Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1997-11-10
2001-09-18
Chevalier, Robert (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000
Reexamination Certificate
active
06292623
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to technology to advance quality of an image (a search picture) that image data recorded on the magnetic tape is reproduced at high speed, particularly to a data reproducing method, a reproducing speed control apparatus and a reproducing apparatus that it is possible to reproduce more image data by using plural reproducing heads.
2. Description of the Prior Art
In a video tape recorder for recording and reproducing a television signal by using a magnetic tape, a digital video tape recorder (a digital VTR) is proposed as it is possible to record and reproduce without degrading substantially the television signal. Further, in case that the magnetic tape used for the digital VTR is stored into a cassette, it is also called a digital video cassette tape recorder (a digital VCR).
The digital VCR records a voice signal and an image signal including a control signal and so on into the magnetic tape as digital data and obtains the image signal by reproducing the digital data recorded on the magnetic tape.
An area on the magnetic tape on which the digital data of the image signal is recorded by the digital VCR is called a track. The track is generally an inclined recording track (a helical track) recorded and formed by scanning the magnetic tape by a recording heads installed on a rotating drum inclined to the longitudinal direction, that is, to the traveling direction of the magnetic tape.
The digital VCR is possible to control degradation of the signal to the minimum by using data error correcting technology because the image signal recorded to and reproduced from the magnetic tape is the digital signal. Therefore, it has a characteristic, that it is comparatively easy to edit the magnetic tape on which the image signal is recorded and to reproduce it by changing speed, different from a conventional analog VCR.
In the digital VCR (simply VCR below), when the image data (a moving picture) recorded on the magnetic tape is reproduced (search) at high speed faster than the original reproducing speed which is the same speed as the recording speed, the reproducing head scans over plural tracks. That is, any image data recorded on one track is not scanned and any image data necessary for reproducing one screen is not reproduced.
As a result, a search picture becomes rough comparing with the image reproduced at the original reproducing speed, includes noise, therefore, quality of the picture becomes inferior.
As above mentioned, a main cause of a deterioration of the quality of the search picture is that the image data reproduced from the magnetic tape by scanning once by the reproducing heads decreases as the reproducing speed becomes faster. Therefore, by increasing the number of the reproducing heads provided on the rotating drum, the image data is also reproduced as much as possible in reproducing the search picture and it is tried to advance the quality of the search picture.
Relation between disposing of the reproducing heads on the rotating drum and reproducing speed will be described referring to FIG.
14
.
FIG. 14A
shows configuration of reproducing heads at least necessary for reproducing image data at the original speed and an example of the configuration of two heads that a set of the reproducing heads A
1
and B
1
which azimuth angles are different each other is disposed.
Here, the azimuth angle is the angle that inclines a gap of the recording head for recording and forming each track on the opposite side of the direction of forming the track each other in order to prevent signals of the adjacent tracks on the magnetic tape from interference. Usually this azimuth angle is approximately from several to 10 degrees and it is possible to record at high density without providing a guard band and so on by setting properly this value.
In the VCR of the configuration of two heads having + and − azimuth, it is known that the reproducing speed (the search speed) S in reproducing the search picture may be set to satisfy the following an expression (1).
S
=(
T/
2)×
n
±0.5 [Times Speed] (1)
(n is an integer and T is the number of helical tracks number for recording image data of one screen.)
Because the reproducing head of + azimuth angle is rushed into a first track of T tracks forming one screen by a first scanning by the drum, into a second track by a second scanning, into a third track by a third scanning . . . , therefore, the search speed of the traced track is changed one after another by every scanning of the drum, and the image data of adjacent frames about time is continuously reproduced.
Further, it is particularly effective for the VCR using the shuffling pattern to dispose the image data of Macro Blocks adjacent on the screen together on the magnetic tape in order to renew an area as large as possible on the screen by scanning once to choose the search speed to the double speed given by the expression (1). Such shuffling pattern is used in case of the large Macro Block (for example, 16 pixels×16 scanning lines) that is a fundamental unit in case of forming the screen by using the image compressing technology as below mentioned.
FIG. 14B
shows an example of the configuration of 4 heads that another set of reproducing heads A
5
and B
5
that the azimuth angles are different each other is added to the configuration of two heads as shown in
FIG. 14A
at the opposite positions on the rotating drum.
When the search speed S shown by the expression (1) is chosen in the VCR of 4 heads configuration, the data on the track of the same track number reproduced by plural reproducing heads having the same azimuth angle each other at the speed of some times (for example, n=2, 4, . . . ) each other overlaps each other, therefore, it is impossible to make use of the reproducing heads increased for increasing amount of the image data that it is possible to reproduce by scanning once. It is also similarly in the VCR of 8 heads configuration as shown in
FIGS. 14C and 16
heads configuration as shown in FIG.
14
D.
However, it was vague that it was effectively possible to use the plural reproducing heads to the maximum when any speed except the search speed S satisfying the expression (1) was set.
As above mentioned, as relation between the configuration of the reproducing heads and the reproducing speed was not clear in the VCR that the plural reproducing heads were installed on the rotating drum, even if the plural reproducing heads had been installed, they did not always work effectively.
SUMMARY OF THE INVENTION
The present invention was achieved for solving the problem as above mentioned, and an object of the present invention is to provide an image data reproducing method which is possible to obtain a search picture with high quality, a reproducing speed control apparatus, and a recording/reproducing apparatus by finding search speed that it is possible to reproduce image data as much as possible by using the most effectively plural reproducing heads in reproducing a search picture and by setting to the speed.
A data reproducing method according to the present invention proposed for solving the problem as above mentioned is the data reproducing method that plural sets of reproducing heads disposed on a rotating drum reproduce data recorded on a magnetic tape at the speed faster than the fixed original reproducing speed, and is characterized by including a first step for setting traveling speed of the magnetic tape so that traces on the magnetic tape of the reproducing heads each other do not overlap fit for the number of sets of the plural reproducing heads, and a second step for traveling the magnetic tape at the traveling speed set by the first step and for reproducing the data recorded on the magnetic tape.
Further, a reproducing speed control apparatus according to the present invention is the reproducing speed control apparatus that plural sets of reproducing heads disposed on a rotating drum control to reproduce data recorded on
Iwamoto Tetsuya
Sugiyama Akira
Chevalier Robert
Frommer William S.
Frommer & Lawrence & Haug LLP
Shallenburger Joe H.
Sony Corporation
LandOfFree
Data reproducing method, reproducing speed control apparatus... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Data reproducing method, reproducing speed control apparatus..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Data reproducing method, reproducing speed control apparatus... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2517982