JPH0215160B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a left and right channel separation circuit for playback signals in a digital audio playback device that plays back stereo audio signals recorded on a digital audio disk, audio PCM tape, or the like.

Prior Art In a digital audio system using a compact disk, etc., a stereo signal is sampled at a certain sampling frequency fs (for example, fs = 44.1 KHz) and quantized, and the left channel (L-ch) and right channel (R-ch) are Audio signals are recorded in alternating chronological order.

Therefore, when a signal recorded in this manner is to be reproduced by a digital audio reproducing device, the reproduced signal must be separated into L-ch and R-ch audio signals.

One method is to perform this separation using the digital audio signal detected by the signal detector as is, and then convert it into an analog audio signal for each channel. There is a method of separating into channels.

The present invention is directed to a left/right channel separation circuit using the latter method, and conventionally a circuit as shown in FIG. 1 has been used.

To briefly explain this with reference to Figure 2,
For example, when detected from a compact disc by a signal detector such as a laser pickup (not shown),
The EFM demodulated and reproduced digital audio signal is converted into an analog audio signal (voltage signal) S _A by the D/A conversion circuit 1 .

As shown in Fig. 2a, this signal S _A has an L-ch signal in the first half Ts/2 of a cycle of Ts = 1/fs corresponding to the sampling frequency fs during recording, and a L-ch signal in the second half Ts /2, R-ch signals appear alternately.

Therefore, this signal S _A is transferred to the L-ch sample and hold circuit 2 and the R-ch sample and hold circuit 3.
Enter each.

In the L-ch sample hold circuit 2, the second
As shown in Figure b, the input signal is sampled and held by the L-ch punching pulse P _L generated within the first half of the period Ts, and an L-ch signal as shown in Figure d is obtained. Pass it through low pass filter 4
The high-frequency components are removed through the audio signal Ls, and the audio signal Ls as shown in FIG.

On the other hand, in the R-ch sample hold circuit 3,
As shown in Fig. 2c, the input signal S _A is sampled and held by the R-ch punching pulse P _R generated within the second half of the period Ts, and the R-ch punching pulse P R as shown in Fig. 2e is sampled and held. A signal S _R is obtained, which is passed through a low-pass filter 5 to remove high-frequency components to become an audio signal Rs as shown in g of the same figure, amplified by an amplifier 7, and outputted to an R-ch output terminal 9.

However, in such a conventional digital audio playback device, the audio output signals Ls and Rs of the left and right channels separated by the left and right channel separation circuit of the playback signal have a 1/2 ( A phase difference of 1/2 of the sampling period will occur.

Therefore, there is a problem in that the reproduced stereo sound does not faithfully reproduce the recorded source sound.

Purpose This invention was made in order to solve such problems, and is capable of completely separating the playback signal into left channel and right channel signals in a digital audio playback device without generating a phase difference. The purpose is to

Structure Therefore, in the digital audio playback device according to the present invention, the left and right channel separation circuit for the playback signal converts the playback audio signal converted into an analog signal by the D/A conversion circuit into an analog signal, and converts the playback audio signal into an analog signal by dividing the playback audio signal into an analog signal by the first half period of the cycle corresponding to the sampling frequency at the time of recording. A hold circuit is provided to hold the output of the hold circuit using a punching pulse generated within the period, and the output of this hold circuit and the analog audio signal from the D/A conversion circuit are processed by first and second sample and hold circuits, respectively, within the second half of the above period. Samples and holds are performed using punching pulses generated at the same time, and each sampled and held signal is passed through a low-pass filter and output as reproduced audio signals for the left channel and the right channel.

Embodiments Embodiments of the present invention will be described below with reference to FIGS. 3 and 4.

FIG. 3 is a block circuit diagram of a left and right channel separation circuit showing one embodiment of the present invention, and parts corresponding to those in FIG. 1 are given the same reference numerals.

The D/A conversion circuit 1 converts a digital audio signal detected by a signal detector and demodulated by EFM into an analog audio signal (voltage signal) S _A as shown in FIG. 4a, as in the conventional example. A signal in which an L-ch signal and an R-ch signal appear alternately every 1/2 of the period Ts corresponding to the sampling frequency is output.

The hold circuit 10 consists of an integrating capacitor C and an analog switch SW, and when the L-ch punching pulse P _L generated within the first half of the period Ts becomes "1" as shown in FIG. When the SW is turned on, the input signal S _A from the D/A conversion circuit 1 is momentarily charged to the capacitor C and stored, and even when the analog switch SW is turned off, the next punching pulse P _L is "1" and the analog switch SW is turned on again (during the period Ts), hold the memorized value,
The L-ch hold signal as shown in Figure 4c
Output S _H.

The L-ch sample and hold circuit 2, which is the first sample and hold circuit, is connected to this hold circuit 1.
0 output signal S _H is input, and as shown in _FIG .
Obtain the L-ch punching signal S _L as shown in figure e,
This is passed through a low-pass filter 4 to remove high frequency components, and is amplified by an amplifier 6 to output an L-ch reproduced audio signal Ls to an L-ch output terminal 8 as shown in FIG.

On the other hand, the second sample and hold circuit R-
Similarly to the conventional example, the ch sample and hold circuit 3 inputs the analog audio signal S _A from the D/A conversion circuit 1 and samples and holds it using _{the R} -ch punching pulse PR. Obtain an R-ch punching signal S _R as shown in f, pass it through a low-pass filter 5 to remove high frequency components, and amplify it in an amplifier 7 to obtain an R-ch reproduced audio signal Rs as shown in h in the same figure. is output to the R-ch output terminal 9.

In this way, as is clear from Fig. 4g and h, the L-ch and R-ch reproduced audio signals
No phase difference occurs between Ls and Rs.

It goes without saying that the present invention is applicable not only to digital audio systems using compact disks but also to other digital audio systems such as audio PCM tape systems.

Effects As described in the embodiments above, according to the left and right channel separation circuit for the playback signal in the digital audio playback device according to the present invention, the playback signal can be separated into left channel and right channel playback audio signals without generating a phase difference. Since the signals can be separated, the recorded source signal can be faithfully reproduced in stereo.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing an example of a left and right channel separation circuit for reproduced signals in a conventional digital audio playback device, FIG. 2 is a signal waveform diagram of each part, which also provides an explanation of its operation, and FIG. FIG. 4, which is a block circuit diagram showing one embodiment of the invention, is a signal waveform diagram of each part, which also provides an explanation of its operation. 1...D/A conversion circuit, 2...L-ch sample hold circuit, 3...R-ch sample hold circuit, 4, 5...Low pass filter, 6,
7...Amplifier, 8...L-ch output terminal, 9...
R-ch output terminal, 10...Hold circuit, C...
... Integrating capacitor, SW... Analog switch.

Claims (1)

[Claims] 1. A digital audio playback device that samples and quantizes a stereo signal at a certain sampling frequency and plays back a signal in which left channel and right channel audio signals are alternately arranged in time series. a D/A conversion circuit that converts the digital audio signal into an analog audio signal; and a punching pulse generated within the first half period of the period corresponding to the sampling frequency of the analog audio signal output from the D/A conversion circuit. a first sample and hold circuit that samples and holds the output of the hold circuit using a punching pulse generated within the second half of the period; and an output from the D/A conversion circuit. a second sample-and-hold circuit that samples and holds an analog audio signal generated in the second half of the cycle using a punching pulse generated in the latter half of the cycle; A circuit for separating left and right channels of a reproduced signal, comprising a pair of low-pass filters that remove the left and right channel audio signals and output them as reproduced audio signals of the left channel and the right channel, respectively.