GB2600692A

GB2600692A - Displaying attributes of a time-varying signal

Info

Publication number: GB2600692A
Application number: GB2017324.1A
Authority: GB
Inventors: Jack Wise Tomos
Original assignee: Solid State Logic Ltd
Current assignee: Solid State Logic Ltd
Priority date: 2020-11-02
Filing date: 2020-11-02
Publication date: 2022-05-11
Also published as: GB202017324D0

Abstract

Attributes of one or more time varying signals are displayed, in which a background colour 312 is adopted in response to a first attribute and a spatially movable pointer or needle 104 moves relative to the background in response to a first time varying signal. The coloured background may change colour from e.g. green to red to represent the mode of operation of the meter, a peak value of the signal, or a second signal. The pointer may show the signal average over time. The meter display may be emulated by a computer on a screen. The meter may form part of a multi-channel audio mixing desk. The pointer may represent attenuation in a compression process and the background colour may show gain in an amplification process. Alternatively, the colour may represent peak versus average compression mode. A second pointer may also be displayed showing a second audio channel for stereo sound. In this case the background colour indicates phase difference between left and right channels.

Description

Displaying Attributes of a Time-Varying Signal

CROSS REFERENCE TO RELATED APPLICATIONS

This is the first application for a patent directed towards the invention and the subject matter.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for visually displaying attributes of a time varying signal.

It is known to display volume levels of time varying signals using meters, which tend to average out signals. As an alternative, it is also known to provide devices that illuminate if a signal exceeds a predetermined threshold.

However, in known systems, the amount of information presented to an operative at any one location is limited.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided an apparatus for visually displaying attributes of a time-varying signal, as set out in claim 1. According to a second aspect of the present invention, there is provided a method of visually displaying attributes of a time-varying signal, as set out in claim 11.

Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings. The detailed embodiments show the best mode known to the inventor and provide support for the invention as claimed. However, they are only exemplary and should not be used to interpret or limit the scope of the claims. Their purpose is to provide a teaching to those skilled in the art. Components and processes distinguished by ordinal phrases such as "first" and "second" do not necessarily define an order or ranking of any sort.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS Figure 1 shows a rack-mountable audio compressor; Figure 2 shows an exploded view of the magnetoelectric meter identified in Figure 1; Figure 3 shows three images of the magnetoelectric meter identified in Figure 1; Figure 4 illustrates deployment of the invention within a digital audio workstation; Figure 5 illustrates deployment of the invention within an audio mixing desk; Figure 6 details a rendered image, showing a virtual version of the embodiment described with reference to Figure 1; Figure 7 shows an embodiment for selectively monitoring input gain or output gain; Figure 8 shows an embodiment in which compression mode is indicated; Figure 9 shows an embodiment in which a second time varying signal controls the adoption of background colour; Figure 10 shows a compressor in which colour adoption is selected and held to show the presence of peak levels; Figure 11 details the meter time constant emulator process identified in Figure 10; Figure 12 details the peak hold and hue calculation process identified in Figure 10; Figure 13 illustrates time varying signals being selected from different audio channels; Figure 14 shows a side chain compressor with background colour selection determined by makeup gain levels; Figure 15 shows an embodiment including a gate and a compression process, where a background colour is adopted to show the status of the gate; and Figure 16 shows an embodiment of a meter having two needles showing levels of respective stereo signals with background colour adoption indicating the relative phase between the stereo channels.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Figure 1 A rack mountable audio compressor 101 is shown in Figure 1, having a magneto-electric meter 102. The magneto-electric meter 102 is an example of an apparatus for visually displaying attributes of time-varying signals. The meter includes a display region having a background 103. However, unlike standard meters, a colour for background 103 is adopted in response to a first attribute.

A spatially moving element, in this example a needle 104, is configured to move relatively to the background 103 in response to a first time-varying signal. In this example, the first time-varying signal represents a level of attenuation or gain reduction deployed in response to a compression control signal.

In this example, a first button 111 activates the compressor, such that compression is applied to an input signal resulting in a compressed output signal, as described with reference to Figure 10.

A second button 112 may be selected when the device is to be configured to operate as a side chain compressor, wherein the control signal is derived from an alternative audio source, as described with reference to Figure 13.

A first rotary control 121 allows a threshold level to be defined. This represents the audio level at which compression will start to take effect. A second rotary control 122 allows an attack parameter to be determined, specifying the rate at which the compression process will start to take effect. A third rotary control 123 allows a ratio to be specified, thereby determining the extent to which the audio signal is compressed when it exceeds the threshold. A fourth rotary control 124 allows a release parameter to be specified, to set the rate at which compression is removed when the input signal falls below the threshold. A fifth rotary control 125 allows a makeup gain value to be specified, thereby controlling the extent to which the compressed signal is subsequently amplified in order to optimise the available dynamic range.

Figure 2 An exploded view of the magneto-electric meter 102 is shown in Figure 2. In this example, an ammeter is fed from a full wave rectifier, such that a current received from a first processing system 202 causes an angular displacement of the needle 104. In implementations of this type, the needle 104 will have mass, which in turn will reduce the rate of response; resulting in an integrating or smoothing of the input signal. Thus, in graphical representations of needles of this type, as described with reference to Figures 4 to 6, the ballistics of the needle should be taken into account if realistic needle to movement is to be emulated on a visual display unit.

In an embodiment, the meter includes one or more colour-selectable light-emitting devices, thereby allowing the colour of the light emitted by the light-emitting devices to be selected in response to the adoption of a background colour. In the example shown in Figure 2, three light-emitting devices are provided, identified as a first light-emitting device 211, a second light-emitting device 212 and a third light-emitting device 213.

A device driving circuit 214 provides four lines to the light-emitting devices representing a power line 215, a ground line 216, a clock line 217 and a data line 218. The data line 218 specifies the colour of the light emitting devices, with this data being clocked from the first device, to the second device and then onto the third device in response to the clock signal provided on clock line 217. However, as will be appreciated, other protocols may be adopted for supplying colour data to the light-emitting devices in alternative embodiments.

In order to evenly spread the colour generated by the light-emitting devices when viewed through the ammeter 201, a light diffuser 219 is positioned between the light-emitting devices and the ammeter.

Figure 3 Three images of the magneto-electric meter 102 are shown in Figure 3, at a first instant 301, a second instant 302 and the third instant 303.

At the first instant 301, colour data representing a first attribute are supplied to the background colour input 311, resulting in the adoption of a green background 312. A meter input 313 receives a time varying signal locating the needle 104 at needle position 314.

At the second instant 302, a background colour input 321 receives colour data representing a different value for the first attribute, resulting in the adoption of a blue background 322. A meter input 323 receives the first time-varying signal resulting in the needle 104 being located at needle position 324. Similarly, at the third instant 303, a background colour input 331 receives data for a first attribute having a different value again, resulting in the adoption of a red background 332. A meter input 333 receives the time-varying signal resulting in the needle 104 being located at needle position 334.

Figure 4 In the embodiment described with reference to Figures 1 to 3, the spatially movable element is implemented as a needle that rotates against a scale presented on a background. It should be appreciated that other types of spatially movable elements could be provided to convey substantially similar information. However, it is also recognised that the presentation of familiar elements is appreciated in many fields and as such, when implementing systems of this type digitally, it is sometimes desirable to retain the look and feel of previously deployed mechanical systems.

A general-purpose visual display unit 401 is shown in Figure 4, receiving video data from a computer system executing the instructions of a digital audio workstation. Manual input is provided by means of a keyboard 402 and a mouse 403. The digital audio workstation instructions present an operative with graphical user interfaces. These may include, for example, a timeline user interface 404, along with interfaces 405, 406 and 407 relating to particular effects; possibly supplied to the digital audio workstation environment in the form of plug-ins.

The third effects interface 407 is derived from executable instructions emulating the operations performed by the compressor described with reference to Figure 1. Thus, in this embodiment, the display region of the third effects interface 407 comprises an array of pixels and image data is rendered in response to the first attribute and the first time-varying signal; further details of which will be described with reference to Figure 6.

Figure 5 An audio mixing desk 501 is shown in Figure 5 that includes dedicated audio controls 502 and an image display panel 503. The image display panel includes a second visual display unit 504, substantially similar to that described with reference to Figure 4. Thus, within the audio mixing desk, it is possible for an array of pixels to be supported upon which image data is rendered in response to the first attribute and the first time-varying signal.

Again, in this embodiment, the spatially movable element is graphically represented as an angularly displaceable needle in the rendered image data.

Figure 6 A rendered image, of the type identified at 407 or of the type identified at 504 is detailed in Figure 6. Thus, in the digital audio workstation described with reference to Figure 4 or the audio mixing desk described with reference to Figure 5, a meter image 601 is presented, that emulates the physical needle described with reference to Figure 1.

In an embodiment, this image may be selected from a collection of stock images, such that the selected image presents the required data. Alternatively, in the present embodiment, functions are executed that generate the image data in response to receiving the first attribute and the first time-varying signal. In an embodiment, the background and the needle are drawn as separate elements, with the background adopting the appropriate colour.

A graphics framework is used that allows the elements to be drawn and different meter configurations may be selected from a library. Thus, in response to manual configurations, the first attribute and the first time-varying signal, it is possible to change properties of the image, such as the background colour, the needle position and the number of graduations.

In an embodiment, functions are provided within which parameters can be changed to alter components, such as the background colour, with a resulting image then being created in real time. In this way, a virtual needle 602 can be seen moving against a virtual background 603, with the colour of the background changing in response to the first attribute.

In the virtual image shown in Figure 6, the graphical user interface also provides a first virtual control 611 for controlling attack, a second virtual control 612 for controlling release, a third virtual control 613 for controlling the compression ratio, a fourth virtual control 614 for controlling the compression threshold and a fifth virtual control 615 for controlling the makeup gain; thereby displaying the graphical user interface to an operative in a way that is familiar.

Figure 7 The embodiments described herein provide a method of visually displaying attributes of a time-varying signal. A region with a background is displayed and a background colour is adopted in response to a first attribute. A spatially movable element is displayed over the background and the spatially movable element is moved relative to the background in response to a first-time varying signal.

This functionality may be deployed in many environments, many of which will go beyond the particular embodiments described herein which relate to the processing of audio signals. Many applications are possible and three broad application areas will be identified herein.

Firstly, a time varying signal may be processed within an environment capable of operating in different modes. Thus, it is possible for a time varying signal to be shown by the moving element (the meter) with the mode of operation being identified as the first attribute, such that the mode of operation will be made immediately clear to an operative by the colour of the meter being observed.

Secondly, it is possible for different properties of the same time varying signal to be displayed. Thus, for example, the meter could represent average values, due to the actual ballistics of a real meter or due to emulated ballistics of a virtual meter; with a background colour being adopted to represent peak values.

Thirdly, it is possible for the first attribute, controlling colour adoption, to be derived from a second time-varying signal, with the time varying signal, controlling element movement, been derived from the first time-varying signal. These two signals could be related in some way although, in alternative implementations, they could be derived from totally different sources. A situation of this latter type will be described with reference to a side chain compressor.

In an embodiment, a mode of operation is performed upon the first time-varying signal and the first attribute, controlling colour, may represent this operational mode. Consequently, a first background colour is adopted in response to selecting the first mode of operation and a second background colour is adopted in response to selecting the second mode of operation. An example of this approach is illustrated in Figure 7. The first time-varying signal is an audio signal but this signal could represent any other type of variable for which it is possible to process electrical representations thereof.

In the example, an input audio signal is processed to produce an output audio signal, a first mode of operation selects the input audio signal as the first time-varying signal and a second mode of operation selects the output audio signal as the first time-varying signal.

The input audio signal is received at an audio input 701 which is then supplied to an audio processor 702 via a first gain adjustment device 703. An output from the audio processor 702 is supplied to an audio output 704 via a second gain adjustment device 705.

A switch 706 is controlled by a manually controlled selector 707. In a first mode of operation, with the switch in the configuration shown in Figure 7, an output from gain adjustment device 703 is supplied to a meter 708, resulting in movement of needle 709 being determined by the output from gain adjustment device 703. In addition, the manually controlled selector 707 supplies a colour selection signal to the meter 708, thereby illuminating the meter in a first adopted colour. Thus, the meter may be shown in a green colour when this first selection is made.

In response to manual operation of the manually controlled selector 707, switch 706 may be placed in its alternative configuration, such that the meter needle 709 will be controlled in response to the output from the second gain adjustment device 705. Furthermore, in response to this manual operation, an alternative colour control signal is supplied to the meter 708 such that, for example, the meter may now adopt a blue colour.

To emphasise this functionality, in an embodiment, a green colour may be adopted for the first gain adjustment device 703 and a blue colour may be adopted for the second gain adjustment device 705. Thus, in this way, the input audio signal is modifiable in response to a first manual control and the output audio signal is modifiable in response to a second manual control. The first manual control is illuminated, or passively coloured, in the first background colour and the second manual control is illuminated, or passively coloured, in the second background colour. Thus, in an embodiment, the relevant colour could be deployed as a knob cap.

Figure 8 An alternative embodiment is shown in Figure 8, where the first time-varying signal is an audio signal and input signals are compressed by dynamically applying gain reduction. A first mode of operation performs an averaging compression mode, while a second mode of operation performs a peak compression mode. The spatially movable element is moved in response to the degree of gain reduction applied. A first background colour is adopted during the average compression mode and a second background colour is adopted during the peak compression mode.

An audio input 801 supplies an audio input signal to a dual mode compressor 802. An output signal from the dual mode compressor 802 is supplied to an audio output 803.

Movement of a needle 804 is controlled in response to an output from the dual mode compressor 802 representing applied gain reduction. A second signal from the dual mode compressor 802 identifies the compression mode adopted. Thus, in this way, the meter adopts a first colour of, say, green when the average compression mode is selected, with a second colour of say blue being adopted when the peak compression mode is selected.

Figure 9 In the examples described with reference to Figure 7 and Figure 8, the spatially movable element receives a time varying signal but the background colour was adopted in response to a mode selection. In the embodiment shown in Figure 9, the first attribute is also a time-varying signal, which may be identified as a second time-varying signal. The first time-varying signal and the second time-varying may be derived from a third time-varying signal.

In the example shown in Figure 9, the third time varying signal takes the form of an audio input signal received at an audio input 901 and supplied to an audio output 902. A first processor 903 receives the audio input signal (the third time varying signal) to produce the first-time varying signal which is used to control movement of a (virtual) needle 904. A second processor 905 also receives the audio input signal and supplies a second time varying signal to

control the adoption of the background colour.

Figure 10 An embodiment is shown in Figure 10 in which the third time varying signal is an audio-related compression-control signal, in which the first time-varying signal indicates gain reduction values specified by the compression control signal. The second time-varying signal (controlling the adoption of background colour) indicates held peak values of the compression control signal.

An audio input 1001 receives an audio input signal and an output signal is supplied to an audio output 1002. Compression is achieved by use of a variable gain process 1003, which in turn provides an input to an output signal process 1004 followed by a makeup gain process 1005.

The input audio signal is supplied to a signal processing environment 1006 before being supplied to a level detection process 1007. The level detection process 1007 determines the extent to which gain reduction is required, taking account of the predetermined threshold, ratio, attack and release as previously described.

In addition to controlling the variable gain process 1003, the output from the level detection process 1007 is supplied as a first time-varying signal to a meter 1008 and as a second time-varying signal to the meter 1008. The first-time varying signal is supplied via a meter-time-constant-emulator process 1009, described further with reference to Figure 11. The second time varying signal, for adopting background colour, is supplied to the meter 1008 via a peak-hold and hue-calculation process 1010, described further with reference to Figure 12.

Figure 11 The meter time constant emulator process 1009 identified in Figure 10 is detailed in Figure 11. At step 1101, angle calculation is performed to determine the position of the needle as displayed against the meter background. Thereafter, at step 1102, a stage selection is made, to determine whether the compression process is in its attack stage, that is to say ramping up the degree of applied compression or whether it is in its release stage where the applied compression is being removed.

When implemented digitally, it is possible to emulate the characteristics of a real mechanical meter of the type described with reference to Figure 1.

However, it is also possible to change these characteristics to enhance the usefulness of the information conveyed to an operative. Thus, in this embodiment, the averaging effect of a real meter is seen as a disadvantage, in that it reduces the ability of the operative to perceive peak values.

Consequently, on selecting the attack portion at step 1102, the needle is drawn immediately at step 1103; thus, without delay, a needle-drawing process is performed at step 1103.

However, if it is determined that the compressor is in its release state, a low-pass filtering process is performed at step 1104 before invoking the draw-needle process at step 1103. Thus, the needle will experience a rapid response during the attack phase with a filtered slower response during the release phase.

Figure 12 The peak-hold and hue-calculation process 1010 identified in Figure 10 is detailed in Figure 11. As previously described, the moving needle tracks the gain reduction signal with just a little delay during the release period. In this way, it is possible for an operative to see peak values and take appropriate action. However, it is appreciated that in some environments, exceeding a peak value can create significant problems. Consequently, the second time varying signal indicates these peak values and, in the embodiment, holds them for a predetermined interval; such that they become more apparent to an operative. Thus, while the needle itself may decay away from a peak value, thereby tracking the gain reduction signal reliably, changes to the background colour will persist when a peak threshold has been exceeded.

At step 1201, a threshold detection process is performed asking, on a sample-by-sample basis, whether a threshold has been exceeded. When answered in the affirmative, a peak hold timer is started at step 1202. Thereafter, at step 1203, a particular colour is adopted to confirm that a peak value has occurred which, in an embodiment, is a red colour.

In process 1010 of this embodiment, colour selection is made with reference to hue values, such that the colours themselves are represented in a colour space within which hue can easily be identified. However, for display on conventional visual display units, it is necessary to convert these values of variable hue (with constant luminance and saturation) to red green blue (RGB) colour space, with the conversion being performed at step 1204.

When the question asked at step 1201 is answered in the negative, to the effect that a sample does not exceed the threshold, a question is asked at step 1205 as to whether the timer has expired. If the question asked at step 1205 is answered in the negative, the peak red colour is held at step 1203, resulting in the meter background retaining its red hue.

Alternatively, if the question asked at step 1205 is answered in the affirmative, to the effect that the timer has expired, a colour fade process is performed at step 1206, effectively fading the colour back to a normal hue. Thus, in an embodiment, the peak colour of red may be faded back to a normal colour of green, with several increments being made to the hue value in order to achieve the fade effect, with each value being converted to RGB colour space.

Figure 13 In previously described embodiments, a first-time varying signal may be derived from a first audio signal and the second time varying signal may be derived from a second audio signal but these audio signals are themselves received from the same audio channel. In an alternative embodiment, a first audio channel 1301 is shown along with a second audio channel 1302. Each audio channel includes a first amplifier 1311/1321, along with a first processor 1312/1322, a second processor 1313/1323 and an output amplifier 1314/1324.

In this embodiment, movement of a needle 1331 is controlled in response to the output from amplifier 1314 of the first signal channel. However, background colour adoption is controlled by the output of the first amplifier 1321 of the second audio channel 1302. These two channels could be included within the mixing desk described with reference to Figure 5, where they would be configured to process different audio components of the same overall production.

Figure 14 An alternative embodiment is illustrated in Figure 14 that provides compression; and is similar to the embodiment described with reference to Figure 10. Thus, an audio input 1401, an audio output 1402, a variable gain process 1403, an output signal process 1404, a makeup gain process 1405, a signal processing environment 1406, a level detection process 1407, a meter 1408, a meter-time-constant-emulation process 1409 and a peak-hold and hue-calculation process 1410 are substantially similar to similarly numbered components shown in Figure 10.

In the embodiment of Figure 10, the level detection process 1007 received the local input signal, this being the same signal upon which gain reduction was applied by the gain reduction process 1003. These operations may be referred to as taking place within the same signal channel, such as channel 1301. In the embodiment of Figure 14, an external input 1411 is supplied to process 1406. Thus, this may be received from a second signal channel, such as channel 1302. In this way, gain reduction applied to the local signal is determined by level characteristics of a second signal, in a process usually referred to as side-chain compression.

to Like the embodiment described with reference to Figure 10, the movement of needle 1412 displayed against a background 1413 of the meter 1408 is derived from the gain reduction control signal. However, in this embodiment, colour adoption for the meter background 1413 is determined by the extent of makeup gain deployed by the makeup gain process 1405. Thus, in some situations, excessive makeup gain may have been applied which can be displayed to an operative by presenting an appropriate colour.

In an embodiment, a green colour may indicate that too little gain is being applied and that the available headroom could be optimised to a greater extent. Similarly, if too much gain is being applied, which could result in digital clipping for example, a red colour is displayed to an operative. In a further refinement, an amber colour could be displayed to an operative when working within what may be considered an optimum level setting.

Figure 15 An embodiment is shown in Figure 15 in which an audio signal is supplied to a compression process via a gate. The gate has an open status allowing audio signals to be applied to the compression process. In addition, the gate has a closed status that prevents audio signals being applied to the compression process. The compression process applies a degree of attenuation to the audio signal, assuming the signal has been allowed to pass through the gate. In this embodiment, the first time-varying signal (driving the needle of the meter) is derived from the degree of attenuation applied during the compression process. The second time varying signal (controlling background colour adoption) is derived from the status of the gate.

An audio signal is supplied to an audio input 1501 and an output signal is received from an audio output 1502. The input signal is supplied to a first level detection process 1503. If the level of the incoming signal is above a predetermined gate threshold 1504, the gate remains open, as indicated by a switch 1505, allowing the signal to pass to a gain reduction process 1506. The output from gain reduction process 1506 undergoes additional audio processing at additional audio processing step 1507 before being supplied to a makeup amplifier 1508.

If the signal received from the switch 1505 is below the compressor threshold 1509, the signal is allowed to pass to the additional audio processing stage 1507 without further adjustment. However, if the level of the signal exceeds compressor threshold 1509, compression is applied in accordance with predetermined parameters as described with reference to Figure 1.

In addition to being supplied to the input of the gain reduction process 1506, the output from switch 1505 is also supplied to a second level detection process 1510. Thus, as the input signal becomes larger than the compression threshold 1509, the second level detection process 1510 will control the gain reduction process 1506, such that gain reduction is applied. This first time-varying signal is also supplied as the needle input to a meter 1511 thus, as previously described, a needle 1512 of the meter 1511 will move in accordance with the level of gain reduction that is being applied by the gain reduction process 1506.

In addition, the meter 1511 also receives control signals for backlight adoption. These are received as time varying signals from the first level detection process 1503, indicating that the gate is open, as illustrated in Figure 15 or has been closed; such that switch 1505 is placed in its alternative configuration. Thus, in an embodiment, the meter 1511 may be illuminated in green, say, when the gate is open and then illuminated in, say, red when the gate is closed. This in turn provides a clear indication to an operative as to why compression is not being applied at a particular section of audio, given that the meter will be illuminated in red, indicating that the gate has been activated and that the gain reduction process 1506 will not be receiving an input signal.

Figure 16 A further embodiment is shown in Figure 16. In addition to a first spatially movable element 1601, a second spatially movable element 1602 is also provided, both of which are configured, in this example, to rotate with respect to a background 1603.

An audio input 1604 receives a stereo audio input signal which is then conveyed to an audio output 1605. The audio signal consists of a right channel 1606 and a left channel 1607. Movement of the first needle 1601 is determined by the level of the right audio channel 1606, with movement of the second needle 1602 being controlled by the left audio channel 1607.

Both channel signals are supplied to a phase comparator process 1608, resulting in the production of a first attribute signal 1609 being supplied to the meter; such that background colours are adopted to give an indication of the phase difference between the right channel audio signal and the left channel audio signal. Thus, for example, when relatively in phase, a green background colour could be adopted whereas when out of phase, a red background colour could be adopted.

Claims

CLAIMSThe invention claimed is: 1 An apparatus for visually displaying attributes of time-varying signals, comprising: a display region having a background, wherein the colour of said background is adopted in response to a first attribute; and a spatially-movable element configured to move relatively to said background in response to a first time-varying signal.
2. The apparatus of claim 1, further comprising one or more colour-selectable light-emitting devices, wherein the colour of light emitted by said light emitting devices is selected in response to the adoption of a background colour.
3. The apparatus of claim 1 or claim 2, wherein said spatially-movable element is an angularly-displaceable needle.
4. The apparatus of claim 3, wherein said needle forms part of a magnetoelectric meter.
5. The apparatus of claim 1, wherein: said display region comprises an array of pixels; and image data is rendered in response to said first attribute and said first time-varying signal.
6. The apparatus of claim 5, wherein said spatially-movable element is graphically represented as an angularly-displaceable needle in said rendered image data.
7. The apparatus of claim 5 or claim 6, wherein said array of pixels is supported within a multi-channel audio mixing desk.
8. The apparatus of any of claims 1 to 7, further comprising a processor configured to perform processing operations upon an audio signal, wherein: a processing operation is conducted in accordance with a selected mode of operation; said first attribute represents the selected mode of operation; and said audio signal presents said first time-varying signal.
9. The apparatus of any of claims 1 to 7, further comprising a processor configured to perform processing operations upon an audio signal, wherein: said first time-varying signal is derived from said audio signal; and said first attribute is a second time-varying signal derived from said audio signal.
10. The apparatus of any of claims 1 to 7, further comprising a processor configured to perform a compression process and an amplification process upon an audio signal, wherein: said first time-varying signal is derived from an attenuation signal representing the degree of compression applied by said compression process; and said first attribute is a second time-varying signal representing the amount of gain deployed by said amplification process.
11. A method of visually displaying attributes of a time-varying signal, comprising the steps of:displaying a region with a background;adopting a background colour in response to a first attribute; displaying a spatially-movable element over said background; and moving said spatially-movable element relatively to said background in response to a first time-varying signal.
12. The method of claim 11, wherein: a mode of operation is performed upon said first time-varying signal, non-exclusively selected from a first mode of operation and second mode of operation; and said first attribute represents said operational mode selection, such that a first background colour is adopted in response to selecting said first mode of operation and a second background colour is adopted in response to selecting said second mode of operation.
13. The method of claim 12, wherein said first time-varying signal is an audio signal; an input audio signal is processed to produce an output signal; said first mode of operation selects said input audio signal as said first time-varying signal; and said second mode of operation selects said output audio signal as said first time-varying signal
14. The method of claim 13, wherein: said input audio signal is modifiable in response to a first manual control; said output audio signal is modifiable in response to a second manual control; said first manual control is identified with said first background colour; and said second manual control is identified with said second background colour.
15. The method of claim 12, wherein said first time-varying signal is an audio signal; an input signal is compressed by dynamically applying gain reduction; said first mode of operation performs an averaged compression mode; said second mode of operation performs a peak compression mode; said spatially-movable element is moved in response to the degree of said gain reduction applied; said first background colour is adopted during said averaged compression mode; and said second background colour is adopted during said peak compression mode.
16. The method of claim 11, wherein said first attribute is a second time-varying signal.
17. The method of claim 16, wherein said first time-varying signal and said second time-varying signal are derived from a third time-varying signal
18. The method of claim 17, wherein: said third time-varying signal is an audio-related compression control signal; said first time-varying signal indicates gain reduction values specified by said compression control signal; and said second time-varying signal indicates held peak values of said compression control signal.
19. The method of claim 18, further comprising the steps of producing said held peak values by providing an instant attack for said background colour change followed by low pass filtering upon release back to an initial colour.
20. The method of claim 17, wherein: said third time-varying signal is an audio signal; said first time-varying signal indicates substantially instantaneous loudness/peak levels of said audio signals; and said second time-varying signal indicates longer term loudness.
21. The method of claim 16, wherein: said first time-varying signal is derived from a first audio signal; said second time-varying signal is derived from a second audio signal; and said first audio signal and said second audio signal are received from the same audio channel
22. The method of claim 17, wherein: an audio input signal is supplied to a compression process to produce a compressed audio signal by dynamically attenuating said audio input signal by a degree of compression; said compressed audio signal is amplified to produce an output signal; said first time-varying signal is derived from said degree of compression, thereby moving said spatially-movable element in response the attenuation applied to said input signal; and said second time-varying signal is derived from said output signal, thereby adopting a colour in response to the level of said output signal.
23. The method of claim 22, wherein said degree of compression is determined by a compression control signal derived from an alternative audio signal.
24. The method of claim 17, wherein: an audio signal is supplied to a compression process via a gate; said gate has an open status, allowing said audio signal to be applied to said compression process; said gate has a closed status, preventing said audio signal being applied to said compression process; said compression process applies a degree of attenuation to said audio signal; said first time-varying signal is derived from said degree of attenuation during compression; and said second time-varying signal is derived from the status of said gate.
25. The method of claim 11, further comprising the steps of: displaying a second spatially-movable element over said background; and moving said second spatially-movable element relatively to said background in response to a first (right/left) channel of a stereo audio signal; wherein: said first time-varying signal (moving said first spatially-movable element) is moved in response to the second (left/right) channel of said stereo audio signal; and said first attribute is the phase difference between said first channel and said second channel.