JPH04344358A - playback device - Google Patents

Abstract

PURPOSE:To provide the reproducing device suitable for circuit integration and for smooth frame synchronization. CONSTITUTION:A drum 2 outputs a regenerative signal by rotating and scanning a built-in head against a tape. A tracking control means 4 controls the tape travelling so that each head can trace the track of the tape. A frame detection means 5 detects the track number information of the regenerative signal and output a regenerative frame signal. A frame phase correction means 6 detects the phase difference between the reference and regenerative frame signals and realizes the synchronization between the reference and regenerative frames by making the tracking control means 4 adjust the travelling according to the value. Thus, as the number of connections of means required for the frame phase correction can be reduced and the frame phase difference is detected and corrected, the frame synchronization can be completed in a short time.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing apparatus for reproducing information signals recorded as diagonal tracks on a magnetic tape by a rotary head.

0002

2. Description of the Related Art In a reproducing apparatus for reproducing information signals recorded as diagonal tracks on a tape, a helical scan is normally performed using a rotating head. On the other hand, signals recorded on a tape are divided into tracks due to this reproduction method. As an example of image signals, consumer VT
In the case of R (VHS etc.), 1 field is 1 track,
One frame is recorded as two tracks. When reproducing this, a control signal (usually one pulse per frame) is recorded on a linear track provided separately from the diagonal track, and tracking control is performed using this signal. As a result, each head is correctly on-track. At this time, there may be a case where there is a separate reference frame signal to be synchronized, as in the case of a run-up section of continuous recording. In such a case,
Frame synchronization can be easily achieved by directly or indirectly comparing the phases of an external frame reference and a control signal reproduced from the tape, and by reflecting the result in tracking control.

[0003] There are also examples where one frame is divided into 20 to 24 tracks, such as a commercial digital VTR (D1). In this case as well, a control track exists, and a servo signal of 1 pulse per drum rotation (4 tracks) and a frame signal of 1 pulse per frame are recorded.
Control similar to that can be performed using a frame signal (for example, the magazine "Broadcasting Technology" 1990, Vol. 43, No. 1)
2 etc.).

0004

[Problems to be Solved by the Invention] In the example of the above-mentioned consumer VTR, the frame has two azimuth tracks (positive and negative) on the tape.
Since it is completed in one book, frame synchronization can also be achieved at the same time by performing tracking control using a tracking signal (in this case, a control signal) without special frame information. However, when the number of tracks per frame increases, there is a problem that frame synchronization cannot be achieved with this alone.

[0005] In the example of a business VTR, frame information is also recorded. However, all signals, including tracking in consumer VTRs, are recorded on linear tracks, and occupy an area different from the original information signal. Therefore, from the viewpoint of the information recording density on the tape, there is a problem in that it becomes redundant.

[0006]

[Means for Solving the Problems] In order to solve the above problems, the reproducing apparatus of the present invention has data of a predetermined length as one frame, one frame of data is divided and recorded on a plurality of diagonal tracks, and each track has one frame. a drum that outputs a playback signal by rotating a head to scan a tape that includes track number information that goes around every two frames and runs in the longitudinal direction of the tape;
Reference generating means for generating a reference rotation signal that is a rotation reference for the drum and a reference frame signal that is inverted for each frame; and tracking control that controls tape running so that each head on the drum traces a track on the tape. means for detecting track number information included in the reproduced signal and outputting a binary reproduced frame signal according to whether the frame is even/odd; and frame phase correction means for eliminating a frame phase difference between the reproduced frame signals.

[0007]

According to the present invention, with the above-described structure, synchronization with the reference frame can be achieved by performing optimal phase correction according to the reproduced frame phase detected from the track number information in the tracks on the tape.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A reproducing apparatus according to an embodiment of the present invention will be described below with reference to the drawings. (FIG. 1) is a block diagram of an embodiment of a playback device of the present invention. In the figure, 1 is a tape, 2 is a drum, 3 is a reference generation means, 4 is a tracking control means, 5 is a frame detection means, and 6 is a frame phase correction means. The operation of the playback device configured as described above is roughly as follows.

First, the drum 2 rotates in synchronization with a reference rotation signal generated by the reference generating means 3, reads data from the tape 1 wound around the drum 2 by a head mounted on the drum 2, and generates a reproduction signal. Output. The tracking control means 4 feeds the tape 1 in the direction of the arrow and at the same time controls the tape feeding so that the head correctly traces the track.

On the other hand, the frame detection means 5 detects the track number in the reproduced signal and outputs a binary reproduced frame signal depending on whether the frame is even or odd. If this reproduced frame signal shows a phase mismatch with the reference frame, the phase correction means 6 detects this phase difference and corrects the tracking control to eliminate this phase difference.

[0011] Note that when a frame reference exists outside the apparatus, such as when performing continuous recording, a reference frame signal is input from the outside to the input terminal p. In the reference generation means 3, the internal clock is phase-synchronized with the external reference signal using a PLL or the like. As a result, the reference generating means 3 generates each signal in synchronization with the external reference signal, making external synchronization possible.

Next (FIG. 2), the frame detection means 5
The operation of the frame phase correction means 6 will be explained in more detail. (FIG. 2) is a time chart showing signals of various parts of the reproducing apparatus of this embodiment. In addition, in the following, drum 2 has 18
The following explanation will be based on a case where two heads having different azimuth angles are mounted at positions facing each other at 0 degrees, and a four-head configuration is used for 2-channel reproduction, and one frame is composed of 10 tracks. However, this is a limitation for ease of explanation and does not impair the generality of the present invention in any way.

First (FIG. 2(a)) is a reference frame signal,
(FIG. 2(c)) represents the reference rotation signal. drum 2
Since it rotates in synchronization with the reference rotation signal (FIG. 2(c)), it rotates 2.5 times per frame and scans 10 tracks. On the other hand (FIG. 2(d)) is the track number of the reproduced signal, which is extracted from a head having an azimuth corresponding to an even track number. The frame detection means 5 detects the track number of this reproduced signal and outputs "H" level during the period of track numbers 0 to 9, and "L" level during the period of track numbers 10 to 19. This is (Figure 2(e)
) is the reproduced frame signal shown in FIG.

[0014] The reason why the frame signal has a 2-frame period for both reference and playback is that the main application of the playback device of the present invention is the playback of video signals, and the period including the color information of the composite video signal is 2 frames. Therefore, in order to ensure the continuity of the final output video signal, playback from the tape and signal processing must also operate in synchronization with this. The frame phase correction means 6 uses the reference frame signal (
The reproduced frame is synchronized with the reference frame through two steps: receiving a) and the reproduced frame signal (e), ``detecting their phase difference,'' and then ``acting on the tracking control means 4 to eliminate the phase difference.'' However, the first stage process can be realized, for example, as follows.

That is, the time from the rise of the reference frame signal to the rise of the reproduced frame signal is measured, and the frame phase difference is calculated from the time and the period of the reference frame signal. This is the most direct and simplest method, but it requires waiting for the edges of the reference and playback frame signals, making the detection time somewhat longer. In order to achieve faster response, the following implementation method may be used.

First, inside the frame phase correction means 6, from the reference frame signal and the reference rotation signal (FIG. 2(b)
) Create the signal shown in This is an intra-frame reference track number that goes around in one frame. Note that the reason why the value is incremented by 2 every half rotation of the drum is because this example is for 2ch playback. Next, playback frame signal (e)
to detect changes in its level. At the time of detection,
For example, at the point indicated by the arrow in FIG. 2(e), the playback frame is at the beginning position. If you read the reference track number at this time, it represents the phase difference within the frame. In this example, it is "4". Next, the levels of the reference frame signal and the reproduction frame signal at that time are compared, and if they match, the previous value is used as the frame phase difference (delay on the reproduction side). If they do not match, the frame phase difference is determined by subtracting 10, the number of tracks in one frame, from the intra-frame phase difference. If the obtained frame phase difference is positive, the reproduction side lags behind the reference, and if it is negative, it leads. In the example shown in FIG. 2(e), the levels of the reference and reproduction frame signals do not match, so the frame phase difference is 4-10=-6, resulting in an advance of 6 tracks.

[0017] Now that the frame phase difference has been determined, the process proceeds to the second step, ``eliminating the phase difference.'' This can be accomplished in various ways, but basically the tape running speed is lowered or raised from the normal speed to eliminate the delay. Specifically, for example, the tape running speed may be changed for a certain period of time at a ratio according to the amount of phase difference, or the tape running speed may be changed to a predetermined speed for a period of time corresponding to the amount of phase difference, or the speed may be changed according to a time calculated from the amount of phase difference. This can be achieved by forcibly accelerating or decelerating the vehicle. Therefore, depending on the implementation method, the frame phase correction means 6 instructs the tracking control means 4 to change the speed control target, or gives forced acceleration/deceleration commands, thereby adjusting the phase difference. to eliminate it. Note that although these series of functions of the frame phase correction means can be realized by hardware, they can be more easily realized in software by using a processor.

As described above, according to this embodiment, the reproduction signal can be synchronized with the reference frame signal using the track number information recorded in the track. The frame phase correction means requires at least two signals, a reference frame signal and a reproduced frame signal. The number of signal lines is an important factor that affects the number of terminals and wires when each block is integrated, and this embodiment is suitable for integrated circuit integration. Furthermore, when the control relationships such as the frame phase correction means 6, the tracking control means 4, and the rotation control means included in the drum 2 are integrated into one circuit, the reference rotation signal can be used in the frame phase correction means. The method shown in FIG. 2 can be adopted, making it more practical.

[0019] Generally, the means for controlling the rotation within the drum uses a signal that indicates the actual rotational position of the drum relative to the reference rotation signal and is also used for switching the head switch or head amplifier. May be used in place of a signal.

Next, regarding another embodiment of the present invention (FIG. 3)
Explain with reference to. (FIG. 3) is a time chart for explaining the operation of the frame detection means, in which (a) is a reference frame signal and (b) is a reproduced frame signal. now(
Consider a case where the track number information in the reproduced signal cannot be read for some reason during the arrow period in FIG. 3). In the previous embodiment, the output in such a case is not defined, but it is assumed that the previous value is held during that period, and the reproduced frame signal is changed from "L" to "L" at the time when it can be read after that, as shown by the broken line. Suppose that it is changed to "H". Since the subsequent frame phase correction means captures the edge of the reproduced frame signal and sets it as the beginning of the frame as described above, the signal indicated by the broken line clearly conveys incorrect information regarding the reproduced frame. Therefore, by holding the "L" level as shown by the solid line, erroneous detection can be prevented, although the detection timing will be delayed. Therefore, the frame detection means may output the information only when it detects the track number indicating the beginning of the frame among the track number information of the reproduced signal. Note that this embodiment has the same structure as the previous embodiment except for the frame detection means.

Note that the number of tracks per frame and the configuration of the drum are merely examples, and the present invention is not limited to these configurations.

Regarding the tracking control means,
The method is not particularly limited as long as it controls the head scanning so that it rides on the track on the tape. The ATF method using frequency division multiplexed pilots, the area division ATF method, and the method using the linear track control signal shown in the conventional example can be similarly applied.

[0023]

As described above, according to the present invention, the phase difference between the reference frame and the reproduced frame is detected, and the correction operation is performed to the frame synchronization point based on the detected value. Synchronous pull-in can be performed in a short time. Furthermore, since the number of lines required to be supplied to the frame phase correction means is at least two, a system suitable for integration can be constructed. Furthermore, since a linear track is not required for frame information, the amount of information that can be recorded per unit area can be increased accordingly.

Furthermore, by holding the previous value except at the beginning of each reproduced frame, the frame detecting means prevents incorrect information from being transmitted to the frame phase correcting means even if track number information cannot be extracted from the reproduced signal. can be prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a playback device according to an embodiment of the present invention.

FIG. 2 is a time chart showing signals of various parts.

FIG. 3 is a time chart illustrating the operation of frame detection means.

[Explanation of symbols]

1 Tape 2 Drums 3 Standard generation means 4 Tracking control means 5 Frame detection means 6 Frame phase correction means

Claims (2)

[Claims] Claim 1: Data of a predetermined length is defined as one frame, one frame of data is divided and recorded on a plurality of diagonal tracks, each track includes track number information that goes around in two frames, and the data is recorded on a tape running in the longitudinal direction. a drum that rotates and scans the head to output a reproduction signal; a reference generating means that generates a reference rotation signal that is a rotation reference of the drum and a reference frame signal that is inverted for each frame; and each head on the drum. tracking control means for controlling tape running so as to trace tracks on the tape; and frame detection for detecting track number information included in the reproduction signal and outputting a binary reproduction frame signal according to whether the frame is even or odd. and frame phase correction means for acting on the tracking control means to eliminate a frame phase difference between the reference frame signal and the reproduction frame signal. 2. Claim 1, wherein the frame detection means holds the previous value except at the beginning of each reproduced frame.
The playback device described.