CN109314499B

CN109314499B - Audio equalization system and method

Info

Publication number: CN109314499B
Application number: CN201780035219.7A
Authority: CN
Inventors: E·格罗斯曼
Original assignee: Dolby Laboratories Licensing Corp
Current assignee: Dolby Laboratories Licensing Corp
Priority date: 2016-06-07
Filing date: 2017-06-06
Publication date: 2023-09-29
Anticipated expiration: 2037-06-06
Also published as: CN109314499A; WO2017214086A1

Abstract

A variable resolution graphic equalizer provides an improved interface for controlling gain values across the entire audio spectrum using a number of narrowband filters (e.g., 120). The improved interface allows a user to select a frequency range for graphical equalization and automatically map a reduced and fixed number of sliders to the selected range based on the number of filter bands that fall within the selected range. In an audio processing system, a particular user interface region is highlighted to display a selected frequency range and a selected corresponding slider, allowing the entire audio spectrum to be quickly and accurately equalized using the number of narrowband filters.

Description

Audio equalization system and method

Cross Reference to Related Applications

The present application claims priority from U.S. application Ser. No. 62/346,657, filed on 7, 6, 2016, and European patent application Ser. No. 16173346.4, filed on 7, 6, 2016, which are incorporated herein by reference in their entirety.

Technical Field

One or more implementations relate generally to graphical interfaces for audio processing, and more particularly to user interfaces for graphical equalizers having a large number of filter bands.

Background

Equalization is used to adjust or level the frequency response of sound over the audio spectrum or portions of the audio spectrum (e.g., 20Hz to 20 kHz). The equalizer cuts or increases the energy of a specific frequency band to obtain a desired frequency response characteristic. Equalization may be used to produce a flat frequency response across the spectrum by compensating for ambient or playback frequency response errors, or to enhance certain frequency ranges to enhance certain sound characteristics.

For music production and reproduction, graphic and parametric equalizers are the most common types of equalizer used. Graphic equalizer uses several audio filters/amplifiers, each centered on a specific frequency in the audio range, with corresponding sliding or rotating potentiometer controls that allow the user to individually control and typically see the gain settings for each of these bands on the graph. The parameter equalizer achieves more specific control over a given frequency band by providing three adjustments: selection of center frequency, adjustment of bandwidth definition (Q), and level or gain control of center frequency.

Software-implemented equalizers are typically used as part of Digital Audio Workstation (DAW) applications for editing and producing audio files through graphical user interfaces and tools. An example of software DAW is the current Pro Tools program available from Evi Technology, inc. (Avid Technology) for use with MS-Windows and Apple Macintosh computers. The basic Pro Tools or other DAW programs have software modules for multitrack tape recorders and mixers, and other digital processing functions presented to the user through a Graphical User Interface (GUI) that typically simulates a hardware product counterpart to allow the user to alter and mix multiple recordings and audio into a final produced audio program (e.g., song, message, movie soundtrack, etc.). Equalization works through graphs, parameters, half parameters, peaks, and program equalizers are typically set as part of the DAW suite, or as a software plug-in for the DAW program.

In addition, equalizers are typically included in many types of sound reproduction systems, including those used to reproduce movie dubbing in commercial movie theatres. In this context, the equalizer is used to compensate for frequency response errors in a playback environment (e.g., a theater or auditorium). In such applications, there may be many speakers in the auditorium, for example current Dolby panoramic sound (Dolby Atmos) facilities typically have 40 or 50 or more speakers, each of which requires individual equalization. Thus, this equalization process is typically automated ("Auto-EQ"), saving operator time, however, the results must be reviewed by the operator (and typically require manual correction). Thus, even though such systems include Auto-EQ, EQ (controlled using either software or hardware) is typically incorporated into such systems.

The current method of controlling an equalizer in an audio production or playback system is implemented using either a software GUI or a hardware system incorporating a physical knob or attenuator. Various products provide a wide variety of user interfaces for controlling underlying equalization techniques, ranging from very simple (one user control, e.g., knob) to very complex (tens of user controls), and one user interface may be more suitable for a given application than the other user interfaces. For example, a GUI for a lake processing module (previously made by dolby) requires a user to draw a desired equalization curve on a graph on the GUI, while a graphic equalizer implemented using a dedicated knob or slider on a hardware device allows quick and intuitive control, but lacks the accuracy of the GUI graph.

Furthermore, the underlying EQ implementation affects what control the user can exercise on. For example, graphic equalizer implementations typically consist of a relatively large number (e.g., 32) of individual EQ sections, each of which has a narrow range of adjustability, while parametric equalizers typically consist of a small number (e.g., 3) of EQ sections, each of which has a greater degree of adjustability. One important consideration for the improved EQ interface is the use of a graphical equalizer-style control that uses an underlying EQ implementation like a lake equalizer, which is made up of an ultra-large number of graphical EQ-style elements (e.g., 120 controls), and thus is only suitable for certain types of human-machine interfaces, such as drawing graphs as currently implemented in the current implementation of lake EQ products. While this high-band count gives advantages in terms of accuracy over the audio range of 20Hz to 20kHz (i.e., 12 bands per octave rather than the conventional 3 bands per octave), each of the 10 octaves requires 12 controls, for a total of 120 controls, which is expensive for a hardware interface and burdensome to operate for both hardware and software user interfaces.

Thus, there is a need for a "hybrid" graphic equalizer interface that provides a simple set of controls that map well into both hardware implementations and computer-based GUIs, and that allows for overall gain control of the audio spectrum without requiring an excessive number of controls or graphics, and that requires minimal effort on the part of the user to implement a certain gain curve, that is, an efficient workflow.

The subject matter discussed in the background section should not be assumed to be prior art merely because it is mentioned in the background section. Similarly, the problems mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously identified in the prior art. The subject matter in the background section is merely representative of various methods, which may themselves be inventions.

Disclosure of Invention

Embodiments relate generally to an equalizer system and a method of controlling an equalizer by: the gain values of the frequency bands are adjusted by a first equalizer UI section having a plurality of attenuators each setting a gain value assigned to a particular set of underlying EQ elements of the attenuators and a second equalizer UI section selecting a frequency range for equalization by the first equalizer section. The second equalizer UI section determines a frequency range within which the first UI section operates, automatically assigning a set of one or more underlying EQ elements to each attenuator in the first UI section.

Embodiments include a method of implementing control of an audio equalizer by: providing a first set of controls to equalize frequency response across the audio spectrum in a manner similar to a graphic equalizer, wherein each single attenuator controls a plurality of underlying graphic EQ elements, wherein each control in the first set of controls sets gain values assigned to the plurality of underlying EQ elements of the control; and providing a second set of controls defining operation of the first set of controls. To achieve this, the second set of controls includes two controls defining a frequency range therebetween; the first control sets a frequency lower limit and the second control sets a frequency upper limit. This frequency range is used to determine the behavior of each control in the first set of controls, assigning a specific set of underlying EQ elements (similar to the Q elements of the fixed center frequency and graphic EQ) to the control and determining how the settings of the control affect the gain values that are thereby transferred to the underlying EQ elements. Using an algorithm to determine the behavior of the attenuator implies that the value transmitted by the attenuator to its underlying EQ element may or may not be linearly related to the setting of the attenuator control; for example, a smoothing, curve fitting, or other refinement may be utilized to achieve a desired resulting overall frequency curve for the equalizer system based on moving a given attenuator.

The first set of controls may be provided as faders implemented as linear variable resistive devices in a graphical equalizer format (in hardware) or as graphical representations of faders in a software GUI, or in any other mechanical or graphical form, with the result that each fader always represents an audio gain value in decibels (dB) or in other units that is positive or negative or zero. The second set of controls may be provided as rotary knobs (e.g., potentiometers in a hardware implementation or graphical widgets in a software GUI), or in any other mechanical or graphical form, with the result that each control helps define a frequency range having a lower frequency limit and an upper frequency limit, e.g., in Hz. Example the second control group may consist of a lower frequency limit, an upper frequency limit, and an offset, while adjusting the effect of the first two controls is to move the selected range up or down within the total frequency spectrum. As an example, if the lower limit is set to 20Hz and the upper limit is set to 100Hz, this would result in a width range of 80Hz, and increasing the offset control value by a value of 100Hz would shift the 80Hz frequency range to 120Hz to 200Hz. This provides only an example of how the second set of controls may define the frequency range, and many other arrangements are possible, such as adjusting borderlines on a graph on a GUI or employing a touch sensitive hardware device.

For any application where the equalizer is now or in the future, for example for processing audio files in a DAW or for processing live audio at a concert or movie show, the control may comprise a graphical user interface element that controls the gain characteristics over the audio spectrum.

In an embodiment, there may be any number of bottom EQ elements and any number of attenuators in the first control section. In the specific example with 120 underlying EQ elements and 8 faders in the first set of controls, each fader controls 15 (120/8=15) EQ elements if the frequency range is set by the second control to 20Hz to 20 kHz. As another example, for the narrowest frequency range supported in this example configuration, each attenuator will control exactly one EQ element, enabling 1/12 octave accuracy control for each of the 8 attenuators.

In an embodiment, the first and second sets of controls are provided as software elements in a software implemented equalizer program, wherein the frequency range set by the second set of controls is displayed on a frequency response graph of the graphical user interface. Additionally, the resulting EQ curve set by the combination of the two control groups may be shown on the frequency response graph. Other relevant information may also be superimposed on the frequency response plot, such as a fourier frequency domain plot of the live audio signal. Other related EQ controls may also exist in the EQ GUI, such as a selector between "replace" and "add" modes that determines whether the effect of moving the fader would offset any existing EQ curves in the current area of the fader's control or would completely replace any existing EQ curves with curve segments corresponding to new fader values.

Embodiments further relate to an equalizer system for adjusting gain values of frequency components across a frequency spectrum, the equalizer system having: a first set of equalizer controls including a plurality of attenuators, each attenuator setting a gain value for a unique center frequency in the audio spectrum; and a second set of equalizer controls that select a frequency range for equalization by the first set of equalizer controls and automatically map a subset of attenuators of the plurality of attenuators to the selected frequency range based on a number of filter bands belonging within the selected frequency range. In the system, a first control in the second set of equalizer controls selects a center frequency of a subset of faders, and second and third controls in the second set of equalizer controls define a width (in Hz) of a frequency range around the given center frequency. The result of these user interface settings for the underlying EQ implementation is that each attenuator is assigned a set of underlying EQ elements, which are calculated algorithmically to correspond to the selected frequency range. The first set of equalizer controls may consist of a graphical equalizer-style arrangement of 8 or 16 individual attenuators, and the underlying graphical EQ implementation may include 120-band equalizers with 120 individual narrowband filters applying gain values set by the multiple attenuators. The equalizer system may be a hardware component for a hardware-based audio processing system, or it may be a software program for use in an audio production or reproduction system having a Graphical User Interface (GUI) to facilitate user control of the EQ during production or reproduction of audio content.

Embodiments of a graphical user interface for controlling a graphical equalizer in a digital audio processing product are further described, the graphical user interface having: a display area showing a frequency response plot over a 20Hz to 20kHz audio spectrum, such as a frequency response bar chart or frequency response plot; a graphic equalizer display area showing a plurality of attenuators controlling gain values of respective center frequencies of the spectrum; and a method within a GUI (e.g., a set of controls) whose purpose is to select a frequency range for equalization by a graphic equalizer and automatically map each of a plurality of attenuators to a corresponding frequency range to be implemented as a number of EQ filter elements belonging within the selected frequency range, and simultaneously make gain adjustments to individual underlying EQ elements as initiated by movement of the attenuators and subsequently determined by an algorithm. The selected frequency range is indicated on the display as a highlighted portion of the display area and the subset of attenuators is displayed as another highlighted portion of the display area. The set of frequency range selection controls in the display area may include a left frequency knob, a right frequency knob, and an offset knob for controlling an offset between the right frequency and the left frequency.

Embodiments are still further directed to methods of manufacturing and using or deploying an equalizer as part of an audio production or reproduction system under some embodiments.

Incorporated by reference

Each publication, patent, and/or patent application mentioned in this specification is incorporated herein by reference in its entirety to the same extent as if each individual publication and/or patent application was specifically and individually indicated to be incorporated by reference.

Drawings

In the following drawings, like reference numerals are used to refer to like elements. Although the following figures depict various examples, the one or more implementations are not limited to the examples depicted in the figures.

Fig. 1 illustrates a digital audio system utilizing an equalizer interface in accordance with some embodiments.

Fig. 2A illustrates an example graphical equalizer interface controllable through a DAW user interface, according to some embodiments.

Fig. 2B illustrates an interface for a parameter equalizer and corresponding equalization functions that may be controlled through a DAW user interface, in accordance with some embodiments.

Fig. 3 illustrates a graphical user interface display for a hybrid equalizer under some embodiments.

Fig. 4 provides an example illustration of a possible setting of a range bar for a hybrid equalizer interface under some embodiments.

Fig. 5 illustrates an example hybrid equalizer incorporated into the EQ GUI under some embodiments.

Detailed Description

Systems and methods are described for a user interface for controlling a graphical equalizer implementation consisting of a large number of filter elements (e.g., twelve elements per octave within 10 octaves, 120 total filter elements). The interface represents a mix between the user interface for the graphic equalizer and the user interface for the parameter equalizer. Specifically, the interface presents to the user a number of sliders (e.g., eight) and a method of selecting a frequency range within which the sliders operate. An example set of controls for selecting a frequency range may consist of three knobs, including (1) a lower frequency knob (2) an upper frequency knob and (3) an offset knob (which slides the entire range selected by the first two knobs up or down in the frequency range).

Aspects of one or more embodiments described herein may be implemented in an audio production or reproduction system that processes audio content. Implementations may in principle be implemented in any of the analog or digital domains using one or more computers or processing devices executing software instructions, but common implementations are in the digital domain. Any of the described embodiments may be used alone or in any combination with one another. While various embodiments may be motivated by various deficiencies with the prior art, which may be discussed or referred to at one or more of the description, such embodiments do not necessarily address any of these deficiencies. In other words, different embodiments may address different deficiencies that may be discussed in the specification. Some embodiments may address only some of the drawbacks or only one of the drawbacks that may be discussed in the specification, and some embodiments may not address any of these drawbacks.

Fig. 1 illustrates an audio processing system utilizing an equalizer interface in accordance with some embodiments. Such an interface with an Equalizer (EQ) function or process implemented in either software or hardware may be referred to herein as a "hybrid equalizer" or a "variable resolution graphic equalizer. As shown in the system 100 of fig. 1, input audio 102, such as an audio stream, is processed by an audio system 104 to produce a final audio product 110. The audio input and processed may include any type of audio content, such as music, dialog, sound effects, ambient noise, etc., and may be stored in any suitable digital format for audio processing. In an embodiment, the audio system 104 is embodied as a computer software application for recording, processing, and producing or reproducing the input audio stream 102, and may be executed as an application on a single computer (e.g., a desktop or laptop computer) or as a stand-alone unit (e.g., a computer-based embedded audio device), or in a network of computers accessed through a central user interface. The interface for the audio system 104 provides GUI tools to allow the user to input 106 settings and commands to alter and mix the audio stream 102 to produce the end product 110.

The audio system 104 may be an integrated system that may include any of a mixing control surface (e.g., a 24 or 48 track mixer), an audio input/output interface, an audio format converter, and one or more signal processing functions. Controls may be presented to a user through a GUI represented as a graphical representation of familiar hardware components, such as a mixing console (e.g., with faders and cans), a sound recorder (e.g., with play/stop/pause buttons), and a frequency response output plot. The user input 106 includes an interface that allows the user to graphically manipulate GUI input and display controls as if the user were controlling an actual hardware device.

In an embodiment, the audio system 104 may include a number of signal processing modules that modify the audio stream 102 through functions such as filtering, gain control, and the like. One or more equalization functions may also be provided as part of the product 104. Alternatively, the balancing function may be provided by a plug-in 108, which plug-in 108 interfaces with the product software via an API (application programming interface) or similar mechanism. With respect to the following disclosure, although embodiments may be described with respect to an equalizer or equalizer function provided by plug-in 108, it should be noted that such an equalizer may be implemented as an inherent or integrated equalizer within the audio system or software 104 thereof.

Equalizer 108 represents a graphical equalizer that achieves individual gain control for a particular frequency by setting a virtual slider or attenuator control. Fig. 2A illustrates an example graphical equalizer interface controllable via a GUI, according to some embodiments. As shown in fig. 2A, the graphic equalizer 202 includes a first row of sliders for one channel of a stereo audio file and a second row of sliders for a second channel. Each slider controls the gain of a particular frequency or frequency range centered around a particular frequency. The slider determines the gain setting (up or down, e.g., in the range of + -6 dB) for each corresponding frequency. The example of fig. 2A illustrates a 30 band graphic equalizer with center frequencies set at 3 bands per octave across 20Hz to 20kHz, starting from 26Hz, 31Hz, 40Hz, 50Hz, etc. up to the 20kHz spectrum. Other numbers of bands are common, but more than 3 bands per octave are generally rare. The graphic equalizer function implements a second order filter function in each of the frequency bands. The bandwidth definition (Q) around the center frequency of each band is typically fixed, but the level is adjustable by a slider. The GUI for the graphic equalizer may further include: a display area 204 that displays the frequency response of the combined effect set by the current EQ filter; and a real-time fourier-domain display of the audio output showing the effect on the audio signal when the slider control is changed.

In an embodiment, a user interface for the audio system 104 controls a graphic equalizer having a large number of filter bands, such as about 120 bands (12 bands per octave of the audio spectrum multiplied by 10 octaves in the frequency range). The interface is a hybrid between a conventional user interface for a graphical equalizer (e.g., shown in fig. 2A) and a user interface for a parameter or parameter-class equalizer (e.g., shown in fig. 2B). Fig. 2B illustrates an interface for a parameter equalizer and corresponding equalization functions that may be controlled through a user interface in accordance with some embodiments. The example of fig. 2B illustrates controlling this equalizer by a physical or user interface icon version of a rotary knob (as opposed to a slider of a graphical equalizer), however, it should be noted that there are many possible ways to define the settings of a parametric equalizer. For example, other types of potentiometers, such as switch rows, sliders, and drag control points on the curves on the GUI that depict the response of the filter, are other possible examples of UIs for parameter EQ. In general, a parametric equalizer consists of few filter elements (e.g., 1 to 4), however, each of those filter elements has more settings than any of the filter elements of the graphic equalizer, allowing the impact of a given filter element to be controlled in more detail, yet the implementation is more complex and each filter element requires more user controls, so there are rarely a large number of such filters in an audio system. For the embodiment of fig. 2B, the parametric equalizer settings include the level (e.g., increase or decrease), center or dominant frequency, and bandwidth or range (Q) of the equalizer's frequency response. Like the graphic equalizer, each frequency may be increased or decreased by a desired magnitude (+/-6 dB or +/-12 dB), but unlike the graphic equalizer, the center frequency across the entire spectrum may be controlled to be nearly any frequency as the frequency potentiometer sweeps across the entire spectrum, as opposed to the finite center frequency of the graphic equalizer. For example, while the graphic equalizer may have a control with a fixed center frequency of 20Hz at a fixed Q value, the parameter equalizer may be adjusted to control a center frequency of 15Hz, 25Hz, or 30Hz (etc.) with a variable Q value. The bandwidth (also referred to as Q) control determines the shape of the bell-shaped curve of the filter response to vary between a high and thin curve and a shallow and wide curve around a selected center frequency. The effect of using multiple parametric filter elements is that their individual responses increase together, with the resulting filter response covering the entire audio spectrum. In contrast, in a graphic equalizer, the center frequencies of the individual frequency bands are set such that they overlap each other only minimally and are thus substantially independent of each other.

Fig. 3 illustrates a graphical user interface display for a variable resolution equalizer under some embodiments. As stated above, equalizer interface 300 enables control of a substantially "hybrid" equalizer that combines a conventional user interface for graphical equalizer 316 and a user interface for a parameter or parameter-like equalizer. Specifically, the interface presents a fixed number of sliders (e.g., eight) to the user, as well as a way to specify the frequency range that the sliders or any subset of sliders control. For the example of interface 300, the frequency range control section includes three control knobs 304 through 308. The control knob adjusts the frequency range required for equalization, which includes a left frequency knob 304, a right frequency knob 308, and an offset knob 306, the offset knob 306 adding an offset to the frequency range specified by the right and left frequencies. The offset control 306 is generally provided for convenience, as the range may be explicitly selected with only left and right frequency knobs. Depending on the frequency range selected by control knobs 304 and 308 and the number (N) of available filter bands (i.e., filter elements implemented in the underlying equalizer implementation), a slider selection process is used to assign a range of adjacent EQ elements to each slider.

The GUI embodiment of FIG. 3 thus includes a method of enabling control of an audio equalizer by providing controls 316 to equalize frequency responses across an audio spectrum, wherein each control sets gain values assigned to a plurality of underlying EQ elements of the control, and a second set of controls (304, 306, 308) defining operation of the control 316. Control 304 sets a lower frequency limit and control 308 sets an upper frequency limit to define a frequency range, which in turn is used to determine the behavior of each attenuator 316. The slider selection process assigns a specific set of bottom EQ elements to each attenuator, which may include elements similar to the fixed center frequency and Q elements of the graphic EQ, and determines how the setting of the control affects the gain value that is thereby transferred to the bottom EQ elements. Determining the behavior of the fader using the slider selection process implies that the value transmitted by the fader to its underlying EQ element may or may not be linearly related to the setting of the fader control; in an embodiment, a smoothing, curve fitting, or other refinement may be utilized to achieve a desired resulting overall frequency curve for the equalizer system based on moving a given attenuator 316.

As an example, the embodiment of fig. 3 shows an underlying graphic EQ implementation of an equalizer (n=120) that is 120 bands, with bands 309 numbered from 1 to 120, with bands 1, 60, and 120 noted (note that the illustrations may not be drawn to scale exactly). For this example, the frequency range bars 304 and 308 are configured to cover the selected frequency band 315, such that the fully complementary 8 attenuators control these frequency bands. Although fig. 3 shows an EQ system having 120 frequency bands, embodiments are not so limited and N may be any practical number based on system capabilities and requirements. Thus, in the preferred embodiment, the graphic equalizer is a high-multiple frequency band EQ, and N may be any number, including up to 1000 frequency bands. Note that, in general, the width of each of the frequency bands 309 is constant.

In general, the equalizer control operates within an audio spectrum that includes 20Hz to 20kHz (10 octaves) (although a greater range is also possible). The first set of controls (graphic EQ) includes a set of M attenuators for a graphic equalizer implementation of N frequency bands, where N is any number between 30 and 1000, and M is any number much smaller than N, typically 8 or 16. The frequency range set by the second set of controls covers a K-band range, where K is the number of frequency bands included in the range, e.g. in case of n=120, then the frequency band/octave is 120/10 octave=12 frequency bands, so one octave range covers 12 frequency bands, 12 frequency bands covering 12 frequency bands per attenuator, and the minimum range set by the frequency range covers eight frequency band ranges having one frequency band per attenuator (n=120, m=8, k=8, 8/8=1 per attenuator frequency band).

Fig. 3 illustrates a general application of the variable resolution graphic equalizer GUI with respect to selecting a frequency range, dividing by the number of frequency bands, and assigning these frequency bands to attenuators. Other examples of possible configurations of the variable equalizer UI are as follows. For a first example, a user selects a frequency range spanning 2 octaves; this range spans a set of 24 filter elements (12 elements/octave 2=24); there are 8 attenuators available, so 3 EQ bands are automatically allocated to each attenuator (using a simple algorithm: 3 bands/attenuator=24 bands/8 attenuators). Depending on the selection process (which may include a smoothing sub-process to smooth the resulting value to more evenly match it to the adjacent frequency band), moving the attenuator thus results in tuning the 3 underlying EQ elements. For a second example, the user selects a frequency range spanning 10 octaves; this range spans a set of 120 filter elements (12 elements/octave 10=120); there are 8 attenuators available, so 15 EQ bands are automatically allocated to each attenuator (using a simple algorithm: 15 bands/attenuator = 120 bands/8 attenuators). Moving the attenuator results in tuning of the 15 underlying EQ elements. For a third example, the user selects a frequency range that spans 2/3 octaves; this range spans a set of 8 filter elements (12 elements/octave 2/3=8); there are 8 attenuators available, so 1 EQ band is automatically allocated to each attenuator (using a simple relationship: 1 band/attenuator=8 band/8 attenuator). Moving the attenuator results in tuning exactly one underlying EQ element, i.e. allows to control the underlying equalizer to the finest extent theoretically possible for the EQ implementation. This user interface thus works as a graphic equalizer with only 8 attenuators (and frequency range selector) for 120 attenuators. This reduced number of controls allows each control to be displayed larger (making it easier to operate on the GUI) while the resulting control group still occupies far less GUI footprint than the graphical EQ of 120 faders. In other words, this EQ interface improves usability and reduces screen footprint while maintaining the full frequency response adjustment capability of the underlying equalizer implementation.

As stated above, in the example of fig. 3, the bottom layer graphic EQ implementation is an N-element equalizer, where N is equal to 120 (12 bands/octaves 10 octaves in the range of 20Hz to 20 kHz). Such 120-band EQ may be provided by a lake EQ signal processing implementation, but other implementations are possible, and N may be any practical number (e.g., from 30 to 1000) depending on implementation requirements and system capabilities. For the 120-band embodiment of EQ316, there are eight attenuators, with each attenuator controlling a set of one or more graphical EQ bands; thus for a frequency range spanning 120 bands, each attenuator controls 15 bands (120/8=15). The number of frequency bands controlled by each attenuator is typically equal and is determined by the attenuator selection process. For example, given a frequency range of 1 octave, at 12 bands/octaves there are 12 available usable bands and 8 available attenuators, so the number of bands per attenuator is bands_in_frequency_range/number_of_faders, thus 120/8=15. Alternatively, a particular attenuator may be configured to control fewer or more frequency bands than other attenuators (e.g., where the bands_in_frequency_range/number_of_faders are not integers) depending on the particular slider selection process used. The operation of the faders in the graphic equalizer 316 is controlled by the setting of the frequency range control in section 310. The range bars 312 and 314 are controlled by the left frequency 304 and right frequency knob settings, respectively. In a touch screen implementation of the GUI, the range bars 312, 314 may be dragged directly on the screen by a user sliding the bars accordingly. These range bars define a frequency range, which in turn defines the number of EQ frequency bands controlled by each attenuator.

Thus, for the example of fig. 3, if the frequency range is set to a width of 2 octaves, this corresponds to 3 bands per attenuator (2 octaves 12 bands/octaves = 24 bands, 24 bands/8 attenuators = 3 bands/attenuators). If the frequency range is narrowed to a range of 8 frequency bands, there will be one frequency band per attenuator, and if the frequency range is widened to a range of 32 frequency bands, there will be 4 frequency bands per attenuator. This relationship applies to the case where there are eight attenuators 316, and other configurations of the number of attenuators are also possible. The situation that the number of frequency bands in the frequency range is not divisible by the number of available attenuators can be solved in many possible ways; one way is to limit the user's choice of the width of the frequency range to be constrained to only the number of frequency bands that are exactly divided. Another possible improvement is to use only a subset of the available attenuators, for example to allow the use of a band range count that is divisible by 7 or 6 instead of divisible by 8 only. It is also possible to make more sophisticated algorithms, or simpler algorithms, that can dither values to meaningfully distribute the frequency bands among the available attenuators, such as manually selecting the number of frequency bands/attenuators via dedicated controls; other solutions are also possible.

The offset control knob 306 moves the frequency range defined by the range bar along the continuous frequency range 20Hz to 20 kHz. The number of graphic EQ bands controlled by each attenuator may change as the width of the frequency range changes. For example and as shown in fig. 4, for frequencies from 20 to 1000Hz, the range bar may be set to a narrow frequency range (i.e., containing a small number of frequency bands, e.g., 8) (panel 402); the range bar may be set to contain a greater number of frequency bands, say 24 (panel 404); or it may be set to a width of 100 bands (panel 406). Fig. 4 is intended to provide only an example illustration and any possible setting of a configurable range bar control, and the band line 309 is not shown for clarity. It should be noted that a simple implementation may choose to limit the user's choice of width with the frequency band count divided by the number of attenuators available (e.g., by any integer between 1 and 8). It is also possible that a user may intentionally want to limit the number of faders, for example if they intend to assign these controls to a programmable hardware control surface having only a certain number of available assignable controls, for example 4 controls.

The embodiment of fig. 3 illustrates selecting a frequency range 315 controlled by a graphical EQ control (fader) 316, as set by left frequency control 304 and right frequency control 308 with optional offset 306. In alternative embodiments, the selected frequency range 315 may also be set by alternative controls of the second set of controls, such as a selector for "number of fader bands" e.g., 1 to 15 in the case of 120 bands and 8 faders, and an offset control to move the currently selected range along the audio range. Furthermore, the number of bands per attenuator may be specified separately for each attenuator, and the number of bands may be a very wide range; for example, if the frequency ranges are matched for a total of one correction, then a 32 band attenuator would be useful. For this embodiment, the width of the attenuator, as displayed in the GUI, may be somewhat proportional to the number of frequency bands it controls. In this way, the variable resolution of each attenuator may be changed in the GUI to substantially or proportionally match the respective resolution of the frequency range selection. In another alternative embodiment, the system and GUI may be configured to contain and control frequency bands that extend beyond the audible frequency range. For example, a lake EQ implementation uses 120 bands of 20Hz to 20kHz, but generally includes even more bands above and below the range, for a total of 131 bands (i.e., where the central 120 bands are 20 to 20 k). This illustrates that in general, the number of frequency bands is not essentially critical, and that any number of frequency bands over the various spectrums of interest are possible.

In some embodiments, the interface additionally provides controls for specialized operations (e.g., curve smoothing) on two or more frequency bands. It is also possible to apply some algorithms during operation of the interface to determine the vertical displacement (i.e., gain change) of each band. For example, if a user raises a slider that affects several frequency bands, the values of all frequency bands mapped to the slider may be raised by the same size, or alternatively the frequency bands near the edges of the range may be moved somewhat less ("scaled") to transition less abruptly to the adjacent region. Similarly, the overall frequency band range may appear as some sort of functional or type shape (e.g., sine wave) that controls the relationship between moving a single control slider and its effect on each individual frequency band mapped to the slider.

In an embodiment, the hybrid equalization interface may be implemented or provided as a plug-in application for certain audio processing software, such as Avid Pro tools, or it may be integrated into any product that uses multi-band EQ technology, such as dolby CP850 movie processor or any other equalizer with a large number of filter bands. The hybrid equalization interface may also be embodied as a stand-alone user interface control for a large multi-band equalizer. This user interface may even be applied in other domains, where a series of points define a curve that must be manipulated, such as a scientific device.

It should be noted that components referred to as "control knobs," "attenuators," "sliders," "rotary knobs," and other similar descriptors may be implemented as potentiometers (variable resistors) in the form of rotary switches, linear switches, or other variable resistance devices, and may be implemented as hardware components or virtual hardware (software) components that control some audio processing or DSP processing, such as gain control, as described herein. The components may also be implemented by other techniques, such as a two-finger touch screen gesture (e.g., a "pinching" motion to adjust the frequency range).

The user interface for the hybrid equalizer may include other graphical user elements and display areas to serve as a stand-alone product or plug-in to other audio system software (or hardware) components. Fig. 5 illustrates an example hybrid equalizer incorporated into an equalizer GUI under some embodiments. As shown in fig. 5, the interface display is comprised of a plurality of different display regions, including a control region 504, a frequency response and EQ curve display region 506, a graphic EQ attenuator display region 508, and an attenuator control region 510. Control region 504 contains some input regions that control or invoke functions for the equalizer. The start, end and move buttons correspond to the left/right/offset control knobs shown in fig. 3. The display areas corresponding to these settings are shown as highlighted areas 507 in the EQ curves within the frequency response display area 506. Some other functions related to the selection process and settings may also be included in region 504; some examples are shown. The graphic EQ attenuator control area 508 is below the frequency response display area 506. As previously described, the frequency range defined by the setting of the selection control knob 502 affects the behavior of the attenuators, and one possibility is that some attenuators will be active and others will be inactive (e.g., if the number of frequency bands in the frequency range is divisible by 7 but not divisible by 8, only 7 attenuators may be active). The display area 509 is indicating that only 3 of the 8 faders are currently active. The selection of the attenuator 509 may change as the selection region 507 moves along the frequency response display region 506. The fader count selection control 505 may allow a user to select between 8 and 16 faders, as one number or other number may be more appropriate depending on the size of the available display area and ease of use (e.g., control size) considerations. Some other functions related to attenuator selection and setting may also be included, as shown (but not limited to those shown) in the optional control display area 510.

It should be noted that the components and arrangement of GUI elements in fig. 5 are intended for illustrative example purposes only, and embodiments are not so limited. Many other configurations and components may be used or included, depending on the system requirements and application. Standard GUI features such as highlighting, color coding, mouse-over text insertion, hidden controls, etc. may be used in conjunction with the GUI display of fig. 5.

The variable resolution graphic equalizer described herein provides an improved way of controlling gain values across the entire audio spectrum using a number of narrowband filters, such as (but not limited to) 120 filter elements. The variable resolution graphic equalizer provides the ability to select a frequency range for equalization and automatically map a set of sliders to the selected range based on the number of filter bands that fall within the selected range.

Although the embodiments have been described with respect to implementations as software programs for use with a software DAW, it should be noted that such embodiments may also be incorporated in a hardware equalizer. For hardware system embodiments, the audio processor may implement analog and/or digital circuitry to process audio content provided in an analog or digital format.

Embodiments are also implemented in certain sound processors, such as a CP850 dolby panoramic sound movie processor for use with movies and 3D audio content, but any other similar movie audio or professional/consumer audio processing may also be used.

Throughout the description and claims, unless the context clearly requires otherwise, the word "comprise" and the like should be construed in an inclusive sense as opposed to a exclusive or comprehensive sense; i.e., as "including but not limited to". Words using the singular or plural number also include the plural or singular number, respectively. In addition, the words "herein" and "hereinafter" and words of similar import refer to the present application as a whole and do not refer to any particular portions of this application. When the word "or" is used in reference to a list of two or more items, the word encompasses all of the following interpretations of the word: any one of the items in the list, all of the items in the list, and any combination of the items in the list.

While one or more implementations have been described by way of example and in accordance with specific examples, it should be understood that one or more implementations are not limited to the disclosed examples. On the contrary, it is intended to cover various modifications and similar arrangements as will be apparent to those skilled in the art. The scope of the appended claims is, therefore, to be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.

Illustrative embodiments

Embodiments relate to a method of implementing control of an audio equalizer by: providing a first set of controls to equalize frequency response over the audio spectrum, wherein each control in the first set of controls sets a gain value for a respective center frequency; and providing a second set of controls that specify a frequency range within the audio spectrum, which in turn determines the number of bands of the audio spectrum controlled by each control in the first set of controls. In this method, the first set of controls may be provided as attenuators implemented as linear variable resistive devices in a graphical equalizer format, and the second set of potentiometers may be provided as rotary knobs in a parametric equalizer format. The first set of controls and the second set of controls may include graphical user interface elements that control frequency-specific gain characteristics over an audio spectrum of a digital audio stream processed in the digital audio system. The first set of controls and the second set of controls may include hardware components that control gain characteristics over an audio spectrum of audio content processed in an analog or digital audio processing system.

Embodiments further relate to a method of implementing control of an audio equalizer for N frequency bands, where N+.30, the method comprising: providing a first set of M controls, where M < N, for equalizing a frequency response over the audio spectrum by controlling gain values of frequency bands of the audio spectrum; and providing a second set of controls that specify a frequency range within the audio spectrum, wherein K frequency bands of the audio spectrum that belong to the specified frequency range are allocated to the first set of M controls for controlling the corresponding K gain values by the first set of M controls.

In an embodiment of any of the above methods, the second set of controls is configured to enable adjustment of the size of the specified frequency range, i.e. to increase or decrease the selected frequency range, to thereby adjust the number of frequency bands K controlled by the first set of M controls.

In an embodiment of any of the methods described above, the second set of controls is configured to limit the frequency range to be designated as K-divisible by M, and after designating the frequency range as K frequency bands, K/M frequency bands are assigned to each control of the first set of M controls. In another embodiment of any of the methods above, the second set of controls is configured to limit the designation of the frequency range as K may be divided by a frequency range of integers greater than 1 and less than or equal to M, and after designating the frequency range as K frequency bands, Z controls in the first set of M controls are selected and K/Z frequency bands are assigned to the selected Z controls in the first set of M controls. Optionally, the second set of controls is further configured to limit the frequency range designated as K+.M.

In an embodiment of any of the above methods, the audio spectrum comprises 20Hz to 20kHz (10 octaves), the first set of controls comprises a set of M attenuators for a graphic equalizer implementation of N frequency bands (where N is any number between 30 and 1000 and M is any number much smaller than N, typically 8 or 16), further wherein the frequency range set by the second set of controls covers a range of K frequency bands (where K is the number of frequency bands included in the range, e.g. in the case of n=120, then the frequency band/octave is 120/10 octaves = 12 frequency bands, so one octave range covers 12 frequency bands), the range of K frequency bands covers 12 frequency bands per attenuator, and the minimum range set by the frequency range covers eight frequency band ranges with one frequency band per attenuator (n=120, m=8, k=8, per attenuator frequency band=8/8=1).

The first and second sets of controls may be provided as software elements in a software implemented equalizer program, and wherein the frequency range set by the second set of controls is displayed as a first highlighted region of a frequency response graph of the graphical user interface, and the selected fader in the first set of controls and corresponding to the range may be displayed in a second highlighted region of a graphical equalizer portion of the graphical user interface. The method may implement curve smoothing between two or more adjacent frequency bands when their values are controlled by the attenuator according to an algorithm. Embodiments further relate to an equalizer system that adjusts gain values of frequency components across a frequency spectrum, the equalizer system having: a first set of equalizer controls including a plurality of attenuators, each attenuator setting a set of gain values for a filter, each gain value being set to a neighboring but unique center frequency in the frequency spectrum; and a second set of equalizer controls that select a frequency range for equalization as controlled by the first set of equalizer controls and automatically map a subset of the attenuators in the plurality of attenuators to the selected frequency range based on a number of filter bands belonging within the selected frequency range. A second set of controls selects a frequency range that defines the number of frequency bands in the range and algorithmically determines a mapping of the set or subset of attenuators to the selected frequency range. The first set of equalizer controls may include a graphical equalizer having 8 or 16 (or any other integer number) individual faders. In an embodiment, the graphical equalizer user interface controls a 120-band equalizer having 120 (or any number of 30-1000) individual narrowband filters applying gain values set by a plurality of attenuators.

Embodiments further relate to an equalizer system that adjusts gain values for N frequency bands over an audio spectrum, where N+.30, the equalizer system comprising: a first set of M equalizer controls for setting gain values for bands of the audio spectrum, where M < N; and a second set of equalizer controls that selects a frequency range for equalization by the first set of M equalizer controls, wherein K frequency bands that fall within the selected frequency range are allocated to the first set of M controls for controlling corresponding K gain values by the first set of M controls.

In an embodiment of any of the above systems, the complete subset of attenuators includes a range of 120 frequency bands (or any number N,30 to 1000) for eight (or any number F, e.g., 4 to 100) attenuators, with each attenuator having a frequency band, and the smallest subset of attenuators includes a range of eight frequency bands, with each attenuator having a frequency band. The equalizer system may be a hardware component for a hardware or software based audio processing system. The equalizer system may be a software program used in a digital audio system having a Graphical User Interface (GUI) to facilitate control of a product used to make or reproduce audio. For a software embodiment, a first set of equalizer controls is displayed as a virtual graphical equalizer component having faders as user-controllable graphical icons, and wherein a second set of equalizer controls provides a way to establish a frequency range, for example, by using a user-controllable rotary knob. The selected frequency range may be displayed as a highlighted portion of the frequency response portion of the GUI, and wherein the subset of attenuators is displayed as a highlighted portion of the virtual graphical equalizer component.

Embodiments are still further directed to a graphical user interface for controlling a graphical equalizer in a digital audio system, the graphical user interface having: a frequency response display area showing a frequency response curve over a frequency spectrum for an audio program; a graphic equalizer display area showing a plurality of attenuators controlling gain values of respective center frequencies of the spectrum; and a set of controls that allow a frequency range to be selected for equalization by the graphic equalizer stage and automatically map an attenuator subset of the plurality of attenuators to the selected frequency range based on a number of filter bands belonging within the selected frequency range. The selected frequency range is typically displayed as a highlighted portion of the frequency response display area, and wherein the subset of attenuators is displayed as a highlighted portion of the graphic equalizer display area. The attenuators may include 8 or 16 (or any other number) individual attenuators. The graphic equalizer includes an N-band equalizer having N individual narrowband filters applying gain values set by a plurality of attenuators, where N is any number between 30 and 1000. In an embodiment, a set of controls displayed in the display area defines a left frequency marker, a right frequency marker, and optionally a shift knob for panning the markers together up or down in the 20Hz to 20kHz audio range.

Embodiments are still further directed to a graphical user interface for controlling a graphical equalizer for N frequency bands in a digital audio system, where N+.30, the graphical user interface comprising: a frequency response display area showing a frequency response plot over the frequency spectrum of the audio program; a graphic equalizer display area showing a plurality of M first controls controlling gain values of bands of a spectrum, where M < N; and a second set of controls that enable: selecting a frequency range for equalization by the M first controls; a subset of the plurality of M first controls is mapped to K frequency bands belonging to the selected frequency range for controlling corresponding K gain values by the subset of first controls.

In an embodiment, the subset may include less than M first controls, but may also include all M first controls.

Various aspects of the present invention may be appreciated from the example embodiments (EEEs) listed below.

EEE 1. A method of implementing control of an audio equalizer, comprising:

providing a first set of controls to equalize frequency response over the audio spectrum, wherein each control in the first set of controls sets a gain value for a respective center frequency; and

a second set of controls is provided that specifies a frequency range within the audio spectrum, which in turn determines the number of bands of the audio spectrum controlled by each control in the first set of controls.

EEE 2. The method according to enumerated example embodiment 1, wherein the first set of controls is provided as attenuators implemented as linear variable resistive devices in a graphical equalizer format, and wherein the second set of potentiometers is provided as rotary knobs.

EEE 3. The method according to enumerated example embodiment 1, wherein the first and second sets of controls comprise graphical user interface elements that control frequency-specific gain characteristics over the audio spectrum of a digital audio stream processed in a digital audio system.

EEE 4. The method according to the enumerated example embodiment 1, wherein the audio spectrum comprises 10 octaves of 20Hz to 20kHz, and wherein the first set of controls comprises a set of M attenuators for a graphic equalizer implementation of N frequency bands, further wherein the frequency range set by the second set of controls encompasses the range of K frequency bands.

EEE 5. The method of example embodiment 4, where N is any number between 30 and 1000 and M is any number much smaller than N, such as in the range of 8 to 24, and where K is the number of frequency bands included in the range.

EEE 6. The method of example embodiment 5 as enumerated, wherein the first and second sets of controls are provided as software elements in a software-implemented equalizer program, and wherein the frequency range set by the second set of controls is displayed as a first highlighted region of a frequency response graph of the graphical user interface, and wherein selected attenuators in the first set of controls and corresponding to the range are displayed in a second highlighted region of a graphical equalizer portion of the graphical user interface, the method further comprising implementing curve smoothing between two or more adjacent frequency bands when their values are controlled by one or more attenuators.

EEE 7. An equalizer system for adjusting gain values of frequency components across a spectrum, comprising:

a first set of equalizer controls comprising a plurality of attenuators, each attenuator setting a gain value for a set of filters, the gain values each being set to a neighboring but unique center frequency in the spectrum; and

a second set of equalizer controls that selects a frequency range for equalization as controlled by the first set of equalizer controls and automatically maps a subset of attenuators of the plurality of attenuators to the selected frequency range based on a number of filter bands belonging within the selected frequency range.

EEE 8. The system of example embodiment 7 as enumerated wherein the second set of controls selects a frequency range defining the number of frequency bands in the range and algorithmically determines a mapping of the set or subset of attenuators to the selected frequency range.

EEE 9. The system according to enumerated example embodiment 8, wherein the equalizer system is one of: a hardware component for a hardware or software based audio processing system, or a software program for use in a digital audio system having a Graphical User Interface (GUI) to facilitate user control of a product for producing or reproducing audio.

EEE 10. The system according to enumerated example embodiment 9, wherein the first set of equalizer controls is displayed as a virtual graphical equalizer component having the fader as a user-controllable graphical icon, and wherein the second set of equalizer controls provides a way to establish a frequency range, for example, by using a user-controllable rotary knob.

EEE 11. The system according to the enumerated example embodiment 10, wherein the selected frequency range is displayed as a highlighted portion of the frequency response portion of the GUI, and wherein the subset of attenuators is displayed as a highlighted portion of the virtual graphical equalizer component.

EEE 12. A graphical user interface for controlling a graphical equalizer in a digital audio system, comprising:

a frequency response display area showing a frequency response curve over the frequency spectrum of the audio program;

a graphic equalizer display area showing a plurality of attenuators controlling gain values of respective center frequencies of the spectrum; and

a set of controls that allow a frequency range to be selected for equalization by the graphic equalizer stage and automatically map a subset of attenuators of the plurality of attenuators to the selected frequency range based on a number of filter bands belonging within the selected frequency range.

EEE 13. The graphical user interface according to enumerated example embodiment 12, wherein the selected frequency range is displayed as a highlighted portion of the frequency response display area, and wherein the subset of attenuators is displayed as a highlighted portion of the graphical equalizer display area.

EEE 14. A graphical user interface according to an enumerated example embodiment 13, wherein the graphical equalizer comprises an N-band equalizer having N individual narrow band filters applying gain values set by the plurality of attenuators, and wherein N is any number between 30 and 1000.

EEE 15. A graphical user interface according to the enumerated example embodiment 14, wherein a set of controls displayed in the display area defines a left frequency marker, a right frequency marker, and optionally an offset knob for panning the markers together up or down in the 20Hz to 20kHz audio range.

Claims

1. A method of implementing control of an audio equalizer for N frequency bands, where n+.30, the method comprising:

providing a first set of M controls, where M < N, for equalizing a frequency response over an audio spectrum by controlling gain values of frequency bands of the audio spectrum;

providing a second set of controls that specify a frequency range within the audio spectrum, the specified frequency range comprising K frequency bands of the audio spectrum;

assigning one or more unique frequency bands of the K frequency bands to respective ones of the first set of M controls; a kind of electronic device with high-pressure air-conditioning system

The specified frequency range is displayed through a graphical user interface, wherein the M controls are displayed as highlighted portions of a graphical equalizer display area of the graphical user interface, and wherein left and right frequency markers displayed in the display area indicate lower and upper boundaries of the specified frequency range.

2. The method of claim 1, wherein the first set of M controls are provided as faders and/or the second set of controls are provided as rotary knobs, and wherein each fader sets a gain of the one or more unique frequency bands of the K frequency bands assigned to the respective control.

3. The method of claim 1 or 2, wherein the first and second sets of M controls comprise graphical user interface elements that control frequency-specific gain characteristics over the audio spectrum of a digital audio stream processed in a digital audio system and wherein graphically displayed offset knobs pan the left and right frequency markers together up or down within the audio spectrum.

4. The method of claim 1 or 2, wherein the audio spectrum comprises 10 octaves of 20Hz to 20 kHz.

5. The method of claim 1 or 2, wherein N is any number between 30 and 1000 and/or M is in the range of 8 to 24.

6. The method of claim 1 or 2, wherein the second set of controls is configured to enable adjustment of the size of the specified frequency range, thereby adjusting K.

7. The method of claim 1 or 2, wherein the second set of controls is configured to limit the frequency range specified as K-available-by-M frequency ranges, and wherein after specifying a frequency range as K frequency bands, K/M frequency bands are assigned to each control in the first set of M controls.

8. The method of claim 1 or 2, wherein the second set of controls is configured to limit the frequency range to be designated as K possible by an integer greater than 1 and less than or equal to M, and wherein after designating a frequency range as K frequency bands, Z controls of the first set of M controls are selected and K/Z frequency bands are assigned to the selected Z controls of the first set of M controls.

9. The method as recited in claim 8, further comprising:

two or more adjacent frequency bands are smoothed because their values are controlled by one or more controls in the first set of controls.

10. An equalizer system for adjusting gain values of N frequency bands over an audio spectrum, wherein n+.30, the equalizer system comprising:

a first set of M equalizer controls for setting gain values for a frequency band of the audio spectrum, where M < N;

A second set of equalizer controls that selects a frequency range for equalization by the first set of M equalizer controls, the selected frequency range comprising K frequency bands, wherein each of one or more unique frequency bands of the K frequency bands is assigned to a respective control of the first set of M controls; a kind of electronic device with high-pressure air-conditioning system

Displaying a graphical user interface of the selected frequency range, wherein the M controls are displayed as highlighted portions of a graphical equalizer display area of the graphical user interface, and wherein left and right frequency markers displayed in the display area indicate lower and upper boundaries of the selected frequency range.

11. The system of claim 10, wherein the equalizer system is one of: a hardware component for a hardware or software based audio processing system, or a software program for use in a digital audio system having a graphical user interface GUI to facilitate user control of a product for producing or reproducing audio, wherein optionally:

the first set of M equalizer controls includes M faders and is displayed as a virtual graphical equalizer component having M faders as user-controllable graphical icons and the second set of equalizer controls provides a way to establish a frequency range.

12. The system of claim 11, wherein the second set of equalizer controls establishes a frequency range using a user-controllable rotary knob.

13. A graphical user interface for controlling a graphical equalizer for N frequency bands in a digital audio system, wherein n+.30, the graphical user interface comprising:

a frequency response display area showing a frequency response plot over an audio frequency spectrum of the audio program;

a graphical equalizer display area showing a plurality of M first controls controlling gain values of bands of the audio spectrum, where M < N; and

a second set of controls that enable selection of a frequency range for equalisation by the M first controls; mapping a subset of the plurality of M first controls to the K frequency bands belonging to the selected frequency range for controlling the corresponding K gain values by the subset of first controls,

wherein the selected frequency range is displayed as a highlighted portion of the frequency response display area, and wherein a subset of the first controls is displayed as a highlighted portion of the graphical equalizer display area, and wherein a left frequency marker indicating a lower boundary of the frequency range selected by the second set of controls and a right frequency marker indicating an upper boundary of the frequency range selected by the second set of controls are displayed in the frequency response display area.

14. The graphical user interface of claim 13, wherein the second set of controls includes an offset knob for translating the left frequency marker and the right frequency marker together up or down.