Data processing: generic control systems or specific application – Specific application – apparatus or process – Digital audio data processing system
Reexamination Certificate
1999-11-30
2003-12-02
Lee, Ping (Department: 2644)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Digital audio data processing system
C381S001000
Reexamination Certificate
active
06658310
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of entering a digitized audio signal into a data processing apparatus, such as a personal computer, method of transmitting the audio signal, and audio signal transmitting apparatus and audio signal receiving and reproducing apparatus which permit transmission of the audio signal according to this signal transmitting method.
2. Prior Art
When a computer receives stereo audio signals, analog signals may be input via analog input terminals, and converted into PCM (Pulse Code Modulation) data in the inside of the computer, or digital audio signals may be input via serial ports, such as RS-232C, or SCSI (Small Computer System Interface) ports, for example. In the former method, however, the input signals in the analog format are likely to be affected by noise from the computer. The latter method has a problem of a slow input speed, and, in most cases, cannot be used for exclusively inputting audio signals.
In view of the above situation, an audio input interface has been developed which is designed to convert digitized audio signals into serial data, and transmit the serial data via an exclusive digital audio input terminal, such as SPDIF, as shown in FIG.
1
.
In the conventional audio interface as shown in
FIG. 1
, analog audio signals SL, SR of left (L) and right (R) channels are converted into digital signals by respective A/D converters
101
,
102
, and packeted by a packet circuit
103
to be converted into serial data, which is then transmitted to a personal computer
200
. On the side of the personal computer
200
, the received serial data are synchronized by a PLL (phase-locked loop) circuit, and the resultant packet data is decoded by a decoding circuit
202
and reassembled into original digital data. Thus, the circuit arrangement tends to be complicated, with a result of an increased cost.
The other method of transmitting digitized audio signals may be roughly classified into a method of transmitting the input signals after converting them into analog signals, and a method of transmitting the digital signals as they are.
FIG. 2
shows an example of the former method. In this example, digital audio signals of L channel and R channel which are reproduced in a reproducing system (not shown) are converted into corresponding analog audio signals by respective D/A converters
301
L and
301
R, and then amplified by respective amplifiers
302
L and
302
R. The analog audio signals of the two channels obtained from the amplifiers
302
L and
302
R are then transmitted over respective cables
303
L and
303
R, amplified by amplifiers
304
L and
304
R, and then generated from speakers
305
L and
305
R.
FIG. 3
shows one example of the method of transmitting audio signals in the form of digital signals. In the example of
FIG. 3
, a packet of digital audio signals of L channel and R channel is transmitted from a digital output circuit
401
. This packet is transmitted to a demodulator circuit
403
over a cable
402
, and is demodulated by this demodulator circuit
403
into the original digital audio signals of the L channel and R channel. These digital audio signals of the respective channels are converted into analog audio signals by D/A converters
404
L and
404
R, amplified by amplifiers
405
L,
405
R, and then generated from speakers
406
L and
406
R.
The above-described prior art method of
FIG. 2
, in which the audio signals are transmitted as analog signals, suffers from deterioration of the quality of sound reproduced from the speakers if noise is superposed on the analog signals during their transmission. Where this method is employed within digital equipment, such as a personal computer, in particular, noise involved in the digital signal system is likely to be superposed on analog audio signals during their transmission, whereby the quality of reproduced sound is considerably deteriorated. On the other hand, the method of
FIG. 3
is advantageous in that the transmitted audio signal, which is a digital, signal, is highly resistant to noise. To implement this method, however, there is a need to provide the digital output circuit for assembling and transmitting a packet of digital audio signals, and the demodulator circuit for demodulating this packet, which may increase the size and cost of the whole apparatus.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide a method of entering an audio signal, which method enables a simple circuit to use input terminals of analog audio signals to enter a digital audio signal into a data processing apparatus, and wherein a transmitted signal is unlikely to be affected by noise even in an environment having a lot of noise.
It is the second object of the invention to provide an audio signal transmitting method that permits an audio signal to be transmitted assuring high resistance to noise, without significantly changing the construction of the known apparatus, and to provide an audio signal transmitting apparatus and an audio signal receiving and reproducing apparatus for transmitting the audio signal according to this method.
To attain the first object, the present invention provides a method of entering an audio signal into a data processing apparatus, wherein analog audio signals of at least two channels as the audio signal are digitized by and transmitted from an audio signal output device on a side of an audio source to an audio signal input device on a side of the data processing apparatus, comprising the steps of a) supplying a clock signal from the audio signal input device to the audio signal output device; b) performing delta-sigma (&Dgr;&Sgr;) modulation on the analog audio signals of at least two channels in the audio signal output device so as to convert each of the analog audio signals of at least two channels into one-bit digital audio data for each of the at least two channels, based on the clock signal supplied to the audio signal output device, c) alternately selecting the one-bit digital audio data for the each channel, based on the clock signal, in the audio signal output device, to perform time-division multiplexing on the one-bit digital audio data for the at least two channels, to thereby produce one-bit multiplex audio data, and d) supplying the one-bit multiplex audio data from the audio signal output device to the audio signal input device.
Preferably, the multiplex audio data and the clock signal are respectively transmitted to the audio signal input device and the audio signal output device, through respective input lines provided in the data processing apparatus for receiving analog audio stereo signals.
Further preferably, the method of entering an audio signal further comprises the step of separating the one-bit multiplex audio data into at least two streams of data corresponding to respective ones of the at least two channels and converting each of the at least two streams of data into multiple-bit PCM data for the each channel in the audio signal input device.
To attain the first object, the present invention also provides a data processing apparatus having an interface comprising a) a block which generates a clock signal to an external device, b) a block which receives multiplex audio data produced by one-bit quantization of audio data of at least two channels in synchronization with the clock signal and time-division multiplexing of the quantized audio data based on the clock signal in the external device, and c) a block which processes the received multiplex audio data in synchronization with the clock signal.
To attain the second object, the present invention provides a method of transmitting an audio signal from an audio signal transmitting apparatus to an audio signal receiving apparatus, comprising the steps of a) performing delta-sigma (&Dgr;&Sgr;) modulation modulation and time-division multiplexing on digital audio signals of at least left channel and right channel as the audio signal in the audio signal transmitting apparatus, to produce bit st
Lee Ping
Morrison & Foerster / LLP
Yamaha Corporation
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