Digital signal recording apparatus using a rotary head

Abstract: In a magnetic recording and reproducing apparatus, an audio signal and a video signal are assigned to a first and a second channels of an ordinary magnetic recording and reproducing apparatus respectively and recorded at a transmission rate twice that of usual rate. Thereby it is possible to record an audio signal without tone quality degradation and record a video signal together with the audio signal.

Description: This invention relates to a digital signal recording apparatus using a rotary head, and more particularly to an improvement of the recording digital audio signal on the recording tracks sequentially arranged slanted on a magnetic tape. Magnetic recording apparatus are known, in which sequentially arranged slanted recording tracks are formed on a magnetic tape using a rotary head and a digital audio signal is recorded on the recording tracks sequentially (referred to as a digital audio tape recorder, hereinafter). In such a digital audio tape recorder, an audio signal is converted into a digital signal for recording or reproduction on the magnetic tape and can be recorded or reproduced effectively by avoiding tone quality degradation by means of execution of an error correcting procedure. It would be convenient if a video signal could be recorded together with the audio signal by this kind of digital audio tape recorder. It has been considered (see, e.g. JP-1-272384 and US-A-4710826) that the audio signal and the video signal would be recorded together by compressing them. However, in this case there is a degradation problem in the tone quality of the audio signal. There is also a further problem that it is impossible to obtain sufficient image quality since, in such case, an information rate of only 515 - 768 [kbps] which is newly obtained by compressing the audio signal can be assigned to the video signal. Further, when recording is performed in this manner, it is impossible to reproduce a magnetic tape on which signals are recorded by means of an ordinary digital audio tape recorder, because the information compressed is recorded on the tape. JP-2-235486 and EP-A-371456 disclose the recording of audio and video signals on a DAT system in accordance with the pre-characterizing portion of claim 1 and in which the two or four channels available in the normal audio mode are divided between the audio and video signals. EP-A-241014 discloses recording audio and video signals in slant tracks on a VTR system. JP 63-155877 discloses a method of providing a high definition mode in a VTR by switching the compression rate of the signals and the speed of the tape and tape head. Thus a high definition signal is recorded as two azimuth tracks per field in the same pitch as in a standard mode. In view of the foregoing, an object of this invention is to provide a digital signal recording apparatus using a rotary head in which improved recording of a digital audio signal and a digital video signal can be satisfactorily achieved on a magnetic tape. According to the present invention, there is provided a magnetic recording apparatus for recording audio or audio and video signals, the apparatus comprising: a rotary drum mounting a magnetic head, a servo means for rotating said rotary drum at a predetermined rotation speed and running a magnetic tape at a predetermined running speed wound around said rotary drum in an audio recording mode for sequentially forming recording tracks slantingly on the magnetic tape, to record left and right channel digital audio signals provided at a first data transmission rate in said tracks; a signal processing means for providing an audio and video recording mode for recording left and right channel digital audio signals and digital video signals, and a signal recording means for supplying said signals output from said signal processing means to said magnetic head wherein the signal processing means, assigns the digital audio signal to a one of the left and right channel recording regions of said tracks and the digital video signal to the other channel recording region of said tracks; characterised in that in said audio and video recording mode, the servo means rotates said rotary drum at a rotation speed twice said predetermined rotation speed and runs said magnetic tape at a running speed twice said predetermined running speed; and in that the signal processing means provides the signals to the magnetic head at a second data transmission rate double the first transmission rate; to record the left and right channel audio signals and the video signal alternately in said regions of said tracks. Thus the rotary drum is rotated at a rotation speed twice the rotation speed in an ordinary recording and the magnetic tape runs at a running speed twice the running speed in the ordinary recording. The digital audio signal DA1 and the digital video signal DV1 are provided at a transmission rate twice the transmission rate in the ordinary recording to convert into a recording signal, which then is recorded on the tracks formed on the magnetic tape. Thus with the invention a digital signal recording apparatus uses a rotary head in which a digital audio signal and a digital video signal are recorded on a magnetic tape without tone quality degradation of the digital audio signal. By arranging the digital audio signal and the digital video signal using the first and second recording channels (L) and (R), respectively, and recording the digital audio signal and the digital video signal at a rate twice the ordinary transmission rate, it is possible to record the audio signal with the same tone quality as in the case of recording at the usual transmission rate. Further, for the digital video signal, it is possible to assign the same amount of information as that of the digital audio signal so that it is possible to record the digital video signal together with the digital audio signal. In a magnetic recording and reproducing apparatus according to the present invention, it is also possible to reproduce the magnetic tape having been recorded by means of a rotary head rotating at an ordinary rotation speed by switching the processing speed of the apparatus. The invention will be further described by way of non-limitative example with reference to the accompanying drawings, in which like parts are designated by like reference numerals or characters and in which:- Fig. 1 is a block diagram showing a stationary image recording apparatus according to an embodiment of the present invention; Fig. 2 shows a format of recording signal thereof; Fig. 3 is a block diagram showing a digital audio tape recorder; Fig. 4 shows a recording format of an existing digital audio tape recorder; and Fig. 5 shows a recording format of this embodiment. Preferred embodiments of this invention will be described with reference to the accompanying drawings: In Fig. 1, 1 depicts a stationary image recording device as a whole, an audio signal SA1 and a video signal SV1 outputted from a video tape recorder (VTR) as a signal source 2 are processed in a preprocessing circuit 3 to be recorded on a magnetic tape. The preprocessing circuit 3 supplies the audio signal SA1 and the video signal SV1 to analog to digital conversion circuits (A/D) 5 and 7 to convert them into a digital audio signal DA1 and a digital video signal DV1, respectively. A memory control circuit 9, in recording, accumulates the digital video signal DV1 in a sequential memory circuit 10 and outputs it as a digital video signal DRV to a synthesizing and separating circuit 12 at a transmission rate of about 1.5 [Mbps]. Against this, the memory control circuit 9, in reproduction, accumulates the digital video signal DPV outputted from the synthesizing and separating circuit 12 in the memory circuit 10 and when the accumulation corresponds to 1 frame, outputs them sequentially to a digital conversion circuit (D/A) 14 at a predetermined transmission rate as a digital video signal DV2. By this, the stationary image recording device 1 outputs the video signal SV2 or SV1 outputted from the digital to analog conversion circuit 14 or the video tape recorder 2 through a selector circuit 16 to a monitor 18 selectively so that a video signal recorded or reproduced can be monitored. The synthesizing and separating circuit 12, in recording, receives a digital video signal DRV outputted from the memory control circuit 9 together with the digital audio signal DA1 and outputs them to a digital audio tape recorder (DAT) 13. In this case, as shown in Figs. 2A and 2B, the synthesizing and separating circuit 12 synthesizes the right and left channel signals (indicated by symbols L and R) of the digital audio signal and the digital video signal DRV (indicated by symbol V) to produce a recording signal DR. That is, in a digital audio signal DN (Fig. 2A) standardized for the digital audio tape recorder (DAT), right and left channels are alternatively successive on the basis of a sampling frequency of 48 [kHz], while the synthesizing and separating circuit 12 arranges the right and left channel digital audio signal DA1 successively on the basis of a frequency of 96 [kHz] twice sampling frequency described above. Subsequently the recording signal DR (Fig. 2B) is formed so that the digital video signal DV1 succeeds the signal DA1. Further, in this case, the synthesizing and separating circuit 12 outputs the recording signal DR at a transmission rate of 3.06 [Mbps] which is approximately twice the usual transmission rate of 1.5 [Mbps]. By this, in the preprocessing circuit 3, the digital audio signal DA1 is outputted to the digital audio tape recorder at a transmission rate twice the usual rate and outputs the digital video signal DRV at the same transmission rate as that of the digital audio signal DA1. Against this, the synthesizing and separating circuit 12 in reproduction process to convert the reproduction signal DP outputted from the digital audio tape recorder 13 in reverse manner to the case of recording and outputs it as a digital video signal DPV and a digital audio signal DA2 separately. By this, it is possible to monitor the video signal SV2 reproduced by the digital audio tape recorder 13 through the preprocessing circuit 3. Further, by converting the reproduced digital audio signal DA2 in to an analog signal through a selector circuit 19 and a digital to analog conversion circuit (D/A) 20 and outputting it to a amplifier (AMP) 22, it is possible to monitor the reproduced digital audio signal. Further, according to demand, the recording digital audio signal DA1 can be monitored instead of the reproduced digital audio signal, by switching contacts of the selector circuit 19. Fig. 3 shows the arrangement of the digital audio tape recorder 13. In recording, a digital signal processing circuit (DSP) 26 converts the recording signal DR inputted sequentially thereto into a signal to be sequentially recorded on the magnetic tape 28. In reproduction, the digital signal processing circuit (DSP) 26 outputs a reproduction signal SP which is obtained from a signal sequentially reproduced from the magnetic tape 28. The digital audio tape recorder 13 switches its operation mode corresponding to a control information DC from a system control circuit 25. In this embodiment, the system control circuit 25 operates at a processing speed twice that in the case of usual process. The digital signal processing circuit 26 outputs a clock signal CK for the reference in operation to the preprocessing circuit 3 and, in recording, stores the recording signal DN in the memory circuit 30, sequentially. In this case, the digital signal processing circuit (DSP) 26 operates at a processing speed twice the usual processing speed and processes the recording signal DR in synchronism with the preprocessing circuit 3 through the use of the clock signal CK. By this, in the digital signal processing circuit 26, the digital audio signal DA1 and the digital video signal DRV sequentially inputted at a time frame of 96 [kHz] are stored in predetermined regions of the memory circuit 30 and thus data is interleaved for example at every 15 [msec] time period. Further, at this time, the digital signal processing circuit 26 assigns the digital audio signal DA1 and the digital video signal DRV to data memory regions of the memory circuit 30 where the right and left channels of the digital audio signal should be assigned in an ordinary interleave process (interleaved with every 30 [msec] time period, usually) and interleaves them, by processing the recording signal DR at a processing rate twice the processing rate of the preprocessing circuit 3 synchronously therewith. Further, the digital signal processing circuit 26 produces a parity sign for check and correction of error of the recording signal DR stored in the memory circuit 30 and then 8-10 modulates the parity sign and the recording signal DR and outputs it to an amplifier circuit (AMP) 32. The amplifier circuit 32, in recording, amplifies the recording signal SR outputted from the digital signal processing circuit 26 and outputs it to the magnetic heads 38A and 38B. At this time, the rotary drum 34 is driven by a servo circuit 40 to rotate at a rotation speed twice its ordinary rotation speed. The magnetic tape 28 runs under control of the servo circuit 40 at a running speed twice its ordinary running speed, as is the rotary drum 34. Further, the magnetic tape 28 runs while wound on the rotary drum 34 by a length corresponding to 90°. The magnetic heads 38A and 38B are mounted on the rotary drum 34 with an angular interval of 180°. Fig. 4 is a recording signal pattern shown in a case where signals are recorded at usual recording speed on the magnetic tape. In existing digital audio tape recorder, the magnetic tape 28 and the rotary head 34 are driven at the usual speed. That is, the digital audio signal of the sampling frequency of 48 [kHz] is recorded according to the format standardized for the digital audio tape recorder (DAT). The respective recording track is divided into 2 sections in longitudinal direction and the digital audio signal is recorded sequentially with every 30 [msec] time period such that the right and left channels alternate. Fig. 5 is a data recording pattern on the magnetic tape in the embodiment according to the present invention. When, as in this embodiment, the data is processed at the rate twice the ordinary case and the digital audio signal DA1 and the digital video signal DV1 are converted into the recording signal SR by assigning them to the right and left channels, respectively, it is possible to record the digital audio signal DA1 and the digital video signal DRV in manner of separating each other and sequentially on the magnetic tape 28. That is, in the magnetic tape 28, each recording track is divided into 2 regions in longitudinal so that the digital audio signal DA1 for the right channel and the left channel is recorded on the one of the regions as well as the digital video signal DRV is recorded with every 15 [msec] time period on the other of the regions. Further, at this time, the recording regions for the digital audio signal DA1 and the digital video signal DRV are arranged alternately according to the recording format of the digital audio tape recorder. By doing so, it is possible to record the digital audio signal DA1 at a rate twice the ordinary rate through the magnetic tape running system driven at a rate twice the ordinary rate of the digital audio tape recorder. As a result, it is possible to assign, to the digital audio signal DA1, the same data amount as can be assigned to the ordinary digital audio tape recorder. Further, as to the signal processing format itself, it can be processed in as in a manner as to the ordinary digital audio tape recorder. Thereby the digital audio signal DA1 can be recorded without tone quality degradation of the audio signal. The digital video signal DRV can be recorded at a rate of 1.536 [Mbps] assigned to the right and left channels of the ordinary digital audio tape recorder. Therefor, the video signal can be recorded together with the digital audio signal. Against this, in reproduction, the digital signal processing circuit 26 receives the reproduction signal SP outputted from the magnetic heads 38A and 38B through the amplifier circuit 32 and outputs them after sequential demodulation. That is, the digital signal processing circuit 26 derives the reproduction clock from the reproduction signal SP and then demodulates the reproduction signal SP on the basis of the reproduction clock. Further, the digital signal processing circuit 26 stores the reproduction data demodulated in the memory circuit 30, performs the error check and correction. Subsequently the digital signal processing circuit performs a reverse-interleave processing and outputs a resultant reproduction signal DP to the preprocessing circuit 3. By this, the reproduced digital audio signal SA2 and the digital video signal SV2 are outputted to the monitor 18 through the preprocessing circuit 3. The tracking control circuit 42 derives a pilot signal from the reproduction signal SP for tracking control and a tracking error signal ER is produced on the basis of ATF (automatic track finding). By this, in the digital audio tape recorder 13, the servo circuit 40 controls the magnetic tape running system according to the tracking error signal ER so that the tracking control is performed reliably. In the construction mentioned hereinbefore, in recording, the video signal SV1 is converted by the analog to digital conversion circuit 7 into the digital video signal DV1 and then outputted at the predetermined transmission rate through the memory control circuit 9. On the other hand, the audio signal SA1 is converted by the analog to digital conversion circuit 5 into the digital audio signal DA1 and then synthesized by the synthesizing and separating circuit 12 with the digital video signal DV1. At this time, the digital video signal DV1 is synthesized with the digital audio signal DA1 such that these signals are alternatively continuous with a predetermined time period in synchronism with the operation of the digital audio tape recorder 13, resulting in the recording signal DR whose transmission rate is twice compared with the ordinary digital audio tape recorder and whose digital audio signal DA1 and the digital video signal DV1 are assigned to the right and left channels, respectively. The recording signal DR is outputted to the digital audio tape recorder 13 operating at the processing rate twice the ordinary one and after interleaved therein recorded sequentially on the magnetic tape 28 together with the error check and correction sign. Thus, by recording the digital audio signal DA1 by means of the digital audio tape recorder 13 converting the transmission rate twice and operating at the processing rate twice, there is no tone quality degradation of the digital audio signal DA1. Further,it is possible to assign to the digital video signal DV1 the same information amount as that of the digital audio signal DA1 and record it on the magnetic tape. In reproduction, the reproduction signal SP outputted from the magnetic heads 38A and 38B is demodulated by the digital signal processing circuit 26 and outputted sequentially to the preprocessing circuit 3. By this, the reproduction signal DP from the digital signal processing circuit 26 is separated to the digital audio signal DA2 and the digital video signal DV2 in reverse fashion to the recording and then outputted to the amplifier 22 and the monitor 18, resulting in that the audio signal and video signal can be recorded and reproduced easily. Further, the magnetic tape recorded by the ordinary digital audio tape recorder can be easily reproduced by merely switching the operating rate of the digital audio tape recorder 13. Although, in the above mentioned embodiment, the present invention was described as applied to recording and reproducing a stationary image, the present invention is not limited thereto and is applicable to recording and reproducing a moving image. In such case, by providing a video signal compression and expansion circuit instead of the memory control circuit 9 and the memory circuit 10, the moving image can be more effectively recorded and reproduced.

Claims: A magnetic recording apparatus for recording audio or audio and video signals, the apparatus comprising: a rotary drum (34) mounting a magnetic head (38A,B), a servo means (40) for rotating said rotary drum (34) at a predetermined rotation speed and running a magnetic tape at a predetermined running speed wound around said rotary drum (34) in an audio recording mode for sequentially forming recording tracks slantingly on the magnetic tape (28), to record left and right channel digital audio signals (DA1) provided at a first data transmission rate in said tracks; a signal processing means (5,7,9,12) for providing an audio and video recording mode for recording left and right channel digital audio signals and digital video signals, and a signal recording means (26,32) for supplying said signals output from said signal processing means (5,7,9,12) to said magnetic head (38A,B) wherein the signal processing means (5,7,9,12), assigns the digital audio signal to a one of the left and right channel recording regions of said tracks and the digital video signal to the other channel recording region of said tracks; characterised in that in said audio and video recording mode, the servo means (40) rotates said rotary drum (34) at a rotation speed twice said predetermined rotation speed and runs said magnetic tape (28) at a running speed twice said predetermined running speed; and in that the signal processing means (5,7,9,12) provides the signals to the magnetic head (38A,B) at a second data transmission rate double the first transmission rate; to record the left and right channel audio signals and the video signal alternately in said regions of said tracks. Magnetic recording apparatus according to claim 1, further comprising: a means (5) for analog to digital converting an input analog audio signal. Magnetic recording apparatus according to claim 1 or 2, further comprising: a means (7) for analog to digital converting an input analog video signal. Magnetic recording apparatus according to claim 1, 2 or 3, wherein said digital video signal is temporarily stored in a memory (10) and then is provided for signal processing. Magnetic recording apparatus according to any one of the preceding claims, wherein the first transmission rate is 1.5 Mbps and the second data transmission rate is 3.06 Mbps. Magnetic recording and reproducing apparatus wherein the recording apparatus is in accordance with any one of the preceding claims and including means (12,19,20,22,9,10,14,16,18) for reproducing the magnetic tape while running it at said predetermined running speed.

Inventors: FUKAMI TADASHI, FUKUDA SHINICHI, NOGUCHI MASAYOSHI, YAMADA MAKOTO, FUKAMI, TADASHI, FUKUDA, SHINICHI, NOGUCHI, MASAYOSHI, YAMADA, MAKOTO
Applicants: SONY CORP, SONY CORPORATION
Application year: 1991
Main classification: G11B20
IPC codes: G11B5, H04N5, G11B20