Electrical audio signal processing systems and devices – With mixer
Reexamination Certificate
1997-04-04
2001-01-30
Harvey, Minsun Oh (Department: 2747)
Electrical audio signal processing systems and devices
With mixer
Reexamination Certificate
active
06181798
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
Not applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable
BACKGROUND OF THE INVENTION
This invention relates to an audio signal fader control system and an operating method therefor.
Audio signal mixing is conventionally performed using an audio mixing desk which may have analog audio mixers or be digitally operated. In an analog audio mixer the audio signal is modified between input and output of the mixer by an editor applying gain and attenuation to the audio signal using slider fader controls.
In a digital system, the signal is processed with a digital signal processor (DSP) and values for gain and attenuation from fader controls are generated using an analog to digital converter (ADC) which communicates with the DSP.
The values generated by either the analog or the digital system are usually stored and later played back. If a digital system is used then digital position values are converted back to a voltage using a digital to analog converter (DAC), which voltage is used to drive a motorized fader control.
The process of driving a motorized fader control from stored or computed audio level control values is called “dynamic automation”. When playing back the stored audio, the editor may modify the audio signal by revising the motorized fader control position. In this respect it is usual for the motorized fader control to have the motor drive disabled when the control is touched by an editor so as to avoid the motor being burned out. When the editor modifies the fader control position to modify the audio during playback mode, the new fader position is stored.
A discussion of digital audio and digital fader controls can be found in “The Art of Digital Audio”, 2nd Edition by John Watkinson at Section 2.8, page 48, published by Focal Press, ISBN 0-240-51320-7.
A problem with motorized fader controls is that they have inertia and that it takes a period of time for the fader to arrive at a new desired position. Furthermore, the fader control is usually located in a control console which is connected over a network to a host computer system. The network introduces communication delays which again lead to a time error in the motorized fader control arriving at a desired position.
The object of this invention is to provide dynamic automation with the capability of moving the motorized fader control to be at a desired position at a required time.
BRIEF SUMMARY OF THE INVENTION
According to a first aspect of this invention there is provided an audio signal fader control system including control means for receiving signals output by a motorized fader control means and for applying control signals to said fader control means, host computer means connected to said control means by transmission path means, and timing means associated with said control means and said host computer means for arranging said control signals from said host control means to be transmitted to said control means so that said control means is able to drive said fader control means to a desired position a predetermined period before said fader control means is actually required to be at said desired position.
Preferably said fader control means desired positions are in discrete steps and said control means includes interpolation means for interpolating locations of said fader control means between said desired points.
Conveniently, said host control means has a CPU and a real time clock, and said control means has counter means supplying data relative to a predetermined cyclical position of said counter means to said host CPU so as to provide synchronisation between said counter means and said host CPU.
Advantageously said host CPU has arithmetic means for adding said predetermined period to said real time and subtracting the real time at which said predetermined position of said counter means provides said synchronisation, and dividing the result by the control means counter means cycle rate to provide a predetermined value of said counter means, which predetermined value is used to drive said fader control means.
Advantageously said host control means is arranged to write a fader control means position to said control means at an integer multiple of said control means cycle rate, thereby providing over sampling of said control means.
According to a second aspect of this invention there is provided a method of operating an audio signal fader control system having control means for receiving signals output by a motorised fader control means and for applying control signals to said fader control means and a host computer means connected to said control means by transmission path means including the steps of arranging said control signals from said host control means to be transmitted to said control means so that said control means is able to drive said fader control means to a desired position a predetermined period before said fader control means is actually required to be at said desired position.
REFERENCES:
patent: 5054077 (1991-10-01), Suzuki
Gray Francis I.
Harvey Minsun Oh
Tektronix Inc.
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