Abstract:
Audio content on a compact disc is displayed as an image of a rotating vinyl record, thus enabling a disc jockey to obtain a visual indication of the nature of the content on the disc. The apparatus comprises a manually operable joystick which can be used to operate a compact disc player, and to cause it to play the content on the basis of the viewed image of the vinyl record, thus simulating the complete (including the visual aspect of the content recorded on a vinyl disc) functional capability of a traditional record deck and vinyl record in a compact disc player.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates, inter alia, to the visual representation of audio content, such as music, which when recorded on one or more types of data storage medium gives no visual indication to the naked eye of the nature of the content thus recorded. One example of the use of the present invention is the display of audio content recorded on a compact disc and which represents recorded music, in the visual form that the same or corresponding content would have to the naked eye when recorded on a traditional vinyl disc.  
           [0003]    2. Description of Related Art  
           [0004]    Currently, in spite of the widespread adoption of digitally recorded audio material in the form of compact discs, and more recently in the form of MP3 digital audio files, the vast majority of disc jockeys (“DJ&#39;s”) use conventional vinyl records, played on special arrangements of record “turntables” or “decks”. The arrangement of record decks typically involves having two turntables, so that the DJ can cue up a track on one record while the other is playing, or can mix music from a track on one record into the music from a track on the other record. Typically mixing will include playing music from one track over another (for example as one piece of music fades and the other starts) to provide a seamless transition from one track to another, or “scratching”= 0  during which the DJ rapidly moves one of the turntables back and forth over a short distance, causing the stylus of the turntable to move correspondingly back and forth within the spiral groove on the record, to create a characteristic sound. The reliance on the use of traditional vinyl discs and record decks is anomalous given the lower cost of recording on more modern media such as compact discs, and accordingly attempts have been made to provide special compact disc players, known as “CD decks” which aim to provide the DJ with the same capability as conventional record decks. For example CD decks include a large “jog wheel”, which effectively provides manual control of the CD turntable to enable scratching. Notwithstanding this however, the use of CD decks remains low.  
         SUMMARY OF THE INVENTION  
         [0005]    One aspect of the present invention lies in an appreciation of a functional capability provided to the DJ by a traditional vinyl record which is not available with existing CD decks. The majority of existing record decks for DJ&#39;s include a “target light” or “cue lamp” provided in respect of each turntable on the deck, and this allows a DJ to see the radial position of the stylus (which is useful for cueing up a track on the record). However, because the target lamp typically has a high angle of incidence to the record (i.e. subtends a small angle with respect to the surface of the record), it has the effect of illuminating the top surface and interior edges of the spiral groove on the vinyl record. Because different frequencies and amplitudes of recorded sound give rise to differing groove patterns having differing reflectances, the light reflected from a particular part of the record will be indicative of the nature of the audio content recorded on the vinyl at that location. This effect is enhanced once the record is rotating, because repetitive elements (such as drum beats or bass lines) reveal themselves as periodic variations in the groove&#39;s reflectance pattern. It is thus possible for a DJ to see a visual representation of the nature of the audio content stored on the record, which in turn enables the DJ to position the stylus by placing the stylus at an appropriate point on the record.  
           [0006]    A further aspect of the present invention provides an apparatus for substantially replicating this functional capability so that audio content recorded on a first type of data storage medium which gives no visual indication to the naked eye of the nature of the content is visually represented in a useful manner.  
           [0007]    Accordingly, an aspect of the present invention provides DJ apparatus comprising:  
           [0008]    an audio player which generates an audio playback signal from a recording medium storing musical content;  
           [0009]    a processor connected to the audio player, and adapted to: read the content and generate a visual representation of variation in at least one parameter of the content with time on a curvilinear time axis; signify an instantaneous value of the parameter on the time axis with a cursor; and synchronise temporal progression of the instantaneous value of the parameter with the audio playback signal;  
           [0010]    a visual monitor connected to the processor, and on which the visual representation, including the cursor, is displayed;  
           [0011]    a manual actuator, connected to the processor, and which enables a user manually to override relative motion of the cursor and time axis during the aforesaid synchronised temporal progression;  
           [0012]    wherein the processor is additionally adapted, upon actuation of the actuator, to operate the audio player to generate an audio playback signal corresponding to instantaneous relative motion of the cursor and time axis.  
           [0013]    The use of a curvilinear axis enables extremely efficient use of image space so that it is possible to display to a user, at any given moment, a visual representation of a much larger amount of content than would otherwise be the case. Preferably the visual representation is an image of a vinyl record, with the at least one parameter being at least frequency, and more preferably amplitude (which therefore implicitly includes frequency information). The image of the record is, according to the best mode of the invention, substantially the same as the appearance of a vinyl record on which the content is recorded, and so would be familiar to users of traditional record decks.  
           [0014]    Typically, the content will be stored for playback in a digital audio format, having been originally recorded from an analogue audio signal, and will enable the use of standard digital data storage (such as compact discs) and data readers (such as a CD player) to produce the audio playback signal. The apparatus of the present invention will thus provide the user with the visual display capability of a traditional analogue record deck, enabling manual intervention in the playback via the actuator, and using visual feedback from the map.  
           [0015]    The invention may be applied equally to provide this capability in conjunction with other audio content storage media, such as magnetic tapes (irrespective of whether an audio signal is recorded as analogue or digital data) to provide the user with a real time visual indication of the nature of the audio content recorded thereon.  
           [0016]    A further aspect of the present invention provides a method of varying playback speed of musical content on an audio player which generates an audio playback signal from a recording medium storing the content, comprising the steps of:  
           [0017]    generating a visual representation of variation in at least one parameter of the content with time on a curvilinear axis, signifying an instantaneous value of the parameter on the time axis with a cursor, and synchronising temporal progression of the instantaneous value of the parameter with the audio playback signal;  
           [0018]    intervening in the synchronised temporal progression by moving the cursor and curvilinear time axis relative to each other; and  
           [0019]    operating the audio player to generate an audio playback signal corresponding to relative motion of the cursor and time axis resulting from the intervention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    Embodiments of the invention will now be described, by way of example, and with reference to the accompanying drawings, in which:  
         [0021]    [0021]FIG. 1 is a schematic illustration of a first form of apparatus embodying aspects of the present invention;  
         [0022]    [0022]FIG. 2 is a schematic illustration of a further form of apparatus embodying aspects of the present invention. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0023]    Referring now to FIG. 1, a digital storage medium (DSD)  10 , such as a compact disc, has digital audio content, typically music, stored thereon, which is readable by means of a reader  12 . The reader  12  is connected, via a switch node  14  to a digital-to-analogue converter (DAC)  16  and a processor unit  18 . The processor unit  18  controls the operation of, inter alia the reader  12 , the DAC  16  and the switch node  14  in dependence upon input signals from a user console  20 , i.e. in order to give effect to instructions input at the console by a user, requiring that audio content on a particular storage medium is output as an audio playback signal to a listener, or mapped (an explanation of which follows). Content on the storage medium is therefore read by the reader  12  in response to an instruction from the processor  18  following a suitable input instruction from a user. Upon receipt of a user instruction requiring the audio playback of the content, the processor  18  actuates the reader  12  to read the audio content from the storage medium  10 , and switches the output of the reader  12 , via switch node  14  to the DAC  16 . The output node  22  of the DAC is typically connected via an adjustable signal amplifier  24  (the gain of which is adjustable at the console  20  to provide volume control) to one or more audio transducers such as a loud speaker  26 . The “play” functional capability of the system is thus in effect identical to that of a standard audio CD player, with the reader  12 , the processor  18 , and the DAC  16  combining to perform this function. Upon receipt of an instruction from the console  20  to map the audio content on the storage medium, the processor  18  actuates the reader  12  and switch node  14  to read the audio content from the storage medium  10  and to transmit the audio content to the processor  18 . The processor then analyses the audio content, and, by means of suitable software, compiles a visual representation, here having the form of a map  40 , which in the present embodiment is a series of amplitude values of the audio content with respect to time. It is not necessary to use amplitude, and any suitable parameter may be used to create the visual representation, such as frequency. Amplitude is however preferred because it implicitly includes frequency information. This map  40  is then stored by the processor in a random access memory (RAM)  28 . Upon receipt of an appropriate command from the console  20  the processor  18  is able to retrieve the map from the RAM  28  to generate an image of the map  40  upon a monitor  30 . In the example of FIG. 1 the visual image of the map  40  is simply a graph  42  showing the variation in the amplitude of the audio content stored in the storage medium  10  with respect to time.  
         [0024]    Once audio content from the storage medium has been mapped, the map image  42  is automatically generated on the monitor  30  whenever a “play” command is received at the processor  18  from the console  20 . In such a situation the processor  18  switches audio content from the reader  12  through the DAC  16  to create an audio playback signal, and then to the output terminal  22 , and thus the loud speaker  26 . However, in contrast to the simple “play” operation described above, the audio content is initially switched to the DAC  16  via the processor  18 . This process enables the processor  18  to display a cursor on the map image  42 , whose instantaneous position on the image is synchronised with the audio playback signal coming out of the loud speaker  26 . In the present example the cursor is simply an arrow  32  relative to which the graph of amplitude against time moves, to indicate the amplitude of the audio signal at any given moment T in time.  
         [0025]    Providing a map image which moves relative to the cursor requires more processing capability, but this has the advantage of being able to display large data map images without having to refresh the image on the monitor, as would be required with a static map image.  
         [0026]    By monitoring the position of the cursor on the map, a DJ is given an indication of, for example, when the beat of the music changes, or whether the music is louder or softer without listening to the music. This enables a DJ for example to locate a particular type of music on the storage medium rapidly, which is frequently necessary for example so that the DJ can synchronise two pieces of music. In one embodiment of the system described a further piece of music can be played on a second duplicate system of the system thus far described, although this has the disadvantage of requiring two readers, DACs etc. In a further embodiment the RAM  28  is sufficiently large to store a map of the audio content from a storage medium and a copy of the audio content itself. The audio content from the RAM may be “played” (i.e. switched through the DAC  16  by the processor to generate an audio signal by the processor  18 ) and mapped in response to appropriate commands from the console  20  is the same way as described above. Thus to the user, the functional capability of the system is identical to that of two separate systems once the audio content to be stored in the RAM  28  has been mapped.  
         [0027]    In a further modification of the system described thus far, a manual actuator is provided, here having the form of a joystick  50 . The joystick  50  is connected to the processor  18 , and enables a DJ to intervene manually with the audio player (whether this is a traditional player or a “player” in which an audio signal is generated from audio content stored in the RAM). By moving the joystick the DJ can alter the position of the cursor  32  on the map  40 , and the processor is programmed to access and play the audio content at the instantaneous cursor position. The cursor  32  may thus be said to operate as a “virtual stylus”.  
         [0028]    The reader  12  of the various embodiments described in connection with FIG. 1 is preferably a high speed reader, i.e. it operates at a faster speed than is necessary in order to retrieve the audio content from the storage medium and convert the audio content to an audio playback signal to play the audio signal at its intended speed. This enables rapid mapping of audio content, while still permitting the audio content to be read at standard speed (i.e. the speed necessary in order to generate a playback signal for playing at its intended speed), either by means of direct control of the reader from the processor  18 , or by the use of buffers, for example. However it would be possible nonetheless to use standard speed data readers, although the audio content would ideally have to be mapped in advance and the use of the virtual stylus to control the player is then only possible in respect of audio content stored in the RAM.  
         [0029]    Referring now to FIG. 2, wherein like elements are depicted with the same reference numerals, a high speed reader  12  is operable by the processor  18  in the manner previously described to read and store audio content on storage medium DSD 2  in RAM  28 . In this example an audio playback signal generated from audio content DSD 1 , stored on the storage medium  10  is playing at loud speaker  26 , while the audio signal generated from audio content on DSD 2  is playing in headphones  126 . The monitor shows an image of the map of the audio content on DSD 2 , but the content on both DSD 1  and DSD 2  have been mapped, and selection of which map is to be displayed at any instant is possible via the console  20 , as well as the selection of a split screen mode in which both map images are visible. The map images in this embodiment have the form of virtual vinyl records on which the audio content on DSD 1 , DSD 2  is recorded; the cursor is depicted as a stylus  132  moving across the surface of the vinyl record disc. The position of the stylus image on either of the virtual vinyl records in adjustable using the joystick  50 , with selection of the map in respect of which the joystick is operable being possible via the console  20 . In a preferred embodiment the joystick  50  is integrated into the console  20  for ease of use.  
         [0030]    The processor is thus controllable from the console  20  to move the cursor  132  to a particular position on an image of what the audio content would look like in the event that it had been recorded on a vinyl record disc (the medium most favoured by current DJ&#39;s), in order to play the audio signal corresponding to the audio content at the new cursor position. The volume of either output channel may be faded out etc. in the same way as with existing systems in order to mix audio playback signals generated from audio content on storage media DSD 1  and DSD 2 .