JP2011211676A - Single clock sharing type computer system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of music reproduction and editing quality and deterioration of video or image processing quality caused by noise generated by utilizing clocks generated from a number of different oscillators in a computer performing music editing, music reproduction or image/video editing and reproduction, to decrease the number of oscillators to be used and further, to reduce a delay time for timing to synchronize music and video or a plurality of devices.SOLUTION: The present invention relates to a clock for operating a CPU or a peripheral circuit being used for one or more computers, and a peripheral device or an external device which utilizes the clock is operated by using a clock generated from a single reference clock.

Description

  The present invention relates to an audio / video signal processing computer apparatus and an external connection device for audio / video processing.

  A clock that serves as a reference for digital operation is used for a CPU (microprocessor) and peripheral interface circuits constituting the computer and external devices connected to them. The clock is usually generated by using a crystal resonator in terms of practical accuracy and cost, converted to a clock having a different frequency by a frequency conversion circuit using a PLL, and used in a circuit connected to the CPU. The clock used for the audio and video recording / playback equipment connected to the peripheral interface circuit and the clock used for the video recording / playback equipment have different modules and use different frequencies. Different crystal resonators are used, and there is a difference frequency “beat” due to minute frequency deviations generated from different crystal resonators and a phase noise of different components. Phase noise degrades audio signals and video signals and has an adverse effect.

  On the other hand, high-precision crystal oscillators and rubidium transmitters are used to improve sound quality and video quality in professional equipment for music production and video production, and digital peripherals that handle music playback and multimedia for high-quality sound playback. Editing and playback are performed for the purpose of high sound quality and high image quality using a high-precision reference clock, but the peripheral interface device connected to these devices and the operation clock of the CPU use a crystal resonator as usual. Therefore, the influence of frequency deviation and the noise generated from them become signal noise and shielded wire connected to the peripheral interface circuit, or radio noise to the air, and increase the jitter of digital peripheral devices and word clock. The negative effects of demodulating audio signals were inevitable. In addition, devices using a microprocessor often handle clocks of the same frequency, and the influence of the “beat” on the music signal due to minute frequency deviations due to clock accuracy differences is inevitable. When the frequency of the difference is low or an unintended detection circuit is generated, the analog signal may be directly affected, and the influence on the sound quality is further increased.

  When performing digital audio reproduction, when synchronizing with other devices, a clock corresponding to a sampling frequency called a word clock is used. The word clock is an effective means for timing different digital audio outputs for each device, and the sampling theorem ensures that the original analog signal is completely demodulated when operating at the correct frequency and ideal clock. However, in reality, since it is not synchronized with the clock of the CPU etc. that controls them, the “beat” and “noise” to the word clock due to the minute frequency deviation generated from different clocks. The influence is unavoidable, and the word clock is a reference on the frequency side at the time of audio demodulation. Therefore, when noise is superimposed on the word clock and there is a jitter component, it is converted to an analog signal by D / A conversion. It will adversely affect the sound quality. In addition, many crystal oscillators with different characteristics must be used to construct a system that includes a computer, so noise is generated at various frequencies and timings, such as phase noise and directly generated noise. It is not easy to do.

  As a means of obtaining higher performance than the word clock when performing digital reproduction, a device that uses a frequency closer to the internal clock as a reference clock, such as a clock that is 256 times the word clock used in the final internal processing of data transmission. However, since the timing is different from the operation clock of the CPU that controls them, the influence of noise from the clock and a minute frequency deviation cannot be avoided as with the word clock.

  Computer time management uses an internal timer, a reference time via the Internet, or a reference time signal used from the outside, but the accuracy and resolution of the timer is insufficient for processing such as audio-video editing and playback. In addition, there are many cases where multiple computers are used to improve processing efficiency. However, accurate processing is not required for video and audio recording, recording, and playback where fine timing is a problem unless high-precision clocks are used. Since it is impossible, the word clock is always used, and the word clock is not synchronized with the internal processing timer or the operation clock, so that more noise is generated.

By using a large number of clocks of the same frequency or adjacent frequencies with different oscillators in the CPU, peripheral circuits, audio and video circuits, the “beat” that occurs from minute frequency deviations is suppressed, and the effect on audio and video signals Avoid. When processing using multiple computers, clocks generated from different oscillators with the same frequency will be used, and even minute frequency deviations will be a problem. In order to achieve this, it is necessary to make the shift of the frequency of the clocks used at the same time have the same tendency so as to prevent a minute deviation in the frequency of each clock. For example, Patent Document 1 discloses a method of switching between a synchronous clock and an asynchronous clock for transmitting data sent to a notebook computer that receives a synchronous clock from a docking station with high reliability.
Japanese Patent Publication No. 11-305868

In addition, audio processing using an external synchronization clock such as a high-precision crystal or high-precision rubidium clock is performed as a means of quality improvement in audio reproduction. The purpose of synchronizing the audio reproduction start timing and the final audio reproduction equipment Since it becomes a synchronization signal for demodulation on the time axis side, it is necessary to avoid the influence of noise generated from the clock used by the computer that controls them on the synchronization clock for audio processing or to eliminate noise and noise effectively. Sound quality cannot be obtained. For example, Patent Document 2 describes a means for facilitating noise countermeasures outside a microcomputer by making the pattern of noise radiated after standby release constant.
Japanese Patent Publication No. 10-31528

  In order to achieve the above object, the present invention comprises the following arrangement. It has a structure that inputs an external clock for operating the devices that make up the CPU and computer, and generates an internal clock that synchronizes the deviation with the same accuracy as the external device, thereby making the frequency deviation the same trend and the same frequency. Even when there is a clock to be used, it is possible to prevent a “beat” from occurring and to make a device with less noise generated from the clock. In the present invention, the operation clock around the CPU is generated by using the same clock as the operation clock generation to the CPU, so that the frequency deviation of the CPU peripheral interface and the peripheral circuits connected to them are unified in the same tendency. Furthermore, by generating a video and audio processing clock from the same reference clock, these frequency deviations also have the same tendency. As the clock used in the CPU and the interface connected to the CPU and peripheral circuits, a clock injected from the outside may be used as it is, or it may be used after frequency conversion inside. Any circuit may be used as the frequency conversion method, but ideally, the frequency accuracy does not change and the phase noise does not increase.

  According to the structure of the present invention, the following excellent effects can be exhibited. The external clock supplied to the CPU is the same frequency as the external device because the CPU, the interface circuit connected to the CPU, and all the circuits connected to them operate with the same clock. Have the same tendency and the same amount of deviation in the same direction, and the “beat” due to the frequency difference signal caused by these will basically not occur, and a system configuration with less adverse effects of the clock on the sound and video becomes possible. Even in the case of clock frequencies that are not synchronized at different frequencies, the clocks are generated from the same clock, so the accuracy tends to be the same, and even if environmental changes such as time and temperature change occur, the deviation of each clock tends to be the same As a result, the change in unnecessary noise components is reduced. Further, since the generated noise has the same clock accuracy, the passband can be narrowed even when the noise is removed by a filter, and the noise can be efficiently removed. Since the configuration of the present invention can be operated in synchronism with an external device, the operation of all devices can be covered with a single oscillator, which is advantageous in terms of cost when configuring a high-accuracy device. . In addition, when using multiple computers in parallel, all computers operate with the same clock by synchronizing each computer with the same clock, and the frequency shift tends to be the same. Generation of noise due to the difference frequency is suppressed, and the timing of computer processing is the same. Note that the clock supply method and circuit system, oscillator and clock type, clock waveform format, and the waveform and format of the signal generating the clock may be anything, and can be modified without departing from the present invention. It is.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating a structure representing an embodiment of the present invention. FIG. 2 is a configuration diagram when the configuration of FIG. 1 is configured by a plurality of computers. FIG. 3 is a configuration diagram when the clocks of a plurality of computers are generated externally. FIG. 4 is a block diagram of a general digital video / audio processing computer using the present invention. FIG. 5 is a diagram for explaining the influence when different clocks are used.

  In FIG. 1, a computer 130 that processes video and audio uses a computer clock (CLK0) 141 converted to the same frequency as the crystal oscillator 152 using the frequency conversion circuit 102 using the external reference clock 101, and converts the internal frequency of the computer. Each circuit is converted into a CPU and peripheral circuit clock (CLK2), an interface circuit clock (CLK3), a video circuit clock (CLK4), a sound circuit clock (CLK5), an external bus clock (CLK6), etc. Used in The reference clock a111 and the reference clock b112 output from the external reference clock 101 are the same clock. The word clock 114 and the word clock 115 used by the external sound circuit 104 and the D / A converter 105 are generated by the word clock generator 103 using the reference clock a111 output from the external reference clock 101, and the external sound. The circuit 104 and the D / A converter 105 are supplied and synchronized. Since the clock generated by the external reference clock 101 is used even if a clock of the same frequency exists in the inside constituted by these, the center frequency is basically the same to move within the frequency accuracy range. Thus, there is no frequency difference and no “beat” occurs. Further, the word clock a 114 and the word clock b 115 generated by the word clock generator 103 and the clock CLK 2 and the clock CLK 3 generated by the frequency conversion circuit 153 used inside the computer depend on the accuracy of the external reference clock 101. In addition, the phase noise components basically have the same tendency. The frequency conversion circuit 102 and the word clock generator 103 may have any structure, and may be internal or external to the computer 130, but inherit the accuracy of the external reference clock 101, such as a PLL circuit and a frequency divider. It is desirable to use such as. Further, when using a plurality of frequencies, it is more desirable to store a plurality of frequency conversion circuits in the same module so that the operation due to temperature change is not affected. The configuration of the present invention may be any computer or peripheral circuit using a clock, may be connected by an internal bus, or may be connected externally. Also, any clock frequency, signal format, and waveform may be used. The clock transmission may be any system such as a coaxial cable, optical cable, or wireless communication, but it is preferable that the phase difference does not occur.

  FIG. 2 is a configuration diagram when the configuration of FIG. 1 is configured by a plurality of computers. A clock 202 generated by the external reference clock 201 is connected to a plurality of devices such as a computer 231, a computer 232, a computer 233, and a computer 234. Since each clock is generated from one reference clock, the accuracy of the clock does not depend on the environment around each computer or the internal environment. In FIG. 2, the number of units is four, but the number is not limited to four, and one or more units may be used, and the external reference clock 201 may be supplied in the same manner. The frequency conversion circuit 221 and the frequency conversion circuits 222, 223, and 224 inside the computer respectively convert the internal clock 203, the internal clock 204, and the internal clock 205 to frequencies used internally. In this case, since the frequency conversion circuit 221, the frequency conversion circuit 222, the frequency conversion circuit 223, and the frequency conversion circuit 224 are in the computer 231, the computer 232, the computer 233, and the computer 234, they are converted into frequencies as necessary. There may be a plurality of frequency conversion circuits when there are several types of required frequencies. The device that supplies the external reference clock 201 is not limited to a computer, and may be simultaneously supplied to a device that uses a clock, such as a video editing / playback device or an audio device such as music editing / playback, as shown in FIG.

  FIG. 3 shows a configuration example in the case where the clock frequency required by the computer is the same as that shown in FIG. 2, and the clock 302 supplied from the external reference clock 301 is converted and generated by the frequency conversion circuit 311. 303 is supplied to the computer 321, the computer 322, the computer 323, and the computer 324, respectively. In this case, all the devices to which the clock 303 is supplied are operated with the same clock. That is, the accuracy of the clock of each individual computer basically does not depend on the environment of the individual computer. Furthermore, it becomes possible to perform a completely synchronized operation by supplying a reference clock such as a digital music playback word clock or video synchronization clock to each computer.

  FIG. 4 is a diagram in which the present invention is applied to an apparatus for digitally editing video and audio as a configuration example of a device using a clock. Clocks 402, 403, and 404 generated by the external reference clock 401 are clocks having the same frequency, and are input to the frequency conversion circuit 411, the frequency conversion circuit 412, and the word clock generator 413, respectively, and are necessary for the connected device. The clock 421, the clock 422, the clock 423, and the clock 424 are converted. Of the generated clocks, the clock 422 generated by the frequency conversion circuit 412 is converted by the frequency conversion circuit 434 as a clock used in the computer 430 and used by the CPU, peripheral circuit 435 and interface circuit 436. The clock 421 converted by the frequency conversion circuit 411 is used by the graphic circuit 437 inside the computer 430. In the graphic circuit, a video signal is generated to be displayed on a processor or monitor for image processing. However, since the clocks are generated from the same external reference clock 401, the accuracy of each frequency becomes the same and the frequency is the same. The range of deviation due to the different displacement is suppressed. Further, by using the word clock 423 generated by the word clock generator 413 in the sound circuit 439 and the D / A converter 441, noise components when the music signal is generated from the digital PCM data are used inside the computer 430. The same tendency as the clock 421, clock 422, clock 432, and clock 433, and the adverse effect on the sound quality is reduced.

  FIG. 5 is a diagram for explaining the influence when different clocks are used. For explanation, a reference signal is compared as a signal (a). That is, the period 521 and the period 522 are the same, the period 523 is the same as the period, and only the phase is shifted. The period 524 is slightly longer than the other periods. In these signals, when the ideal frequency is exactly the same signal and only the phase is shifted, a phase difference 511 and a phase difference 512 are generated. However, this difference does not change with time and does not “beat”. However, when the frequency is slightly shifted, a phase difference 513 and a phase difference 514 are generated, and the difference generally changes with time due to an influence on the crystal resonator such as a temperature change. These period deviations are caused by the deviation of the average frequency in the clock having the same frequency display, and the deviation caused by the temperature change and the secular change. When there is a slight period difference, a “beat” generated from the difference between the period 523 and the period 524 occurs. The difference in frequency is that even if a crystal oscillator with the same frequency is used, a slight frequency deviation occurs, and the change due to temperature and the secular change are not a constant rate of change. This means that clocks that cause deviations in various frequencies are used. In the present invention, in order to generate a clock used in different devices and different computers from a single external reference clock, the frequency deviation is basically governed by the external reference clock, and the deviation shifts in the same direction. No effect arises from the frequency deviation described in FIG.

It is a block diagram concerning the present invention. It is a block diagram at the time of comprising the structure of FIG. 1 with several computers. It is a block diagram at the time of generating the clocks of a plurality of computers or peripheral devices externally. It is a block diagram using a computer for general digital video / audio processing. It is a figure explaining the influence when using each different clock.

101 External reference clock 102 Frequency conversion circuit 103 Word clock generator 104 External sound circuit 105 D / A converter 111 Reference clock a
112 Reference clock b
113 Computer clock CLK1
114 Word clock a
115 word clock b
116 SPDIF digital signal 121 Analog audio output 130 Computer 141 Computer clock CLK0
142 CPU and peripheral circuit clock CLK2
143 Interface circuit clock CLK3
144 Video circuit clock CLK4
145 Sound circuit clock CLK5
146 External bus clock CLK6
151 Clock changeover switch 152 Crystal oscillator for computer 153 PC internal frequency conversion circuit 154 CPU and peripheral circuit 155 Interface circuit 156 Graphic circuit 157 Sound circuit 201 External reference clock 202 Clock CLK0
203 Internal clock CLK1
204 Internal clock CLK2
205 Internal clock CLK3
206 Internal clock CLKn
221 Frequency conversion circuit 1
222 Frequency conversion circuit 2
223 Frequency conversion circuit 3
224 Frequency conversion circuit n
231 Computer 1
232 Computer 2
233 Computer 3
234 computer n
301 External reference clock 302 Clock CLK0
303 Computer clock 311 Frequency conversion circuit 321 Computer 1
322 Computer 2
323 Computer 3
324 computer n
401 External reference clock 402 Clock 403 Clock 404 Clock 411 Frequency conversion circuit 1
412 Frequency conversion circuit 2
413 Word clock generator 421 Clock CLK0
422 clock CLK1
423 Word clock 424 Word clock 430 Computer 431 Crystal oscillator 432 Clock 2
433 Clock 3
434 Frequency conversion circuit 1
435 CPU and peripheral circuit 436 Interface circuit 437 Graphic circuit 438 Digital audio circuit 439 SPDIF digital output 441 D / A converter 451 Analog audio output 452 Analog audio output 453 Video output 501 Signal (a)
502 Signal (b)
503 Signal (a)
504 Signal (c)
511 Phase difference 512 Phase difference 513 Phase difference 514 Phase difference 521 Period 522 Period 523 Period 524 Period

Claims (3)

  A computer system characterized by using an external device and a single reference signal or a clock generated from a single reference clock as the operation clock of the CPU   A single reference signal or a clock generated from a single reference clock is used for a CPU and an interface circuit connected to the CPU and a circuit using a clock connected to the interface circuit. Computer   In a system composed of a plurality of different computers, a plurality of computers operate using a single reference signal or a clock generated from a single reference clock in a circuit that uses the CPU or clock of those computers. Computer system characterized by

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