Method and apparatus for leveling and equalizing the audio output of an audio or audio-visual system

• US 6,195,438 B1
• Filed: 09/08/1997
• Issued: 02/27/2001
• Est. Priority Date: 01/09/1995
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Corporation Of America (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Corporation Of America (Panasonic Holdings Corporation)
• Inventors: Yumoto, Hideki, Rzeszewski, Theodore S.
• Primary Examiner(s): Nguyen, Duc
• Application Number:
  US08/925,318
• Time in Patent Office: 1,268 Days
• Field of Search: 381/98, 381/100-103, 381/104, 381/106-107, 381/109
• US Class Current: 381/103
• CPC Class Codes: H03G 3/001 Digital control of analog signals
• CPC Class Codes: H03G 5/005 of digital signals

Abstract

A microcomputer for automatically controlling the sound in an audio or audio-visual system. Incoming audio signals from multiple channels are combined and fed to a pair of detector-rectifier circuits. One detector-rectifier circuit is a smoothing circuit with a time constant longer than that of the other detector-rectifier circuit. The signals with a longer time constant are fed to the microprocessor to control the volume function of an audio or audio-visual system. The signals with a shorter time constant are fed to the microprocessor to equalize the source frequency spectrum of an audio or audio-visual system.

Claims

1. A method of digitally processing audio signals of an audio or audio-visual system to automatically adjust the sound output characteristics of the system, comprising the steps of:

(a) comparing a time divided audio signal to a predefined threshold value for determining if said audio signal is above said predefined threshold value,

wherein said predefined threshold value represents a low level audio signal;

(b) subtracting a predetermined value from said time divided audio signal if said audio signal exceeds said predefined threshold value,

wherein said predetermined value is approximately equal to the maximum magnitude of said audio signal divided by a value ranging approximately from 2 to 4, and

wherein said substraction step results in a control signal that is within a range set by the said predetermined value;

(c) multiplying a user selectable volume level setting by said control signal so as to obtain a scaled control signal; and

(d) adding said scaled control signal to the selectable volume setting level.

2. The method of digitally processing audio signals according to claim 1, further comprising the steps of:

(e) squaring said time divided audio signal;

(f) summing n consecutive values of said time divided audio signal generated by said squaring step so as to generate a summing result; and

(g) calculating the square root of said summing result and utilizing the result in steps (a)-(d).

3. The method of digitally processing audio signals according to claim 2,

wherein said time divided audio signal comprises signals from multiple channels.

4. The method of digitally processing audio signals according to claim 2, further comprising the steps of:

performing steps (e)-(g) on the signals associated with each of said multiple channels so as to generate a plurality of results; and

adding said plurality of results to one another.

5. The method of digitally processing audio signals according to claim 2, further comprising the steps of:

(h) calculating an absolute value of said time divided audio signal; and

(i) summing the last n values of said time divided audio signal generated by said absolute value calculation step and utilizing the result in steps (a)-(d).

6. The method of digitally processing audio signals according to claim 5,

wherein said time divided audio signal comprises signals from multiple audio channels.

7. The method of digitally processing audio signals according to claim 6, further comprising the steps of:

performing steps (h)-(i) on the signals associated with each of said multiple audio channels so as to generate a plurality of results; and

adding said plurality of results to one another.

8. The method of digitally processing audio signals according to claim 1, further comprising the steps of:

checking for a mute on-off condition after said control signal is multiplied to said selectable volume setting level, and

returning to step (a) under a mute on condition.

9. A digital audio leveling apparatus for an audio or audio-visual system to automatically adjust the volume characteristics of the system, comprising:

a digital audio decoder operative for decoding audio signals into multi channel audio signals;

a digital volume controller coupled to an output of said digital audio decoder for generating volume controlled audio signals;

a microprocessor coupled to an output of said digital audio decoder and to an input of said digital volume controller for controlling the volume of the audio signals generated by said digital volume controller; and

a digital audio amplification unit coupled to an output of said digital volume controller,

wherein said microprocessor classifies said audio signals into a voice category, a musical category and an undecided category and compensates for power variations in said audio signals on the basis of said classification to maintain a substantially constant volume from said digital audio amplification unit.

10. A digital audio leveling apparatus for an audio or audio-visual system to automatically adjust the volume characteristics of the system, comprising:

a digital audio decoder operative for decoding audio signals into multi channel audio signals;

a digital volume controller coupled to said digital audio decoder for accepting said multi channel audio signals;

a microprocessor coupled to an output of said digital volume controller and to an input of said digital volume controller for controlling the volume of the audio signals generated by said digital volume controller; and

a digital audio amplification unit coupled to an output of said digital volume controller,

wherein said microprocessor classifies said audio signals into a voice category, a musical category and an undecided category and compensates for power variations in said audio signals on the basis of said classification to maintain a substantially constant volume from said digital audio amplification unit.

11. A method of digitally processing audio signals of an audio or audio-visual system to automatically adjust the sound output characteristics of the system, comprising the steps of:

summing audio signals from multiple audio channels;

sampling the summed audio signals at a first sampling rate for use in leveling the volume of the summed audio signals;

sampling the summed audio signals at a second sampling rate for equalizing the source frequency spectrum of the summed audio signals,

wherein the second sampling rate is higher than the first sampling rate;

processing the summed audio signals sampled at a first rate for leveling the volume of the summed audio signals via digital calculations; and

processing the summed audio signals sampled at a second rate for equalizing the source frequency spectrum of the summed audio signals via digital calculations,

wherein a substantially constant volume and an equalized frequency spectrum is maintained in the sound of the audio or audio-visual system.

12. The method of digitally processing audio signals according to claim 11, further comprising the step of:

amplifying audio signals from multiple audio channels prior to said step of summing audio signals from multiple audio channels.

13. The method of digitally processing audio signals according to claim 11, further comprising the steps of:

selecting a condition that controls the processing steps by processing only the summed audio signals sampled at said first rate, only the summed audio signals sampled at said second rate, both the summed audio signals sampled at said first rate and the summed audio signals sampled at said second rate, or neither the summed audio signals sampled at said first rate nor the summed audio signals sampled at said second rate; and

processing the summed audio signals sampled at a first rate, and/or at a second rate, or not at all, depending on the condition selected.

14. The method of digitally processing audio signals according to claim 13, further comprising the step of:

displaying the selected condition on the audio or audio-visual system.

15. The method of digitally processing audio signals according to claim 14, further comprising the step of:

displaying information reflecting the status of the volume of the summed audio signals sampled at said first rate during the processing of such signals and/or the status of the frequency spectrum of the summed audio signals sampled at said second rate during the processing of such signals.

16. The method of digitally processing audio signals according to claim 11,

wherein the equalizing of the source frequency spectrum by said step of processing the summed audio signals sampled at a second rate is carried out in a gradual manner.

17. A method of digitally processing audio signals of an audio or audio-visual system to automatically adjust the sound output characteristics of the system, comprising the steps of:

summing audio signals from multiple audio channels;

sampling the summed audio signals at a sampling rate for use in leveling the volume and for equalizing the source frequency spectrum of the summed audio signals;

summing a number of sampled audio signals over a period of time and dividing the summed sample of audio signals by the number of samples over a period; and

processing the audio signals sampled over a period of time and divided by the number of samples over a period by leveling the output and equalizing the source frequency spectrum of the summed audio signals via digital calculations,

wherein a substantially constant volume and an equalized frequency spectrum is maintained in the sound of the audio or audio-visual system.

18. The method of digitally processing audio signals according to claim 17, further comprising the step of:

amplifying audio signals from multiple audio channels prior to said step of summing audio signals from multiple audio channels.

19. A method of digitally processing audio signals of an audio or audio-visual system to automatically adjust the sound output characteristics of the system, comprising the steps of:

automatically leveling the volume of audio signals;

classifying said audio signals into a voice category, a musical category and an undecided category; and

altering a source frequency spectrum of the audio signals by automatically adjusting equalizer settings on the basis of said classification,

wherein a substantially constant volume and an equalized frequency spectrum is maintained in the sound of the audio or audio-visual system.

20. An apparatus for digitally processing audio signals of an audio or audio-visual system for automatically adjusting the sound output characteristics of the system, comprising:

an adder for summing audio signals from multiple audio channels;

means for sampling the summed audio signals at a first sampling rate for use in leveling the volume of the summed audio signals;

means for sampling the summed audio signals at a second sampling rate that is higher than said first sampling rate for equalizing the source frequency spectrum of the summed audio signals; and

a microprocessor receiving samplings of the summed audio for processing the summed audio signals sampled at a first rate for leveling the volume of the summed audio signals via digital calculations and for processing the summed audio signals sampled at a second rate for equalizing the source frequency spectrum of the summed audio signals via digital calculations,

wherein a substantially constant volume and an equalized frequency spectrum is maintained in the sound of the audio or audio-visual system.

21. The apparatus for digitally processing audio signals according to claim 20, further comprising:

an amplifier for each channel connected to said adder for amplifying the audio signal in the channel prior to being inputted to said adder.

22. The apparatus for digitally processing audio signals according to claim 20, further comprising:

a digital volume and tone control receiving the volume leveled and frequency spectrum equalized signals from said microprocessor.

23. The apparatus for digitally processing audio signals according to claim 20, further comprising:

means for selecting a condition for controlling said microprocessor to process only the summed audio signals sampled at said first rate, only the summed audio signals sampled at said second rate, both the summed audio signals sampled at said first rate and the summed audio signals sampled at said second rate, or neither the summed audio signals sampled at said first rate nor the summed audio signals sampled at said second rate,

wherein said microprocessor processes audio signals by leveling the volume of the audio signals, or by equalizing the source frequency spectrum of the audio signals, or by both leveling the volume of the audio signals and by equalizing the source frequency spectrum of the audio signals, by not performing either function, depending on the condition selected.

24. The apparatus for digitally processing audio signals according to claim 23,

wherein said selecting means comprises a switching means.

25. The apparatus for digitally processing audio signals according to claim 24,

wherein said selecting means comprises a menu on a display screen of an audio-visual system and a remote control device for making a selection from said menu.

26. The apparatus for digitally processing audio signals according to claim 23, further comprising:

means for displaying a selected condition on the audio or audio-visual system.

27. The apparatus for digitally processing audio signals according to claim 23, further comprising:

means for displaying information reflecting the status of the volume of the summed audio signals sampled at said first rate during the processing of such signals and/or the status of the frequency spectrum of the summed audio signals sampled at said second rate during the processing of such signals.

28. The apparatus for digitally processing audio signals according to claim 27,

said displaying means displays the status of the volume of the summed audio signals sampled at said first rate during the processing of such signals and/or the status of the frequency spectrum of the summed audio signals sampled at said second rate during the processing of such signals.

29. An apparatus for digitally processing audio signals of an audio or audio-visual system for automatically adjusting the sound output characteristics of the system, comprising:

an adder for summing audio signals from multiple audio channels;

means for sampling the summed audio signals at a sampling rate for use in leveling the volume and for equalizing the source frequency spectrum of the summed audio signals; and

a microprocessor receiving the samplings of the summed audio signals and leveling the volume of the output and equalizing the source frequency spectrum of the summed audio signals via digital calculations, said microprocessor classifying said summed audio signals in a voice category, a musical category and an undecided category,

wherein a substantially constant volume and an equalized frequency spectrum is maintained in the sound of the audio or audio-visual system.

30. The apparatus for digitally processing audio signals according to claim 29, further comprising:

an amplifier for each channel connected to said adder for amplifying the audio signal in the channel prior to being inputted to said adder.

31. An apparatus for digitally processing audio signals of an audio or audio-visual system for automatically adjusting the sound output characteristics of the system, comprising:

means for classifying said audio signals into a voice category, a musical category and an undecided category;

an automatic equalizer for altering a source frequency spectrum of audio signals by automatically adjusting equalizer settings depending on the content of the source frequency spectrum; and

an audio leveler for automatically leveling the volume of audio signals,

wherein said audio leveler is electrically interfaced with said automatic equalizer, and

wherein a substantially constant volume and an equalized frequency spectrum is maintained in the sound of the audio or audio-visual system.