: After executing the transfer of the U-bit data or the C-bit data, the operator sets the input device.
Unless the end of the measurement operation is instructed by 16, the operation returns to the state of waiting for the data transfer instruction, and the U / C bit reception data acquisition circuit 7 sends the V / U / C bit Data transfer to the output data storage memory 2 is performed.

Further, in the apparatus of the embodiment, utilizing the function of creating bit data in the V / U / C bit output data storage memory 2, the C bit data or U bit data transferred to this memory 2 is stored. Some can be modified to generate new digital audio signals.

In the procedure shown in FIG. 2, the operation for starting the measurement operation and the operation for starting the data transfer are performed separately. However, the input device 16 is provided with a dedicated key for instructing the data transfer. Can be changed so that data transfer is performed by one operation.

[0040]

As is apparent from the above description of the embodiment, the digital audio signal generator of the present invention has the following features.
Since the U-bit data and the C-bit data extracted from the received digital audio signal can be incorporated into the own signal, the digital audio signal to be output can be created easily and quickly.

The received C-bit data or U
It is also easy to create a new digital audio signal by changing a part of the bit data.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a digital audio signal generation device according to the present invention;

FIG. 2 is a flowchart showing a data transfer procedure in the embodiment;

FIG. 3 is a diagram illustrating a format of a digital audio signal.

FIG. 4 is a diagram showing a conventional digital audio signal generator.

FIG. 5 is a diagram showing a conventional digital audio signal measuring device;

FIG. 6 is a diagram showing a timing of a signal output by a reception separation circuit of the measurement device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Audio / sample data generation circuit 2 V / U / C bit output data storage memory 3 Parity addition circuit 4 Preample addition / biphase modulation circuit 5 Output physical level conversion circuit 6 Timing generation circuit 7 U / C bit reception data capture Circuit 8 Audio sample analysis circuit 9 Reception separation circuit 10 Input physical level conversion circuit 11 CPU 12 ROM 13 RAM 14 Display circuit 15 Display device 16 Input device 17 CPU bus

Continuation of the front page (56) References JP-A-3-127383 (JP, A) JP-A-1-73945 (JP, A) JP-A-1-49174 (JP, A) JP-A-63-300466 (JP) , A) (58) Fields surveyed (Int. Cl. ⁷ , DB name) G11B 20/18

Claims (1)

(57) [Claims] 1. A digital audio signal generator for outputting a digital audio signal including C-bit data and U-bit data, comprising the steps of: receiving a digital audio signal; Separating means for separating U-bit data; audio having a specified frequency and amplitude;
Audio sample data to generate audio sample data
Data generation circuit, and the audio sample for including the C-bit data or U-bit data separated by the separation means as C-bit data or U-bit data of the output digital audio signal.
A digital audio signal generator, comprising multiplexing means for multiplexing with data .