GB2276753A - Recording method and system - Google Patents

Abstract

Source material is recorded on a recording medium by playing (12) the source material in a first pass, deriving (18) a control signal responsive to a parameter of the played source material, processing (16) the source material in a second pass for adjusting the parameter of the played source material in accordance with the control signal and recording (14) the processed source material on a recording medium. For recording digital signals on a recording medium, for example for optical disc mastering, a maximum digital recording level value (e.g. for an optical disc) is prestored and then a control signal is derived by determining a digital source parameter value corresponding the maximum signal level from the complete first pass of the source material, then determining a scaling control signal in dependence upon the relative values of the digital recording reference parameter value and the digital source parameter value. The source material played during the second pass is then linearly scaled in accordance with the scaling control signal and the linearly scaled digital signals are recorded on the optical disc. This enables the full range of digital values and/or the full dynamic range of the recording medium to be exploited. The various steps can be controlled automatically by a sequence controller (20). <IMAGE>

Description

RECORDING METHOD AND SYSTEM The invention relates to a recording system and method for recording signals on a recording medium.

When recording source signals on a recording medium, it is often necessary to modify the source signals before recording. For example, when recording audio tracks on a recording medium such as a tape or a compact disc, it is often desirable that each track has the same peak level so that, on replay, the user does not have to adjust the volume of the recorded material between tracks.

In particular, when digital recording is used, it is desirable that the source material is recorded with the peak signal level having the maximum possible recordable binary value in order to take full advantage of the available range of digital values and/or the available dynamic range. Traditionally, when mastering a compact disc (CD) in recording studios, the signal level of the source material is adjusted manually and "on the fly" during production of the CD master recording. In other words, the adjustment is made as the material is recorded.

The traditional method has a number of disadvantages. In the first place, the manual adjustment method is time consuming and is subject to error. For example, too low a level may be set so that the maximum dynamic range is not utilized, or too high a level may be set so that digital overload (over level recording) occurs. Also, continual adjustment of the signal on the fly means that relative signal levels of the original recording within a passage to be recorded are not reproduced faithfully.

An object of the present invention is to mitigate the problem discussed above.

In accordance with a first aspect of the invention, there is provided a recording system for recording signals on a recording medium, the recording system comprising: means for playing source material; a controller connected to the playing means to receive the source material played in a first pass for deriving a control signal responsive to a parameter of the played source material; a signal processor connected to the playing means to receive the source material played in a second pass and to the controller to receive the control signal derived from the first pass for processing the played source material in the second pass to modify the parameter in accordance with the control signal; and recording means connected to the signal processor for recording the processed source material on a recording medium.

The invention thus enables one or more parameters of the source material automatically to be adapted to the requirements for recording on the recording medium. The invention finds particular, but not exclusive application to the recording of digital signals on the recording medium. Where the parameter is the signal level of the played source material, the invention enables the recording level of the source material automatically to be adjusted to benefit from the full range of digital values available for and/or the available dynamic range of the recording medium.

For deriving the control signal, the controller preferably comprises: means for storing a recording reference parameter value; means for determining a source parameter value from the played source material; and means for determining the control signal in dependence upon the relative values of the recording reference parameter value and the source parameter value.

Preferably, the signal processor linearly scales the played source material in accordance with the control signal whereby the relative signal levels of the source material can be preserved in the recorded material.

Preferably, for adjusting the signal level of the source material to take full advantage of the available range of digital values and/or the available dynamic range of the recording medium, or of, for example, an optical disc where the recording medium forms a master for recording optical discs, the recording reference parameter value is a maximum signal level, for example for recording on the recording medium or on a compact disc, and the source parameter value determining means determines the maximum signal level source parameter value from the first pass of the source material.

Preferably, the recording system comprises a sequence controller which: during a first pass, causes the playing means to play the complete source material a first time and causes the controller to derive the control signal; and during a second pass, causes the playing means to play back the source material a second time, the controller to output the control signal, the signal processor to process the played source material in accordance with the control signal and the recording means to record the processed source material.

In a preferred embodiment of the invention for recording digital signals on the recording medium: the player outputs digital source material signals; the controller comprises means for storing a maximum digital recording value, source parameter value determining means for determining a digital source parameter value corresponding the maximum signal level from the first pass of the source material and means for determining a scaling control signal in dependence upon the relative values of the digital reference parameter value and the digital source parameter value; the signal processor linearly scales the played source material in accordance with the scaling control signal; and the recording means records linearly scaled digital signals on the recording medium.

The invention finds particular, but not exclusive application to the mastering of an optical recording medium such as an optical disc where the maximum digital recording value is that for recording information on the optical disc.

In accordance with a second aspect of the invention, there is provided a recording method wherein source material from a playing means is recorded on a recording medium by means of a recording means, the method comprising the steps of: - playing the source material in a first pass; - deriving a control signal responsive to a parameter of the played source material; - processing the source material in a second pass for adjusting the parameter of the played source material in accordance with the control signal; and - recording the processed source material on a recording medium.

The invention also includes a method of mastering a compact disc which comprises the steps of the method defined above followed by a further step of using the recording on the recording medium as a master for producing an optical disc.

In accordance with further aspects of the invention, there are provided a recording medium and an optical disc recorded in accordance with the method of the invention.

The invention will be described hereinafter by way of example with reference to the accompanying drawings, throughout which like parts are referred to by like references and in which: Figure 1 is a schematic block diagram of a recording system in accordance with the invention; Figure 2 is an overall flow diagram of the operation of the system of Figure 1; Figure 3 is a flow diagram illustrating the steps for deriving a control signal for use in the system of Figure 1; Figure 4 is a schematic block diagram of a control signal generator of the system of Figure 1; Figure 5 is a flow diagram of the processing of source material for recording; and Figure 6 is a schematic diagram of a signal processor of the system of Figure 1.

Figure 1 is an overall system diagram of a recording system 10 in accordance with the invention for recording digital audio signals on a recording medium which is used as a master for the manufacture of optical discs.

The recording system comprises a source material player 12, for example a conventional audio recording/playback machine, and a recorder 14, which may also be a conventional audio recording/playback machine. The recording/playback machines may be conventional tape machines, or could be solid state recording/playback devices, or implemented in any other suitable technology. Also, although in the present description it is assumed that the recording system is used for recording audio information, it is equally applicable to the recording of video or other signals.

The output of the player 12 is passed to a signal processor 16 via an audio signal connection 16S, which modifies a parameter or parameters of the output of the player before being passed via an audio signal connection 14S to the recorder 14 for recording.

A control signal generator 18 is also connected to receive the output of the player 12 via an audio signal connection 16S. A system controller 20 is connected to receive prerecorded time control signals via the connection 12T from the player 12 and via the connection 14T from the recorder 14. The time control signals are prerecorded in a conventional manner by "pre-stripe" recording. The system controller is also connected to the player 12 via the connection 12C, to the recorder 14 via the connection 14C and to the control signal generator 18 via the connection 18C. The control signal generator 18 is connected to the signal processor 16 via a connection 16C. The connections shown in solid lines represent audio signal paths and the connections shown in dot dash lines represent control signal paths. Of course, in other examples of the invention for processing information signals other than audio signals, (e.g.

video) the information signals would be passed via the signal connections "S" illustrated using solid lines.

The player 12 and the recorder 14 are provided with conventional control inputs so that their operation may be controlled remotely and are provided with conventional time code outputs for indicating time control signals for the current position within the source material in the case of the player 12 and the recording in the case of the recorder 14.

The system controller can be implemented in any appropriate manner to perform the functions described below. Preferably it is implemented in the form of a suitably programmed microprocessor-based controller with the connections 12T, 12C, 14T, 14C and 18C being connected thereto by conventional interfaces. The system controller can be programmed with initial and final time control signals defining the start and the end of the source material to be played and of the recording to be made using conventional user operable input devices.

The operation of the recording system of Figure 1 will now be described with reference to the flow chart of Figure 2.

In step S21, the system controller 20 issues control signals via control path 12C to the player 12 to cause this to start to replay the source material. At the same time, the system controller issues a command via the control path 18C to the control signal generator 18 to cause this to start the process for deriving a control signal for controlling the signal processor 16. The system controller monitors the operation of the player 12 using the time control signals supplied on the connection 12T.

In step S22, the system controller 20 causes the player to play the complete source material to be recorded and, during this time, causes the control signal generator 18 to monitor at least one parameter of the source material output from the player in order to generate the control signal in a manner to be described later.

At the end of this first pass of the source material, in step 23, the system controller causes the player to reset the source material. If the player 12 is a tape player, for example, the resetting of the player 12 comprises rewinding the tape to the beginning of the source material.

In step S24, the system controller causes the player to start playing the source material and, at substantially the same time, causes the recorder 14 to start recording. The exact timing of the starting of the player and recorder is arranged to take into account the physical construction of the player and recorder device and any time delays relating to the specific implementations of the signal processor 16 as will be apparent to one skilled in the art. The control signals for controlling the player 12 and the recorder 14 are passed from the system controller via control connections 12C and 14C, respectively. The system controller monitors the current position of the player 12 and the recorder 14 by means of the time control signals passed via connections 12T and 14T, respectively.

In step S25, the system controller causes the player to perform a second pass of the source material, with the source material output from the player being processed by the signal processor 16 in response to the control signal CS from the control signal generator 18. The output of the signal processor forms the signals which are recorded by the recorder 14. At the end of the source material, as detected by means of the time control signals on connection 12T, the system controller terminates the recording process in step S26.

The recording recorded on the recording medium by the recorder 14 can then be used, in a conventional manner, as a master for recording optical discs.

Figure 3 explains in more detail step S22 of Figure 2 for deriving a control signal.

In step S31, a variable MAXSIG is set to zero. The variable MAXSIG is used to indicate the maximum signal level of the source material from the player 12.

In step S32, the first signal SIG of the source material is received from the player 12. In step S33, the absolute value (i.e.

the magnitude) of the received signal SIG is compared to the variable MAXSIG. The absolute value of SIG is compared as, in an audio system, SIG can be positive or negative. If the signal SIG has a higher absolute value than indicated by the value of MAXSIG, then, in step S34, MAXSIG is set equal to the absolute value of SIG. Otherwise, the value of MAXSIG is not changed. In step S35, if a further signal SIG is received, then control passes back to step S33, otherwise control passes to step S36. When control passes to step S36, this means that the first pass of the source material from the player 12 is complete.

In step S36, the value of the control signal CS is set equal to a value RECMAX divided by the value MAXSIG. The value RECMAX indicates the maximum permissable recording value for the recording medium used on the recorder 14. Where, for example, the recording made by the recorder 14 is subsequently used as a compact disc master recording, the value RECMAX equals the largest digital value which can be stored on the optical disc. For example, in a conventional 16-bit audio system, the maximum value which can be recorded is 7FF (hex) and the largest negative value is 800 (hex). Accordingly, in this case RECMAX could be set to 7FF (hex). In step S37 the value of CS is stored.

Figure 4 is a schematic block diagram of apparatus suitable for performing the method steps of Figure 3. Successive source material signals SIG from the player 12 are received via signal connection 18S into a register 60. The absolute value of the content of the register 60 is compared to the content of a register 62 used to hold the maximum signal level MAXSIG of the source material yet encountered. The register 62 is initially reset to zero in response to a signal from a control unit 74 at input R. Thereafter, the registers 60 and 62 are clocked in response to control signals from the control unit 74 at respective inputs C. The comparator 64 is also responsive to control inputs from the control unit 74 to compare the current values in the registers 60 and 62.

If the comparator 64 determines that the absolute value of SIG in the register 60 is greater than the value of MAXSIG in the register 62, the comparator outputs a control bit to the AND gate 66 which causes the value in the register 60 to be latched into the register 62 to update the value of MAXSIG. In this way, the value of MAXSIG corresponds to the largest value of SIG yet received during the first pass of the source material.

At the end of the first pass of the source material, the value of MAXSIG in the register 62 corresponds to the highest signal level of the source material.

A register 68 contains the maximum signal level RECMAX which can be recorded on the recording medium of the recorder 14. The register 68 can comprise an input (not shown) from the system controller 20 for changing the value stored therein in dependence upon the particular recording medium used. Alternatively, the register 68 could be provided as a read only store if the control system is to be used for recording a single type of recording medium.

After completion of the first pass (step S36 of Figure 3) the value of RECMAX in register 68 is divided by the value of MAXSIG in register 62 by means of a divider 70 and the output thereof is stored in a control signal (CS) register 72.

Figure 5 is a flow diagram illustrating the steps of recording the source material on a recording medium by the recorder during a second pass of that source material. In step S51, a first signal SIG is received by the player 12. In step s52, the value of SIG is multiplied by the control signal CS. In step S53, the processed SIG value is recorded on the recording medium. In step S54, if there is a further signal SIG to be recorded (i.e. the end of the second pass has not been reached) then control passes back to step S52, otherwise (at the end of the second pass of the source material) control passes to step s55 and the process terminates.

Figure 6 is a schematic overview of the signal processor 16.

In principle, the signal processor comprises a multiplier 76 for multiplying the value of SIC received by the signal processor 16 by the value of the control signal CS. The output value of SIG is then passed to the recorder 14 for recording.

It can be seen that by deriving a control signal CS which is formed by dividing the maximum permissable recording signal level by the maximum signal level of the source material encountered during the first pass (CS = RECMAX/MAXSIG), and then multiplying each signal of the source material by this control signal (modified SIG = SIG * CS), a linear scaling operation on each of the signals of the source material is performed to expand, or contract, as appropriate, the signal levels to accurately fit within the available range of signal levels (dynamic range) for recording. In other words a signal having the value MAXSIG is multiplied by CS (i.e. modified MAXSIG = MAXSIG * (RECMAX/MAXSIG) = RECMAX) to give the maximum recordable value RECMAX, with signals having lower signal levels being scaled proportionally.

Particularly in the case of digital recording equipment where the scaling operation can be performed arithmetically, the invention enables the available range of digital values and/or the available dynamic range to be used fully and accurately.

Although a particular embodiment of the invention has been described above, it will be appreciated that many modifications and/or additions are possible within the scope of the invention.

Thus, for example, although the invention has been described particularly in the context of digital recording equipment, it will be appreciated that the invention is equally applicable to analogue recording equipment. Also, although in the described embodiment a separate player and recorder are provided, in other embodiments of the invention these may be implemented by a combined recording/playback device.

Also, although the invention has been described for modifying the signal levels of the source material, the invention is also applicable to other parameters which require adjustment before recording. Rather than measuring the level of each signal of the source material, only selected signals might be sampled in particular embodiments, the sampled signals either being localised within the source material or scattered throughout the source material.

Although in the particular embodiment a linear scaling is performed by the signal processor 16, it will be appreciated that alternative scaling operations could be provided by the use of an appropriate function generator, for example, where signal compression is employed. Moreover, although, in the above embodiment only the signal level is varied, in alternative embodiments a number of parameters could be measured and used in connection with a function generator to modify the signals from the player 12 in a more complex manner.

Although, in the embodiment described, a constant processing criterium (i.e. a single control signal CS) is used, in alternative embodiments it may be desired to change to processing criteria throughout the source material. For example, different maximum signal levels, MAXSIG could be detected for different passages in the source material and a different control signal CS could be generated for each of those passages, whereby the peak levels of different passages of the source material could be individually adjusted.

In the described embodiments the time control signals are pre-recorded on the recording medium by pre-stripe recording.

However, in other embodiments, the time control signals can be recorded in real time with the audio or other signals.

Although the recording system preferably includes a system controller for fully automating the recording, the invention also provides for a recording system which is manually controlled without the system controller.

The invention finds particular application in the mastering of optical discs but finds general application in the context of recording information on other recording media. Indeed, it will be appreciated that the invention is not limited solely to the recording of audio information, but is also suitable for use in recording video or other signals.

Claims (21)

1. A recording system for recording signals on a recording medium the recording system comprising: means for playing source material; a controller connected to the playing means to receive the source material played in a first pass for deriving a control signal responsive to a parameter of the played source material; a signal processor connected to the playing means to receive the source material played in a second pass and to the controller to receive the control signal derived from the first pass for processing the played source material in the second pass to modify the parameter in accordance with the control signal; and recording means connected to the signal processor for recording the processed source material on a recording medium.

2. A recording system according to claim 1 wherein digital signals are recorded on the recording medium.

3. A recording system according to claim 1 or claim 2 wherein the parameter is the signal level of the played source material.

4. A recording system according to any one of the preceding claims wherein the controller comprises: means for storing a recording reference parameter value; means for determining a source parameter value from the played source material; and means for determining the control signal in dependence upon the relative values of the recording reference parameter value and the source parameter value.

5. A recording system according to claim 4 wherein the recording reference parameter value is a maximum signal level for recording and the source parameter value determining means determines the maximum signal level source parameter value from the first pass of the source material.

6. A recording system according to claim 5 wherein the signal processor linearly scales the played source material in accordance with the control signal.

7. A recording system according to any one of the preceding claims comprising a sequence controller which: during a first pass causes the playing means to play the complete source material a first time and causes the controller to derive the control signal; and during a second pass causes the playing means to play back the source material a second time, the controller to output the control signal, the signal processor to process the played source material in accordance with the control signal and the recording means to record the processed source material.

8. A recording system according to any one of the preceding claims wherein: the player outputs digital source material signals; the controller comprises means for storing a maximum digital recording value as a digital recording reference parameter value, source parameter value determining means for determining a digital source parameter value corresponding to the maximum signal level from the first pass of the source material and means for determining a scaling control signal in dependence upon the relative values of the digital recording reference parameter value and the digital source parameter value; the signal processor linearly scales the played source material in accordance with the scaling control signal; and the recording means records linearly scaled digital signals on the recording medium.

9. A recording method wherein source material from a playing means is recorded on a recording medium by means of a recording means, the method comprising the steps of: - playing the source material in a first pass; - deriving a control signal responsive to a parameter of the played source material; - processing the source material in a second pass for adjusting the parameter of the played source material in accordance with the control signal; and - recording the processed source material on a recording medium.

10. A recording method according to claim 9 wherein digital signals are recorded on the recording medium.

11. A recording method according to claim 9 or claim 10 wherein the parameter is the signal level of the played source material.

12. A recording method according to any one of claims 9, 10 or 11 wherein: - the method comprises the step of prestoring a recording reference parameter value; and - the step of deriving a control signal responsive to a parameter of the played source material comprises the sub-steps of: - determining a source parameter value from the played source material; and - determining the control signal in dependence upon the relative values of the recording reference parameter value and the source parameter value.

13. A recording method according to claim 12 wherein the recording reference parameter value is a maximum signal level for recording and the source parameter value is determined to be the maximum signal level from the first pass of the source material.

14. A recording method according to claim 13 wherein the signal processor linearly scales the played source material in accordance with the control signal.

15. A recording method according to any one of claims 9 to 14 which comprises automatically controlling, during a first pass, the playing of the complete source material a first time and the determination of the control signal and, during a second pass, the playing of the source material a second time, the output of the control signal, the processing of the played source material in accordance with the control signal and the recording of the processed source material.

16. A recording method according to any one of claims 9 to 15 for recording digital signals on the recording medium, wherein the source material is supplied as digital signals, and wherein: - the method comprises a step of prestoring a maximum digital recording level value as a digital recording reference parameter value; - the step of deriving a control signal responsive to a parameter of the played source material comprises: - determining a digital source parameter value corresponding the maximum signal level from the complete first pass of the source material; and - determining a scaling control signal in dependence upon the relative values of the digital recording reference parameter value and the digital source parameter value; - the played source material is linearly scaled in accordance with the scaling control signal; and - linearly scaled digital signals are recorded on the recording medium.

17. A method of recording optical discs comprising the steps of: - recording a master using a recording method according to any one of claims 9 to 16; and - using the master to produce the optical discs.

18. A recording medium recorded in accordance with the method of any one of claims 9 to 16.

19. A compact disc recorded by the method of claim 17.

20. A recording system substantially as hereinbefore described with reference to the accompanying drawings.

21. A recording method substantially as hereinbefore described with reference to the accompanying drawings.