KR0171124B1 - Head drum and apparatus for playing in a video on demand system - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a playback apparatus for an on-demand video system, and includes a first head (R HEAD) having a predetermined azimuth angle and a first head (R HEAD) located at a position of 180 degrees with the first head (R HEAD). Second head (L HEAD) having a different azimuth angle, and a third head (R ') having the same azimuth angle as the first head (R HEAD) and having a step as wide as the track-to-track width of the video tape. A first switch SW1 having a HEAD and selectively connected to the first head R HEAD according to a first switching signal; A second switch SW2 connected to a second head L HEAD and selectively switched according to a second switching signal; A third switch SW3 connected to a third head R 'HEAD and selectively switched according to a third switching signal; First, second, and third switches connected to the first, second, and third switches SW1, SW2, and SW3, and selectively output signals applied from the first, second, and third switches SW1, SW2, and SW3 according to control signals. Selectively outputs the third buffers 31, 32, 33 and the first, second, and third switching signals, and at the time when the tape starts running, the scanning of the corresponding track of the first head R The signals read by the second and third heads L and R 'are stored in the buffers 32 and 33, and the signals read by the first and second heads R and L are first read when the tape runs normally. And a microcomputer for storing in the second buffers 31 and 32 and controlling the buffers 31, 32 and 33 to alternately output the data in the buffers 32 and 31 after outputting the data stored in the buffer 33. 50; The apparatus further includes a reproduction signal processor 40 which reproduces and outputs a signal applied from the first, second, and third buffers 31, 32, and 33.

Description

Playback device on demand video system

1 shows a video head drum according to the invention.

2 is a schematic block diagram of a playback apparatus of an on-demand video system according to a preferred embodiment of the present invention.

3 is a waveform diagram for head switching according to the present invention.

* Explanation of symbols for main parts of the drawings

10: head portion 20: switch portion

30: buffer unit 40: playback signal processing unit

50: micom

The present invention provides a digital data stream in which video and audio signals recorded on a video tape of a time compressed video cassette recorder (VCR), that is, a video on demand system (VOD), are data compressed and time compressed. TECHNICAL FIELD The present invention relates to a playback apparatus, and more particularly, to a playback apparatus of an on-demand video system that enables more accurate scanning and playback of tracks of a video tape on which a digital data stream is recorded.

In general, the storage and transmission of video signals are becoming digital due to the advantages of high quality and multifunction of video signals, and there is a VOD system that is currently being studied as one of the home appliances to meet them.

The VOD system stores a digital video and audio signal, that is, a digital data stream (movie), that has been compressed using a moving picture express group (MPEG) method, which is a video compression standard technique, in a storage server. The digital data stream is transmitted to the user's station in a short time at a rate corresponding to a predetermined multiple of the normal playback and recording speed, and the terminal user can record it on a video tape and play it back for viewing.

Therefore, at home, by receiving a video signal for a short time and recording it on a video tape, the communication network fee can be saved considerably.

On the other hand, in the VOD system currently being developed, the compressed data is decompressed and reproduced while driving and stopping the capstan motor at a predetermined cycle during regeneration.

That is, the digital data stream is read by scanning a predetermined track while driving the video tape, and the digital data stream read out while the video tape is stopped is decoded and decompressed and reproduced.

Next, the video tape is read after reading the digital data stream of the next track while driving the video tape again, and the operation of decoding and decompressing and reading out the read digital data stream is repeatedly performed.

However, as described above, at the initial stage when the video tape starts to travel in a stationary state, the video tape cannot be driven at a predetermined predetermined traveling speed, so that the video head cannot accurately scan the track of the video tape.

In more detail, the video signal is alternately recorded on the video tape by the first head and the second head in which Azimuth is opposite to each other, and during playback, the first head and the second head are alternately recorded on the tape. The video signal is scanned and read.

However, as described above, in the video on demand system, playback of the video tape is repeated while the video tape starts and stops. When the video tape starts to travel in the stopped state, the first head starts scanning, at which time the video tape maintains a normal predetermined traveling speed. There is a problem in that the tracks of the videotape cannot be accurately scanned because they cannot be maintained, and therefore, video signals cannot be reproduced clearly.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to start a driving that cannot maintain a predetermined speed of a video tape when intermittently driving and playing a video tape in an on-demand video system. In the early stage of the present invention, there is provided a playback device of an on-demand video system capable of accurately scanning and playing back tracks of a videotape.

A feature of the present invention for achieving this object is a first head having a predetermined Azimuth angle in a Video On Demand System, and positioned at 180 degrees with the first head and different from the first head. A second head having an azimuth angle, and a third head having the same azimuth angle as the first head and having a step equal to the track-to-track width of the video tape to read and reproduce the signal recorded on the video tape. An apparatus, comprising: a first switch connected to a first head and selectively switched in accordance with a first switching signal; A second switch connected to the second head and selectively switched according to the second switching signal; A third switch connected to a third head and selectively switched according to a third switching signal, and a signal connected to the first, second and third switches, and applied from the first, second and third switches, according to a control signal A control unit for controlling the first, second, and third buffers and the switching of the first, second, and third switches and outputting the first, second, and third buffers; Outputs the first, second and third switching signals for turning off the first, second and third switches during the time that one head scans a predetermined track, and during the time when the second and third heads respectively scan the corresponding track. After outputting the second and third switching signals for turning on the second and third switches, the first and second switches are operated for a time period during which the first and second heads scan the corresponding tracks until the running of the tape is finished. First and second switching to turn on respectively Outputs a signal, outputs the second and third switching signals after the video tape starts running, outputs a third buffer first after the end of the scanning time, and then outputs a second buffer, and then outputs the first and second A controller for outputting a switching signal to output the control signal for sequentially outputting the first and second buffers after the end of the scanning time; The present invention provides a reproduction apparatus in an on-demand video system including a reproduction signal processor for reproducing and outputting a signal applied from the first, second, and third buffers.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view showing a video head according to the present invention, wherein the first head R HEAD is a head for scanning and reading a predetermined track recorded on the video tape at the same azimuth angle, and the second head L The HEAD is positioned with an azimuth angle opposite to the first head R HEAD at a position of 180 degrees and is a head for scanning by reading the next track, that is, the next track scanned by the first head R HEAD.

The first head R HEAD and the second head L HEAD described above are conventional heads, and the third head R 'HEAD added in the present invention has the same azimuth angle as the first head R HE4D. It is mounted in a position having a step as wide as the width between the second head (L HEAD) and the track.

2 is a schematic block diagram of a playback apparatus in an on-demand video system according to a preferred embodiment of the present invention, wherein the head unit 10, the switch unit 20, the buffer unit 30, and the reproduction signal processing unit ( 40 and the microcomputer 50.

In the figure, the head portion 10 is composed of a first head (R HEAD), a second head (L HEAD) and a third head (R 'HEAD) to alternately scan a predetermined track of the video tape to scan digital data. Read the stream.

In addition, the switch unit 20 includes a first switch SW1, a second switch SW2, and a third switch SW3, respectively, and selectively switches according to the first, second, and third switching signals from the microcomputer 50. It is turned on to output the digital data stream from the head portion 10.

In addition, the buffer unit 30 includes first, second, and third buffers 31, 32, and 33 to buffer the digital data streams from the switches SW1, SW2, and SW3 according to the control signal of the microcomputer 50. To print.

On the other hand, the reproduction signal processing unit 40 decodes and expands the digital data stream applied from the buffer unit 40 into a displayable signal and outputs it to a monitor (not shown).

Then, the microcomputer 50 switches the first, second, and third switching signals and buffers due to the rotation period of the head drum, not shown, to selectively turn on the switches SW1, SW2, and SW3 with the switch unit 20. Outputs a control signal for selectively outputting the buffers 31, 32, 33 of the unit 30, and causes the reproduction signal processing unit 40 to have heads R applied from the buffers 31, 32, 33. , L, R 'HEAD) control to decode, expand and output the digital data stream into a displayable signal.

Next, an operation process of the present invention including the above-described configuration unit will be described in detail with reference to FIG.

First, as described above, the video-on-demand system intermittently runs the video tape, and reads and reproduces the digital data stream in the running section of the video tape.

Accordingly, the microcomputer 50 rotates the head drum on which the heads R, L, and R 'HEAD are mounted at the predetermined predetermined speed when switching to the regeneration mode.

Next, while driving the video tape, the first head R HEAD should scan the track R 'to read the digital data stream, but at this time, since the running speed of the video tape does not maintain the predetermined speed, the microcomputer ( 50 passes through the half cycle of the head drum, i.e., when the first head R HEAD contacts the video tape without scanning, without turning on the switch SW1.

Next. The second and third switching signals are applied to turn on the second and third heads L and R 'HEAD at the start point of the half cycle when the second head L HEAD contacts the video tape.

Then, as described above, the second and third heads L and R 'HEAD simultaneously scan the tracks R' and L of the video tape to read the digital data streams into the buffer 32 and the buffer 33, respectively. Is buffered.

Next, the microcomputer 50 applies a control signal to the buffer unit 30 to output the buffer 32 and the digital data stream buffered in the buffer 33, wherein the digital data stream buffered in the buffer 33 is output. Since it is the preceding data, it is output first, and then the buffered digital data stream is output to the buffer 31.

Next, when the first head R HEAD comes in contact with the video tape again, the video tape travels at a predetermined speed which is normally set, thereby applying a first switching signal for turning on the switch SW1 to perform the next track (R). The digital data stream is read by scanning, and the read digital data stream is buffered and output to the buffer 31 by the control signal of the microcomputer 50.

Next, at the time when the second head L HEAD contacts the video tape, a second switching signal for turning on the switch SW2 is applied, and the digital data stream read out at the next track L of the video tape is likewise It is output after being buffered in the buffer 32.

Thereafter, the first and second switching signals are repeatedly applied to scan a predetermined reproduction unit (6 tracks in the present invention) to read out the digital data stream, and then stop running of the video tape.

The reproduction signal processing unit 40 decodes and decompresses the read digital data streams (six tracks) stored in the memory in the reproduction signal processing unit 40 so as to be displayed and outputs them to a monitor (not shown).

Next, the above-described reproduction process is repeatedly performed while driving the video tape again before the digital data stream read out by the above-described process is completely displayed on the monitor (e.g., about one third remaining).

As described above, according to the present invention, the first track to be scanned at the beginning of the videotape starts running without scanning so that the videotape maintains the normal speed, and when the next track is scanned, up to the previous track to pass through at the same time. By scanning, more accurate track scanning has the effect of obtaining clear picture quality.

Claims (1)

In the Video On Demand System, the first head R HEAD having a predetermined azimuth angle and the first head R HEAD are positioned at 180 degrees and different from the first head R HEAD. A second head L HEAD having an azimuth angle, and a third head R HEAD having the same azimuth angle as the first head R HEAD and having a step equal to the track-to-track width of the video tape. A device for reading and reproducing a signal recorded on a video tape, comprising: a first switch (SW1) connected to the first head (R HEAD) and selectively switched according to a first switching signal; A second switch (SW2) connected to the second head (L HEAD) and selectively switched according to a second switching signal; A third switch SW3 connected to the third head R 'HEAD and selectively switched according to a third switching signal; First, second, and third switches SW1, SW2, and SW3 connected to the first, second, and third switches SW1, SW2, and SW3 to selectively output signals applied from the first, second, and third switches SW1, SW2, and SW3 according to control signals; Two, three buffers 31, 32, 33; Selectively outputting the first, second and third switching signals, and ending scanning of the corresponding track of the first head R at the time when the tape starts running. The signals read to the second and third heads L and R 'are stored in the buffers 32 and 33, and the first and second heads R and L are read during normal driving of the tape. The stored signals in the first and second buffers 31 and 32, control the buffers 31, 32 and 33, and after outputting the data stored in the buffer 33, the buffers 32 and 31. A microcomputer 50 for alternately outputting data of; And a reproduction signal processor (40) for reproducing and outputting a signal applied from the first, second, and third buffers (31, 32, 33).