GB2198574A

GB2198574A - Audio deck controller

Info

Publication number: GB2198574A
Application number: GB08728107A
Authority: GB
Inventors: Michael James Denner
Original assignee: DENNER ROSEMARY JEANNE
Current assignee: DENNER ROSEMARY JEANNE
Priority date: 1986-12-04
Filing date: 1987-12-01
Publication date: 1988-06-15
Also published as: GB8629043D0; GB8728107D0

Abstract

The musical beat frequencies of two or more audio signals from decks 10, 11, are measured and made equal, if possible, and brought into phase agreement. The system operates by using processors 17 to measure the beats-per-unit time of each of the two audio signals converted to digital form, and producing control signals dependent on a comparison in a main processor 22. The control signals alter the speed of one of the decks, thus altering the beats-per-unit time of the corresponding input from the deck whose speed has been altered. An alarm system, actuable when the difference in beats-per-unit time of the two inputs exceeds a predetermined level, prevents control which involves excessive changes in pitch of the music. The system is used to provide compatibility between the beat of a piece of music ending on one deck and that of another beginning on a second deck. <IMAGE>

Description

AUDIO DECK CONTROLLER The present invention relates to a system for controlling two or more audio decks, such as record players, cassette decks, or compact disc players.

When playing music, particularly in discos and other public situations, it is often desirable to synchronise one audio deck to another in order to achieve continuity between the end of a piece of music on one deck and the beginning of another piece of music on another deck. The most important factor when synchronising the decks is to ensure that the two pieces of music have the same beatsper-minute ratio at the time of transition from one to the other. Therefore, it is necessary for the person playing the music to control the two decks in order to synchronise them, and this has had to be done manually. Record decks are available for which the speed of rotation can be varied by suitable manual controls, and the operator adjusts those manual controls until he can hear that the two decks are synchronised.

Recently, systems have been developed which can detect the beats-per-minute ratio of a deck, and display that as a number, but it remains necessary to control the decks manually. These existing systems are operated by manually "tapping" with the beats, and the system then converts this into a number. The difficulty of such systems is that to synchronise two decks, two different tapping operations must be carried out, which requires a high degree of co ordination.

Another problem with these existing systems is that any change in the beats-per-minute ratio of a record results in the system becoming unsynchronised, unless the operator re-synchronises it by tapping a new beat ratio and adjusting the deck controls. Furthermore, since the beatsper-minute ratio of records differs greatly, these operations have to be carried out for every record.

The present invention seeks to overcome these problems by providing an electronic system which receives the music output from two or more decks, compares the outputs, and controls the speed of the decks until they are synchronised.

In order to do this, the preferred arrangement converts the audio (analogue) outputs from the two (or more) decks into corresponding digital signals, which are each analysed to determine the beats-per-unit time value for that deck. A central comparator then compares these values and controls the decks in accordance with the ratio of the two values to synchronise the frequency of the beats-per-unit time of the two signals. Preferably, this is done by adjusting electronically the speed of one deck relative to the other, so that one acts as a "master" and the other acts as a "slave". Normally, the "master" is the piece of music which is finishing and the "slave" is the music about to start, and normally means will be provided for switching between decks as to which is the "master" and which is the "slave".

One possible problem with such a system is that although the decks may be synchronised in their beats-perminute ratio, the beats themselves may be out of phase.

Therefore, in a further development of the present invention, the system controls the deck speeds in order to adjust the phase of the beats of one relative to the other.

In this way it becomes possible automatically to ensure that both the beats-per-minute ratio and the phase of the beats are completely synchronised.

Since the present invention continuously monitors the deck output, any change in the beats-per-minute ratio of a record may automatically be compensated for within the system. One potential problem, however, is that the changes of speed of a piece of music must not be too great, because otherwise the changes of pitch which occur become unacceptable. Therefore, the central comparator may detect whether the difference between the beats-per-minute values of the two pieces of music are too far apart to be synchronised, and a suitable warning can then be given.

This warning may be e.g. a visual signal. A visual signal may also be given of the beats-per-minute value of each deck (as a number), and this enables the operator to note the beats--per-minute value of a particular piece of music, so that he can select music pairs which are sufficiently compatible for synchronisation to be possible. The system may also provide a further visual display to indicate when the two decks are synchronised.

An embodiment of the present invention will now be described in detail, by way of example, with reference to the accompanying drawing, in which the sole figure shows a block diagram of an audio deck controller being an embodiment of the present invention, connected to a pair of decks.

In this embodiment, two audio decks 10,11 are to be synchronised. As illustrated in the drawing, these decks are record players, but the invention is equally applicable to e.g. cassette decks, or compact disc players. Each deck 10,11 is connected to the input of a corresponding analysis channel 12,13 of a monitor which receives the audio output from the deck 10,11 and derives from the audio output a beats-per-minute value for that deck 10,11. Considering the analysis channel 12 on the left-hand side of the drawing, the audio output is fed via a filter 14 and gain control unit 15 to an analogue-to-digital converter 16.

The audio output, then converted to a digital signal, is fed to a processor 17 which analyses that signal to derive the beats-per-minute value. This operation is controlled by a suitable program stored in a memory 18. A clock 19 controls the calibration of the analogue-to-digital converter 16 and the processor 17.

Preferably, the analysis channel 12 is provided with an output generally indicated at 20 to one channel of a pair of headphones 21, so that the operator can hear the audio output from the deck 10. This system is known as a split-cue previewing system.

The analysis channel 13 for the deck 11 on the righthand side of the drawing is identical to the analysis channel 12, and the same numerals are used. Here the output 20 to the headphones 21 goes to the other side of the headset.

The beats-per-minute values derived by the processors 17 of the channels 12 and 13 are each fed to a central comparator 22 of the monitor which determines, by means of a program stored in memory 23, whether the two music signals are synchronised, and if not, it generates an output to an inteface module 24 from which control signals pass to the motors of the decks 10,11. In this way the comparator 22 can control the relative speeds of the decks, and so bring the music signal from one into synchronisation with that of the other, for example, by equalising the beats-per-minute values of the two signals, or possibly by making one twice the value of the other. This arrangement also permits the phases of the music signals to be brought into correspondence by suitable detection of the beats by channels 12 and 13 and comparison of their phases by the comparator 22.

In addition to controlling the deck motors, the comparator 22 may also activate a display 25, which indicates the beats-per-minute value of each deck 10,11 as a number, and also may feed a signal to a further display 26 which indicates whether the signals are synchronised.

Display 26 may also have a display showing visually the beats-per-minute of each deck, and possibly a further indication when the beats-per-minute values of the two decks are too far apart to be synchronised. As mentioned above, if these ratios are too far apart, an attempt to synch ron is e the music signals would result in an unacceptable change in the pitch of the music.

Although described above with reference to the synchronisation of music signals from a pair of decks 10,11, the present invention is equally applicable to the synchronisation of music signals from three or more decks.

The further deck would have an analysis channel similar to those 12,13 described above, and feed a third signal into the comparator 22.

Claims

1. An electronic controller for controlling at least two audio decks, having at least two audio inputs, each for receiving an audio signal from a corresponding one of the decks, and a monitor for comparing the audio signals and generating control signals for controlling the decks so as to synchronise the audio signals.

2. An electronic controller acccording to claim 1, wherein the monitor is adapted to determine the beats-perunit time of the audio signal from each audio input.

3. An electronic controller according to claim 2, wherein the monitor is adapted to generate control signals so as to synchronise the frequency of beats-per-unit time of the audio signals.

4. An electronic controller according to claim 2 or claim 3, wherein the monitor is adapted to generate control signals so as to synchronise the phase of the beats-perunit time of the audio signals.

5. An electronic controller according to any one of claims 2 to 4, wherein the monitor includes means for determining if the difference in beats-per-unit time of the audio signals is greater than a predetermined amount, and the system includes a warning display activatable by the monitor to display when that difference exceeds the predetermined amount.

6. An electronic controller according to any one of the preceding claims wherein there is a display activatable by the monitor to display when the audio signals are synchronised.

7. An electronic controller substantially described herein, with refernece to and as illustrated in the accompanying drawing.

8. An audio deck system, comprising at least two audio decks, an electronic controller according to any one of the preceding claims, the audio inputs of which are connected to respective decks, and the monitor of which is connected to the driver of the decks.

9. An audio deck system according to claim 7, wherein the monitor is adapted to keep the speed of one of the decks constant and adjust the speed of the other deck to synchronise them.