JPH04335286A - Digital audio tape recorder - Google Patents

Abstract

PURPOSE:To shorten a search time by making a tape run at a super high speed when the difference between the present positional information and an object positional information of the magnetic tape exceeds a prescribed value, and by retrieving a subcode when the difference between the running position and recording position of the tape attains the prescribed value in accordance with the specified calculation. CONSTITUTION:A read-out is started from the start point of magnetic tape 1, and an indexing information and an absolute time are stored, and also the number of rotation of a take-up reel 3 is counted by a measuring circuit 17. The thickness of tape 1 is calculated by a tape thickness arithmetic circuit 21, and the running time from the start point of tape 1 is calculated by an arithmetic circuit 18 in accordance with data of rotational cycle from the circuit 17 and data of tape thickness. Next, when a retrieval command is issued from an operation part 15, the time informations of present position and object position stored in storage circuits 11, 13 are compared in a comparator circuit 12, and the high speed running is executed when the difference exceeds the prescribed value. Then, the subcode is read out from the time point when the difference between the running positional information and object time information obtained from the circuit 18 becomes within the prescribed value.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary head type digital audio tape recorder which digitizes audio signals, records them as PCM signals on a magnetic tape, and reproduces them.

0002

[Prior Art] A digital audio tape recorder (hereinafter referred to as DAT) records digitized audio signals as program information on magnetic tape, and also sub-signals to assist in recording and reproducing the audio signals. Recorded as a code. The subcode includes data such as the sampling frequency, quantization rule, number of channels, track pitch, etc. necessary for playing back the recorded audio signal, as well as start ID, program number, absolute time from the beginning of the tape, etc. necessary for high-speed search. There is data on this.

Data necessary for high-speed searching is recorded in sub-data areas set at both ends of each track of the magnetic tape, and includes a start ID and program number PNO.
The absolute time ATM is continuously recorded for each track for about 300 frames from the start position of each program information. During a high-speed search, the magnetic tape is run at a speed approximately 200 times faster than when running at a constant speed (during playback or recording), and at the same time the rotating drum is rotated so that the relative speed between the magnetic tape and the magnetic head is always constant. The number of subcodes recorded on the magnetic tape is changed to stably read the subcodes recorded on the magnetic tape.

FIG. 4 is a diagram showing the relationship between the search speed and the rotational speed of the rotary drum when the relative speed between the magnetic tape and the magnetic head is kept constant. In the figure, the horizontal axis shows the double speed value for the tape speed (8.15 mm/s) during constant speed running, and the vertical axis shows the drum rotation speed. As is clear from this figure, when the running speed of the magnetic tape in the forward direction (FWD) is multiplied by 200, the number of revolutions of the rotating drum is approximately 3.
000 rpm, and when the running speed of the magnetic tape in the rewinding direction (REW) is multiplied by 200, by setting the rotation speed of the rotating drum to about 1000 rpm, the relative speed becomes equal to the rotation speed of 2000 rpm during constant speed running.

[0005] As described above, since the rotation speed of the rotating drum is proportional to the search speed, it is high in the FWD mode and R
In EW mode, the relative speed can be kept constant by setting it low. If the search speed is increased more than this, for example, if the search speed is increased to 400 times in FWD mode, the rotational speed of the rotating drum will reach approximately 4000 rpm, and the drum motor will not be able to keep up with this in terms of reliability. Furthermore, when the speed is set to 400 times in the REW mode, the number of revolutions of the rotating drum approaches zero, making it impossible to read the subcode.

Therefore, in the case of such an ultra-high-speed search, the running time of the magnetic tape is determined by detecting the rotational speed of the reel on which the magnetic tape is wound, without depending on the subcode, and the running time of the magnetic tape is The running speed of the magnetic tape can be read from the subcode from the point when the position approaches the start position of the target program information2.
An information retrieval device has been proposed that reduces the speed to 00x and switches to normal high-speed search (Japanese Patent Laid-Open No. 2-33
(See Publication No. 787).

[0007]

By the way, when the running time (position) of a magnetic tape is determined by detecting the number of revolutions of a reel, the thickness of the magnetic tape has a large influence as a parameter. Conventionally, running time was calculated using the average thickness of multiple types of magnetic tape as a fixed value, but since the thickness of magnetic tape varies depending on the tape length and tape manufacturer,
If a magnetic tape with a tape thickness that differs greatly from the fixed value is used, a large error will occur between the absolute time representing the actual running time and the calculation time, as shown in FIG. In the figure, line a is when a magnetic tape whose tape thickness is thicker than the fixed value is used, line b is when a magnetic tape whose tape thickness is the same as the fixed value is used, and line c is when a magnetic tape whose tape thickness is thinner than the fixed value is used. This is the case when used.

[0008] As described above, an error occurs between the absolute time and the calculation time depending on the thickness of the magnetic tape used. The position was set with some margin from the starting position. For this reason, there is a limit to the reduction in search time.

[0009] This invention provides an ultra-high-speed search mode (first
The point at which the transition from the search mode (Search mode) to the high-speed search mode (Second search mode) in which subcodes can be read is
The purpose is to shorten the search time by locating the target program information close to the start position.

0010

[Means for Solving the Problems] A digital audio tape recorder according to the present invention includes a first storage means that sequentially reads position information recorded on a magnetic tape and stores it as current position information, and a search program. a second storage means for storing positional information indicating the recording position of information on the magnetic tape as target positional information; and a tape for calculating tape thickness information of the magnetic tape from the number of revolutions of a reel on which the magnetic tape is wound. Thickness calculation means, running position calculation means for obtaining magnetic tape running position information from reel rotation speed and tape thickness information, and comparison means for comparing current position information or running position information with target position information. If the difference between the location information and the destination location information exceeds a predetermined value, the first search mode is used to compare the destination location information and the travel location information using a comparing means, and from the point when the comparison result matches the predetermined value, the second search mode is started. The present invention is characterized in that the recording position of the program information is searched for by switching to the search mode and comparing the target position information and the current position information using a comparing means.

[0011]

[Operation] In this invention, when the current position of the magnetic tape and the recorded position of the program information to be searched are separated by a predetermined value or more, the constant relative speed servo of the rotating drum is canceled and the first search mode is set; Run magnetic tape at ultra-high speed. In this state, it is impossible to read the subcode recorded on the magnetic tape, so the running position of the magnetic tape is calculated from the number of rotations of the reel and the tape thickness of the magnetic tape calculated by the tape thickness calculation means.

When the difference between the running position of the magnetic tape and the recording position of the program information reaches a predetermined value, a switch is made to the second search mode in which the subcode recorded on the magnetic tape can be read, and from then on, the subcode is read. The current position of the magnetic tape is determined from the absolute time, and the recording position of the target program information is searched.

[0013] In this way, when the first search mode detects the number of revolutions of the reel and calculates the running position of the magnetic tape, the thickness of the magnetic tape is also taken into consideration. can be calculated accurately, and the first
The time point at which the search mode is switched to the second search mode can be brought closer to the recording position of the target program information.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an embodiment of a digital audio tape recorder according to the present invention. In the figure, a magnetic tape 1 is wound between a supply reel 2 and a take-up reel 3, and a capstan 4
and is wound around a rotating drum 6 by a loading mechanism such as a pinch roller 5. Two magnetic heads 7a and 7b are attached to the rotating drum 6, facing each other by 180 degrees, and are adapted to read program information (music information) and subcodes recorded on the magnetic tape 1.

[0015] Among the subcodes, data such as start ID, program number PNO, absolute time ATM, etc. necessary for high-speed search are recorded in subdata areas set at both ends of each track of the magnetic tape 1. , the program number of each program information, the absolute time of the start position, etc. are recorded at the beginning of the tape as table of contents information TOC.

After the outputs of the magnetic heads 7a and 7b are amplified to an appropriate level by a head amplifier 8, the program information is supplied to an audio system (not shown) and converted into an acoustic signal, and the subcode is sent to a subcode reproduction circuit 9. The table of contents information TOC is separated and reproduced by the table of contents information storage circuit 1.
0, the absolute time ATM is stored in the current time storage circuit 11, respectively.

The comparison circuit 12 compares the absolute time ATM or tape running time (described later) stored in the current time storage circuit 11 with time information from the target time storage circuit 13 in which the recording position of the program information to be searched is stored. , and outputs this comparison result to the control section 14. The control section 14 is a system controller that controls the entire device, and controls the operations of each section in response to commands such as recording, playback, and search from the operation section 15.

The detector 16 detects reel pulses generated as the take-up reel 3 rotates, and sends the detection results to the reel rotation period measuring circuit 17. The measuring circuit 17 measures the rotation period of the take-up reel 3 by counting reel pulses, and supplies the measurement result to the tape running time calculation circuit 18. The arithmetic circuit 18 calculates the running time of the magnetic tape 1 from the starting end based on rotation period data supplied from the measuring circuit 17 and tape thickness data to be described later, and outputs the calculation result to the changeover switch 19.

The changeover switch 19 is the current time memory circuit 11
Alternatively, one of the outputs of the tape running time calculation circuit 18 is selected based on a switching signal from the control section 14 and is supplied to the comparison circuit 12. The tape thickness data supplied to the tape running time calculation circuit 18 is controlled by switching the output of either the tape thickness fixed value storage circuit 20 or the tape thickness calculation circuit 21 based on a switching signal from the control unit 14. This is data supplied via the changeover switch 22. The thickness data stored in the tape thickness fixed value storage circuit 20 is an average value calculated in advance from the thicknesses of multiple types of magnetic tapes, and the thickness data output from the tape thickness calculation circuit 21 is obtained from the reel rotation period measurement circuit 17. This data is calculated from the rotation period of the output take-up reel 3.

The tape thickness calculation circuit 21 calculates the tape thickness from the rotation period of the reel at the start and the rotation period of the reel after 30 to 40 rotations after the start. The deceleration position memory circuits 23 and 24 store the distance (time) from the start position of the program information to be searched for the position at which to switch from the super high speed mode in which subcode reading is not possible to the high speed mode in which subcode reading is possible during high speed search. ), the deceleration position storage circuit 23 stores relatively short time data da, and the deceleration position storage circuit 24 stores relatively long time data db (d
a < db ) are respectively stored. One of the time data da and db is selected by a changeover switch 25 which is controlled based on a switching signal from the control section 14, and is supplied to the control section 14.

The initial positions of the changeover switches 19, 22, and 25 are as shown in the figure, that is, the changeover switch 19 is on the current time storage circuit 11 side, the changeover switch 22 is on the tape thickness fixed value storage circuit 20 side, and It is assumed that the switches 25 are switched to the deceleration position storage circuit 24 side.

Next, the high-speed search operation of the present invention will be explained with reference to the flowchart shown in FIG. First, when the magnetic tape 1 is set in the device, the magnetic heads 7a and 7b start reading information from the starting end of the magnetic tape 1, the read information is amplified by the head amplifier 8, and the table of contents information TOC is stored in the table of contents information. circuit 10
The absolute time ATM is stored in the current time storage circuit 11.

At the same time, the reel pulse generated by the rotation of the take-up reel 3 is detected by the detector 16, the number of rotations is counted by the measuring circuit 17, and the rotation period of the reel 3 is supplied to the arithmetic circuit 18. . Further, the tape thickness calculation circuit 21 calculates the thickness of the loaded magnetic tape 1, and when the calculation is completed, notifies the control unit 14 of the completion of the calculation. The calculation circuit 18 calculates the running time of the magnetic tape 1 from the starting end based on the rotation period data measured by the measurement circuit 17 and the tape thickness data supplied from the storage circuit 20 or the calculation circuit 21.

Next, when a search command for arbitrary program information is issued from the operation unit 15, the control unit 14 indicates the start position of the program information to be searched from the table of contents information TOC stored in the table of contents information storage circuit 10. The time information is read out and stored in the target time storage circuit 13 (step S1).

Next, it is determined whether or not the tape thickness calculation process in the tape thickness calculation circuit 21 has been completed (step S2). If the calculation process has been completed, the selector switch 22 is switched to switch the tape thickness calculation circuit 21 The tape thickness data obtained in Step 1 is supplied to the arithmetic circuit 18, and at the same time, the changeover switch 25 is switched to supply the time data da stored in the deceleration position storage circuit 23 as the first set value d1 to the control section 14. S3). If not, the fixed value stored in the tape thickness fixed value storage circuit 20 is supplied as is to the arithmetic circuit 18, and the time data db stored in the deceleration position storage circuit 24 is used as the first set value d1. Select as is (step S4).

It takes at least about 3 minutes for the tape thickness calculation circuit 21 to calculate the tape thickness, and it may take more than 20 minutes depending on the tape winding position. Therefore, when performing a high-speed search immediately after loading the magnetic tape, , the time data db is selected as the first set value d1.

Next, the comparison circuit 12 compares the time information indicating the current position of the magnetic tape 1 stored in the storage circuit 11 with the target time information stored in the storage circuit 13 (step S5). As a result of the comparison, if the two pieces of time information match, the current position of the magnetic tape 1 is already at the position of the program information to be searched, so the control unit 14 sets the system to playback mode and runs the system (step S6). ), terminates the search operation.

As a result of the comparison, if the target position is closer to the end of the tape (forward) than the current position, the control unit 14 instructs a forward search and determines the difference between the current time and the target time, that is, the distance. (Step S7). If the distance is greater than the first set value d1, the control unit 14 sets the system to 300x FWD mode (step S
8). In this FWD mode, the constant relative speed servo of the rotary drum is released, the rotating drum is rotated at a constant speed of, for example, about 2000 rpm, the switch 19 is switched to the arithmetic circuit 18 side, and the running position of the magnetic tape 1 is obtained from the arithmetic circuit 18. The comparison circuit 12 compares the information with the target time information stored in the storage circuit 13 (step S7).

If the distance is less than the first set value d1 and greater than or equal to the second set value d2 (d2 < d1), the control unit 14 sets the system to the 200x FWD mode (step S9). In this FWD mode,
The constant relative speed servo of the rotating drum is enabled to read the subcode recorded on the magnetic tape 1, and the switch 19 is switched to the storage circuit 11 side, and the absolute time ATM of the read subcode is used as current position information. It is supplied to the comparator circuit 12.

[0030] If the distance is less than the second set value d2,
The control unit 14 sets the system to a lower-speed CUE mode (step S10), and repeats the process until the current time matches the target time (step S11). When the two times match, the control unit 14 commands the playback mode and starts playing (
Step S6), the search operation is ended.

[0031] As a result of the comparison in step S5, if the target position of the magnetic tape 1 is on the tape starting end side (rearward) than the current position, the control unit 14 instructs a backward search, and searches from the current time to the target time. The difference, that is, the distance, is determined (step S12). If the distance is greater than the first set value d1, the control unit 14 controls the system to
The mode is set to double speed REW mode (step S13). This R
In the EW mode, the constant relative speed servo of the rotary drum is released, the rotating drum is rotated at a constant speed of, for example, about 2000 rpm, the switch 19 is switched to the arithmetic circuit 18 side, and the running position information of the magnetic tape 1 obtained from the arithmetic circuit 18 is set. The comparison circuit 12 compares the target time information stored in the storage circuit 13 with the target time information stored in the storage circuit 13.
(Step S12).

If the distance is less than the first set value d1 and greater than or equal to the second set value d2, the control unit 14 sets the system to the 200x REW mode (step S14). In this REW mode, the switch 19 is switched to the storage circuit 11 side, the constant relative speed servo of the rotating drum is enabled, and the subcode information recorded on the magnetic tape 1 can be read, and the absolute value of the read subcode is The time ATM is supplied to the comparison circuit 12 as current position information.

If the distance is less than the second set value d2, the control unit 14 sets the system to a lower speed REV mode (step S15), and repeats this until the current time matches the target time (step S16). When the two times match, the control unit 14 commands the play mode to run the play (step S6), and ends the search operation.

Next, a series of these processes will be explained with reference to an operational diagram shown in FIG. In the figure, the horizontal axis is the tape position, and the vertical axis is the speed number. First, a case where the tape thickness calculation process in the tape thickness calculation circuit 21 has not been completed will be described. In this case, time data db is selected as the first set value d1.

First, when a search command is issued at position p1, since position p1 is a predetermined distance d1 or more away from position p4 where the program information to be searched is recorded,
The FWD mode (first search mode) is set at 300 times the speed, and the process advances to position p2, which is a distance d1 away from position p4. Between positions p1 and p2, the running position is determined from the rotational speed of the reel 3 on which the magnetic tape 1 is wound.

[0036] The distance from position p2 to position p3 is 200
This becomes double-speed FWD mode (second search mode). The position p3 is a second setting value d2 away from the position p4. After position p3, the program advances to position p4 where program information is recorded in a lower speed CUE mode. position p2
-p4, the absolute time ATM is read from the subcode recorded on the magnetic tape 1, and the current position of the magnetic tape 1 is determined from this absolute time ATM. In this way, the target position p
When the number reaches 4, the search operation ends and the program information is reproduced in PLAY mode.

If the tape thickness calculation process in the tape thickness calculation circuit 21 has been completed, the first set value d1
As such, time data da (<db) is selected. In this case, the process proceeds from position p1 to position p2' in 300x FWD mode (first search mode), and proceeds from position p2' to position p3 in 200x FWD mode (second search mode). In this case, since the tape thickness calculation process has been completed, the running position of the magnetic tape in the first search mode can be determined fairly accurately, and the first You can proceed in search mode. Therefore, the search time can be reduced accordingly.

[0038]

According to the present invention, the thickness of the magnetic tape is also calculated and determined during the first search mode in which the running position of the magnetic tape is determined by detecting the number of rotations of the reel. The running position of the tape can be determined accurately. Therefore, the time point at which the first search mode is switched to the second search mode can be brought closer to the recording position of the target program information, making it possible to significantly shorten the search time.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of FIG. 1;

FIG. 3 is an explanatory diagram of the operation in FIG. 1;

FIG. 4 is a diagram showing the relationship between search speed and drum rotation speed.

FIG. 5 is a diagram showing the difference between absolute time and tape running calculation time due to variations in tape thickness.

[Explanation of symbols]

1 Magnetic tape 2, 3 Reel 10 Table of contents information storage circuit 11 Current time storage circuit 12 Comparison circuit 13 Target time storage circuit 16 Detector 17 Reel rotation period measurement circuit 18 Tape running time calculation circuit 19, 22, 25 Changeover switch 20 Tape thickness Fixed value storage circuit 21 Tape thickness calculation circuit 23, 24 Deceleration position storage circuit

Claims (3)

[Claims] 1. A first storage means for sequentially reading position information recorded on a magnetic tape and storing it as current position information, and position information indicating a recording position on the magnetic tape of program information to be searched. second storage means for storing target position information; tape thickness calculation means for calculating tape thickness information of the magnetic tape from the rotation speed of the reel on which the magnetic tape is wound; a running position calculating means for obtaining running position information of the magnetic tape from tape thickness information; and a comparing means for comparing the current position information or the running position information with the target position information; If the difference between the location information exceeds a predetermined value, the comparison means compares the destination location information and the traveling location information as a first search mode, and from the time when the comparison result matches the predetermined value, a second search mode is performed. The digital audio tape recorder is characterized in that the digital audio tape recorder searches for the recording position of the program information while comparing the target position information and the current position information with the comparing means. 2. In claim 1, the tape thickness calculation means supplies a predetermined fixed value as tape thickness information to the traveling position calculation means while the tape thickness calculation process is not completed. Digital audio tape recorder. 3. In claim 1, the predetermined value for determining the point in time when switching from the first search mode to the second search mode is determined when tape thickness calculation processing in the tape thickness calculation means has been completed. is the first predetermined value d
a, and when the arithmetic processing is not completed, a second predetermined value db, which is larger than the set value da, is set.