JPH0772978B2 - Digital audio signal playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DAD (Digital Audio Disk) or a DAT (Digital Audio T), which is recorded by digitizing an audio signal.
ape) and the like, and relates to a digital audio signal reproducing apparatus for extracting and reproducing a digital audio signal from a medium.

When playing back audio signals recorded on DAD or DAT, it has the characteristic that the playback audio signal has a wider dynamic range than conventional analog records. Because of this, while you can enjoy music with a very large range from pianissimo to fultessimo, when you can't hear the low-level pianissimo part due to the ambient noise, or if you turn up the volume to hear this, you suddenly enter the high-level fulnessimo. Surprise and discomfort can occur. Therefore, when there is a lot of noise in the surroundings or during easy listening, there was a demand to compress and reproduce the dynamic range.

The present invention has been made in view of the above points, and divides a digital audio signal extracted from a recording medium into two systems,
A digital audio signal reproducing device capable of obtaining an audio signal with a compressed dynamic range by providing a time difference between the two and controlling the volume of the other audio signal by the envelope signal of the preceding audio signal. It is a thing.

An embodiment of the present invention will be described below with reference to the drawings. First
The figure is a block diagram showing one embodiment of the present invention.
FIG. 2 is a signal waveform diagram for explaining the operation.
In the figure, (1) is an input terminal of a digital audio signal extracted from a recording medium via an optical pickup or a magnetic head, (2) is a delay circuit, (3) is a first digital-analog conversion circuit, ( 4) is the low-pass filter,
(5) is an automatic level control circuit, (6) and (7) are switches, (8) is an audio output terminal, (9) is a second digital-analog conversion circuit, (10) is an envelope detection circuit, and (11) is It is a compensation circuit.

For the terminal (1), for example, a compact disk type DAD
A 16-bit quantized digital audio signal with a sampling frequency of 44.1 kHz, which is demodulated and processed by an optical pickup, is applied. This signal is delayed by the delay circuit (2) and the digital-analog converter (3)
Then, the number of quantized bits recorded, for example 16 bits, is converted into an analog signal, and an audio signal (12) (Fig. 2A) having a wide dynamic range is obtained through the low-pass filter (4). This signal is a at switch (6) (7)
The level is controlled by the automatic level controller (5) through the contact to the audio output terminal (8) or through the b contact of the switches (6) and (7) to be output to the audio output terminal (8). On the other hand, the digital audio signal from the terminal (1) is sent to the second digital-analog conversion circuit (9) as 8
Bit converted to analog signal (13) (Fig. 2B). That is, only the high-order 8 bits of the digital audio signal of 16 bits of quantization bit are taken out and analog conversion is performed. Performing analog conversion with a small number of bits does not require such a minute change as an analog output, and if the number of bits is small, the digital-analog conversion circuit becomes simple and a commercially available inexpensive IC (integrated circuit) is used. This is because it can be done. The envelope signal of this analog signal (13) is taken by the envelope detection circuit (10) to obtain an envelope signal (14) (Fig. 2C) proportional to the volume level, and this signal (14) is supplied to the compensation circuit (11). In addition, the signal (1
5) get This is a form of a signal (14) that takes out a certain level x ₁ or more, and can be easily obtained by giving an offset to the diode. This signal (15) is applied to the automatic level control circuit (5) and controls its gain G. The relationship between the gain G of the automatic level control circuit (5) and the magnitude x of the input signal (14) to the compensation circuit (11) is shown in FIG. That is, when the magnitude x of the signal (14) is a certain value x ₁ or less and the control signal (15) is not given from the compensation circuit (11), the gain G of the automatic level control circuit (5) is constant but controlled. The gain decreases when the signal (15) is applied. This is shown in FIG. The automatic level control circuit (5) is inserted into the output circuit of the low-pass filter (4) when the switches (6) and (7) are turned on to the b contact, and the audio signal (12) is sent to the automatic level control circuit (5). Will be output via. Therefore, the level of the high volume signal portion of the audio signal (12) is lowered by the control signal (15) from the compensating circuit (11), and as shown in FIG. 2E, the compressed audio signal of the dynamic range. (16) is obtained at the output terminal (8). In this signal processing system, the delay time of the delay circuit (3) is set in consideration of the following two. One is that the control signal applied to the automatic level control circuit (5) has a narrower signal band than the signal passed through the first digital-analog conversion circuit (3) and thus has a long delay time. The other is that it is more natural to compress the volume by the control signal (15) prior to the time when the audio signal (12) produces a large volume.

In the above description, an example in which the compensation circuit (11) lowers the gain in the high volume part is shown, but as shown in FIG. be able to.

Further, not only the level is controlled by the compensating circuit (11), but also the time axis is operated, so that the dynamic range can be compressed without the unnatural feeling. That is, although it has been described above that the compression is performed slightly before the rising portion of the loud sound, it does not feel unnatural to release the compression with a slight delay at the falling portion. For this purpose, the automatic level control circuit (5 The control signal (15) to () should be held a little.

As described above, according to the present invention, in a digital audio signal reproducing apparatus for reproducing an audio signal from a medium on which a digitized audio signal is recorded, a delay unit for delaying the reproduced audio signal and an output of the delay unit. Level control means for controlling the level of the signal, envelope detection means for taking the envelope of the audio signal before delay, and compensation means for controlling the gain of the level control means with a predetermined characteristic based on the envelope signal from the detection means. The delay time of the delay means compensates the relative delay of the envelope signal with respect to the audio signal, and the gain control of the level control means is performed prior to the rising portion of the large volume generating portion of the audio signal. And set it to the falling part of the high volume generating part. Since it is configured to release the gain control of the level control means on the line, it can be obtained with a simple digital audio signal reproducing apparatus capable of compressing the dynamic range without an unnatural feeling configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a signal waveform diagram for explaining its operation, and FIG.
FIG. 6 is a control characteristic diagram of an automatic level control circuit used in the embodiment of the present invention. In the figure, (2) is a delay circuit, (3) is a first digital-analog conversion circuit, (5) is an automatic level control circuit,
(9) is a second digital-analog conversion circuit, (10) is an envelope detection circuit, and (11) is a compensation circuit.

Claims (1)

[Claims] 1. In a digital audio signal reproducing apparatus for reproducing an audio signal from a medium on which a digitized audio signal is recorded, a delay means for delaying the reproduced audio signal and a level of an output signal of the delay means are controlled. And a compensating means for controlling the gain of the level controlling means with a predetermined characteristic based on the envelope signal from the detecting means. The delay time of the means is set so that the relative delay of the envelope signal with respect to the audio signal is compensated and the gain control of the level control means is performed prior to the rising portion of the large volume generating portion of the audio signal. Along with the trailing edge of the high volume generator, Digital audio signal reproducing apparatus characterized by being configured to release the gain control of the control means.