Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reissue Patent
1998-08-05
2001-08-07
Tran, Thai (Department: 2812)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000, C375S240010
Reissue Patent
active
RE037312
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a digital recording and/or reproducing apparatus of a video signal, and more particularly, to a recording apparatus for carrying out bit rate reduction coding of a video signal and digitally recording the coded video signal on a recording medium, a reproducing apparatus capable of digitally reproducing a video signal at a changeable or extraordinary speed from a recording medium having such video signal recorded thereon, and a recording/reproducing apparatus having such digital recording and reproducing functions.
2. Description of the Background Art
In recent years, an apparatus has been developed for recording digitally a video signal on a recording medium and reproducing digitally the same from the recording medium. One such typical apparatus is the so-called digital video cassette recorder (referred to as “digital VCR” hereinafter) which is available for practical use. In such a conventional digital VCR, a digital video signal which is in a bit rate reduction coded (bandwidth compressed) state for the purpose of reducing the enormous amount of information to a level suitable for recording and reproduction is recorded on a magnetic tape and reproduced therefrom using a rotary head.
FIG. 1
is a block diagram schematically showing a structure of the conventional digital VCR using the bit rate reduction coding method. Such conventional digital VCR is disclosed in Japanese Patent Laying-Open No. 2-220270, for example.
Referring to
FIG. 1
, at the time of recording, a digital video signal provided from a video signal source not shown is supplied to a block shuffling circuit
101
included in a digital VCR. The block shuffling circuit
101
divides the digital video signal into a plurality of blocks, each of which is formed of a plurality of pixels and has a certain size, to rearrange the video signal data on the basis of such blocks.
Then, the digital video signal rearranged by the block shuffling circuit
101
is applied to a bit rate reduction coding circuit
102
where the bit rate reduction coding of data on the basis of each block is carried out to realize an amount of information suitable for recording onto a tape. More specifically, the video signal of each block entered into the bit rate reduction coding circuit
102
is subjected to the well-known orthogonal transform coding, and then subjected to a variable length coding process according to the information amount of each block. As a result, reduction of the data amount, i.e., bit rate reduction coding of the video signal is realized. The video signal is further supplied to an error correction coding circuit
103
.
The error correction coding circuit
103
adds an error correction code (parity) to the block data thus subjected to bit rate reduction coding, and supplies the same to a synchronizing signal and ID signal applying circuit
104
. The synchronizing signal and ID signal applying circuit
104
adds a synchronizing signal and an ID signal to the supplied video signal to provide the same to a modulation circuit
105
.
The modulation circuit
105
modulates the supplied signal while suppressing the direct current (DC) component thereof to record the same on the above-described block basis on a magnetic tape
107
as a recording medium via a magnetic head
106
.
At the time of reproduction, recorded data on the tape
107
are reproduced via a magnetic head
108
to be demodulated by a demodulation circuit
109
. The demodulated video signal is supplied to a synchronizing signal and ID signal detection circuit
110
where detection of the synchronizing signal and ID signal is carried out. Then, the video signal is applied to an error correction decoding circuit
111
.
The error correction decoding circuit
111
carries out error correction of the applied video signal. The corrected data is subjected to variable length decoding and inverse orthogonal transform processes for each block by a decoding and concealment circuit
112
to restore the original data of each block. On the other hand, concealment processing of a video signal is carried out for the portion of data where error correction could not be carried out in the error correction decoding circuit
111
.
The data thus subjected to the error correction and decoding process is supplied to a block de-shuffling circuit
113
where the data is rearranged in a manner opposite to that by the block shuffling circuit
101
of the recording system. As a result, the video signal arranged in the original form, i.e., the same form as that at the time of recording is reproduced. The data signal of the block de-shuffling circuit
113
is output appropriately to be provided to a monitor device and the like not shown.
The digital VCR which processes the video signal on the basis of blocks as described above has the following disadvantage, compared with the digital VCR (e.g., D1-format digital VCR) which processes the video signal on the basis of pixels.
In the case where the video signal is processed on the basis of blocks, reproduction at an extraordinary speed such as a high speed search is usually carried out by displaying image data belonging to a plurality of different fields as one reproduced picture on a screen. More specifically, in the case where the processing of a signal is carried out on the basis of pixels and the shuffled pixels are recorded on and reproduced at a high speed from a track, the image data belonging to the plurality of fields are dispersed in the whole picture, so that unnatural discontinuity does not generate in the picture, and thus the picture can has good quality. Meanwhile, in the case where the data are recorded on the basis of blocks including the plurality of pixels and are reproduced at a high speed, blocks belonging to different fields may be adjacent to each other in the reproduced picture and a boundary between such small blocks is visually recognized. If a large number of small blocks belonging to different fields are reproduced in the minutely mixed manner, such boundaries are also generated minutely, resulting in the reproduced picture which appears as if a mosaic pattern processing has been applied. As a result, the quality of the reproduced picture in the high speed reproduction remarkably decreases.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a digital recording and/or reproducing apparatus of a video signal, in which quality of a reproduced picture in an extraordinary speed reproduction is improved.
Another object of the invention is to provide a digital recording and/or reproducing apparatus of a video signal, which prevents a mosaic pattern in a picture reproduced by a high speed reproduction.
According to the invention, a digital recording apparatus for digitally recording a digital video signal includes a circuit for forming a plurality of blocks each including the digital video signal of a plurality of pixels, a circuit for encoding the digital video signal for each of the plurality of blocks, a circuit for controlling a code amount to be constant on the basis of one or more of the plurality of blocks to form a fixed length block, a circuit for encoding the fixed length blocks for error correction, which is to be made at the time of reproduction and thereby forming error correction blocks, a circuit for rearranging the error correction blocks so that the error correction blocks included in the blocks, which are adjacent to each other on a screen, are adjacent to each other on a recording medium, the screen is horizontally and/or vertically divided into N (N is a positive integer) rectangular regions, and data for the N rectangular regions are recorded on N tracks, respectively, and a device for recording the rearranged error correction blocks on the recording medium.
According to another aspect of the present invention, an apparatus for reproducing digitally a digital video signal recorded as described above includes a device for detecting, at a changeable speed, error correction blocks recorded on
Sharp Kabushiki Kaisha
Tran Thai
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