JP3252601B2 - Digital magnetic reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a consumer digital VTR for reproducing a compressed video signal, and more particularly to a control method for improving image quality in variable speed reproduction at an arbitrary speed different from a normal reproduction speed.

[0002]

2. Description of the Related Art In a consumer digital VTR, an image compression technique is used to reduce the amount of data recorded on a magnetic tape. As an example of the image compression technique, a so-called MPEG method is generally used.

In the MPEG system, a video is constructed by using a difference between frames. Therefore, when high-speed reproduction is performed, the continuity of data of the preceding and succeeding frames is lost. Can not.

For this reason, as a high-speed reproduction method of a VTR utilizing image compression by the MPEG system, for example, "FIRST S
CAN TECHNOLOGY FOR DIGITAL VIDEO TAPE RECORDERS (I
EEETransactions on Consumer Electronics Vol.39, No.
3, AUGUST 1993) ".

In this method, video data for high-speed playback is placed at a specific position on a magnetic tape that matches the scanning locus of the playback head according to the tape speed so that images can be decoded even during high-speed playback. Are recorded separately and separately. This enables high-speed reproduction, such as search and shuttle reproduction, even on tapes recorded by compression in the MPEG format.

[0006]

However, when the variable speed reproduction is performed by the above-described conventional method, there are the following problems.

That is, when the control is switched from the normal reproduction state to the control of the high-speed reproduction, or when the reproduction speed is changed in the high-speed reproduction state, it is necessary to reduce the tape speed in order to correctly scan each variable speed track. Since the change control and the position control of the reproducing head are required, there is a slight time delay before data can be normally obtained. Therefore, during this time, since the correct data is not reproduced from the tape and the image cannot be decoded, no image is displayed on the television screen, and the image is displayed every time the high-speed reproduction is switched or when the speed is changed in the high-speed reproduction state. Is interrupted, resulting in an unsightly state.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a television receiver with which a video signal cannot be decoded even when a reproduction signal from a tape is interrupted, such as when switching from normal reproduction to high-speed reproduction. An object of the present invention is to provide a control method capable of outputting a video signal and improving image quality.

[0009]

In order to solve the above-mentioned problems, the present invention processes a signal reproduced by a head in accordance with a predetermined format and makes the reproduced signal normal.
Or the reproduction signal processing circuit for outputting an identification signal that identifies whether a decoding processing circuit for decoding the decompressed video signal the compressed digital video signal, a memory for storing a video signal, condensate
A video signal output circuit for outputting the issue video signal, the video signal in response to the identification signal output from the reproduction signal processing circuit
Control means for controlling the output circuit, wherein the control means
During variable speed playback at any speed different from normal playback,
When transitioning from the playback state to the high-speed playback
When transitioning from the raw state to the normal playback state, or at high speed playback
When changing the playback speed in the state, the playback signal processing circuit
If the playback signal is not normal due to the identification signal output from
If it is determined , the immediately preceding video signal is output from the memory .
The configuration is such that control is performed as follows.

[0010]

When the reproduction speed is changed and the signal is no longer reproduced from the tape, the immediately preceding video signal is read from the memory and switched and output by the switching means, so that a stable video is obtained without interruption of the video output. be able to.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a digital magnetic reproducing apparatus according to the present invention will be described below by taking an application to a digital VTR as an example.

FIG. 2 shows an example of a track pattern on a magnetic tape in a digital VTR, which corresponds to triple speed and ninth speed in the forward (forward) direction.

In FIG. 2, reference numeral 21 denotes a scanning trajectory of the reproducing head during normal reproduction, 22 denotes a scanning trajectory of the reproducing head at 3 × speed reproduction, 23 denotes a scanning trajectory of the reproduction head at 9 × speed reproduction, and 24 denotes a blank space. The portion is an area where video data for normal playback is recorded, the shaded portion like 25 is video data for 3x speed playback, and the shaded portion like 26 is 9x speed playback data. This is the part where the data is recorded.

First, a digital VT to which the present invention is applied
The recording method of R will be described.

As shown in FIG. 2, compressed data 24 obtained by compressing video of one frame is recorded on one track on a magnetic tape. When performing this compression, it is necessary to perform compression at a high compression ratio without deteriorating the image quality as much as possible.
Well-known MPEG utilizing correlation between frames
Is used.

Furthermore, compressed video data to be reproduced during high-speed reproduction is also recorded on each track. These compressed data for high-speed reproduction do not require high image quality, and it is necessary to be able to decode a video from reproduced partial data. Therefore, a compression method for each frame is adopted, and the data is compressed at a high compression rate. The compressed data for high-speed reproduction for one frame is divided into several tracks and recorded according to the reproduction speed.

As an example of the recording position of the compressed data, the recording position of the compressed data for triple speed is shown at 25 in FIG. The reproduction head 4 of the present digital VTR operates at 22.times.
Scan obliquely over three tracks as shown in FIG. Therefore, in order to perform the triple speed reproduction, the data 25 for the triple speed reproduction is divided and recorded at a specific position of each of the three tracks according to the scanning locus of the reproducing head 4.

Similarly, in 9-times speed reproduction, the reproducing head 4 scans across 9 tracks as shown at 23 in FIG. 2, so that the data 26 for 9-times speed reproduction is divided into nine tracks and recorded. Will be.

In FIG. 2, 3 (forward) direction
Although the example of recording at double speed and ninth speed is shown, it is of course possible to perform recording at an arbitrary reproduction speed as needed. Recording for high-speed reproduction in the reverse (reverse) direction is also possible.

Next, the first embodiment of the present invention will be described with reference to the drawings, taking an application to a digital VTR as an example.

FIG. 1 shows a block diagram of a first embodiment of the present invention. In FIG. 1, 1 is a take-up reel for winding a magnetic tape, 2 is a magnetic tape, 3 is a supply reel for supplying a magnetic tape, 4 is a reproducing head for reproducing signals recorded on the magnetic tape, and 5 is a magnetic tape. A capstan control circuit for controlling a capstan motor (not shown) for controlling a feed speed and a relative position (phase) of the head with respect to a recording track on the tape; and 6, a drum control for controlling a rotational speed and a rotational phase of the head 4 A control circuit 7 for controlling the entire system; a reproduction signal processing circuit 8 for processing a signal reproduced by the head in accordance with a predetermined format; a decoding processing circuit 9 for expanding a compressed signal and decoding a video;
Reference numeral 12 denotes a video signal selection circuit comprising a memory 10 for storing a video signal and switching means 11 for switching and outputting a decoded video signal and a video signal stored in the memory, and 13 a signal output terminal.

Next, the operation of the digital VTR of the first embodiment when reproducing at a normal speed will be described.

When a reproduction operation start command is input by the control means 7, the drum control circuit 6 starts controlling a drum motor (not shown) for controlling the rotation speed and phase of the head 4,
At the same time, the capstan control circuit 5 controls the rotation speed of the capstan motor, causes the magnetic tape 2 to run at a predetermined speed, and controls the phase so that the reproducing head 4 correctly scans the center of the recording track. This phase control is performed, for example, by a DAT (Digital Audio Tape Recorder).
It can be easily realized by using the well-known area division ATF method, etc., and the specific control thereof is not directly related to the gist of the present invention. The reproducing head 4 is controlled to a predetermined rotation speed and phase by well-known control.

Under these controls, the reproducing head 4 is moved to the position shown in FIG.
The center of the track on the magnetic tape 2 is scanned along the locus 21.

The recording signal on the magnetic tape 2
And the data is taken out by the reproduction signal processing circuit 8 as data of a predetermined format. The decoding processing circuit 9 decodes the extracted data in a predetermined procedure and outputs the decoded data as video data.

Further, the control means 7 controls the switching means 11 so that the memory 10 is set to the writing state and the decoded signal is output to the output terminal 13 at the time of reproduction.

Since the memory 10 is in the writing state, the video signal decoded by the decoding processing circuit 9
0 is sequentially written. The video signal decoded by the decoding processing circuit 9 is output to the output terminal 13 through the switching means 11.

Next, the operation of the digital VTR of the first embodiment when high-speed reproduction is performed will be described with reference to triple speed as an example.

When an instruction for triple speed reproduction is input by the control means 7, the capstan control circuit 5 controls the rotation speed of the capstan motor so that the running speed of the magnetic tape 2 becomes three times that of the normal reproduction. The rotation phase of the head 4 is controlled so that the traveling locus of the head 4 becomes 22 in FIG. 2, that is, at a position where the triple-speed reproduction data can be correctly reproduced. This phase control is performed, for example, by detecting a deviation from a track address or the like written in the recording data and controlling the deviation to be zero, that is, by controlling the head to scan a desired track. After the phase is pulled in, the tracking control is performed by the above-mentioned ATF control or the like. The specific method can be easily performed by a well-known control technique, and the gist of the present invention is directly Details are omitted because they are not relevant.

With the above control, the data for triple-speed reproduction starts to be reproduced from the time when the reproducing head 4 correctly scans the recording track of the data for triple-speed reproduction, and is reproduced by the reproduction signal processing circuit 8 as data of a predetermined format. Taken out. The decoding processing circuit 9 decodes the image using the data 25 for triple speed from the extracted data. The decoded image is written to the memory 10 and output to the output terminal 13 as in the case of normal reproduction.

In the above example, the triple speed has been described.
At double speed, the same processing is performed except that the tape feed speed is different and that the data 26 for 9 × speed is used. The same applies to other reproduction speeds.

Although the normal reproduction and the high-speed reproduction have been described above, the tape feed speed differs between the normal reproduction and the high-speed reproduction, and the track scanned by the reproduction head 4 also differs. Further, even at high speed reproduction, both the tape feed speed and the track are different depending on the reproduction speed such as 3 × speed and 9 × speed. Therefore, after switching the reproduction speed as described above, it takes a little time until the tape feed speed matches the new reproduction speed, and the phase control of the head is completed and the reproduction head 4 scans the desired track. A delay occurs. During that time, a correct signal is not reproduced from the magnetic tape 2 and the decoding processing circuit cannot decode the image.

Therefore, the digital VTR of the first embodiment
Then, while a correct signal is not reproduced from the magnetic tape 2 and an image cannot be decoded, a video signal is read from the memory 10 and output to the output terminal 13. This detailed operation will be described below.

When changing the reproduction speed, the control means 7 changes the operation of the memory 10 from writing to reading.
Subsequently, the switching means 11 is switched so that the video signal read from the memory 10 is output to the output terminal 13. Thus, the video signal decoded immediately before is read from the memory 10 and repeatedly output.

Next, the control means 7 controls the capstan control circuit 5, sets the tape feed speed to the specified speed, and controls the phase so that the reproducing head 4 scans a predetermined track. During this time, a correct signal is not reproduced from the magnetic tape 2 and a video signal is not decoded. Instead,
The video signal stored in the memory 10 is output to the output terminal 13.

Next, when the feed speed of the magnetic tape 2 becomes a predetermined value and the reproducing head 4 scans a predetermined track, the reproduction signal processing circuit 8 identifies the data reproduction to be normal. A signal is sent to the control means 7. When the control means 7 detects this identification signal, it switches the switching means 11 to output the output of the decoding processing circuit 9 to the output terminal 13
And the memory 10 is again controlled to the write state.

In the above operation, the relationship between the change in tape speed and the control of video output when switching between normal playback and high-speed playback and when the playback speed is changed during high-speed playback are shown in FIGS. b)

With the above operation, when shifting from the normal reproduction state to the high-speed reproduction operation, when changing the speed during the high-speed reproduction operation, or when returning from the high-speed reproduction to the normal reproduction state, the video is lost due to tracking loss. Even if it is impossible to decode the video, it is possible to solve the situation that the video is interrupted, and it is possible to improve the image quality in the high-speed playback operation.

In the first embodiment shown in FIG. 1, the video signal selection circuit 12 for selecting a video signal is arranged after the decoding processing circuit 9, and the selected signal is output to the output terminal 13. However, this is not particularly limited,
The video signal selection circuit 12 is arranged before the decoding processing circuit 9,
A video signal before performing a decoding process is selected and a decoding processing circuit 9 is selected.
The configuration may be such that the signal input to the decoder is switched, or furthermore, the memory included in the decoding processing circuit 9 is added or shared so that the video signal is selected.
Various modifications can be easily made without changing the gist of the present invention.

Further, in the first embodiment shown in FIG. 1, the video signal selection circuit 12 is constituted by the memory 9 and the switching means 10, but it can be constituted by the memory 9 alone. An example in which this is applied to a digital VTR is shown in FIG. 4 as a second embodiment.

In the case of selecting and outputting an input signal in the video signal selection circuit 12 shown in FIG. 4, the input signals are sequentially stored in a memory and read out from the memory at a predetermined timing. Therefore, the input signal is output as it is after a predetermined time. When selecting and outputting the signal stored in the memory, stop the write operation to the memory,
Only a predetermined read operation is repeated. Since the contents of the memory are not updated, the signal input immediately before is continuously output. Thereby, the same effect can be obtained even if the switching means 10 is omitted.

Next, another invention will be described.

FIG. 1 shows a digital VTR having a built-in decoding circuit. However, the decoding processing circuit is not built in the VTR, and the video signal is expanded using a decoding processing circuit included in a tuner or the like. It is also possible. An example in which the present invention is applied to a digital VTR without a built-in decoding processing circuit will be described below.

FIG. 5 is a block diagram of a digital VTR according to a third embodiment of the present invention.

In FIG. 5, reference numerals 1 to 8 and 10 to 13 are the same as those in FIG.

The digital VTR according to the third embodiment will now be described.
The operation at the time of performing the normal reproduction will be described.

When a reproduction operation start command is input by the control means 7, the drum control circuits 6 and 6 are operated in the same manner as in the first embodiment.
The capstan control circuit 5 is controlled. As a result, the reproducing head 4 scans the center of the track on the magnetic tape 2 like the locus 21 in FIG.

The recording signal on the magnetic tape 2
And the data is taken out by the reproduction signal processing circuit 8 as data of a predetermined format.

At the time of reproduction, the control means 7 controls the memory 1
The switching means 11 is controlled so that 0 is set to the writing state and the signal on the side processed by the reproduction signal processing circuit 8 is output to the video output terminal 13. In the present embodiment, the video signal selection circuit 12 comprises the memory 10 and the switching means 11. In this case, the memory 10 is set to the writing state, and the video signal processed by the reproduction signal processing circuit 8 is written to the memory. Also, the reproduction signal processing circuit 8
Is controlled to be output to the output terminal 13 through the switching means 11.

Next, the operation of the digital VTR according to the third embodiment in the case where high-speed reproduction is performed will be described with reference to triple speed as an example.

When a command for triple speed reproduction is input by the control means 7, the capstan control circuit 5 is controlled, and the head 4 scans a track on which data for triple speed reproduction is recorded.

When the reproducing head 4 has correctly scanned the recording track of the data for triple speed reproduction, the data for triple speed reproduction starts to be reproduced, and the reproduction signal processing circuit 8 takes out the data as data of a predetermined format. The reproduced signal is written to the memory 10 and output to the output terminal 13 as in the case of normal reproduction.

In the above example, the triple speed has been described.
At double speed, the same processing is performed except that the tape feed speed is different and that the data 26 for 9 × speed is used. The same applies to other reproduction speeds.

As in the first embodiment, when the reproducing speed is changed, a slight time delay occurs before the reproducing head 4 scans a desired track. During this time, a correct signal is not reproduced from the magnetic tape 2.

Therefore, the digital VTR of the third embodiment is
During the period in which a correct signal is not reproduced from the magnetic tape 2, the video signal is read from the memory 10 and the output terminal 13
Output to

When changing the reproduction speed, the control means 7 changes the operation of the memory 10 from writing to reading.
Subsequently, the switching unit 11 is controlled so that the video signal read from the memory 10 is output to the output terminal 13. As a result, the video signal reproduced immediately before is read from the memory 10 and repeatedly output.

Next, the control means 7 controls the capstan control circuit 5, sets the tape feed speed to the specified speed, and controls the phase so that the reproducing head 4 scans a predetermined track. During this time, a correct signal is not reproduced from the magnetic tape 2. Instead, a video signal stored in the memory 10 is output to the output terminal 13.

Next, when the feed speed of the magnetic tape 2 becomes a predetermined value and the reproducing head 4 scans a predetermined track, the reproduction signal processing circuit 8 identifies the data reproduction to be normal. A signal is sent to the control means 7. When the control means 7 detects this identification signal, it controls the video signal selection circuit, switches the switching means 11 to output the output of the decoding processing circuit 9 to the output terminal 13, and controls the memory 10 to the write state again. I do.

With the above operation, when shifting from the normal reproduction state to the high-speed reproduction operation, when changing the speed during the high-speed reproduction operation, or when returning from the high-speed reproduction to the normal reproduction state, the video is lost due to tracking failure. Even if it is not possible to reproduce correctly, it is possible to eliminate the situation that the video is interrupted, and it is possible to improve the image quality in the high-speed reproduction operation.

In the third embodiment shown in FIG. 5, a video signal selection circuit 12 for selecting a video signal is arranged after the reproduction signal processing circuit 8, and the selected signal is output to the output terminal 13. However, this is not particularly limited, and various modifications can be easily made without changing the gist of the present invention.

In the third embodiment shown in FIG. 5, the video signal selection circuit 12 is constituted by the memory 9 and the switching means 10, but it can be constituted by the memory 9 alone. This is the same as in the first embodiment.

The embodiments of the present invention have been described above.

In the above embodiment, high-speed reproduction in the forward (forward) direction is taken as an example. However, the present invention is not particularly limited to this and can be similarly applied to high-speed reproduction in the reverse (reverse) direction. Of course. In addition, the high-speed reproduction speed is exemplified by 3 × speed and 9 × speed, but this is not particularly limited, and it is needless to say that high-speed reproduction at an arbitrary speed can be performed if necessary. Various modifications are easy as long as the gist is not changed.

[0064]

As described above, according to the present invention,
When switching from normal playback to high-speed playback, or when changing the playback speed in a high-speed playback state, the video signal is not interrupted even if the signal is not correctly reproduced from the tape and the decoding of the video signal is temporarily interrupted. A digital VTR that outputs a stable video signal can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a digital VTR according to the present invention.

FIG. 2 is a diagram showing a recording pattern on a magnetic tape of the digital VTR according to the present invention.

FIG. 3 is a diagram showing a relationship between a reproduction speed and a video output in FIG. 1;

FIG. 4 is a block diagram showing a second embodiment of a digital VTR according to the present invention.

FIG. 5 is a block diagram showing a third embodiment of a digital VTR according to the present invention.

[Explanation of symbols]

 Reference Signs List 4 reproduction head 5 capstan control circuit 6 drum control circuit 7 control means 8 reproduction signal processing circuit 9 decoding processing circuit 10 memory 11 switching means 12 video signal selection circuit 21 scanning locus of reproduction head during normal reproduction 22 at the time of triple speed reproduction Scanning locus of the reproducing head 23 Scanning locus of the reproducing head at 9 × speed reproduction 24 Record data for normal reproduction 25 Record data for 3 × speed reproduction 26 Record data for 9 × speed reproduction

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-48983 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 5/91-5/956 H04N 5 / 782-5/783

Claims (6)

(57) [Claims] 1. A digital magnetic reproducing apparatus for reproducing a compressed digital video signal by a rotary head, wherein the signal reproduced by the head is processed according to a predetermined format, and whether the reproduced signal is normal or not is determined.
A reproduction signal processing circuit that outputs an identification signal for identification; a decoding processing circuit that expands the compressed digital video signal processed by the reproduction signal processing circuit and decodes the decoded video signal into a video signal; Video signal to output
A signal output circuit, and a control means for controlling the video signal output circuit in accordance with the identification signal outputted from the reproduced signal processing circuit, wherein the control unit, variable speed reproduction of the normal reproduction different from any speed At the time, when the transition from the normal reproduction state to the high-speed reproduction state , when the transition from the high-speed reproduction state to the normal reproduction state, or when the reproduction speed is changed in the high-speed reproduction state, it is output from the reproduction signal processing circuit. Depending on the identification signal
Ri when the reproduced signal is judged not to be normal, digital magnetic reproducing apparatus the previous image signal and controls so as to output from the video signal output circuit. 2. The video signal output circuit according to claim 1, further comprising a memory for storing the video signal, and switching means for switching and outputting the input video signal and the video signal stored in the memory. The digital magnetic reproducing device according to claim 1. 3. A digital magnetic reproducing apparatus for reproducing a compressed digital video signal by a rotary head, wherein the signal reproduced by the head is processed according to a predetermined format, and whether the reproduced signal is normal or not is determined.
A reproduction signal processing circuit for outputting an identification signal for identification; a decoding processing circuit for expanding a compressed digital video signal processed by the reproduction processing circuit to decode the decoded video signal into a video signal; and storing the video signal decoded by the decoding processing circuit And a control unit for controlling the memory in accordance with the identification signal output from the reproduction signal processing circuit. The control unit normally performs a variable speed reproduction at an arbitrary speed different from the normal reproduction. When transitioning from the reproduction state to the high-speed reproduction state , transitioning from the high-speed reproduction state to the normal reproduction state, or changing the reproduction speed in the high-speed reproduction state, the identification signal output from the reproduction signal processing circuit is used.
A digital magnetic reproducing apparatus for controlling, when it is determined that the reproduced signal is not normal, to output the immediately preceding video signal from the memory. 4. A digital magnetic reproducing apparatus for reproducing a compressed digital video signal by a rotary head, wherein the digital magnetic reproducing apparatus processes a signal reproduced by the head according to a predetermined format and determines whether the reproduced signal is normal.
A reproduction signal processing circuit for outputting an identification signal for identification; and a video signal processed by the reproduction signal processing circuit .
That a video signal output circuit, and a control means for controlling the video signal output circuit in accordance with the identification signal outputted from the reproduced signal processing circuit, wherein the control means, any rate of the variable that is different from the normal reproduction At the time of variable speed playback, when shifting from the normal playback state to the high speed playback state , or when shifting from the high speed playback state to the normal playback state, or when changing the playback speed in the high speed playback state, the output from the playback signal processing circuit is output. The identification signal
Ri when the reproduced signal is judged not to be normal, digital magnetic reproducing apparatus the previous image signal and controls so as to output from the video signal output circuit. 5. The video signal output circuit according to claim 1, further comprising a memory for storing the video signal, and switching means for switching and outputting the input video signal and the video signal stored in the memory. The digital magnetic reproducing device according to claim 4. 6. A digital magnetic reproducing apparatus for reproducing a compressed digital video signal by a rotary head, wherein the digital magnetic reproducing apparatus processes a signal reproduced by the head according to a predetermined format and determines whether the reproduced signal is normal.
A reproduction signal processing circuit for outputting an identification signal for identification; a memory for storing a video signal processed by the reproduction signal processing circuit; and control of the memory in accordance with the identification signal output from the reproduction signal processing circuit. Control means for performing, at the time of variable speed reproduction at an arbitrary speed different from normal reproduction, when transitioning from the normal reproduction state to the high-speed reproduction state , or when transitioning from the high-speed reproduction state to the normal reproduction state, Alternatively, when the reproduction speed is changed in the high-speed reproduction state, the identification signal output from the reproduction signal processing circuit is used.
A digital magnetic reproducing apparatus for controlling, when it is determined that the reproduced signal is not normal, to output the immediately preceding video signal from the memory.