Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
2000-03-21
2004-03-23
Chevalier, Robert (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
Reexamination Certificate
active
06711345
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus and a method for recording and reproducing a data stream including an image and sound, and a recording medium for the same.
BACKGROUND OF THE INVENTION
In recent years, CS digital broadcastings utilizing the MPEG2 system format, including an efficiency-enhanced encoding system for moving images, has come into practice.
In the MPEG2 system, encoded image, sound, and like data are called elementary stream. The elementary stream is transmitted in a form named PES (Packetized Elementary Stream) packet. The PES packet has a structure composed of a PES header followed by a PES payload constituting a data portion.
The foregoing CS digital broadcasting utilizes a multiplex system called transport stream. In a transport stream, image, sound, and like data are transmitted by dividing and multiplexing them into a transmission unit called a transport packet having a fixed length of 188 bytes.
When recording and reproducing a data stream, which is encoded with the MPEG2 system on a magnetic tape by using a digital video tape recorder (VTR), during normal playback operation the original image is accurately reproducible, since the recorded packets are reproduced in the sequential order of the recording. In the case of high-speed playback operation, such as a high-speed search, the image can not be reproduced accurately because the packets are reproduced intermittently since a magnetic head traces only a portion of each of a plurality of recording tracks, as the head traces the tracks transversely.
For this reason, a technique has been devised in that an image is recorded in predetermined, discontinuous locations (rectangular areas shown by hatch lines in
FIG. 6
) on a plurality of tracks on a recording medium. The reproduction heads are traceable during a high-speed playback operation so that the image is reproduced by using the data, for example, as shown in FIG.
6
. The rectangular areas shown by hatch lines in
FIG. 6
indicate the recording tracks and arrows indicate the paths of the reproduction heads during the high-speed playback operation.
FIG. 6
also shows that the image can be reproduced if a head “A”, among the two reproduction heads, traces a path
61
and a head “B” traces a path
65
.
One example of the above-described digital VTR of the prior art will now be described hereinafter by referring to the drawings.
FIG. 5
depicts a diagram of a control block of the digital VTR of the prior art. The control block in
FIG. 5
includes: (a) a rotary cylinder
103
(hereinafter referred to as cylinder), of which the outer periphery is provided with a plurality of magnetic recording/reproduction heads for recording and reproducing a signal, and wound for approximately 180° on the cylinder is magnetic tape
104
; (b) a cylinder driving circuit
114
for driving and controlling the rotation of the cylinder
103
; (c) a reproduction process circuit
112
for executing signal processing such as equalization, error correctional decoding, etc. of the signal reproduced by the magnetic recording/reproduction heads on the cylinder
103
; (d) a SB number/track number detection circuit
115
for detecting numbers of a reproduction sync block and a recording track decoded by the reproduction process circuit
112
; (e) a HSW signal generation circuit
105
for producing a rotational phase signal (hereinafter referred to as HSW) for the cylinder based on a rotational position signal and a rotation detecting signal of the cylinder
103
; (f) a CTL head
107
for recording and reproducing a control signal (hereinafter referred to as CTL signal) on and from the magnetic tape
104
; (g) a CTL signal detection circuit
108
for detecting an edge of the reproduced CTL signal; (h) a phase difference detection circuit
109
for detecting a difference in phase of the two signals input to it; and (i) a tape driving circuit
110
for executing a driving control of a capstan motor
111
, which controls a travelling speed of the magnetic tape
104
based on a phasing error input from the phase difference detection circuit
109
. The phase difference detection circuit
109
is also input with signals from three circuits, i.e. the SB number/track number detection circuit
115
, the HSW signal generation circuit
105
and the CTL signal detection circuit
108
.
The conventional digital VTR constructed as above operates in a manner, which will be described hereinafter.
A control operation in the ordinary playback mode is as follows.
The cylinder
103
rotates at a constant speed according to a control output of the cylinder driving circuit
114
. The rotation causes the HSW signal generation circuit
105
to output a HSW signal. The CTL head
107
reproduces a CTL signal recorded in the magnetic tape
104
and a leading edge of the CTL signal is detected by the CTL signal detection circuit
108
. The phase difference detection circuit
109
detects a difference in phase between the HSW signal and the leading edge of the CTL signal input to it.
The detected difference in phase is output as an error signal and it is supplied to the tape driving circuit
110
, which in turn controls a traveling speed and a phase of the magnetic tape
104
with the capstan motor
111
.
The phase control between the HSW signal and the CTL signal is thus executed by the foregoing series of feedback controls so as to maintain the reproduction heads to accurately trace the recording tracks on the magnetic tape.
A control operation in a high-speed playback mode will now be described as follows.
FIG. 6
depicts a tape pattern for the high-speed playback mode, in that arrows with dotted lines indicate the directions and locations where the magnetic heads scan through high-speed playback fields (rectangular areas shown by hatch lines) located discontinuously over a plurality of helical tracks
101
, when the tape speed is octupled. Reference characters
0
a
through
7
b
in
FIG. 6
identify track numbers and the “a” and “b” suffixed to the track numbers indicate corresponding azimuths of the magnetic heads during recording. In the case of the two-head azimuth system of this example, the two magnetic heads “A” and “B” record or reproduce alternately on and from the tracks and angles (azimuths) of magnetizing direction in recording and reproduction by the two heads are altered in order to reduce interference of signals between the adjoining tracks. Therefore, the track “a” recorded with the head “A” is reproducible with the head “A” but not reproducible with the head “B”. The same also applies to the track “b” recorded with the head “B”.
The cylinder
103
is controlled for a constant rotational speed by the cylinder driving circuit
114
based on a reference cycle (not shown in the figure) corresponding to the octuple speed of the tape. The reference cycle in this mode is nearly equal to a reference cycle for the ordinary speed or a reference cycle in the ordinary playback mode.
The magnetic tape
104
is driven by the capstan motor
111
at a speed octuple of the ordinary speed. Therefore, the CTL signal detection circuit
108
outputs a CTL signal divided by eight in order to generally equalize the cyclic period with the HSW signal, since a cycle of the reproduced CTL signal becomes one eighth of that of the ordinary playback speed.
Then, the phase difference detection circuit
109
detects a difference in phase of the CTL output signal with the HSW signal in the same manner as in the case of the ordinary playback. And, the tape driving circuit
110
performs a rotational phase control of the capstan motor
111
to automatically adjust a travelling phase of the magnetic tape
104
.
Incidentally, there are eight different timings for the eight-part division, since the dividing timing for the CTL signal reproduced by the CTL signal detection circuit
108
is not specified. For this reason, a pull-in of phase may be completed while the heads are scanning through fields other than the high-speed playback fields (the areas shown by hatch lines in
FIG. 6
) at a rate of seven
Nakatsu Etsuto
Ochi Atsuo
Tohyama Yasuaki
Usuki Naoshi
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