Dynamic information storage or retrieval – Control of storage or retrieval operation by a control...
Reexamination Certificate
1998-12-15
2004-08-24
Edun, Muhammad (Department: 2655)
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
C369S059100
Reexamination Certificate
active
06781933
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a two channel pseudo play-back apparatus for pseudo reproduction of a multi-channel audio output, and particularly relates to a two channel pseudo play-back apparatus in a personal computer for pseudo reproduction by two channel speakers of multiple channel audio outputs from, for example, DVD-ROMs.
2. Background Art
Conventionally, in a personal computer loaded with a reproducible sound board of sound or music, it was standard to use two channels for outputting an audio output of the medium for playing back.
Examples of reproducible mediums of sound or music in a personal computer include CD-ROM or CD-I (Compact Disc-Interactive). In the play-back of CD-I, there is a system which is capable of obtaining particular sound effect by processing audio signals for right and left channels, as disclosed in Japanese Patent Application, First Publication No. Hei 2-261213. This apparatus is provided with a function for producing particular sound effects using a four-channel mixing circuit and this apparatus comprises a digital audio processing portion containing a four-times over sampling type digital filter, and outputs two channel audio signals using the four channel mixing circuit by individually processing digital audio data for the L channel and the R channel.
Recently, attention has been attracted to an audio data signal system for digital video discs (hereinafter called DVD), which is a high efficiency coding system of AC-3 developed by Dolby Research Institute in the United States. This AC-3 is capable of playing back 5.1 channels of surrounding sounds. The number of channels in this AC-3 system is defined as two right and left front channels, one front center channel, two rear channels, and a low band channel (0.1 channel) for driving a super woofer.
For such audio data of 5.1 channels are reproduced by a personal computer with two audio output channels, two methods are known as described hereinafter.
A stereo play-back apparatus using the first method is described hereinafter with reference to FIG.
4
. The first method comprises the steps of reading compressed digital audio data from a digital video disc-read only memory (DVD-ROM)
11
which stores the compressed audio data, and expanding the compressed data into 5.1 channel audio data by a decoder
12
of the AC-3, and storing expanded data temporarily in a buffer
13
composed of a plurality of buffers
131
to
136
. Subsequently, among digital audio data stored in the buffer
13
, digital audio data (FR and FL) for the left and right front channels are converted into analog signals by respective D/A converters constituted by a left D/A converter (L)
14
and a right D/A converter (R)
15
, and thus converted analog signals are output into the audio signal output lines for playing back by left and right speakers
16
and
17
.
A stereo play-back apparatus using the second method is described hereinafter with reference to FIG.
5
. The same reference numerals are used in
FIG. 5
for the same elements as those of
FIG. 4
, and explanations of the same elements are omitted. The stereo play-back apparatus using the second method comprises the same steps as those described referring to
FIG. 4
, that is, reading compressed digital audio data from the DVD-ROM, expanding the compressed data into digital signals for 5.1 channels using the AC-3 decoder
12
, and storing the expanded data temporarily in the buffer
13
. The steps are followed by mixing audio data for 3.1 channels containing the left front channel (FL), left rear channel (RL), the front center channel (FC), and a super woofer (SU) using a left mixing circuit (L)
21
, converting the mixed data into analog data using a left D/A converter (L)
14
, outputting the analog data into the left audio outputting line for play-back of the sound by a left speaker
16
. Similarly, the audio data for 3.1 channels containing the right front channel (FR), right rear channel (RR), the front center channel (FC), and the super woofer (SU) are mixed using a right mixing circuit (R)
22
, the mixed data are converted into an analog signal using a right D/A converter (R)
15
, and the analog signals are output to a right outputting line for play-back using a right speaker
17
.
Therefore, it is an object of the present invention to provide a pseudo stereo play-back apparatus with two channel speakers, which is capable of playing back a superior surround effect which is not obtainable using a usual two-channel play-back apparatus by processing the multiple channel audio outputs from a recording medium such as DVD-ROM for the two channel audio outputting apparatus.
Another object of the present invention is to provide a pseudo stereo play-back apparatus with two channel speakers, which is capable of playing back a superior surround effect which cannot be obtained with the usual two channel audio output apparatus by pseudo reproduction of the multiple channels by a two channel audio apparatus from a recording medium containing multiple channel audio outputs.
SUMMARY OF THE INVENTION
According to an aspect of the present invention, a pseudo multi-channel stereo play-back apparatus comprises: (a) a decoder for expanding compressed digital audio signals channels stored in a recording medium into digital audio signals for a plurality of channels; (b) a memory means for temporarily storing digital audio signals expanded by said decoder; (c) a phase control circuit for controlling phases of digital audio signals for specified channels which are a part of digital audio signals for all channels stored in said memory means; (d) first and second mixing circuits for mixing the digital audio signals after being transformed by said phase control circuit with other digital audio signals for other channels stored in said memory means; and (e) first and second A/D converters for converting respective outputs of the first and second mixing circuits into analog sound signals.
That is, this aspect of the present invention performs pseudo play-back of a surrounding sound by the steps of expanding the multi-channel digital audio signals stored in a memory, and storing the expanded signals in a memory. Subsequently, among stored signals for all channels, digital audio signals for the left and right rear channels and for the front center channel are subjected to the phase control by the phase control circuit. Further, other digital audio data for the left and right front channels are transferred to the mixing circuits as they are and after they are mixed with the first and second mixing circuits with the phase transformed signals for the rear channels and the front center channel, outputs of the first and second mixing circuits are converted by the first and second D/A converters, respectively, into analog audio signals. The analog audio signals from both converters are played back by two respective speakers located at both left and right positions. Consequently, the present apparatus performs pseudo play-back of a multi-channel surrounding sound with two speakers of a personal computer.
According to another aspect of the present invention, the pseudo multi-channel stereo play-back apparatus comprises: (a) a decoder for expanding compressed digital data stored in said memory device; (b) a memory means for temporarily storing digital data expanded by said decoder; (c) a phase control circuit for controlling phases of the digital audio signals for left and right rear channels and a phase for the front center channel among digital audio signals for all channels stored in said memory means; (d) first and second mixing circuits for mixing the phase transformed digital audio signals for left and right rear channels, digital audio signals for left and right front channels stored in said memory, and the phase transformed digital audio signal of the front center channel; and (e) first and second D/A converters for converting respective outputs of said first and second mixing circuits into analog sound signals.
The pseudo multi-channel stereo
Edun Muhammad
Foley & Lardner LLP
NEC Corporation
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