Digital recording apparatus

Abstract: In a recording apparatus having a digital signal input (6) which can record a digital signal on a recording medium (14), when a condition of the input signal changes during the recording operation the recording apparatus is automatically set into a recording pause mode and such operating mode is indicated to the operator. When the condition of the input signal is stabilized within a predetermined period of time during such recording pause mode, the recording medium (14) is automatically rewound and the recording apparatus is then released from the recording pause mode and recording commences at a location on the recording medium (14) so as to record over any previously recorded unstable signal.

Description: This invention relates to recording apparatus for recording a digital signal on a record medium, and to methods of operating such apparatus. Digital tape recorders that use a rotary head to record an audio signal in the form of pulse code modulated (PCM) digital data on a magnetic tape are frequency called a rotary head-type digital audio tape recorder (R-DAT). In such R-DAT apparatus, a magnetic tape is obliquely wrapped around a small rotary drum of about 30 mm diameter over an angular extent of 90°, for example. Two rotary heads having different azimuth angles are mounted on the drum at an angular separation of about 180°. The heads are rotated at 2000 rpm, for example, and alternately scan the width of the tape by an amount corresponding to the tape wrapping angle of 90°. Typically, the audio signal is sampled at 48 kHz and each sampled value is 16-bit linearly quantized, thereby producing the PCM data. The PCM data are time-compressed in a ratio based upon the tape wrap angle of 90° at every 1/2 rotation period of the heads, and is subsequently recorded on the tape by the heads as a series of adjacent oblique tracks. Upon playback, the PCM data are reproduced from the tape by the two heads and are decoded, time-expanded, and then reconverted into an analogue audio signal. In this kind if digital recorder, in addition to the PCM data, sub-codes such as a time code, a programme number, a start identifying signal or the like are also recorded on each track in specified regions different from those where the PCM data are recorded. Generally, a switch is provided that permits the user to switch input sources, for example, between an analogue audio signal and a digital signal, such as from a broadcast satellite or the like. The selected input signal is then apportioned between the two heads and recorded in oblique tracks on the tape. Upon playback, the signals reproduced by the heads are amplified and passed through a switch before being fed through an error-correction circuit to a digital-to-analogue converter. The output from the error-correction circuit is typically employed to detect the sub-code information, which is used to control a microcomputer included in the recording apparatus. In such digital recorder, if the digital audio signal at the input changes either by being interrupted or by having an altered sampling rate, the recorder continues in the recording mode, which results in an unstable signal being recorded on the magnetic medium, with constant annoying noises during playback. According to the present invention there is provided a recording apparatus comprising: an input terminal to be supplied with a digital signal; recording means for recording on a recording medium the digital signal supplied to said input terminal; recording mode setting means for setting said recording means into a recording mode; pause mode setting means for setting said recording means into a recording pause mode; stop mode setting means for setting said recording means into a recording stop mode; characterized by: detecting means for detecting whether a condition of the digital signal at said input terminal has changed from normal; means for controlling said recording mode setting means to set said recording means in said recording mode and for controlling said pause mode setting means to set said recording means in said recording pause mode when said detecting means detects that the condition of said digital signal has changed during recording of said digital signal by said recording means; means for releasing the operation of said pause mode setting means when said detecting means detects that the condition of said digital signal has returned to normal within a predetermined time while in said pause mode as a result of detecting that said condition had changed and for operating said recording mode setting means to set said recording means to into said recording mode; and means for releasing the operation of said pause mode setting means when said detecting means detects that the condition of said digital signal has not returned to normal within a predetermined time while in said pause mode as a result of detecting that said condition had changed and for setting said recording means in said recording stop mode. According to the present invention there is also provided a method of operating a recording apparatus supplied with a digital signal, comprising the steps of: setting a recording system of the apparatus into a recording mode for recording the digital signal; recording with the recording system on a recording medium (14) the supplied digital signal; characterized by: detecting whether a condition of the supplied digital signal changes from normal during the recording; setting the recording system in a recording pause mode upon detecting that the condition of the digital signal has changed during recording of said digital signal in the recording mode; releasing operation of the pause mode when detecting that the condition for the digital signal has returned to normal within a predetermined time while set in the pause mode as a result of detecting that said condition had changed and setting the recording system in the recording mode; and releasing the operation of the pause mode when detecting that the condition of the digital signal does not return to normal within a predetermined time while in the pause mode as a result of detecting that said condition had changed and setting the recording system in the recording stop mode. Thus an embodiment of recording apparatus according to the invention has an input terminal for receiving a digital signal, a recording mechanism for recording the digital input signal onto a record medium, a detector that detects whether the condition of the digital input signal has changed, and a mode setting system for setting the apparatus into various operating modes including the recording mode, a pause mode, and a recording stop mode. A system is provided for operating a recording mode setting mechanism so that the recording apparatus is set in the recording mode and for operating a pause mode setting mechanism to set the recording apparatus into the pause mode when the detecting signal has changed while the recording apparatus has been in the recording mode. A system is provided to release the pause mode setting mechanism when the detecting means detects that the input condition of the digital input has remained steady for a predetermined period of time while the apparatus is in the pause mode, and thereby operates the recording mode setting mechanism to set the recording mode back into a recording mode. The embodiment then provides a means for releasing the pause mode setting mechanism when the detector detects that the input condition remains changed within a predetermined time while in the pause mode, and for setting the recording apparatus into the stop mode. The invention will now be described by way of example with reference to the accompanying drawings, throughout which like parts are referred by like references, and in which: Figure 1 is a block diagram of an embodiment of recording apparatus according to the present invention; Figure 2 is a flow chart for explaining the operation of the embodiment; and Figures 3A and 3B are pictorial representations of respective modes of operational indicators of the embodiment. The embodiment to be described is an R-DAT recording apparatus as shown in Figure 1, and is operated in accordance with the flow chart of Figure 2. An analogue audio signal fed to an input terminal 1 is supplied through a low-pass filter 2 and through an analogue-to-digital (A/D) converter 3, where it is converted into a digital audio signal using a sampling frequency of 48 kHz and 16-bit linear quantization. The output of the A/D converter 3 is fed to a fixed terminal 4a of a switch 4, whose output in turn is fed to an input of a recording signal generating circuit 5. In the event that an original digital signal is available for recording, it is fed in at the terminal 6 to a digital I/O circuit 41 and as an output therefrom to another fixed terminal 4b of the switch 4. Accordingly, upon operation of the switch 4, either the digitally converted analogue audio signal fed in at the terminal 1 or the original digital signal, which might be provided from a tuner for satellite broadcasts or from another R-DAT recording apparatus, fed in at a terminal 6 is connected to the recording signal generating circuit 5. The timing of the recording signal generating circuit 5 is controlled by a signal from a timing generator 7 so that the recording signal generating circuit 5 can perform the necessary signal processing operations such as the addition of an error-correcting code, data interleaving, modulation, and the like. Accordingly, the output of the recording signal generating circuit 5 is a serial recording data signal corresponding to one track and is fed to an input terminal of a switch 8. The switch 8 switches the input signal between rotary heads 11A and 11B, the switch 8 being alternately changed in position during each respective 1/2 rotation period that corresponds to the tape contact period of the head 11A and of the head 11B, in response to a switching signal from the timing generator 7. This switching signal from the timing generator 7 is preferably produced in response to pulses indicating the rotary phase of the heads 11A and 11B from a pulse generator, not shown. The digital recording data from the switch 8 is fed through recording amplifiers 9A and 9B and then supplied through fixed contents R of switches 10A and 10B to the heads 11A and 11B, respectively, which record the data on a magnetic tape 14 as oblique tracks. The tape 14 is wound between take-up and supply reels 12 and 13, respectively. Upon playback, signals reproduced from the tape 14 by the heads 11A and 11B are fed through fixed contacts P of the switches 10A and 10B, respectively, to playback amplifiers 15A and 15B. The outputs of the playback amplifiers 15A and 15B are fed to the fixed contacts of a switch 16, which is under control of switching signals from the timing generator 7 alternately to change the switch connecting during each 1/2 rotation period that includes the tape contacts periods of the heads 11A and 11B. The output of the switch 16 is fed through an equalizer 17, a comparator 18, and a phase-locked loop (PLL) circuit 19 to an error-correcting circuit 20. In the error-correcting circuit 20 any errors that may be present and that can be corrected by the earlier provided error-correction codes and parity symbols are corrected. The equalizer 17, the comparator 18, and the PLL circuit 19 comprise the so-called electro-magnetic transducing system, as known heretofore. The output of the error-correction circuit 20 is fed to a digital-to-analogue (D/A) converter 21 and converted into an analogue signal that is then passed through a low-pass filter 22 and made available at an output terminal 23. This signal at the terminal 23 then in the appropriate circumstances is the original analogue audio signal that can be fed to a suitable playback transducer of the audio system. The output signal from the error-correcting circuit 20 is also fed into the digital I/O circuit 41, and made available as a digital output at a digital output terminal 24. In addition, the digital output from the error-correcting circuit 20 is also fed to a sub-code microcomputer 25 that operates as an interface to extract the sub-code signal that typically includes the timing code, the programme number, the start ID signal and the like. The operation of the entire recording apparatus is controlled by a system controller 26 that includes a number of operational control buttons or switches, such as a play control, a stop button, and the like that although not shown are necessary for operation of the recording apparatus. Accordingly, the system controller 26 provides suitable control signals to the digital I/O circuit 41 and the error-correcting circuit 20, for example. During recording, digital data at the sampling frequency is fed through the digital I/O circuit 41 that operates to detect any change in sampling frequency Fs that might occur in the incoming digital audio signal fed into the terminal 6. The result of this detection of any change in the sampling frequency Fs is fed to the system controller 26. In the event that a change in the sampling frequency Fs of the incoming digital audio signal is detected by the digital I/O circuit 41, data of various sampling frequencies are sequentially supplied from the system controller 26 to the digital I/O circuit 41, which detects the sampling frequency Fs of the incoming digital audio signal, thereby changing a circuit constant or the like to accommodate for this change in sampling frequency Fs. For example, the sampling frequency of the incoming digital audio signal from a broadcast satellite tuner may have a sampling frequency of 32 kHz, 44 kHz or 48 kHz and it is data concerning these different frequencies that is supplied to the I/O circuit 41 by the system controller 26. The system controller 26 also supplies an input signal to a drum servo circuit 30 that controls a drum motor 31 that rotates the rotary drum (not shown) on which the heads 11A and 11B are mounted. The system controller 26 also provides a control signal to a reel drive circuit 32 that provides drive signals to reel drive motors 33 and 34 that rotate the reels 12 and 13, respectively. The system controller 26 supplies a mode (play, fast forward, reverse) switching signal to the reel drive circuit 32, so that the level of the drive signals supplied to the motors 33 and 34 can be changed accordingly. Similarly, the system controller 26 supplies a control signal to a capstan servo circuit 35 that operates to control a capstan motor 37 that rotates a tape drive capstan 36. Of course, also provided but not shown are a pinch roller for the capstan 36, and a solenoid circuit for controlling the operation of the pinch roller against the capstan 36. The system controller 26 receives as an input signal, in addition to the information from the digital I/O circuit 41, a signal from an RF envelope detecting circuit 38 that has as an input the reproduced digital signal from the switch 16. As pointed out above, one problem present in an R-DAT recording apparatus is that during the recording operation, if the digital signal being fed in at the terminal 6 changes, either the sampling frequency Fs changes or the digital signal is interrupted, the recording operation continuous regardless. It is this situation that produces the undesired signals, such as click or pops and the like, that are recording on the tape 14. Upon operating the apparatus of Figure 1 in correspondence with the procedure shown in Figure 2, this undesirable recording situation can be alleviated. Turning then to the flow chart of Figure 2, following the Start of the operation, it is initially determined at decisional step ST1 whether the digital audio signal fed in at the terminal 6 is being recorded. If such digital input signal at the terminal 6 is not being recorded then the routine simply exists to a Return to the main program command located at the end of this sub-routine. On the other hand, if it is determined at step ST1 that the digital input signal at the terminal 6 is being recorded, then the program proceeds to the next decisional step ST2 where it is determined whether the supply of the digital audio signal at the terminal 6 is being interrupted or not. In this operation, the digital I/O circuit 41 detects the presence or absence of the input audio signal and the results of that detection are supplied to the system controller 26 that carries out the above decision. For example, it is determined that the supply of digital audio signal at the terminal 6 is continuous and not interrupted, as represented by a NO in decisional step ST2, the subroutine goes to the next decisional step ST3. At step ST3 determination is made whether the sampling frequency Fs of the digital audio input signal fed at the terminal 6 is undergoing change. As noted above, in the embodiment of Figure 1, data representing the current sampling frequency is supplied from the system controller 26 to the digital I/O circuit 41 where it is compared with the sampling frequency Fs. Thus, any change of sampling frequency Fs is detected at the digital I/O circuit 41 and the results thereof are fed to and judged by the system controller 26. On the other hand, if it is determined that the sampling frequency Fs of the digital audio signal is not changed, a NO is output at step ST3, and the sub-routine returns to the main operating program. If it is determined that the sampling frequency Fs has changed then the sub-routine moves to step ST4 where the apparatus is set into the pause mode, represented as REC pause. This pause mode is also selected if it is determined to step ST2 that the input signal is interrupted, so that either a sampling frequency change or signal interruption results in the setting of the apparatus into the recording pause made at step ST4. While the apparatus is set into the pause mode in step ST4, the next decision is made at step ST5 as to whether the digital audio signal is being supplied to the terminal 6. If so, the sub-routine moves to decisional step ST6 where it is determined whether the sampling frequency of the digital audio signal has stabilized. Of course, such stabilization can be easily determined by simply detecting the sampling frequency Fs. As pointed out above, in this case, data representing the various sampling frequency values can be sequentially fed from the system controller 26 to the digital I/O circuit 41, wherein such data can be compared with the actual sampling frequency Fs of the signal being received at the terminal 6. The sampling frequency Fs is then detected by the digital I/O circuit 41 and the detection results fed to and judged by the system controller 26. If it is determined that the sampling frequency Fs has not stabilized, a NO is output from the step ST6 and fed to the next decision ST7 where it is determined whether a predetermined period of time, for example, one minute, has passed after the initial setting into the pause mode as that occurred in step ST4. If at step ST7 it is determined that a minute has elapsed from the time that the apparatus is set into the pause mode, the a YES is provided at step ST7, and the sub-routine moves to ST8 where the apparatus is set into the stop pause mode. In the stop pause mode, rotation of the rotary drum on which the heads 11A and 11B are mounted and rotation of the capstan 36 are stopped and the mechanical elements of the apparatus are released from the pause mode and set into the stop mode. Upon having set the mechanism into the stop pause mode, the sub-routine moves to step ST9 that serves to command the light emitting diode that serves as the recording indicator to flash and then the sub-routine returns to the step ST5. On the other hand, if in step ST7 it is determined that the time limit has not elapsed, as represented by a NO, the program then moves back to step ST5 after passing through the step ST9 whereat the recording indicator is caused to flash. Accordingly, when the digital audio signal is not supplied at the terminal 6 or when the sampling frequency is not stable even though the audio signal is being supplied, the recording indicator is caused to flash at step ST9, thereby indicating that the apparatus is set into the recording pause mode. Such recording pause mode is pictorially represented in Figure 3B, which represents a first light emitting diode (LED) 51 that indicates the forward running mode, a second LED 52 that indicates the recording mode, and a third LED 53 that indicates the pause mode of the apparatus. Figure 3B is intended to represent that LEDs 51 to 53 are energized or illuminated, while LED 52 is caused to flash. On the other hand, Figure 3A illustrates that the apparatus is set into the recording mode in which the LEDs 51 and 52 are turned on, while the LED 53 representing pause is turned off. If it is determined in step ST6 that the sampling frequency Fs is stable then the next decisional step ST10 is performed whereat it is determined whether one second has passed since the time the sampling frequency Fs stabilized. If it is determined in step ST10 that the sampling frequency Fs is not stable for a period of one second, then this step is repeated continuously. Thus, when the sampling frequency Fs of the digital audio signal fed in at the terminal 6 is being changed, the necessary switching of the circuit constant and the like will be carried out within a time period of one second. On the other hand, if it is determined in step ST10 that the sampling frequency Fs is stabilized, the sub-routine moves to step ST11 at which the apparatus is set into the reverse or rewind mode. Upon setting the apparatus into the rewind mode, it is then determined in step ST12 whether one second has elapsed. If not, this time check is executed continuously. The provision of setting the apparatus into the rewind mode at step ST11 is performed to erase by an overwriting operation an undesired or unstable signal that was recorded on the tape 14 while the apparatus was set in the pause mode when the supplying of the digital audio signal at the terminal 6 was interrupted or when the sampling frequency Fs was changed. The duration of the time period in step ST12 is not limited to one second but may be longer than the time in which the undesired or unstable signal was recorded. If if it determined that one second has passed after the apparatus was set into the rewind mode, as represented by a YES at step ST12, the sub-routine proceeds to step ST13 where the apparatus is set into the recording mode and the sub-routine returns to the main program. With this embodiment of the invention, if any change in the digital input signal at the terminal 6 takes place, either by the supply of the signal being interrupted or by the sampling frequency Fs being changed, the apparatus is quickly set into the pause mode. If the supply of the digital audio signal to the terminal 6 has not stabilized within one minute after the setting into this pause mode, the apparatus is set into the stop pause mode. In the pause mode, as well as in the stop pause mode, the LED 52 is caused to flash indicating that the apparatus remains set in the recording pause mode. While in the recording pause mode for one second, and after one second has passed the apparatus is then returned to the recording mode. Thus, when the condition of the audio signal being supplied at the terminal 6 changes the apparatus is placed into a pause mode and then into a stop pause mode so that after the input digital signal becomes stabilized, the tape 14 is then rewound by a tape length corresponding to the duration of time during which the undesired or unstable signal was recorded and then recording is commenced again. Therefore, even when the supply of the digital input signal changes any undesirable or unstable signal is prevented from being recorded and an excellent recording is produced. Of course, as seen in the above, when the supply of the digital audio signal to terminal 6 does not stabilize within one minute after the apparatus has been set into the pause mode, then the apparatus is set into the stop pause mode thereby prevent the tape 14 from being damaged. Moreover, because the LED 52 flashes to indicate that the apparatus is set into the recording pause mode, such as the pause mode or the stop pause mode, there is a positive indication to the user that there should be no concern about the existence of a long recording pause mode. In the system of Figure 2, steps ST7 and ST8 are provided in order to protect the tape 14 from being damaged and, thus, are not always required. In addition, the time limit of one minute in ST7 may be selected based upon individual system requirements. Furthermore, although the LED 52 flashes to indicate that the apparatus has been set in the recording pause mode, all of the LEDs 51, 52 and 53, could be made to flash. In addition, an individual indicating element could also be provided. While the above embodiment is directed to a R-DAT recording apparatus using a tape, the invention could be similarly applied to any recording apparatus employing a disc, semiconductor memory, or the like as the recording medium.

Claims: A recording apparatus comprising: an input terminal (6) to be supplied with a digital signal; recording means (11A, 11B) for recording on a recording medium (14) the digital signal supplied to said input terminal (6); recording mode setting means for setting said recording means (11A, 11B) into a recording mode; pause mode setting means for setting said recording means (11A, 11B) into a recording pause mode; stop mode setting means for setting said recording means (11A, 11B) into a recording stop mode; characterized by: detecting means (26) for detecting whether a condition of the digital signal at said input terminal (6) has changed from normal; means (26) for controlling said recording mode setting means to set said recording means (11A, 11B) in said recording mode and for controlling said pause mode setting means to set said recording means (11A, 11B) in said recording pause mode when said detecting means (26) detects that the condition of said digital signal has changed during recording of said digital signal by said recording means (11A, 11B); means (26) for releasing the operation of said pause mode setting means when said detecting means (26) detects that the condition of said digital signal has returned to normal within a predetermined time while in said pause mode as a result of detecting that said condition has changed and for operating said recording mode setting means to set said recording means (11A, 11B) into said recording mode; and means (26) for releasing the operation of said pause mode setting means when said detecting means (26) detects that the condition of said digital signal has not returned to normal within a predetermined time while in said, pause mode as a result of detecting that said condition has changed and for setting said recording means (11A, 11B) in said recording stop mode. Apparatus according to claim 1 further comprising visual indicating means (51 to 53) arranged to flash in response to said means for controlling said pause mode setting means to set said recording means (11A, 11B) into said recording pause mode. Apparatus according to claim 1 further comprising means (26) for determining a position on said recording medium (14) at which said pause mode setting means is operated and for rewinding said recording medium (14) to the position at which said pause mode setting means was set by operation of said pause mode setting means when said detecting means (26) detected that the condition of said digital signal had not changed within a predetermined time while said pause mode and for operating said recording mode setting means to set said recording means (11A, 11B) in said recording mode. Apparatus according to claim 1 wherein said recording medium (14) is a magnetic tape (14). Apparatus according to claim 1 wherein said recording medium (14) is a disc. Apparatus according to claim 1 wherein said recording medium (14) is a semiconductor memory. Apparatus according to claim 1 wherein said recording means (11A, 11B) includes means (5) for recording a signal on said recording medium (14) in the form of a digital signal. Apparatus according to claim 1 further comprising timer means operating in response to said pause mode for measuring said predetermined time. A method of operating a recording apparatus supplied with a digital signal, comprising the steps of: setting a recording system of the apparatus into a recording mode for recording the digital signal; recording with the recording system on a recording medium (14) the supplied digital signal; characterized by: detecting whether a condition of the supplied digital signal changes from normal during the recording; setting the recording system in a recording pause mode upon detecting that the condition of the digital signal has changed during recording of said digital signal in the recording mode; releasing operation of the pause mode when detecting that the condition for the digital signal has returned to normal within a predetermined time while set in the pause mode as a result of detecting that said condition has changed and setting the recording system in the recording mode; and releasing the operation of the cause mode when detecting that the condition of the digital signal has not returned to normal within a predetermined time while in the pause mode as a result of detecting that said condition has changed and setting the recording system in a recording stop mode. A method according to claim 9 further comprising providing a flashing visual indication (51 to 53) in response to setting the recording system in the recording pause mode. A method according to claim 9 further comprising determining a position on said recording medium (14) at which said pause mode is set and rewinding said recording medium (14) to the position at which the pause mode was set and setting the recording system in the recording mode.

Inventors: ASANO HISASHI C O PATENTS DIVI, KIMIZUKA MASANORI C O PATENTS, ASANO, HISASHI C/O PATENTS DIVISION, KIMIZUKA, MASANORI C/O PATENTS DIVISION
Applicants: SONY CORP, SONY CORPORATION
Application year: 1989
Main classification: G11B27
IPC codes: G11B27