JPS60223076A - Pcm reproducer - Google Patents

Abstract

PURPOSE:To eliminate a time delay between the 1st and 2nd channels by applying the digital signal processing to the 2nd channel through a digital filter to delay the 1st channel by a time of 1/2 sampling cycle. CONSTITUTION:The 1st channel is sampled with a sampling frequency 1/Ts, and the sample of the 2nd channel is delayed by Ts/2 to the sample of the 1st channel. The sampling frequency of the output of a digital filter is set at 2/Ts double as much as the original sampling frequency. For the sample of the 2nd channel, the sample position obtained newly by a digital filter is set at a middle point between the old sample point and the original sample point. For the sample of the 1st channel, the sample obtained newly by the digital filter is set at a position separate by Ts/4 from a position before or after the original sample point. Then each new sample is delayed by Ts/2.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a stereo PCM playback device, such as a DAD (digital audio disc) playback device.

Conventional configuration and its problems In recent years, it has been digitally transmitted as an audio source.

More and more things are being recorded.

A conventional PCM playback device will be described below with reference to the drawings. FIG. 1 is a block diagram of an example of a conventional PCM playback device, where 1 is an input signal from a transmission system or a recording medium, 2 is a processing section for this signal, and 4 is a digital input signal.
An analog converter, 6 is a deglitch circuit, and 7 and 8 are analog output signals of the first channel and the second channel, respectively.

The operation of the conventional PCM reproducing apparatus configured as described above will be described below. The input signal is subjected to processing such as de-interleaving and error correction in a signal processing section, and then converted into an analog signal by a dental analog converter. Usually, one digital-to-analog converter performs digital-to-analog conversion on the first channel and the second channel alternately. Thereafter, the deglitch circuit switches the output of the digital-to-analog converter between the first channel and the second channel. Second
The figure is a timing diagram, Ail″l: sample of the first channel, lj sample of the second channel, L
1 and R2%L2 and R2 are samples sampled at the same time, respectively.

This is the input signal for the Cid digital-to-analog converter.

Samples sampled at the same time are converted from digital to analog at different times.

However, as is clear from the explanation of the operation in the above configuration, the first sampled at the same time
Also, when the sample of the second channel is reproduced, the output of the second channel lags behind the output of the first channel.

OBJECTS OF THE INVENTION It is an object of the present invention to perform digital signal processing in which a digital filter delays a signal before entering a digital-to-analog converter in a first channel with respect to a second channel by half the sampling period. The purpose of the present invention is to provide a PCjM playback device that uses one digital-to-analog converter and does not cause a time delay between the first channel and the second channel.

Structure of the Invention The PCM playback device of the present invention samples signals of a first channel and a second channel simultaneously, converts them from analog to digital, and then arranges the signals in the order of the first sample and the second sample for transmission or recording. a signal processing unit that reproduces the signal, a digital filter that blocks high frequency components of each of the first and second channel signals output from the signal processing unit, and a digital-to-analog converter for the output of the digital filter. and a deglitch circuit that divides the output of the digital-to-analog converter into a first channel and a second channel, and the digital filter doubles the sampling frequency and outputs the second channel. For channels, the original sample point and 1/2 of the sampling period from each sample.
Take the sample at a time apart and use it as a new sample.

The first channel is configured so that a sample at a location a quarter of the sampling period away from the original sample point is used as a new sample. This prevents a time delay from occurring between the first channel and the second channel.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 3 shows a block diagram of a PCM reproducing apparatus according to an embodiment of the present invention. In Figure 3, 1 is an input signal from the transmission system or recording medium.

2 is a processing unit for this signal, and up to this point the configuration is the same as the conventional one. 9 is a digital filter, 4 is one digital-to-analog converter, 6 is a deglitch circuit 7t, and 8 are analog outputs of the first channel and the second channel, respectively.

The operation of the PCM reproducing apparatus of this embodiment configured as described above will be explained below. Since the present invention is particularly characterized by the digital signal processing method of the digital filter, this will be explained in more detail using FIG. 4.

In FIG. 4, A shows the first channel sampled at a sampling frequency of 1/Ts, Ll,
L2 is a continuous sample. B shows a state in which the second channel is sampled at a sampling frequency of 1/TS, and R1 and R2U are consecutive samples. Also,
Ll and R1, and L2 and R2 are samples sampled at the same time. C is the input signal of the digital filter, in which the samples of the second channel are delayed by Tl/2 with respect to the samples of the @1 channel.

The above signal is digitally processed by a digital filter, but the sampling frequency at the output of the digital filter is 2/2 times the original sampling frequency.
A case where Ts is reached will be explained.

The samples of the second channel are subjected to the following signal processing by a digital filter. The position of the new sample is set at the point where the original sample is β and the middle point between the original sample.

At E in FIG. 4, new samples R1a and R2a are inserted at the positions where the original samples R1 and R2 were, and new samples R1b and R2b are inserted between the original samples.

The samples of the first channel are subjected to the following signal processing by a digital filter. The new samples (c) are placed at positions TS/4 before and after the original sample.Furthermore, each new sample is delayed by Tl/2.In D of Fig. 4, Lla
is the sample before TS/4 of Ll delayed by TS/2, Llbfd, and the sample after TS/4 of Ll is T
It is delayed by S/2.

The output signal of the digital filter is shown at F in FIG. For example, consider Rla. Rla is filled with a new sample at the same time as R1. Lla, L on both sides of Rla
lb is filled with new samples on both sides of Ll. With the output of the digital filter, the first channel and the second
It is clear that there is no time difference between the channels.

Although this embodiment has described a digital filter in which the sampling frequency is doubled, it is clear that the same operation can be performed even if the sampling frequency is increased by n times (where n is an even number of 4 or more).

As described above, according to this embodiment, by performing digital signal processing to delay the first channel and the second channel using the digital filter, PCiM can be realized without causing a time difference between the first channel and the second channel. A playback device is realized.

Effects of the Invention As is clear from the above explanation, the present invention uses a digital filter to delay the first channel with respect to the NT and 20 channels.
Even in a POM reproducing device having only an analog converter, an excellent effect can be obtained in that there is no time difference between the first channel and the second channel. Due to this effect, the first peak in the high frequency range (nearly one-half of the sampling frequency)
Since the phase difference between the first channel and the second channel is eliminated, there is no need for a phase shifter, which is found in some products.

[Brief explanation of the drawing]

；゛■Figure 1 is a block diagram of a conventional PGM device, and Figure 2 is a block diagram of a conventional PGM device.
Figures A and B are timing diagrams showing the sampling time of the conventional first and second channels, respectively; Figure 2 is a timing diagram showing samples of the output of the signal processing unit during reproduction; Figure 3 is PGM in one embodiment of the present invention
A block diagram of a playback device. 4A and 4B are timing diagrams showing samples during sampling of the first and second channels of the same embodiment, respectively; FIG. 4C is a timing diagram showing samples of the output of the signal processing section during reproduction; FIG. 4 DH is a timing diagram showing a new sample of the first channel; FIG. 4 E is a timing diagram showing a new sample of the second channel; FIG. 4 F is a timing diagram showing a sample of the output of the digital filter. It is a diagram. 2...Signal processing section, 4...One digital/analog converter, 6...Deglitch circuit, 8...Digital filter. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4

Claims (2)

[Claims] (1) A signal processing unit that simultaneously samples the signals of the first channel and the second channel, performs analog-to-digital conversion, and then arranges the first sample and the second sample in that order and reproduces the transmitted or recorded signal. and a digital filter that blocks high-frequency components of each of the first and second channel signals output from the signal processing section;
It is composed of a digital-to-analog converter that converts the output of the digital filter into digital-to-analog, and a deglitch circuit that divides the output of the digital-to-analog converter into first and second channels and outputs the output. The frequency is doubled, and the second channel includes the original sample point and a sample at a time distance of 1/2 the sampling period from each sample.
A PCM playback device characterized in that a new sample is obtained, and in a first channel, a sample at a time spaced from an original sample point by a quarter of a sampling period is selected and used as a new sample. (2) The digital filter has a sampling frequency that is n times the original sampling frequency (where n is an even number of 4 or more), and in the second channel, the sampling frequency is set to a time interval that is an integer multiple of the new sampling period from the original sampling point. The location sample is replaced with a new sample, and the first channel is the original (7)? 2. The PCM playback device according to claim 1, wherein samples at each point in time separated by an integer multiple of the new sampling period and half the sampling period from the 77'' point are used as new samples.