JPH0954907A - Variable rate recording/reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a tracking servo circuit and to surely decide a reproducing mode in a short time. SOLUTION: A tape traveling speed control circuit 7 controls rotation of a capstan 3 when reproduction is started to make a traveling speed of a tape 1 1/2 or below of a standard speed. Thus, respective tracks are traced at least twice by the same azimuth head, and the reproducing data are restored surely regardless of a tracking phase and a track angle. A reproducing mode detection circuit 6 detects mode identification information incorporated in the reproducing data. The tape traveling speed control circuit 7 decides a reproducing rate based on the mode identification information. In such a manner, the reproduction is performed in a short time at the reproducing rate to be selected regardless of the presence of the tracking.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable rate recording / reproducing apparatus suitable for reproducing at a reproduction rate different from the recording rate.

[0002]

2. Description of the Related Art Conventionally, a plurality of signals having different data rates cannot be recorded / reproduced by the same VCR. To solve this problem, the applicant of the present application can record and reproduce information of different signal rates in Japanese Patent Application No. 6-278097 (hereinafter referred to as Document 1) filed earlier. A magnetic recording / reproducing device is proposed. In this proposal, the recording rate is made variable by changing the feeding speed of the magnetic tape according to the recording rate and intermittently tracing the magnetic head according to the recording rate.

That is, when recording is performed at a recording rate of 1 / rth of the maximum recording rate of the VCR (hereinafter referred to as a standard recording rate), the magnetic tape runs only one track while the head makes one trace. The magnetic tape is run at 1 / r times the standard speed with the standard speed. Also, the magnetic head is made to record only once for every r times of tracing. The track pitch of the recording track formed by this proposal is substantially constant regardless of the recording rate. The inclination of the recording track changes slightly depending on the recording rate.

By the way, in recent years, MPEG (Moving Pictu)
With the establishment of image compression technologies such as re Experts Group 2), digitization of images is progressing. Also in television broadcasting, digital broadcasting adopting the MPEG2 system has begun to be studied. In addition, multimedia services that handle audio and video in an integrated manner and are able to provide various information services by images in response to user requests are also being developed.

MPEG2 has a system corresponding to multi-channel broadcasting and multi-media conversion in communication or storage media. That is, MPEG2 is designed to transmit transmission data in units of packets in order to facilitate time division multiplexing of a plurality of images, voices and data. One packet consists of the same type of data,
An identification signal indicating the type of data is added to each packet.
The MPEG2 decoder has a function of extracting a packet having the same PID by referring to an identification signal (PID) from sequentially input packets, whereby only a desired program can be decoded from transmission data. it can. For example, even if a multi-channel data stream including encoded data of a plurality of images A, B, C, ... Is input, a television receiver compatible with the MPEG2 standard displays only one desired image. Is possible.

By the way, it is considered that such a multi-channel data stream is recorded by a VCR (video tape recorder). In this case, if, for example, only one type of data among the transmission data is recorded by the general VCR corresponding to the transmission rate, only the same recording time as when recording all the transmission data can be obtained. On the other hand, when the VCR of Document 1 described above is used, only one or more types of data selected from the transmission data can be recorded at a rate based on the signal rate of each data. It is possible to obtain a longer recording time than that of. For example, select 1
If the data rate of the type of data is 1/3 of the transmission rate of the transmission data, the tape speed specified during normal playback is set to 1/3 of the standard speed and recording and playback are performed to triple the data rate. The recording time of can be obtained.

Further, it is not necessary to match the recording rate with the reproduction rate, and the recording rate can be made higher than the reproduction rate to shorten the time required to record a predetermined program. For example, it is assumed that image data having a data rate reduced to 5 Mbps by compressing data of a predetermined program is transmitted using a channel having a maximum transmission rate of 20 Mbps (bits / second). This image data may be transmitted at a data rate of 5 Mbps together with other image data, or only this image data may be transmitted at a transmission rate of 20 Mbps. 20 Mb
Assuming that the program is transmitted at ps, if this program is a 2-hour program, the transmission will be completed in 30 minutes.

On the other hand, when the image data transmitted at 20 Mbps is recorded by a VCR having a standard recording rate of 40 Mbps, this VCR is 1 / the standard recording rate.
Recording will be performed at a rate of 2. In order to reproduce this program and display it normally, it is necessary to reproduce the recorded program in 2 hours, so that the reproduction may be carried out at a rate ⅛ of the standard recording rate of the VCR.

That is, in this case, the recording rate and the reproduction rate are different. When reproduction is performed at a rate different from the recording rate during reproduction, the trace of the magnetic head extends over a plurality of recording tracks, so it is possible to determine the recording rate during reproduction. However, the reproduction rate to be selected during reproduction is unknown. Therefore, at the time of recording, information about a reproduction rate to be selected at the time of reproduction (hereinafter referred to as mode identification information) is recorded in, for example, a video auxiliary area on a magnetic tape. At the time of reproduction, first, tracking control is performed to surely trace the video auxiliary area to reproduce the mode identification information, and then the reproduction mode such as the tape speed is determined based on this information.

In other words, a tracking servo circuit is required for surely tracing the video auxiliary area at the start of reproduction. Further, the reproduction mode cannot be determined until the tracking becomes stable, and it takes a relatively long time to normally reproduce the program. Furthermore, if tracking is not performed accurately, it may not be possible to select the playback mode.

[0011]

As described above, conventionally, a tracking servo circuit is required to surely reproduce the mode identification information, and it takes a relatively long time to normally reproduce the program. There was a problem that it would end up. Furthermore, if tracking is not done correctly,
There is also a problem that it may not be possible to select the playback mode.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a variable rate recording / reproducing apparatus which does not require a tracking servo circuit for reproducing mode identification information.

It is another object of the present invention to provide a variable rate recording / reproducing apparatus capable of shortening the time required to detect a mode identification signal and outputting reproduced data reliably in a short time.

[0014]

A variable rate recording / reproducing apparatus according to the present invention has recording tracks formed at a constant track pitch regardless of the recording rate, and a reproduction rate to be selected on the recording track at the time of reproduction. By reproducing the tape on which the mode identification information shown is recorded by a head provided on the peripheral surface of a rotating cylinder that rotates at a predetermined speed to obtain a reproduction signal, and by controlling the running speed of the tape, First tape running speed control means for tracing each recording track by the head having the same azimuth at least twice, reproduction mode detection means for detecting the mode identification information from the output of the reproduction means, and reproduction rate to be selected The tape running speed is set based on the mode identification information detected by the reproduction mode detecting means for setting. It is obtained and a second tape traveling speed control means for controlling.

In the present invention, the first tape running speed control means controls the running speed of the tape when the reproduction is started, and causes the head of the same azimuth to trace the recording track at least twice. As a result, it is possible to surely reproduce the record data regardless of the presence or absence of tracking and the recording track angle. The reproduction signal from the reproduction means is given to the reproduction mode detection means,
Mode identification information is detected. The second tape running speed control means controls the tape running speed so that the reproduction rate indicated by the mode identification information can be obtained. In this way, reproduction is performed at the reproduction rate that should be selected during reproduction.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a variable rate recording / reproducing apparatus according to the present invention.

Predetermined information is recorded on the tape 1 by the variable rate magnetic recording / reproducing apparatus described in Reference 1. That is, the tape 1 is recorded by changing the tape speed according to the recording rate. By intermittently tracing the magnetic head, the recording track is formed at a constant track pitch regardless of the recording rate. Has been formed. Note that the recording track tilt (recording track angle)
Varies slightly depending on the recording mode. The information recorded on the tape 1 may need to be reproduced at a reproduction rate different from the recording rate, and in a predetermined recording area of the tape 1, mode identification information indicating a reproduction speed (rate) to be selected at the time of reproduction is stored. It is recorded.

The tape 1 is wound around the cylinder 2,
Strike at a predetermined speed by the capstan 3. The cylinder 2 is provided with a head (not shown) on the peripheral surface, and the traveling speed of the tape 1 is set to be equal to or lower than the standard speed with the standard speed being the speed at which the magnetic tape travels one track while the head makes one trace. . The cylinder 2 rotates at a predetermined speed, and the head tracks the recording track of the tape 1 to reproduce the information recorded on the tape 1 and output a reproduction signal to the reproduction circuit 4.

The reproducing circuit 4 outputs reproduced data obtained by subjecting a reproduced signal from the magnetic head to waveform equalization processing, demodulation processing, error correction processing and the like through an output terminal 5. The reproduction data from the output terminal 5 is supplied to, for example, an image signal processing circuit or the like. The output of the reproduction circuit 4 is also supplied to the reproduction mode detection circuit 6. The reproduction mode detection circuit 6 detects the mode identification information contained in the reproduction data and supplies it to the tape running speed control circuit 7. The tape running speed control circuit 7 can control the running speed of the tape 1 by controlling the capstan 3.

In the present embodiment, the tape running speed control circuit 7 is also supplied with a reproduction start signal via the terminal 8. The tape running speed control circuit 7
When the reproduction start signal is input, the tape running speed is set to 1 of the standard speed which is the fastest tape speed of the modes at the time of recording.
Set to any value less than / 2. When the reproduction mode detection circuit 6 detects the mode identification information, the tape traveling speed control circuit 7 drives the tape 1 at the tape traveling speed based on the mode identification information. The capstan 3 is controlled by the tape traveling speed control circuit 7 to rotate so as to drive the tape 1.

Further, the tape running speed control circuit 7 sets the tape speed to 1/2 of the standard speed when the mode identification signal is not detected even after the lapse of a predetermined period from the start of reproduction.
It is supposed to be set again.

If the tape running speed is exactly halved of the standard speed due to the difference in the recording track angle, the track pitch will slightly change. Therefore, the tape running speed must take into consideration the difference in the recording track angle. However, this difference is ignored for simplification of description.

Next, the operation of the embodiment configured as described above will be described with reference to FIG. Figure 2 is 1 on the horizontal axis
FIG. 3 is an explanatory diagram showing a trace locus of a head by a track coordinate method, in which a tape travel amount in a trace unit is taken and a vertical axis represents a length of a recording track unit in a tape longitudinal direction. The shaded area in FIG. 2 indicates the area where the reproduction output can be obtained.

The tape 1 is recorded intermittently based on the ratio of the standard recording rate to the actual recording rate. The recording tracks are formed at a constant track pitch regardless of the recording rate, and the track angle is slightly different for each recording rate. FIG. 2 shows recording tracks recorded at a predetermined recording rate. Numbers in the figure indicate track numbers and the same numbers indicate the same recording tracks. Further, it is assumed that the odd-numbered tracks whose track numbers are odd are recorded in one azimuth and the even-numbered tracks are recorded in the other azimuth.

When reproduction is instructed based on a user operation, a reproduction start signal is given to the tape running speed control circuit 7 via the terminal 8. As a result, the tape running speed control circuit 7 controls the capstan 3 so that the tape 1 runs at a speed equal to or less than 1/2 of the standard speed. The capstan 3 rotates, and the tape 1 sandwiched between the capstan 3 and a pinch roller (not shown) is driven at a speed equal to or lower than 1/2 of the standard speed.
The amount of movement of the tape 1 in the tape running direction when the head traces one track is larger than the track pitch because the recording tracks to be formed are inclined. The running amount of the tape will be described by the moving amount in the direction. The width of the head is assumed to match the track pitch, and the level of the reproduction signal is assumed to be proportional to the width of the recording track traced by the head (on-track amount). Strike at half the speed of. A trace pattern T1 in FIG. 2 shows a trace pattern by a head of one azimuth angle during 1/2 speed reproduction (reproduction when the tape 1 is driven at 1/2 speed of the standard speed). Trace pattern T
The shaded area 1 indicates the reproducible area, and it can be seen that the head of azimuth angle on one side traces all the tracks on one side.

That is, as shown in FIG. 2, at the trace start timing for the first recording track, the head of one azimuth has a tracking phase for tracing the center of the starting end of the first recording track of one azimuth. As a result, as indicated by the hatched portion D1 in FIG. 2, the azimuth head is moved to the first position while the tape 1 advances by a half track pitch.
Stops tracing the recording track. Therefore, at the trace end timing of the first recording track, on the other hand, the center of the azimuth head is traced at a position half shifted from the first recording track. That is, the level of the reproduction signal is maximum at the trace start timing of the first recording track, and is approximately half of the maximum value at the trace end timing.

On the other hand, when the tape 1 advances by one track pitch from the trace start timing of the first recording track by the azimuth head, the tracking phase of the azimuth head, as shown in FIG. The phase is located in the center. Since the running speed of tape 1 is 1/2 of the standard speed, tape 1
While the trace of the azimuth head is completed while advancing by / 2 track pitch, the center of the azimuth head is located at the center of the first recording track and the second recording track at the end timing of this trace as shown by the hatched portion D2. Position to,
The level of the reproduction signal for the first recording track is ½ of the maximum level.

Similarly, next, when the tape 1 runs for a half track pitch, the center of the azimuth head is located at the center of the start end of the third recording track, and the tracing is completed while the tape 1 runs for a half track pitch. To do. Thus
The reproduction shown by the shaded portion D3 is performed. Thereafter, in the same manner, the reproduction indicated by the hatched portion of the trace pattern T1 is performed.

Here, it is assumed that the tracking phase changes and the trace pattern T1 slides downward in FIG. For example, when the trace pattern T1 moves to the lower side of FIG. 2 by 1/2 track pitch, the reproduction signal for the first recording track is obtained at the level from 1/2 to 0 of the maximum level in the shaded portion D1. On the other hand, in the shaded area D2, the reproduction signal for the first recording track is obtained at a level from 1/2 of the maximum level to the maximum level. In this way, when the tracking phase changes and the area in which one of the two traces for one recording track can obtain a reproduction signal of ½ or more of the maximum level is reduced, the other trace always causes the maximum level. The area where a reproduced signal of ½ or more of the above is increased, and the area where a reproduced signal of ½ or more of the maximum level is obtained is one track. That is, regardless of the position of the trace locus, the maximum level of 1 can be obtained from the entire area of each recording track by performing two traces for one recording track.
It is possible to obtain a reproduction signal with a level of ½ or more.

Therefore, if it is possible to reliably restore the recorded information from the reproduction signal when a reproduction signal having a level equal to or higher than 1/2 of the maximum level is obtained, 1 /
It can be seen that when the double speed reproduction is performed, all data can be reproduced intermittently. Since the track pitch of the recording tracks formed on the tape 1 is constant regardless of the recording rate, if the tape 1 is driven at a speed half the standard speed, all data can be reproduced regardless of the recording rate. is there. Furthermore, even if the track angles are different,
By performing the reproduction at the tape speed which is ½ of the standard speed, it is possible to reproduce all the data of one track in the time when the same azimuth head is traced twice regardless of the presence or absence of tracking.

A reproduction signal from a head provided in the cylinder 2 is given to the reproduction circuit 4. The reproduction circuit 4 performs a predetermined reproduction process on the reproduction signal and then outputs the reproduction data to the reproduction mode detection circuit 6. Regardless of the recording rate at the time of recording and the reproduction rate to be selected at the time of reproduction, the tape 1 is driven at a speed of 1/2 or less of the standard speed for reproduction, so that all recorded data can be reliably reproduced. It is possible. The reproduction mode detection circuit 6 extracts the mode identification information included in the reproduction data and outputs it to the tape running speed control circuit 7. The mode identification information indicates the mode to be selected, and the tape traveling speed control circuit 7 controls the capstan 3 so that the tape traveling speed is based on the mode identification information.

In this way, the tape 1 runs in the mode to be selected, and the reproducing circuit 4 performs a predetermined process on the reproduced signal and outputs the reproduced data from the output terminal 5.

The tape running speed control circuit 7 may set the tape speed to 1/2 or less of the standard speed at the start of reproduction, for example, 1/3 of the standard speed. The trace pattern T2 in FIG. 2 shows the trace state in this case.

Now, assuming that the center of the start end of the seventh recording track is a tracking phase traced by one of the azimuth heads, as shown by the hatched portion D5 in FIG. The azimuth head is 0 .. from the start end of the seventh recording track to the 3/4 position.
With respect to the area for 75 tracks, a reproduction signal of ½ or more of the maximum level is obtained. Also, in this tracking phase, as shown by the hatched portion D6, the maximum level is 1/2 or more with respect to the 0.75 track area from the start end side of the fourth recording track to the end thereof. Is obtained.

Therefore, at the time of 3 × speed reproduction, there are overlapped areas where a reproduced signal of ½ or more of the maximum level can be obtained by tracing twice for one track. In the case of FIG. 2, the reproduced signals in the first half of the shaded area D5 and in the second half of the shaded area D6 have a maximum level of 2
The amplitude is / 3 or more, and by using the reproduction signal in this period, the reproduction error rate can be reduced as compared with the case of the tape speed of 1/2 of the standard speed.

Even in this case, a reproduction signal having a level of ⅔ or more of the maximum level can be obtained from the entire area of the recording track regardless of the difference in track angle and the tracking phase.

As described above, in the present embodiment, since the tape running speed is set to ½ or less of the standard speed at the start of reproduction, regardless of the recording rate at the time of recording and the reproduction rate to be selected. Moreover, the mode identification information can be reliably reproduced regardless of the difference in track angle and the tracking phase. For example, if the mode identification data is recorded at least once in one track, the mode identification information can be reproduced by tracing the same azimuth head twice for one track. No tracking servo circuit is required to play back the mode identification information, and the playback mode can be determined without tracking, so the time it takes to play the program normally in the selected playback mode is shortened. can do. Further, there is no possibility that the tracking becomes unstable and the reproduction mode cannot be determined.

In the above embodiment, it is assumed that the reproduced data can be restored when the head width is the same as the track pitch and the on-track amount of the head is ½ or more of the track width. As described above, when the head width is larger than the track pitch, and when the on-track amount of the head required for reproduction is 1/2 or less of the track width, the tape running speed is lower than 1/2 of the standard speed. Even if it is large, all data can be reproduced without tracking. That is, the present invention sets the tape speed at which all data can be reproduced without tracking at the start of reproduction, and even when the tape speed is set higher than 1/2 of the standard speed, the present invention It does not depart from the gist of.

[0039]

As described above, according to the present invention, the tracking servo circuit is not required for reproducing the mode identification information, and the time required for detecting the mode identification signal is shortened to ensure reliable reproduction in a short time. This has the effect that data can be output.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a variable rate recording / reproducing apparatus according to the present invention.

FIG. 2 is an explanatory diagram for explaining operation of the embodiment;

[Explanation of symbols]

1 ... tape, 2 ... cylinder, 3 ... capstan, 4 ... playback circuit, 6 ... playback mode detection circuit, 7 ... tape running speed control circuit

Claims (3)

[Claims] 1. A tape on which recording tracks are formed at a constant track pitch regardless of the recording rate and mode identification information indicating a reproduction rate to be selected at the time of reproduction is recorded on the recording track at a predetermined speed. By controlling the traveling speed of the tape and the reproducing means for tracing by the head provided on the peripheral surface of the rotating rotary cylinder, each recording track is traced at least twice by the head of the same azimuth. First tape running speed control means, reproduction mode detection means for detecting the mode identification information from the output of the reproduction means, and mode identification detected by the reproduction mode detection means for setting a reproduction rate to be selected. Second tape running speed control means for controlling the running speed of the tape based on the information. A variable rate recording / reproducing apparatus characterized by the above. 2. The first tape running speed control means,
At least two tapes of the same azimuth head
2. The variable rate recording / reproducing apparatus according to claim 1, wherein the tape is run for a distance corresponding to one track pitch while being traced once. 3. The first tape running speed control means,
2. The variable rate recording / reproducing apparatus according to claim 1, wherein the tape is driven at a speed that is approximately 1/2 or less of a standard speed of the tape corresponding to a track pitch of the recording track.