Reproducing and post-recording digital signals

Abstract: Apparatus for reproducing and after-recording digital signals in slanting recording tracks (20) arranged sequentially on a recording medium (6) includes a recording subsystem (28) for recording digital signals in each of the tracks (20) and a reproducing subsystem (32) for reproducing digital signals therefrom. The recording and reproducing subsystems (28, 32) include one or more recording and/or reproducing heads (30a, 30b) for scanning the tracks (20) for recording and reproducing digital data therein. A tracking control subsystem (10 to 17, 19) controls tracking of the heads (30a, 30b) with respect to the tracks (20) in a reproducing mode based upon tracking signals (ATF1, ATF2) recorded in both first and second tracking signal recording areas (AT1, AT2) of the tracks located at initial and final scan positions (22, 24), respectively, of each track. In an after-recording mode, the tracking control subsystem (10 to 17, 19) utilises tracking signals (ATF1 or ATF2) recorded in only one of the tracking signal recording areas (AT1, AT2) while recording digital signals in a sub information recording area (AU1, AU2, SC) proximal to the area from which the utilised tracking signals are obtained.

Description: This invention relates to reproducing and after-recording digital signals, particularly (but not exclusively) in commercial applications. Known digital video tape recorders (VTRs) designed for commercial applications digitise and record video and audio signals, as main and sub information signals, respectively, in correspondingly different areas in slanting tracks formed sequentially on a video tape. It has been proposed that such a digital VTR be provided with an after-recording mode of operation in which only an audio signal and a sub code signal are again recorded. Figure 1 of the accompanying drawings illustrates the format of one of a plurality of slanting tracks 20 formed on a video tape by the digital VTR. As shown in Figure 1, the various signals are recorded sequentially in the track 20 by a recording head (not shown) that scans the track beginning at an initial track scan position 22 and proceeding to a final track scan position 24 thereof. As the recording head scans the track 20, starting from the initial track scan position 22, a first automatic track following (ATF) signal recording area AT1 is formed in which a first ATF signal for use in tracking adjustment is recorded. In sequence thereafter, a first audio signal recording area AU1 is formed in the track 20 wherein a first audio signal (also referred to as a first sub information signal) is recorded. Subsequently to the formation of the recording area AU1, a second audio signal recording area AU2 is formed in which a second audio signal (also referred to as a second sub information signal) is recorded. Following the formation of the recording area AU2, a video signal recording area VI is formed in which a video signal (also referred to as a main information signal) is recorded. Following the formation of the area VI, a sub code signal recording area SC is formed in which a sub code signal (also referred to as a third sub information signal) is recorded. Finally, adjacent the final scan position 24, a second ATF signal recording area AT2 is formed in which a second ATF signal is recorded for tracking adjustment purposes. It is often the case that the track angle and the angle at which the head scans the recording tracks do not coincide because of a lack of compatibility between the digital VTR and other apparatus. In that case, an automatic tracking control function is carried out by using the first and second ATF signals reproduced from the ATF signal recording areas AT1 and AT2, respectively, of each of the tracks. In operation, respective tracking error signals are detected from the reproduced ATF signals, and automatic tracking control is then carried out so that the tracking error signals are both minimised. Consequently, the automatic tracking function is carried out so that the scanning locus of the head (indicated by a dashed line x in Figure 1) coincides with the track 20 at the centre of the tape. If the above-described automatic tracking control technique is employed, the video signal is reproduced satisfactorily. However, in the after-recording mode of the digital VTR in which only an audio signal and a sub code signal are recorded, for example, the track 20 and the head scanning locus x do not coincide either in the audio signal recording area or in the sub code signal recording area. Consequently, it may be the case that after-recording cannot be carried out satisfactorily with the use of the above-described automatic tracking control technique. UK Patent Application Publication No. GB-A-2 204 179 (and corresponding German Patent Application Publication No. DE-A-3 809 179) discloses an apparatus according to the pre-characterising part of claim 1 hereof and a method according to the pre-characterising part of claim 6 hereof. According to a first aspect of the invention there is provided apparatus for reproducing and after-recording digital signals in slanting recording tracks arranged sequentially on a recording medium, each of the tracks having a main signal recording area, a first sub information recording area having one of a scan preceding and a scan following relationship with respect to the main signal recording area, a second sub information recording area having one of a scan preceding and scan following relationship with respect to the main signal recording area which is opposite that of the first sub information recording area, and first and second tracking signal recording areas provided adjacent an initial scan position and a final scan position, respectively, of the track, each of the tracking signal recording areas having tracking signals recorded therein, the apparatus comprising: recording means for recording digital signals in each of the tracks; reproducing means for reproducing digital signals from each of the tracks; the recording and reproducing means including scanning means for scanning each of the tracks for respectively recording and reproducing digital data therein; and tracking control means for controlling tracking of the scanning means with respect to one of the tracks in a reproducing mode of the apparatus based upon tracking signals recorded in both of the first and second tracking signal recording areas; the tracking control means being further operative in an after-recording mode of the apparatus, in which digital signals are to be recorded in the first and second sub information recording areas, to control tracking of the scanning means based upon tracking signals recorded in only one of the first and second tracking signal recording areas of a corresponding track; characterised in that: the recording means is operative in the after-recording mode to record digital signals in a selected one of the first sub information recording area and the second sub information recording area, and the apparatus comprises tracking signal selecting means for selecting tracking signals from the one of the first and second tracking signal recording areas having one of a scan preceding and scan following relationship with respect to the main signal recording area which corresponds to that of the selected one of the first and second sub information recording areas. According to a second aspect of the invention there is provided a method of reproducing and after-recording digital signals in slanting recording tracks arranged sequentially on a recording medium, each of the tracks having a main signal recording area, a first sub information recording area having one of a scan preceding and a scan following relationship with respect to the main signal recording area, a second sub information recording area having one of a scan preceding and scan following relationship with respect to the main signal recording area which is opposite that of the first sub information recording area and first and second tracking signal recording areas provided adjacent an initial scan position and a final scan position, respectively, of the track, each of the tracking signal recording areas having tracking signals recorded therein, the method being carried out by using apparatus for scanning the tracks to record and reproduce digital signals therein in selectable after-recording and reproducing modes of the apparatus, respectively; the method comprising: selecting one of the after-recording and reproducing modes of the apparatus; in the reproducing mode of the apparatus, scanning the tracks to reproduce digital signals therefrom while controlling tracking of the scanned tracks based upon tracking signals recorded in both of the tracking signal recording areas in each of the tracks scanned in the reproducing mode; and in the after-recording mode of the apparatus, scanning the tracks to record digital signals in the first and second sub information recording areas thereof while controlling tracking of the scanned tracks based on tracking signals recorded in only one of the tracking signal recording areas in each of the tracks scanned in the after-recording mode; characterised in that: the scanning of the tracks in the after-recording mode comprises recording digital signals in a selected one of the first sub-information recording area and the second sub information recording area while controlling tracking of the scanned tracks based on tracking signals from the one of the first and second tracking signal recording areas having one of a scan preceding and scan following relationship with respect to the main signal recording area which corresponds to that of the selected one of the first and second sub information recording areas. The apparatus and method provide the ability to position a track and a head scanning locus selectively with respect to each other at the sub information recording area selected for recording in the after-recording mode, since tracking control is carried out using the tracking signals from a corresponding selected one only of the tracking signal recording areas. In addition, in the reproducing mode the main information signal can be reproduced satisfactorily since tracking control is carried out with the use of the tracking signals from both of the tracking signal recording areas. Therefore, satisfactory tracking control can be achieved in both the reproducing and after-recording modes. The invention will now be further described, by way of illustrative and non-limiting example, with reference to the accompanying drawings, in which like references are used to identify the same or similar parts throughout, and in which: Figure 1 is a diagrammatic view of a portion of a video tape recording medium illustrating the format of a slanting track recorded by a previously proposed digital VTR; Figure 2 is a block diagram of a digital VTR embodying the invention; and Figure 3 is a diagrammatic view of a portion of a video tape recording medium for use in explaining the operation of the embodiment of Figure 2. Figure 2 shows the principal circuit elements of a digital video tape recording apparatus (digital VTR), for reproducing and after-recording digital signals on a video tape, according to a preferred embodiment of the invention. As shown in Figure 2, a recording section 28 of the digital VTR includes input terminals 1v, 1a and 1s to which are provided a video signal, an audio signal and a sub code signal, respectively, for recording on a magnetic tape 6. A recording signal processor circuit 2 is coupled to each of the input terminals 1v, 1a and 1s to receive the video, audio and sub code signals and serves to combine the received signals sequentially with automatic track following (ATF) signals generated thereby to form a recording signal which it supplies at an output thereof. A recording amplifier 3 of the recording section 28 has an input coupled to the output of the circuit 2 to receive the recording signal, and amplifies the recording signal before supplying it to an output thereof. The output of the recording amplifier 3 is coupled to a first fixed input terminal of a switching device 4. A movable terminal of the switching device 4 is coupled to a pair of rotary recording/reproducing heads 30a and 30b angularly spaced by 180° on a rotary head assembly 5. The movable terminal of the device 4 is coupled as appropriate to the first fixed input terminal thereof to provide the amplified recording signal to the heads 30a and 30b. The heads 30a and 30b scan the magnetic tape 6 to record the amplified recording signal in slanting recording tracks formed sequentially thereon and having the format illustrated in Figure 1. It will be appreciated that various other forms of rotary head assemblies may be used in place of the assembly 5. For example, different numbers of heads and head arrangements (such as one or more pairs of heads each in a unitary assembly) may be employed. A reproducing section 32 of the digital VTR of Figure 2 includes a playback amplifier 7 having an input coupled to a second fixed terminal of the switching device 4. In a reproducing mode of the digital VTR, signals recorded in the slanting recording tracks formed on the magnetic tape 6 are reproduced by the heads 30a and 30b of the rotary head assembly 5 and supplied thereby to the movable terminal of the switch 4 which is then coupled to the second fixed terminal to provide the playback signals to the input of the playback amplifier 7. The playback amplifier 7 amplifies the signals received thereby and supplies them to an output thereof which is coupled to an input of a playback signal processor circuit 8. The playback signal processor circuit 8 recovers a video signal, an audio signal and a sub code signal from the amplified playback signal and supplies the recovered signals to output terminals 9v, 9a and 9s, respectively, of the digital VTR. The amplified playback signals provided at the output of the playback amplifier 7 are also supplied to an ATF signal separating circuit 10 which separates respective ATF signals ATF1 and ATF2 reproduced from the recording areas AT1 and AT2 of each of the slanting recording tracks formed on the magnetic tape 6. The signals ATF1 and ATF2 thus separated by the circuit 10 are supplied thereby through respective switching devices 11 and 12 to corresponding inputs of an adding circuit 13 which additively combines the signals received at its inputs and supplies the combined signals at an output thereof. The output of the adding circuit 13 is coupled to an input of a servo signal processor circuit 14 which produces a servo control signal in response thereto. The magnetic tape 6 is driven by means of a capstan 16 and an associated capstan motor 15 under the control of the servo control signal produced by the servo signal processor circuit 14. A system controller circuit 17 controls the mode of operation of the digital VTR. For this purpose the circuit 17 supplies a mode control signal to a first switch controller circuit 18 which responds thereto by supplying appropriate switching control signals to the switching device 4 thus to control the position of the movable terminal thereof as necessary for the selected reproducing or after-recording mode. In the reproducing mode, the switch controller circuit 18 causes the switching device 4 to couple its movable input terminal to the second fixed terminal thereof to provide the playback signals to the input of the playback amplifier 7. In the after-recording mode, the switch controller circuit 18 selectively couples the movable terminal of the switching device 4 to the first fixed terminal thereof as the heads 30a and 30b scan the areas of the slanting tracks on the tape 6 to be after-recorded. Otherwise the circuit 18 causes the switching device 4 to couple its movable terminal to its second fixed terminal so that the ATF signals from the recording areas AT1 and AT2 of each of the slanting recording tracks scanned by the heads 30a and 30b are supplied to the input of the playback amplifier 7 for tracking control purposes. The system controller circuit 17 also controls the states of the switching devices 11 and 12 according to the mode of operation by supplying a tracking mode control signal to a second switch controller circuit 19 coupled to control inputs of the switching devices 11 and 12. Accordingly, in a normal playback mode of the digital VTR, the switching devices 11 and 12 are both CLOSED under the control of the second switch controller circuit 19, so that the additively combined signals ATF1 and ATF2 from the recording areas AT1 and AT2, respectively, are supplied to the servo signal processor circuit 14. The circuit 14 responds by controlling the travel of the magnetic tape 6 so that the tracking error signals ATF1 and ATF2 are minimised. In the normal playback mode of the digital VTR the head scanning locus is thus as illustrated diagrammatically by a dashed line 36 in Figure 3 so that the head scanning locus then coincides with the track at the centre of the tape. Where only an audio signal is to be recorded in the after-recording mode, the switching device 12 is maintained in an OPEN state while the switching device 11 is CLOSED under the control of the circuit 19. Accordingly, the tracking error signal is then produced by the servo signal processor circuit 14 based only on the signal ATF1 from the recording area AT1, and the servo signal processor circuit 14 consequently controls the travel of the magnetic tape 6 in order to minimise the tracking error signal so produced. As a result, the scanning locus of the head will coincide with the track in the recording area AT1, as illustrated by a chain-dotted line 38 in Figure 3. Where, instead, only a sub code signal is to be recorded in the after-recording mode, the switch controller circuit 19 then maintains the switching device 12 in the CLOSED state, while maintaining the state of the switching device 11 in the OPEN state. Consequently, only the signal ATF2 is supplied to the servo signal processor circuit 14 which responds by producing a servo control signal to minimise only the signal ATF2. The head scanning locus, therefore, will coincide with the track in the recording area AT2, as illustrated by a chain-dotted line 40 in Figure 3. Accordingly, when the digital VTR of Figure 2 carries out after-recording of a first audio signal in the recording area AU1 illustrated in Figure 3 as a first sub information signal, as well as when the VTR records a second audio signal in the recording area AU2 in the after-recording mode as a second sub information signal, automatic tracking control is carried out using the signal ATF1 obtained from the ATF signal recording area AT1 which is positioned in proximity with the first and second audio signal recording areas AU1 and AU2. Consequently, the automatic tracking control function causes the head scanning locus to coincide with the track in the recording area AT1, so that the head scanning locus is proximal to the track in the vicinity of the audio signal recording areas AU1 and AU2. As a result, after-recording of the audio signals in the areas AU1 and AU2 may be carried out in a satisfactory manner. Likewise, when the digital VTR of Figure 2 carries out after-recording of the sub code signal in the recording area SC of Figure 3 as a third sub information signal, automatic tracking control is carried out using the signal ATF2 reproduced from the area AT2 positioned in proximity with the sub code signal recording area SC. As a result, when after-recording of the sub code signal is carried out the automatic tracking control function causes the head scanning locus to coincide with the track in the recording area AT2, so that the head scanning locus is proximal to the track in the vicinity of the sub code signal recording area SC, and after-recording of the sub code signal may thus be carried out in a satisfactory manner. It will thus be seen that the above-described arrangement, which carries out a tracking control function with the use of signals recorded in only one tracking adjustment signal recording area which is near an area of the track in which information is to be recorded in an after-recording mode, provides the ability to bring the track and the head scanning locus near to one another as the head scans the sub information recording area. As a result, after-recording of the sub information signal may be carried out in a satisfactory manner.

Claims: Apparatus for reproducing and after-recording digital signals in slanting recording tracks (20) arranged sequentially on a recording medium (6), each of the tracks (20) having a main signal recording area (VI), a first sub information recording area (AU1, AU2) having one of a scan preceding and a scan following relationship with respect to the main signal recording area (VI), a second sub information recording area (SC) having one of a scan preceding and scan following relationship with respect to the main signal recording area which is opposite that of the first sub information recording area, and first and second tracking signal recording areas (AT1, AT2) provided adjacent an initial scan position (22) and a final scan position (24), respectively, of the track, each of the tracking signal recording areas (AT1, AT2) having tracking signals recorded therein, the apparatus comprising: recording means (28) for recording digital signals in each of the tracks (20); reproducing means (32) for reproducing digital signals from each of the tracks (20); the recording and reproducing means including scanning means (30a, 30b) for scanning each of the tracks (20) for respectively recording and reproducing digital data therein; and tracking control means (10 to 17, 19) for controlling tracking of the scanning means (30a, 30b) with respect to one of the tracks (20) in a reproducing mode of the apparatus based upon tracking signals recorded in both of the first and second tracking signal recording areas (AT1, AT2); the tracking control means being further operative in an after-recording mode of the apparatus, in which digital signals are to be recorded in the first and second sub information recording areas (AU1, AU2, SC), to control tracking of the scanning means (30a, 30b) based upon tracking signals recorded in only one of the first and second tracking signal recording areas (AT1, AT2) of a corresponding track; characterised in that: the recording means (28) is operative in the after-recording mode to record digital signals in a selected one of the first sub information recording area (AU1, AU2) and the second sub information recording area (SC), and the apparatus comprises tracking signal selecting means (17, 19) operative in the after-recording mode for selecting tracking signals from the one of the first and second tracking signal recording areas (AT1, AT2) having one of a scan preceding and scan following relationship with respect to the main signal recording area (VI) which corresponds to that of the selected one of the first and second sub information recording areas (AU1, AU2, SC). Apparatus according to claim 1, wherein the recording means (28) is operative in the after-recording mode to selectively record one of a digital audio signal in one (AU1, AU2) of the first and second sub information recording areas and a digital sub code signal in the other (SC) of the first and second sub information recording areas. Apparatus according to claim 1, wherein the reproducing means (32) is operative to reproduce digital video signals from the main signal recording area (VI). Apparatus according to claim 3, wherein the recording means (28) is operative to record a digital audio signal in the first sub information recording area (AU1, AU2). Apparatus according to claim 4, wherein the recording means (28) is operative to record a sub code signal in the second sub information recording area (SC). A method of reproducing and after-recording digital signals in slanting recording tracks (20) arranged sequentially on a recording medium (6), each of the tracks (20) having a main signal recording area (VI), a first sub information recording area (AU1, AU2) having one of a scan preceding and a scan following relationship with respect to the main signal recording area (VI), a second sub information recording area (SC) having one of a scan preceding and scan following relationship with respect to the main signal recording area (VI) which is opposite that of the first sub information recording area, and first and second tracking signal recording areas (AT1, AT2) provided adjacent an initial scan position (22) and a final scan position (24), respectively, of the track, each of the tracking signal recording areas (AT1, AT2) having tracking signals recorded therein, the method being carried out by using apparatus for scanning the tracks (20) to record and reproduce digital signals therein in selectable after-recording and reproducing modes of the apparatus, respectively; the method comprising: selecting one of the after-recording and reproducing modes of the apparatus; in the reproducing mode of the apparatus, scanning the tracks (20) to reproduce digital signals therefrom while controlling tracking of the scanned tracks based upon tracking signals recorded in both of the tracking signal recording areas (AT1, AT2) in each of the tracks scanned in the reproducing mode; and in the after-recording mode of the apparatus, scanning the tracks (20) to record digital signals in the first and second sub information recording areas (AU1, AU2, SC) thereof while controlling tracking of the scanned tracks based on tracking signals recorded in only one of the tracking signal recording areas (AT1, AT2) in each of the tracks scanned in the after-recording mode; characterised in that: the scanning of the tracks (20) in the after-recording mode comprises recording digital signals in a selected one of the first sub-information recording area (AU1, AU2) and the second sub information recording area (SC) while controlling tracking of the scanned tracks based on tracking signals from the one of the first and second tracking signal recording areas (AT1, AT2) having one of a scan preceding and scan following relationship with respect to the main signal recording area (VI) which corresponds to that of the selected one of the first and second sub information recording areas (AU1, AU2, SC). A method according to claim 6, wherein the scanning of the tracks (20) to record digital signals in the after-recording mode comprises selectively recording one of a digital audio signal in one (AU1, AU2) of the first and second sub information recording areas and a digital sub code signal in the other (SC) of the first and second sub information recording areas. A method according to claim 6, wherein the scanning of the tracks (20) to reproduce digital signals comprises scanning the tracks to reproduce video signals recorded in the main signal recording area (VI) thereof. A method according to claim 8, wherein the scanning of the tracks (20) to record digital signals comprises recording a digital audio signal in the first sub information recording area (AU1, AU2) of the tracks. A method according to claim 9, comprising scanning the tracks (20) to record a sub code signal in the second sub information recording area (SC) of each of the tracks.

Inventors: KUBOTA YUKIO, SENSHU YOICHIROU, KUBOTA, YUKIO, SENSHU, YOICHIROU, Kubota, Yukio, c/o Patents Division, Senshu, Yoichirou, c/o Patents Division
Applicants: SONY CORP, SONY CORPORATION
Application year: 1992
Main classification: G11B20
IPC codes: G11B27, H04N5, G11B5, G11B20, G11B15