JPH0535510B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a PCM audio playback device.

[Conventional technology]

In recent years, PCM for compact disc players, etc.
Audio playback devices have become widely commercially available. In addition to simply listening to the above-mentioned reproduced sound, the reproduced sound is often recorded on tape. There are two types of tape recording: analog recording and PCM recording. In the case of PCM recording, unless the peak value of the reproduced sound is known in advance, it is not possible to accurately determine the dynamic range and S/N before recording. Due to the nature of PCM recording, sudden odd-order distortion occurs when overloaded recording is performed for a short period of time. In analog recording, on the other hand, distortion occurs less often due to the saturation characteristics of tape.

When recording analog audio signals played from a PCM audio playback device back to a PCM recording device,
In order to easily determine the recording level, it is extremely convenient if the PCM audio playback device sends out a reference tone signal that indicates the level of the playback sound. By the way, a PCM audio playback device includes audio signals with different signal levels for each section, such as when recording several songs, so a reference tone signal must also be generated for each section. . However, until now, there has been no PCM audio playback device that sends out such a wide variety of reference tone signals.

[Problem that the invention seeks to solve]

In view of the above circumstances, an object of the present invention is to generate a sine wave with an amplitude equivalent to the maximum value of the audio signal for each meaningful recording section of a recording medium (for example, in the case of music, each song). An object of the present invention is to provide a PCM audio playback device that can generate a reference tone signal and send it out as a reference tone signal.

The sine wave generator is capable of outputting an audio signal by switching it, and is provided with means for storing information for controlling the sine wave generator in advance,
Externally, the recording section can be arbitrarily set and changed, and a sine wave generator controlled by the means sends out reference tone signals corresponding to the recording section.

[Means for solving problems]

There are two types of inventions for generating reference tone signals as a means of solving the problem, depending on whether a digital method or an analog method is used.

First, a digital method will be explained. The apparatus of the first invention includes a level detection section that detects the section maximum level for each recording section, and a tone detecting section that records the section maximum level for the digital audio output from the digital signal section of the PCM audio playback device. It includes a level recording section and a sine wave generating section, which will be described later. Here, the digital signal section is a temporary designation of a section that outputs left and right magnetic division data before DA conversion of the reproducing device. Therefore, when listening to audio, the output of the digital signal section is input to the DA converter and output as left and right channel audio.

The sine wave generating section has means for creating a digital sine waveform corresponding to the maximum audio output of the PCM audio reproduction device, and multiplying the digital sine waveform by a coefficient determined by the section maximum level, After sequentially recording the section maximum level for each recording section in the tone level recording section, data of an arbitrary section is sent from the tone level recording section to the sine wave generating section by an external key control switch. , the output of the sine wave generator is switched and input to the analog converter of the PCM audio reproduction device, and is output as a reference tone signal of the section.

Next, the analog method of the second invention will be explained. The level detection section and tone level recording section are completely the same as those in the above-mentioned invention, but the sine wave generation section includes a reference sine wave oscillator corresponding to the maximum audio output of the PCM audio playback device, and an output of the oscillator for each recording interval. and a programmable attenuator that provides an amount of attenuation determined by the section maximum level.

After recording the section maximum level of each recording section in the tone level recording section, an external key control switch sends the data of an arbitrary section from the tone level recording section to the sine wave generation section and generates the sine wave. The output of the generating section is switched with the output of the PCM audio reproduction device, and outputted as a reference tone signal of the section.

[Effect]

Both the first invention and the second invention have a sine wave generating means with an amplitude corresponding to the maximum level (FS) of the PCM audio reproduction device. Then, detect the maximum level for each recording section in advance,
Record this maximum level.

In the first invention, the sine wave signal is output as a digital signal, and in the second invention, it is output as an analog signal, but both have means for changing the amplitude in accordance with the maximum level for each recording section. There is.

When an arbitrary recording section is selected using an external key control switch, the recorded maximum level signal changes the amplitude of the sine wave signal to the maximum level of that recording section. This sine wave signal is sent to the analog converter in the first invention, and directly in the second invention.
If you switch to the audio output terminal of the PCM audio playback device,
A reference tone signal is sent to the outside.

〔Example〕

The first invention will be explained with reference to the embodiment shown in FIG. 1A. The circuit shown in FIG. 1A is roughly divided into a digital signal section 1, a level detection section 2, a tone level recording section 3, a sine wave generation section 4A, and an analog conversion section 5. The tone level recording section 3 records information regarding the maximum audio level of each recording section as information for controlling the sine wave generating section 4A, and extracts data of any section using an external key control switch 6. , sends the information to the sine wave generator 4.

First, the procedure for storing maximum level information in the tone level recording section 3 will be explained. The level detection section 2 includes an absolute value detection circuit 21, a register 22, a comparison circuit 23, and an AND circuit 24.
When it enters 1, its sign is detected, and if it is a negative number, it is corrected to a positive number and output. When the illustrated signal A is larger than the signal B, the AND circuit 24 is opened and the signal A is latched into the register 22 by the clock (1). Therefore, the output of the register 22 is always the maximum value of the signal being sent. Clock (1) is a clock signal for each word of the signal, and a reset signal is input for each section in which the maximum value is detected.

The maximum value is stored in the memory 31 of the tone level recording section 3, for example, at an address corresponding to the section number under the control of the memory control section 32. As address information, in the case of music, an address corresponding to the song number or song title is determined as appropriate.

The sine wave generator 4A outputs a sine wave having a peak value corresponding to the maximum value of the audio signal in each section as a temporal relationship of digital values (digital sine waveform). That is, the clock (2) from the digital signal section 1 is counted by the counter 41, and the ROM
(1) Sequentially scan 42 addresses. Here, clock (2) has a frequency of _2fs , which is twice the frequency _fs at which the two left and right channels are sampled, respectively.
The ROM (1) 42 is a read-on memory that stores the amplitude value at each time of a sine wave whose peak value is the maximum audio level of the PCM playback device, and this waveform is outputted to the outside by the sequential scanning. .

This sine waveform digital signal is sent to the multiplier circuit 44.
is multiplied by a constant multiplication factor. This multiplication coefficient is stored in the read-only memory ROM (2) 43, and is selected and output when section maximum level information is input from the memory 31 of the tone level recording section 3. Therefore, when the switch control signal is sent from the memory control unit 32, the switch _S1 is connected to the (p) side, and the ROM (2) 43
The multiplication coefficient is sent to the multiplication circuit 44, and the predetermined multiplication coefficient is multiplied by the maximum level of the PCM audio reproduction device, so that a digital sine waveform corresponding to the maximum level of each section is input to the analog converter 5. . The multiplication coefficient is 1 when the maximum level value of the recording section is equal to the maximum level of the PCM audio reproduction device, and a multiplication coefficient corresponding to the maximum level value of each section is read from the ROM (2) 43.

The analog converter 5 converts the signal into an analog signal using a DA converter 51, divides the signal into left and right channels using a multiplexer 52, and sends the signal to a left channel and a right channel using filters 53(1) and 53(2).
The reference tone signal is output to the outside as analog audio through the . A PCM recording device can easily determine its recording input level using either the left or right channel. The operations of each of the above sections are performed by control signals on the control bus of the digital signal section 1, but after the section maximum level is recorded in the memory 31, the external key control switch 6 is operated.
As a result, data of an arbitrary section is sent to the sine wave generator 4, and a reference tone signal of that section is output.

Next, the second invention will be explained with reference to the embodiment shown in FIG. 1B. In the circuit of FIG. 1B, the digital signal section 1, level detection section 2, and tone level recording section 3 are completely the same as those in the first invention.

However, the sine wave generator 4B consists of an (analog) sine wave oscillator 7 and a programmable attenuator 8.
The attenuation amount of the programmable attenuator 8 is determined by the section maximum level recorded in the memory 31 of the tone level recording section 3.
The section maximum level selected by the external key control switch 6 is transmitted to the programmable attenuator 8, and the switches _S2 and _S3 are switched from the audio output side (q) to the reference tone signal side (p). . In this way, a reference tone signal corresponding to the maximum level of each recording section is outputted to the outside.

In the first invention, although the ROM (2) 43 for generating the multiplier coefficient is provided in the sine wave generating section 4A in FIG. 1A of the embodiment, it may be provided in the tone level recording section 3.

〔Effect of the invention〕

As described in detail above, the PCM audio playback device of the present invention can immediately output a reference tone signal corresponding to the signal level of each meaningful recording section (for example, each song in a musical piece) as a reference tone signal. This makes it extremely easy to set the recording input level on the recorder side when PCM recording the playback audio signal of the PCM audio playback device. Furthermore, the present invention is applicable to all PCM recording systems such as compact disc players and audio tape recorders.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention in which a sine wave generating section generates a digital wave in FIG. 1A and a digital wave in FIG. 1B.
The figure is a circuit block diagram that generates analog waves. 1...Digital signal section, 2...Level detection section, 3...Tone level recording section, 4A, 4B...
Sine wave generator, 5... Analog converter, 6... Key control switch, 7... (Analog) sine wave oscillator, 8... Programmable attenuator, 21... Absolute value detection circuit, 22... Register, 23 ... Comparison circuit, 24 ... AND circuit, 31 ... Memory, 32
...Memory control unit, 41...Counter, 42...
ROM (1), 43... ROM (2), 44... Multiplication circuit.

Claims (1)

[Claims] 1. A level detection section that detects the section maximum level for each recording section with respect to the digital audio output from the digital signal section of the PCM audio playback device;
a tone level recording unit that records information regarding the maximum level in the section; a tone level recording section that creates a digital sine waveform corresponding to the maximum audio output of the PCM audio playback device; and multiplication of the digital sine waveform determined by the maximum level in the section. and a sine wave generator having means for multiplying by a coefficient, and after recording the section maximum level of each recording section in the tone level recording section, an arbitrary signal is generated from the tone level recording section by an external key control switch. The data of the section is sent to the sine wave generation section, and the output of the sine wave generation section is switched and inputted to the analog conversion section of the PCM audio reproduction device, and is output as a reference tone signal of the section. PCM audio playback device. 2. A level detection section that detects the section maximum level for each recording section with respect to the digital audio output from the digital signal section of the PCM audio playback device;
A tone level recording unit that records the maximum level of the section, a reference sine wave oscillator that corresponds to the maximum audio output of the PCM audio playback device, and a programmer that provides an attenuation amount determined by the maximum level of the section to the output of the oscillator. and a sine wave generation section having a bull attenuator, and after recording in the tone level recording section, an external key control switch causes data of an arbitrary section from the tone level recording section to be sent to the sine wave generation section. At the same time, the output of the sine wave generator is
1. A PCM audio reproducing device, which outputs a reference tone signal of the section by switching with the output of the PCM audio reproducing device.