JP3143370B2 - Video data recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital VT.
As in R (Video Tape Recorder), a tape serving as a signal recording medium is wound around a rotary head cylinder, and video data compressed by a predetermined image compression method is recorded on a plurality of tracks on the tape by a helical scan method, Alternatively, the present invention relates to a video data recording / reproducing device for reproducing video data from these tracks.

[0002]

2. Description of the Related Art In the ATV (Advanced Television) standard proposed as a next-generation digital broadcasting system in the United States, MPEG (Moving Picture Image), which is an international standard for image compression, is used as a compression method for transmitting image data.
Coding Experts Group) is being adopted. In addition, DVB (Digital Video)
Broadcasting) will also adopt MPEG.

[0003] The MPEG system employs motion compensation prediction, DCT (discrete cosine transform), and variable length coding in data encoding. As shown in the frame configuration of FIG. Depending on the prediction mode, I (intra
-coded) picture, P (predictive coded) picture, B
(bi-directionally predictive coded) pictures. The I picture is an intra-frame coded image, the P picture is an inter-frame predicted coded image predicted from a temporally preceding frame, and the B picture is an inter-frame predicted coded image from preceding and succeeding frames.

FIG. 12 shows a data hierarchical structure of an image in the MPEG system. It is constituted as follows from the lower layer. (Block layer) A block is composed of 8 ×
DCT is executed in this unit. (Macro Block Layer) A macro block is composed of a total of six blocks including four adjacent luminance blocks and two color difference blocks Cb and Cr at the same position on the screen. A (slice layer) slice is composed of a plurality of macroblocks that are connected in the scanning order of an image. (Picture layer) A picture is composed of a plurality of slices,
One image is formed. Depending on the encoding format, it is classified into the above-mentioned I picture, P picture, and B picture. (GOP layer) A GOP (group of pictures) is composed of one or more I-pictures and zero or more non-I-pictures. (Video Sequence Layer) A video sequence is composed of one or a plurality of GOPs having the same image size, image rate, and the like.

On the other hand, HD (High Definition) digital V
The CR Council is studying the standardization of a digital VTR that records and reproduces video signals as digital data. Here, on the magnetic tape, ATV standard data (ATV signal) compressed by the above-described MPEG system is used.
Can be recorded. FIG. 13 shows a digital VT
3 shows a standard signal recording format in R.
As shown in the figure, the track formed on the signal surface of the magnetic tape (1) is composed of an IT including insert data and track information.
It comprises an I area, an audio data area, a video data area, and a subcode data area. Recording speed is N
In the TSC mode, there are 300 tracks per second, and one frame of image is recorded using 10 tracks.

Data is recorded in units called sync blocks, and 135 video data areas are recorded in one track.
Sync blocks can be recorded. The video data is shown in FIG.
As shown in FIG. 4, the data block is treated as a 135 × 77 byte block, and an error correction code including an inner code and an outer code, sync data and ID data are added to the data block, and these data are converted into one data block. It is recorded on the track. The inner code is mainly used for detecting and correcting a random error, and the outer code is mainly used for detecting and correcting a burst error. One sync block is recorded in the order of sync data, ID data, video data, and an error correction code.

By the way, DVB to be adopted in Europe
In (Digital Video Broadcasting), the bit rate of a broadcast signal of one program is, for example, 20 Mbps, 10 Mbps.
It is variably set to an arbitrary value such as ps or 4 Mbps. In contrast, a digital VTR has a bit rate of 2
It is possible to record a signal of 5 Mbps. Therefore, when a DVB signal having a low bit rate is directly recorded on a magnetic tape by a digital VTR, a non-signal portion corresponding to the bit rate difference is generated, and there is a problem in the effective use of the magnetic tape.

To solve this problem, a digital VTR
It is effective to lower the recording rate to the bit rate of the DVB signal. For example, the bit rate of the DVB signal is one third of the recording rate (25 Mbps) of the digital VTR.
(8.33 Mbps), the feed speed of the magnetic tape is reduced to one third of the normal speed, and the signal recording by the rotary head cylinder is performed once in three traces, so that the magnetic tape can be read. Effective use can be achieved. During signal playback, the same tape feed speed as during recording
Under (one third), the reproduced signal may be extracted once in three traces.

[0009]

However, in the case of the above-described signal recording / reproducing method, the achievable recording rate is reduced to an odd number in the case of a 180 ° facing head type rotary head cylinder, and in the double azimuth head type. 1 / natural number
There is a problem that is constrained. Therefore, for example, when recording a signal having a bit rate of 1/3, the cylinder rotation speed and the tape feed speed are reduced to 1/3. A method of setting the feed speed is conceivable. As a result, the track pattern formed on the magnetic tape is usually (1 time)
This is exactly the same as the case where a signal of the rate is recorded. or,
The recording rate is not limited to an odd number or a natural number, and the same pattern is formed even at a real number (1 / n).

However, since the cylinder rotation speed and the tape feed speed at the time of signal reproduction change in accordance with the bit rate of the DVB signal, an equalizing circuit for compensating various distortions for each different bit rate. It is necessary to change the characteristics, which causes a problem that the configuration of the equalization circuit becomes extremely complicated. Further, as the cylinder rotation speed decreases, the amplitude of the signal reproduced from the tape decreases, and there is a problem that the S / N ratio decreases.

It is an object of the present invention to provide a video data recording / reproducing apparatus which has no restriction on the recording rate, has a simple circuit configuration, and does not lower the S / N ratio.

[0012]

According to the present invention, the rotary head cylinder is always rotated at a speed of one time and the magnetic tape is rotated one time at the time of signal reproduction regardless of the signal rate (1 / n) at the time of signal recording. The above problem is solved by running at double speed.

A video data recording / reproducing apparatus according to the present invention comprises:
A tape serving as a signal recording medium is wound around a rotary head cylinder, and video data compressed by a predetermined image compression method is recorded on a plurality of tracks on the tape by a helical scan method, or video data is reproduced from these tracks. A fixed cylinder speed N
In addition, video data can be recorded at a predetermined bit rate M under the tape feed speed v. The video data recording / reproducing device has a bit rate M / n as a characteristic configuration.
When recording (n is a real number of 1 or more) video data on a tape, the cylinder rotation speed is N / n, and the tape feed speed is v / n.
Recording control circuit, and when reproducing video data from the tape, set the cylinder rotation speed to N and the tape feed speed to v
And a normal reproduction control circuit for setting the average bit rate of video data reproduced from the tape to M / n by intermittently feeding the tape.

In the video data recording / reproducing apparatus, tracing during signal reproduction is performed in the same pattern as a track pattern formed on the tape by signal recording.
All of the video data recorded on the tape will be read. Here, the bit rate of the reproduced video data when the tape is running is M, but the bit rate of the reproduced video data is 0 while the tape is stopped. As a result, the average bit rate is M / n. Is set to Therefore, by supplying the video data of the bit rate M / n to the television receiver, a normal reproduced video of the video data can be obtained.

In a specific configuration of the video data recording / reproducing apparatus, a normal reproduction control circuit controls a buffer memory for storing video data reproduced from a tape, and writes and reads video data to and from the buffer memory. hand,
A memory control circuit for setting the bit rate of video data read from the buffer memory to M / n.

In the specific configuration, the reproduced video data having the bit rate M passes through the buffer memory, whereby the video data having the constant bit rate M / n is obtained.

In another video data recording / reproducing apparatus according to the present invention, video data is compressed by a predetermined image compression method, and I-pictures are intra-coded and inter-frame coded by prediction from the past. P picture
It has three image modes of B-pictures inter-coded by prediction from the past and the future, and can record video data at a predetermined bit rate M under a constant cylinder rotation speed N and a tape feed speed v. It is possible. The video data recording / reproducing apparatus is characterized in that when recording video data of a bit rate M / n (n is a real number of 1 or more) on a tape, the cylinder rotation speed is N / n and the tape feed speed is v / N, when reproducing video data from the tape, set a cylinder rotation speed to N, set a tape feed speed to v, and set a predetermined number of I pictures, P pictures and B pictures. Image group GO
By using P as one unit and deleting video data in units of image groups GOP from video data reproduced from tape, video data whose average number of frames per unit time matches a predetermined television broadcasting system can be obtained. And a special reproduction control circuit to be created.

In the video data recording / reproducing apparatus, video data reproduced from a tape is composed of an image group GOP.
, From which a suitable image group GOP is intermittently deleted at a rate where the number of frames per unit time is 1 / n on average, and the remaining image groups GOP are formed. The bit stream is supplied to a television receiver. Here, the video data can be played back in image group units, and the bit rate of the original video data is M / n, whereas the playback rate of the video data is M. Thus, a special reproduction image whose reproduction speed is n times the normal speed can be obtained.

Another video data recording / reproducing apparatus according to the present invention is characterized in that when recording video data of a bit rate M / n (n is a real number of 1 or more) on a tape, the cylinder rotation speed is set to N. / N, a recording control circuit for setting the tape feed speed to v / n, and, when reproducing video data from the tape, setting the cylinder rotation speed to N, the tape feed speed to v, and the video reproduced from the tape. A special reproduction control circuit for extracting only the video data of the I picture from the data and generating video data whose average number of frames per unit time matches a predetermined television broadcasting system based on the video data; With

In the video data recording / reproducing apparatus, video data reproduced from a tape is composed of an image group GOP.
, And one image group further includes an I picture, a P picture, and a B picture. So, from the time series data,
Only I pictures are extracted, and the number of frames per unit time is 1 /
An appropriate I picture or a picture replacing it is interpolated at a rate of n, and a bit stream composed of these pictures is supplied to the television receiver. Here, the video data can be reproduced based on the I picture, and the bit rate of the original video data is M / n, whereas the reproduction rate of the video data is M. Through the demodulation processing by the device, a special reproduction image whose reproduction speed is n times the normal speed is obtained.

Another video data recording / reproducing apparatus according to the present invention has a characteristic feature that the bit rate M / n
When recording (n is a real number of 1 or more) video data on a tape, the cylinder rotation speed is N / n, and the tape feed speed is v / n.
Recording control circuit, and when reproducing video data from the tape, set the cylinder rotation speed to N and the tape feed speed to v
And by deleting the video data in frame units from the video data reproduced from the tape according to the priority order of the B picture, the P picture, and the I picture, the average number of frames per unit time becomes a predetermined value. A special reproduction control circuit for creating video data conforming to the television broadcasting system.

In the video data recording / reproducing apparatus, I
From the time-series data composed of a picture, a P picture, and a B picture, a B picture is deleted first, a P picture is deleted first, and an I picture is further deleted as necessary. The number of pictures is adjusted so that the number of frames per unit time becomes 1 / n on average, and a bit stream composed of the remaining pictures is supplied to the television receiver. Here, in the video data, when only I pictures remain, image reproduction can be performed based on only these I pictures. When I pictures and P pictures that can be predicted from the I pictures remain, Can be reproduced based on the I picture and the P picture. Further, when the B picture that can be predicted from these remains together with the I picture and the P picture, based on the I picture, the P picture and the B picture, To reproduce images. Similarly, in the video data recording / reproducing apparatus, since the bit rate of the original video data is M / n, while the reproduction rate of the video data is M, the reproduction speed is n times the normal speed. A reproduced image is obtained.

Further, another video data recording / reproducing apparatus according to the present invention has a feature that the bit rate M / n
When recording (n is a real number of 1 or more) video data on a tape, the cylinder rotation speed is N / n, and the tape feed speed is v / n.
Recording control circuit, and when reproducing video data from the tape, set the cylinder rotation speed to N and the tape feed speed to v
And a demodulation circuit that demodulates the video data reproduced from the tape and deletes the demodulated data in units of frames from the demodulated data so that the average number of frames per unit time is equal to a predetermined television broadcast. A special reproduction processing circuit for creating video data conforming to the system.

In the video data recording / reproducing apparatus, the video data of the bit rate M reproduced from the tape is demodulated as it is, and the bit rate is M and the number of frames per unit time is n times the normal demodulated data. Is obtained. The demodulated data is intermittently deleted in frame units at a rate where the number of frames per unit time is 1 / n on average, and the remaining frames are supplied to the television receiver. Here, since the bit rate of the original video data is M / n, while the bit rate of the video data supplied to the television receiver is M, the special playback image whose playback speed is n times the normal speed is used. Is obtained.

[0025]

In the video data recording / reproducing apparatus according to the present invention, the cylinder rotation speed and the tape feed speed at the time of signal recording are reduced in accordance with the reduction rate of the recording rate. It may be 1 / the real number of the normal value. Further, since the cylinder rotation speed and the tape feed speed at the time of signal reproduction are one time and constant, the configuration of the equalization circuit for distortion compensation is simple, and the amplitude of the signal reproduced from the tape is small. Therefore, the S / N ratio does not decrease.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention applied to a digital VTR for recording a DVB signal will be specifically described with reference to first to fifth embodiments.
Note that the first embodiment realizes the normal playback mode in which the video playback speed is 1 ×, and the second to fifth embodiments realize the special playback mode in which the video playback speed is n ×. It is.

The signal recording system will first be described for each example common signal recording system. As shown in FIG. 10, a digital VTR has a capstan by winding a magnetic tape (1) around a rotary head cylinder (2).
The magnetic tape (1) is run by driving (3), and recording and reproduction of signals are performed by helical scanning by the rotary head cylinder (2). Below, video data can be recorded at a predetermined bit rate M (25 Mbps). The rotation speed of the rotary head cylinder (2) is controlled by a cylinder rotation control circuit (5). A pair of magnetic heads mounted on the rotary head cylinder (2) are connected to a rotary transformer (4) via a rotary transformer (4). A signal recording circuit and a signal reproducing circuit described later are connected. In addition, capstan (3)
The rotation speed is controlled by a tape feed control circuit (6).

D input to the signal recording circuit shown in FIG.
The VB signal is a broadcast signal of one program received by a DVB receiver (not shown), is subjected to image compression according to the MPEG system, and is a real number n of a normal recording rate M (25 Mbps) of a digital VTR. 1 bit rate (M /
n). The DVB signal is supplied to a recording signal processing circuit.
The signal is input to (30) and subjected to signal processing such as addition of an error correction code. The data output from the recording signal processing circuit (30) is supplied to a modulation circuit (31), where the data is subjected to a predetermined modulation processing, further amplified through a recording amplifier (32), and then the rotary transformer (4). To the rotary head cylinder (2).

The received DVB signal is supplied to a signal rate detection circuit (33), and the signal rate of the DVB signal is detected. Here, the signal rate can be easily detected based on the rate information included in the video Aux shown in FIG. As shown in FIG. 10, the signal rate detection signal n is input to a clock generation circuit (34) to generate a clock to be supplied to a recording signal processing circuit (30) and a modulation circuit (31). Thereby, the recording signal processing circuit (30)
And the modulation circuit (31) performs an operation according to the signal rate of the DVB signal. At the same time, the signal rate detection circuit (3
The signal rate detection signal n obtained from 3) is input to a cylinder rotation control circuit (5) and a tape feed control circuit (6) to set the rotation speed of the rotary head cylinder (2) to N / n and , The feed speed of the magnetic tape (1) is set to v / n.

As a result, regardless of whether or not the value of the real number n is an integer, the magnetic tape (1) has the same track pattern as when video data was recorded at the normal recording rate M (25 Mbps). Track inclination, pitch, bit length, etc.).

First Embodiment As shown in FIG. 1, in the normal reproduction mode, the rotation speed of the rotary head cylinder (2) is set to the normal value N, and the running speed of the magnetic tape (1) is set to the normal value v. Is set to However,
The magnetic tape (1) repeatedly runs and stops under the control of the tape feed control circuit (6) as described later. Thus, the pair of magnetic heads of the rotary head cylinder (2) alternately trace tracks formed on the magnetic tape (1) in the same pattern as when recording a signal. As a result, the two-series video data read from the magnetic tape (1) is supplied to the reproduction amplifier (7) via the rotary transformer (4), amplified, and then rotated by the rotation of the rotary head cylinder (2). The data is converted into time-series data in track order via a selection circuit (8) that can be switched in synchronization.

The time series data is converted to an equalizer / PLL circuit (9)
The signal is supplied to a reproduction signal processing circuit (10) after undergoing equalization processing and phase lock processing for distortion compensation, and is subjected to signal processing such as error correction. Playback signal processing circuit (10)
Is supplied with a clock corresponding to the bit rate M, whereby reproduction data having a bit rate M (25 Mbps) is obtained from the reproduction signal processing circuit (10). Input to (11).

The buffer memory circuit (11) has a write clock corresponding to the bit rate M and a bit rate M / n.
, And a read clock corresponding to. Further, the reproduction data is input to a recording rate detection circuit (12),
The recording rate is detected, and the detection signal n is supplied to the buffer memory circuit (11). As a result, the reproduced data obtained from the reproduced signal processing circuit (10) is written into the buffer memory circuit (11) at a write rate corresponding to the bit rate M, and at the same time, at a read rate 1 / n of the write rate. The data is read from the buffer memory circuit (11) . Further, the data amount X in the memory obtained from the buffer memory circuit (11) is supplied to a tape feed control circuit (6) and is used for intermittent feed control of the magnetic tape (1).

FIG. 2 shows a specific configuration of the buffer memory circuit (11). The reproduction data WD is input to the buffer memory (13), and the memory write control circuit
The write clock WCK, enable WE, and write address WA supplied from (14) are input, and when the enable WE is active, the data WD is written to the address WA in synchronization with the clock WCK. Further, a read clock RCK and a read address RA are input to the buffer memory (13).
Data RD is read from address RA in synchronization with CK.

The write address WA and read address RA are supplied to a data amount calculation circuit (16), and the data amount X in the memory is calculated based on the difference between the two addresses. The data amount calculation circuit (16) determines that the data amount X in the memory is equal to a predetermined upper limit value FUL, for example, the total memory capacity Xm.
Exceeds 90%, a FUL signal is issued to the memory write control circuit (14) and the tape feed control circuit (6), and the data amount in the memory is reduced to a predetermined lower limit value EMP, for example, 10% of the total memory capacity Xm. When it falls below, the memory write control circuit (1
4) and an EMP signal to the tape feed control circuit (6).

When the EMP signal is supplied to the tape feed control circuit (6), the capstan (3) is activated, and the magnetic tape starts running at the speed v as shown in FIG. As a result, the video data is reproduced from the magnetic tape, and the writing of the data to the buffer memory (13) at the rate M is started. At the same time, data is read from the buffer memory (13) at a rate of M / n. Therefore, the data amount X in the memory increases at a rate of M (1-1 / n) as shown in FIG. Then, after a lapse of a predetermined time t, the data amount in the memory becomes the upper limit value FU as shown in FIG.
At the point of time exceeding L, the tape feed is stopped as shown in FIG. 9A, and at the same time, the writing of data to the buffer memory 13 is also stopped. However, data reading at the rate M / n is continued. Therefore, the data amount X in the memory is
As shown in (b), it decreases at the rate of M / n. Then, when the data amount X in the memory falls below the lower limit value EMP, the tape starts running again, and the buffer memory
Writing of the reproduction data to (13) is started. Thereafter, similarly, intermittent feeding of the tape is performed, and a constant bit rate M /
Data reading is performed at n.

The video data of the bit rate M / n obtained from the buffer memory circuit (11) in this manner is output to a television receiver as a DVB signal as shown in FIG. In a television receiver, an MPE is added to a DVB signal.
By performing G demodulation, a normally reproduced video is displayed.

According to the digital VTR of the first embodiment, there is no restriction on the bit rate of the DVB signal to be recorded. Further, the equalizing circuit may be designed for reproduction at 1 × speed, and its circuit configuration is simple. In addition, since the video data is reproduced with the tape traveling speed set to 1x speed, the S / N ratio does not decrease.

Second Embodiment As shown in FIG. 4, in the special reproduction mode at n times speed, the rotation speed of the rotary head cylinder (2) is set to the normal value N and the running speed of the magnetic tape (1) is set to the normal value. v. Thus, the pair of magnetic heads of the rotary head cylinder (2) alternately trace tracks formed on the magnetic tape (1) in the same pattern as when recording a signal. As a result, the two-series video data read from the magnetic tape (1) is supplied to the reproduction amplifier (7) via the rotary transformer (4), amplified, and then rotated by the rotation of the rotary head cylinder (2). Selection circuit that can be switched synchronously (8)
Is converted into time-series data in track order.

The time series data is converted to an equalizer / PLL circuit (9)
After being subjected to equalization processing and phase lock processing, it is input to the reproduction signal processing circuit (10) and subjected to signal processing such as error correction. The reproduction signal processing circuit (10) is supplied with a clock corresponding to the bit rate M, whereby the reproduction signal processing circuit (10) outputs the bit rate M (2
(5 Mbps), reproduction data with n × 30 frames per second is obtained, and the reproduction data is input to the gate circuit (20).

The reproduced data is supplied to a GOP detection circuit (17), and the GOP is detected. The GOP detection signal is supplied to a frame number measurement circuit (18), and the number of frames is measured for each GOP. The GOP can be easily detected based on the GOP information included in the video data shown in FIG. Further, as shown in FIG. 4, the GOP detection signal and the measured value of the number of frames are supplied to the deleted GOP determination circuit (19), and a control signal for opening and closing the gate circuit (20) is created.

FIG. 5 shows a method of controlling the opening and closing of the gate circuit when n = 3. As shown in FIG.
The number of frames in each GOP varies from 25 to 35,
By deleting an appropriate GOP from among these GOPs, the average value of the number of frames is reduced to one third. For this reason, the GO currently being played from the tape
The excess or deficiency of the number of frames when P is selected and when it is deleted is calculated, and the smaller one of the absolute values is adopted depending on whether the absolute value of the excess or deficiency becomes smaller in the case of selection or deletion.

That is, in the examples of FIGS. 5A and 5B, the processing is started from a state where the excess or deficiency of the number of frames is zero. First, GOP-
When the GOP is selected for 1 (30 frames), 60 frames need to be deleted thereafter to reduce the average value of the number of frames to one third. That is, the excess or deficiency of the number of frames is +60. On the other hand, if the GOP is deleted, 30 frames will be insufficient. That is, the excess or deficiency of the number of frames is -30. Therefore, here, "deletion" in which the absolute value of the excess or deficiency of the number of frames is small is adopted.

Next, if the GOP is selected for GOP-2 (25 frames), then 20 frames (−30 + 25 × 2 = 20) must be deleted. In contrast, when the GOP is deleted, 55 frames
(−30−25 = −55). Therefore, "selection" is adopted here. Thereafter, by repeating the same procedure, selection and deletion of GOP units are performed as shown in FIGS. 5A and 5B, and the average value of the number of frames is reduced to one third.

Therefore, the gate circuit (20) shown in FIG.
Is closed in the case of, and opened in the case of "delete", so that the average number of frames per second is 30 from the gate circuit (20).
The video data of the frame is obtained. The video data is output to the television receiver, and undergoes MPEG demodulation by the television receiver, so that a special playback video at n-times speed is displayed. In the special playback video, an image at a normal playback speed is obtained within the selected GOP, and thereafter, skipping to the image of the next selected GOP achieves n-times speed.

According to the digital VTR of the second embodiment, all the video data recorded on the tracks on the magnetic tape are read out to create a special reproduction video.
Compared to n-times speed reproduction using video data for special reproduction recorded on a magnetic tape, a special reproduction video with higher image quality can be obtained.

Third Embodiment As shown in FIG. 6, the cylinder rotation speed and the tape feed speed
This is the same as the embodiment. From the reproduction signal processing circuit (10), reproduction data having a bit rate M (25 Mbps) and the number of frames per second being n × 30 is obtained.
The data is supplied to the picture data memory (21). The reproduced data is supplied to an I-picture detection / memory write control circuit (22) to detect an I-picture and to write video data to the I-picture data memory (21) based on the detection. Controlled. Reading of data from the I picture data memory (21) is controlled by a frame read control circuit (23).

FIG. 7 illustrates the control operation of the I picture detection / memory write control circuit (22) and the frame read control circuit (23). That is, I picture, P picture,
From the playback data (FIG. 3A) consisting of
Only the picture (FIG. 9B) is extracted and stored in the I picture data memory 21 of FIG. Furthermore, 30 frames / s
By controlling the data reading from the I picture data memory (21) based on the frame rate of ec (FIG. 7 (c)), the preceding I picture is interpolated between a pair of successive I pictures. Thus, a frame output consisting only of I-pictures ((d) in the figure) is created. As an interpolation method, a P picture or a B picture with difference information of 0 is used.
(Pz frame) to output the same frame (Fig.
It is also possible to create (e)).

The video data of an average of 30 frames / sec created in this way is output to a television receiver, and undergoes MPEG demodulation by the television receiver to display a special playback video at n times speed. Will be. According to the digital VTR of the third embodiment, a special reproduction image with a smoother motion can be obtained as compared with the digital VTR of the second embodiment.

Fourth Embodiment As shown in FIG. 8, the bit rate M (25 Mbps) obtained from the reproduction signal processing circuit (10), and the number of frames per second is n
The reproduction data of × 30 is input to the gate circuit (27).

The reproduced data is supplied to a picture detection circuit (24)
And the I picture, the P picture and the B picture are detected. These picture detection signals are supplied to a frame number measuring circuit (25), and the number of frames is measured.
Further, the picture detection signal and the measured number of frames are supplied to the deleted frame determination circuit (26), and a control signal for opening and closing control of the gate circuit (27) is created.

As a result, the gate circuit (27) first sets the B data in the reproduction data obtained from the reproduction signal processing circuit (10).
An appropriate picture is gate-blocked according to the priority order of a picture, then a P picture, and finally an I picture, and opening and closing are controlled so that the frame rate of data passing through the gate is 30 frames / sec on average.

As a result, the video data of an average of 30 frames / sec obtained from the gate circuit (27) is output to the television receiver, and is output to the M in the television receiver.
After the PEG demodulation, the special reproduction video at the n-times speed is displayed. According to the digital VTR of the fourth embodiment, a special reproduction image having a smoother motion than that of the digital VTR of the third embodiment can be obtained.

Fifth Embodiment As shown in FIG. 9, the bit rate M (25 Mbps) obtained from the reproduction signal processing circuit (10) is n × 30 frames / sec.
The reproduced data of c is supplied to an MPEG decoder (28), where it is subjected to MPEG demodulation processing to obtain n × 30 frames / s
ec is demodulated to video data. The video data passes through a frame thinning circuit (29), and data is deleted in frame units so that the number of frames becomes 1 / n. The video data of 30 frames / sec obtained in this way is output to the television receiver, and the MPEG demodulation in the television receiver is omitted, and the specially reproduced video at n times speed is displayed. According to the digital VTR of the fifth embodiment, the digital VTR of the other embodiment is
A special reproduction image with the smoothest movement can be obtained as compared with the TR.

The description of the above embodiments is for the purpose of illustrating the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope thereof.
In addition, the configuration of each part of the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made within the technical scope described in the claims.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a first embodiment.

FIG. 2 is a block diagram illustrating a configuration of a buffer memory circuit according to the first embodiment.

FIG. 3 is a graph illustrating intermittent feeding of a tape and a change in the amount of data in a buffer memory according to the first embodiment.

FIG. 4 is a block diagram illustrating a configuration of a second embodiment.

FIG. 5 is a diagram illustrating a GOP selection method according to a second embodiment.

FIG. 6 is a block diagram illustrating a configuration of a third embodiment.

FIG. 7 is a diagram illustrating a frame configuration using I pictures according to a third embodiment.

FIG. 8 is a block diagram illustrating a configuration of a fourth embodiment.

FIG. 9 is a block diagram illustrating a configuration of a fifth embodiment.

FIG. 10 is a block diagram illustrating a configuration of a signal recording system.

FIG. 11 is a diagram showing a frame configuration of the MPEG system.

FIG. 12 is a diagram showing a data hierarchy structure in the MPEG system.

FIG. 13 is a diagram showing a data format of each track on a magnetic tape.

FIG. 14 is a diagram illustrating a data block structure in a digital VTR.

[Description of Signs] (1) Magnetic tape (2) Rotating head cylinder (3) Capstan (10) Reproduction signal processing circuit (11) Buffer memory circuit (12) Recording rate detection circuit (5) Cylinder rotation control circuit (6 ) Tape feed control circuit

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Toguchi 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Inside Sanyo Electric Co., Ltd. (72) Yoshinobu Nishikawa 2-chome Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. (56) References JP-A-7-130089 (JP, A) JP-A-7-203366 (JP, A) JP-A-7-272343 (JP, A) JP-A-8 −306132 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 5/91-5/956 G11B 20/10-20/12 H04N 5/782-5/783

Claims (6)

(57) [Claims] 1. A tape serving as a signal recording medium is wound around a rotary head cylinder, and video data compressed by a predetermined image compression method is recorded on a plurality of tracks on the tape by a helical scan method, or from these tracks. An apparatus for reproducing video data, which is capable of recording video data at a predetermined bit rate M under a constant cylinder rotation speed N and a tape feed speed v, has a bit rate of When recording M / n (n is a real number of 1 or more) video data on a tape, a recording control circuit for setting a cylinder rotation speed to N / n and a tape feed speed to v / n; At the time of reproduction, the cylinder rotation speed is set to N, the tape feed speed is set to v, and the tape is intermittently fed. Video data recording and reproducing apparatus characterized by an average bit rate of data equipped with a normal reproduction control circuit for setting the M / n. 2. A normal reproduction control circuit controls a buffer memory for storing video data to be reproduced from a tape, and controls writing and reading of the video data to and from the buffer memory, and controls a bit rate of the video data read from the buffer memory. 2. The video data recording / reproducing apparatus according to claim 1, further comprising a memory control circuit that sets M / n to M / n. 3. An apparatus for winding a tape as a signal recording medium around a rotary head cylinder and recording video data on a plurality of tracks on the tape by a helical scan method, or reproducing video data from these tracks. The video data is compressed by a predetermined image compression method, and the I-picture is intra-coded, the P-picture is inter-coded by prediction from the past, and the I-picture is inter-coded by prediction from the past and the future. Done B
In a video data recording / reproducing apparatus having three image modes of pictures and capable of recording video data at a predetermined bit rate M under a constant cylinder rotation speed N and a tape feed speed v, When recording M / n (n is a real number of 1 or more) video data on a tape, a recording control circuit for setting a cylinder rotation speed to N / n and a tape feed speed to v / n; At the time of playback, the cylinder rotation speed is set to N, the tape feed speed is set to v, and the video data played back from the tape is set with the predetermined image group GOP composed of the I picture, P picture and B picture as one unit. Create video data whose average number of frames per unit time matches the specified television broadcasting system by deleting video data in image group units from A video data recording / reproducing apparatus, comprising: 4. An apparatus which winds a tape as a signal recording medium around a rotary head cylinder and records video data on a plurality of tracks on the tape by a helical scan method, or reproduces video data from these tracks. The video data is compressed by a predetermined image compression method, and the I-picture is intra-coded, the P-picture is inter-coded by prediction from the past, and the I-picture is inter-coded by prediction from the past and the future. Done B
In a video data recording / reproducing apparatus having three image modes of pictures and capable of recording video data at a predetermined bit rate M under a constant cylinder rotation speed N and a tape feed speed v, When recording M / n (n is a real number of 1 or more) video data on a tape, a recording control circuit for setting a cylinder rotation speed to N / n and a tape feed speed to v / n; At the time of reproduction, the cylinder rotation speed is set to N, the tape feed speed is set to v, and only the video data of the I picture is extracted from the video data reproduced from the tape, and based on these video data, A video data recording / reproducing apparatus, comprising: a special reproduction control circuit for generating video data whose average number of frames per unit time conforms to a predetermined television broadcasting system. 5. An apparatus which winds a tape as a signal recording medium around a rotary head cylinder and records video data on a plurality of tracks on the tape by a helical scan method, or reproduces video data from these tracks. The video data is compressed by a predetermined image compression method, and the I-picture is intra-coded, the P-picture is inter-coded by prediction from the past, and the I-picture is inter-coded by prediction from the past and the future. Done B
In a video data recording / reproducing apparatus having three image modes of pictures and capable of recording video data at a predetermined bit rate M under a constant cylinder rotation speed N and a tape feed speed v, When recording M / n (n is a real number of 1 or more) video data on a tape, a recording control circuit for setting a cylinder rotation speed to N / n and a tape feed speed to v / n; At the time of reproduction, the cylinder rotation speed is set to N, the tape feed speed is set to v, and the video data is reproduced frame by frame from the video data reproduced from the tape by the priority order of B picture, P picture, and I picture. A special playback control circuit for creating video data whose average number of frames per unit time conforms to a predetermined television broadcasting system by deleting the video data. Video data recording and reproducing device. 6. An apparatus which winds a tape as a signal recording medium around a rotary head cylinder and records video data on a plurality of tracks on the tape by a helical scan method, or reproduces video data from these tracks. The video data is compressed by a predetermined image compression method, and the I-picture is intra-coded, the P-picture is inter-coded by prediction from the past, and the I-picture is inter-coded by prediction from the past and the future. Done B
In a video data recording / reproducing apparatus having three image modes of pictures and capable of recording video data at a predetermined bit rate M under a constant cylinder rotation speed N and a tape feed speed v, When recording M / n (n is a real number of 1 or more) video data on a tape, a recording control circuit for setting a cylinder rotation speed to N / n and a tape feed speed to v / n; At the time of reproduction, a reproduction control circuit that sets the cylinder rotation speed to N and the tape feed speed to v, demodulates video data reproduced from the tape, and deletes demodulated data in frame units from the demodulated data. And a special reproduction processing circuit for generating video data whose average number of frames per unit time conforms to a predetermined television broadcasting system. Location.