JP2002100993A - Solid-state audio reproducing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state audio reproducing equipment for making it difficult to produce illegal copy of original digital audio data reproduced from an external storage device and accelerating power consumption reduction, cost reduction and miniaturization in a D/A conversion part. SOLUTION: In this solid-state audio reproducing equipment, composed of a digital audio controller 1 for reproducing and outputting digital audio data recorded in a recording medium 200, which is a semiconductor memory and the D/A conversion part 2 for converting the digital audio data outputted from the digital audio controller 1 into analog and outputting them, for which the digital audio controller 1; and the D/A conversion part 2 are different IC chips, a delta sigma modulator 16 is provided in the output stage of the digital audio controller 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid audio reproducing apparatus for reproducing digital audio data recorded in a semiconductor memory or the like.

[0002]

2. Description of the Related Art A conventional solid audio reproducing apparatus 30
0, as shown in the block diagram of FIG. 4, comprises a digital audio controller 3 and a D / A converter 4, and the digital audio controller 3 and the D / A converter 4 are separate IC chips. The digital audio controller 3 includes a CPU 31, a ROM 32, a RAM 33,
A DSP 34, a media interface 35, and a serial interface 36 are provided. The D / A converter 4 includes a multi-bit D / A converter 41 and a low-pass filter 42.

[0003] On a recording medium 200, which is a semiconductor memory, digital audio data compressed by a predetermined method is recorded. The recording medium 200 is detachable from the solid audio reproducing device 300. In the digital audio controller 3, when the recording medium 200 is mounted, the CPU 31
Controls each unit based on a program stored in the ROM 32, so that the compressed digital audio data is read out from the recording medium 200 via the media interface 35, decompressed by the DSP 34, and Through D
/ A conversion unit 4. At this time, the audio data is stored in the RAM 33 as needed.

The digital audio data serially output from the digital audio controller 3 is D
/ A conversion unit 4 and a multi-bit D / A converter 4
The signal is converted into an analog signal by 1 and then, after a low-pass filter 42 removes frequency components other than the necessary band, the signal is converted into a sound by a speaker or headphones (not shown) connected to the outside.

[0005]

In the above-mentioned conventional solid audio reproducing apparatus, the data transferred between the IC chips is the same digital data as the original digital audio data reproduced from the recording medium. There is a problem that it is easy to illegally copy the original digital audio data. In addition, a D / A converter for converting digital audio data into an analog signal requires a D / A converter having the same number of bits as digital audio data (ie, a D / A converter with high resolution). It has not been possible to promote power consumption, cost reduction, and downsizing.

A digital audio controller and D
If the / A converter is constituted by one chip, the problem of illegal copying is eliminated, but since the manufacturing process of each IC is different, the cost is increased by using one chip instead. Often.

Therefore, the present invention makes it difficult to illegally copy original digital audio data reproduced from an external storage device, and promotes low power consumption, low cost, and miniaturization in the D / A converter. It is an object of the present invention to provide a solid audio reproducing device.

[0008]

In order to achieve the above object, according to the present invention, first means for reproducing and outputting digital audio data recorded in an external storage device, and the first means are provided. Means for converting digital audio data sent from the IC into an analog signal and outputting the analog signal, wherein the first means and the second means are separate ICs
In the solid audio reproducing device which is a chip, the first means converts digital audio data reproduced from the external storage device into 1-bit digital data by delta-sigma modulation and sends it to the second means. Configuration.

According to this configuration, the data transferred between the IC chips becomes digital audio data subjected to delta sigma modulation. Therefore, simply copying the data transferred between the IC chips simply copies the original data reproduced from the external storage device. Digital audio data cannot be copied. In addition, the D / A converter for converting digital audio data into analog data can be constituted by a 1-bit D / A converter.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. As shown in the block diagram of FIG. 1, the solid audio playback device 100 of the present embodiment includes a digital audio controller 1 and a D / A converter 2, and the digital audio controller 1
It is a separate IC chip from the / A converter 2.

Digital audio data compressed by a predetermined method is recorded on a recording medium 200 which is a semiconductor memory. The recording medium 200 is detachable from the solid audio playback device 100. The digital audio controller 1 has a CPU
11, ROM 12, RAM 13, DSP 14, media interface 15, and delta-sigma modulator 16
It has. The D / A converter 2 includes a 1-bit D / A converter 21 and a low-pass filter 22.

In the digital audio controller 1,
With the recording medium 200 mounted, the CPU
11 controls each unit based on a program stored in the ROM 12 so that the compressed digital audio data is read out from the recording medium 200 via the media interface 15 and decompressed by the DSP 14 to obtain the original digital data. After that, the delta-sigma modulator 16 further performs delta-sigma modulation to convert the data into 1-bit D / A signals.
It is sent to the conversion unit 2. At this time, the audio data is stored in the RAM 13 as needed.

As shown in FIG. 2, for example, the delta-sigma modulator 16 includes an interpolation filter 161 for increasing a sampling frequency of a digital signal input from an input terminal IN,
A delay unit 162 for delaying an output signal of a comparator 166, which will be described later, by one sampling period, and adding or subtracting a predetermined value in accordance with the output of the delay unit 162, converts the value of the output multi-bit digital signal into a sampling pulse. Demodulator 163 that updates synchronously with interpolation filter 1 and interpolation filter 1
A differentiator 164 for obtaining a difference between the digital signal of a plurality of bits output from 61 and the output signal of the demodulator 163, an integrator 165 for integrating the output signal of the differentiator 164, and a reference value for the output signal of the integrator 165. And a comparator 166 that quantizes the data to 1 bit by comparing with the above. A 1-bit digital signal output from the comparator 166 is output from the output terminal OUT.

The signal output from the delta-sigma modulator 16 of the digital audio controller 1 is input to the D / A converter 2 and is converted to an analog audio signal by a 1-bit D / A converter 21. After the filter 22 removes frequency components other than the required band, the signal is converted into sound by a speaker or headphones (not shown) connected to the outside.

As shown in FIG. 3, for example, the low-pass filter 22 has an input terminal I for each of the left and right stereo channels.
N _L, IN _R and the output terminal OUT _L, between the OUT _R, resistor 221, 222, 223, capacitors 224 and 225,
The operational amplifier 236 is connected as shown in the figure, and speakers and headphones are respectively connected between the output terminal OUT _L and the reference voltage terminal COM and between the output terminal OUT _R and the reference voltage terminal COM. Connected.

With the above configuration, in the solid audio reproducing apparatus of the present embodiment, the data transferred between the IC chips is delta-sigma modulated digital audio data, which differs from the original digital data due to the modulation. Therefore, the original digital audio data reproduced from the recording medium cannot be copied only by copying the data between the IC chips.

When demodulating original data from a signal subjected to delta-sigma modulation, a large-scale demodulation circuit is required, and a rounding error of a calculation result always occurs during modulation. Audio data cannot be demodulated completely original,
You cannot copy complete data. That is, when copying is repeated using the solid audio reproducing device of the present embodiment, the data is degraded.

Further, regarding a D / A converter for converting digital audio data to analog, a 1-bit D / A
Since it can be constituted by an A converter, low power consumption, low cost, and downsizing can be promoted.

In this embodiment, the recording medium 20
0 is used only, but a receiving interface is provided in place of the media interface 15 to receive data such as a CD from an external device such as a personal computer, and temporarily record the data in the RAM 13 so that the solid It may be used as an audio playback device.

[0020]

As described above, according to the solid audio reproducing apparatus of the present invention, it is difficult to illegally copy the original digital audio data reproduced from the external storage device, and the D / A conversion unit Low power consumption, low cost, and downsizing can be promoted.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a solid audio reproducing device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration example of a delta-sigma modulator in FIG. 1;

FIG. 3 is a diagram illustrating a configuration example of a low-pass filter in FIG. 1;

FIG. 4 is a diagram showing a configuration of a conventional solid audio playback device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Digital audio controller 2 D / A conversion part 11 CPU 12 ROM 13 RAM 14 DSP 15 Media interface 16 Delta-sigma modulator 21 1-bit D / A converter 22 Low-pass filter

Claims (1)

[Claims] A first means for reproducing and outputting digital audio data recorded in an external storage device;
A second means for converting digital audio data sent from the first means into an analog signal and outputting the analog signal, wherein the first means and the second means are separate IC chips; Wherein the first means converts digital audio data reproduced from the external storage device into 1-bit digital data by delta-sigma modulation and sends the digital audio data to the second means. A solid audio playback device characterized by the following.