Data processing: generic control systems or specific application – Specific application – apparatus or process – Digital audio data processing system
Reexamination Certificate
1999-11-05
2004-03-30
Barnie, Rexford (Department: 2643)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Digital audio data processing system
C386S349000
Reexamination Certificate
active
06714825
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to multi-channel audio reproducing devices, and more particularly to a DVD audio reproducing device of a type reproducing DVD audio, that is, super hi-fi (High Fidelity) multi-channel audio recorded on a DVD.
2. Description of the Background Art
A digital versatile disc (DVD) is a recording medium originally developed for video, the capacity of which is more than six times as large as a compact disc (CD). Recording only audio on such large-capacity DVD allows multi-channel reproduction of super hi-fi audio.
By taking the CD as an example, 16-bit linear quantization is carried out at a sampling frequency of 44.1 kHz, realizing two-channel reproduction of audio having a reproduction frequency up to 22 kHz and a dynamic range of 98 dB. On the other hand, as to the DVD audio, by 24-bit linear quantization carried out at the sampling frequency of 96 kHz, for example, six-channel reproduction of audio having the reproduction frequency of 48 kHz and the dynamic range of 144 dB can be realized.
Quality and fidelity of reproduced audio generally mean a level of the upper limit of the reproduction frequency, the dynamic range, and flatness of the frequency characteristics. Hereinafter, the quality and fidelity of reproduced audio only mean the level of the upper limit of the reproduction frequency.
Standards of the DVD audio are still being defined for the practical use. Therefore, there is no conventional DVD audio reproducing device of a type reproducing the DVD audio. Accordingly, described below is a conventional DVD reproducing device used to reproduce video recorded on the DVD and audio accompanying therewith.
FIG. 5
is a block diagram showing the main part of a circuit in the conventional DVD reproducing device, where audio is reproduced.
What is reproduced by the device in
FIG. 5
is video data recorded on the DVD and audio data accompanying therewith. The video data and audio data s are separately reproduced in a different processing circuit. It is thus not described herein how the video data is reproduced.
The audio data recorded on the DVD is audio obtained by, in accordance with MPEG2, for example, encoding and modulating digital audio data converted from analog audio picked up by a microphone, for example. The audio is in the form of multi-channel data (in this example, six-channel data).
Referring to
FIG. 5
, the audio data read from the DVD is provided for a demodulating part
50
, and then is demodulated therein. An output of the demodulating part
50
is supplied to an error correcting part
51
, then any error of which is corrected therein. An output of the error correcting part
51
is supplied to an audio decoding part
52
.
The audio decoding part
52
decodes the provided audio data, and an output thereof is inputted into a DAC part
53
.
The DAC part
53
is structured by a DAC (Digital Analog Converter), for example, and converts the inputted audio data in every channel from digital to analog through time-division processing. Alternatively, the DAC part
53
may be structured by three DACs and each DAC may convert the audio data in two channels, or by six DACs on a channel basis. Note that a fewer number of DACs is better in view of the device size and price if the processing speed of the DAC allows such a reduction.
An output of the DAC part
53
is supplied to an LPF part
54
.
The LPF part
54
is structured by six low-pass filters (LPFs), and extracts any component equal to or lower than a predetermined frequency (so-called cutoff frequency) from an audio signal in the respective given channels so as to output the same as the 1st channel to 6th channel analog audio signals.
In this manner, the analog audio signals in the respective channels outputted from the conventional DVD reproducing device are amplified in a not-shown amplifier, and then are inputted into six speakers as shown in FIG.
6
. Each of the speakers drives a diaphragm in response to the inputted analog audio signals so as to convert the signals into vibrations of air perceivable by user's ears, and then outputs the same.
FIG. 6
is a schematic diagram showing the structure and placement of a conventional speaker system being connected to the conventional DVD reproducing device in FIG.
5
. In
FIG. 6
, the conventional speaker system includes a pair of main speakers-
60
, a pair of rear speakers
61
, a center speaker
62
, and a sub-woofer
63
.
Assuming that the user sits at the center of a room, the pair of main speakers
60
are placed toward the front-left and front-right positions of the user, and the pair of rear speakers
61
are placed toward the back-left and back-right positions of the user. Moreover, placed between the pair of main speakers
60
is the center speaker
62
, and the sub-woofer
63
is placed in a corner.
The center speaker
62
is a speaker mainly for mid-frequency ranges, and is provided to clearly reproduce vocals (human voice). The sub-woofer
63
is a (non-directional) speaker for low-frequency ranges, and enhances the reproduced audio in the ranges.
As is known from the above, the conventional DVD reproducing device shown in
FIG. 5
has the capability of reproducing audio (multi-channel audio data) accompanying the video recorded on the DVD. As the DVD audio is regarded as the multi-channel audio data, the DVD audio reproducing device should be realized, on principle, by utilizing the capability.
Such a DVD audio reproducing device, however, bears the following problem (1).
(1) It is now under study, in the DVD audio specifications, whether or not channels can be different in sampling frequency. If channels vary in sampling frequency, all the best possible 5 use of the large-but-limited DVD capacity is enabled. If this is the case, however, it necessitates a number of the DACs as many as the number of channels. This is because, there is yet no such DAC that converts multi-channel audio data from digital to analog in a time sharing manner while switching the sampling frequency. Further, it is not easy to develop such a DAC. If the device is equipped with a number of the DACs as many as the numbers of channels, size and cost thereof will be enormous.
Moreover, in order to popularize the DVD audio reproducing device, it is important to give consideration to the following issue (2) while pursuing a high-end performance (that is, the attainable superlative performance).
(2) In order to make full use of the high-end performance feasible for the DVD audio, the whole audio system, inclusive of an amplifier and speaker, for example, needs to be high in performance as much as the DVD audio reproducing device. The problem is that, not every user owns such an amplifier or speaker, and these cost a lot together with the DVD audio reproducing device. Accordingly, many users are likely to connect a newly-purchased DVD audio reproducing device to their current or existing audio system for the time being. It is also likely for many users that the high-end performance is not what they are asking for but easy access to DVD audio with their current or existing audio system.
Therefore, it is desirable for the DVD audio reproducing device to be structurally connectable to the existing audio system such as the conventional speaker system shown in FIG.
6
. In such case, the DVD audio reproducing device may not be high-end in performance, but can be easily accessible to high quality DVD audio in high quality.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a DVD audio reproducing device of a type converting DVD audio (multi-channel audio data), from digital to analog, having channels different in sampling frequency by using one or more DACs which are fewer in number than the channels, and then reproducing the converted DVD audio.
Another object of the present invention is to provide a DVD audio reproducing device of a type being structurally connectable to the existing audio system, and being easily accessible to the DVD audio only by connecting thereto.
Th
Barnie Rexford
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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