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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to apparatus and method for detecting an
error status, and apparatus and method for recording information. More
specifically, the present invention relates to the apparatus and the
method for detecting the generation of the error at the time of recording
main information to be recorded on an information recording medium or of
reproducing the main information on the information recording medium.
2. Description of the Related Art
There are many conventional recording devices which records main
information to be recorded on an information recording medium such as an
optical disc as follows: the devices read address information recorded on
the medium in advance. The address information indicates the recording
position of the main information on the medium. Then the devices record
the main information on the medium based on the address information.
Further, even at the time of reproducing the main information on the
medium, the devices may read the address information at first. Then the
devices search the main information on the medium based on the address
information.
However, for example, at the time of recording the main information, the
irradiated position by the light beam to be irradiated on the optical disc
as the information recording medium is unexpectedly skipped from the
position of the track to be correctly irradiated to a different position
by reason of vibration and the like. This phenomenon is called a track
skipping. If the track skipping is happened, the main information is
recorded on the wrong position. Therefore another main information to be
rightly recorded on the position is redundantly recorded.
If the main information is redundantly recorded, the reproduction of the
information is incorrectly executed.
Therefore if the track skipping is happened, it is necessary to detect it
immediately and to suspend reproducing and to restart recording on the
right position.
In the conventional device, it is determined that the track skipping is
happened when continuity of the address information is broken.
However, according to the conventional method of detecting the track
skipping, it takes time to demodulate the address information and obtain
information of the position to record.
Further, if the time to demodulate the address information and obtain the
information of the position to record is longer than necessary time to
record the amount of information corresponding to the maximum amount of
information to be error-corrected at a time while the main information is
reproduced, the main information is not correctly recorded as a unit of
error correction. Therefore the error at the reproduction is not
corrected, that leads to more serious problem.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide apparatus and
method for detecting an error status, and apparatus and method for
recording information which can promptly and accurately detect the error
status, if the error status such as the track skipping and the like is
happened at the time of recording or reproducing.
The above object of the present invention can be achieved by an apparatus
for detecting an abnormal condition at the time of recording or
reproducing information on information recording medium. The apparatus for
detecting an abnormal condition at the time of recording or reproducing
information on information recording medium is provided with: a detecting
device for detecting control information to be detected every
predetermined constant period in the information recording medium at least
either at the time of recording or at the time of reproducing, the control
information to control at least either the recording or the reproduction
of the main information, and a determining device for determining that the
abnormal condition occurs in either the recording or the reproduction, if
no control information is detected every the predetermined constant
period.
According to the apparatus for detecting an abnormal condition at the time
of recording or reproducing information on information recording medium,
the detecting device detects the control information to be detected every
predetermined constant period in the information recording medium at least
either at the time of recording or at the time of reproducing. The control
information such as a pre-information is used for controlling at least
either the recording or the reproduction of the main information. Then if
no control information is detected every the predetermined constant
period, the determining device determines that the abnormal condition
occurs in either the recording or the reproduction.
Therefore the abnormal condition is promptly and accurately detected.
In one aspect of the apparatus for detecting the abnormal condition at the
time of recording or reproducing information on information recording
medium, said detecting device includes a generating device for generating
a gate signal at the timing that the control information is to be detected
in the information recording medium, and said determining device
determines that the abnormal condition occurs if no control information is
detected at the timing indicated by the gate signal.
According to this aspect, the apparatus can be simplified in its structure,
and a presence or absence of the occurrence of the abnormal condition can
be accurately detected.
In another aspect of the apparatus for detecting the abnormal condition at
the time of recording or reproducing information on information recording
medium, said determining device determines that the abnormal condition
occurs if the probability that no control information is detected is
higher than or equal to a predetermined threshold.
According to this aspect, an effect of a noise generated infrequently is
eliminated and the presence or absence of the occurrence of the abnormal
condition can be accurately detected.
In another aspect of the apparatus for detecting the abnormal condition at
the time of recording or reproducing information on information recording
medium, said determining device determines that the abnormal condition
occurs if the probability that no control information is detected is
higher than or equal to a predetermined threshold in a period to record or
reproduce the amount of information corresponding to the maximum amount of
information to be error-corrected at a time while the main information is
reproduced.
According to this aspect, the abnormal condition can be detected soon, and
an error correction at the time of reproduction is rightly executed.
In another aspect of the apparatus for detecting the abnormal condition at
the time of recording or reproducing information on information recording
medium, said information recording medium is an optical disc rotated at a
constant linear velocity, and said control information is recorded every
predetermined amount for the main information on the information recording
medium in advance and includes at least address information indicating a
recording position of the main information on the information recording
medium.
According to this aspect, the presence or absence of the occurrence of the
abnormal condition can be accurately detected.
In another aspect of the apparatus for detecting the abnormal condition at
the time of recording or reproducing information on information recording
medium, said abnormal condition is detected as a track skipping that a
irradiated position by a light beam to be irradiated on an optical disc is
unexpectedly skipped from a position of the track to be correctly
irradiated to a different position.
According to this aspect, the presence or absence of the occurrence of the
track skipping, which is likely to cause an abnormal of detection at the
time of detecting the main information, can be accurately detected.
In another aspect of the apparatus for detecting the abnormal condition at
the time of recording or reproducing information on information recording
medium, said control information is used for controlling a recording of
the main information on the information recording medium, and the
apparatus further comprises a controlling device for controlling the
recording of the main information on the information recording medium on
the basis of the result of the determination by the determining device.
According to this aspect, the occurrence of the abnormal condition at the
time of recording the main information can be promptly and accurately
detected, and it is prevented that the recording of the main information
is executed so that the abnormal condition occurs at the time of
reproducing the main information.
The above object of the present invention can be achieved by method of
detecting an abnormal condition at the time of recording or reproducing
information on information recording medium. The method of detecting an
abnormal condition at the time of recording or reproducing information on
information recording medium is provided with: a detecting process of
detecting control information to be detected every predetermined constant
period in the information recording medium at least either at the time of
recording or at the time of reproducing, the control information to
control at least either the recording or the reproduction of the main
information, and a determining process of determining that the abnormal
condition occurs in either the recording or the reproduction, if no
control information is detected every the predetermined constant period.
According to the method of detecting an abnormal condition at the time of
recording or reproducing information on information recording medium, a
detecting process detects control information to be detected every
predetermined constant period in the information recording medium at least
either at the time of recording or at the time of reproducing. The control
information such as the pre-information is used for controlling at least
either the recording or the reproduction of the main information. Then if
no control information is detected every the predetermined constant
period, a determining process determines that the abnormal condition
occurs in either the recording or the reproduction.
Therefore the abnormal condition is promptly and accurately detected.
In one aspect of the method of detecting an abnormal condition at the time
of recording or reproducing information on information recording medium,
said detecting process includes a generating device for generating a gate
signal at the timing that the control information is to be detected in the
information recording medium, and said determining process determines that
the abnormal condition occurs if no control information is detected at the
timing indicated by the gate signal.
According to this aspect, the method can be simplified in its structure,
and a presence or absence of the occurrence of the abnormal condition can
be accurately detected.
In another aspect of the method of detecting an abnormal condition at the
time of recording or reproducing information on information recording
medium, said determining process determines that the abnormal condition
occurs if the probability that no control information is detected is
higher than or equal to a predetermined threshold.
According to this aspect, an effect of a noise generated infrequently is
eliminated and the presence or absence of the occurrence of the abnormal
condition can be accurately detected.
In another aspect of the method of detecting an abnormal condition at the
time of recording or reproducing information on information recording
medium, said determining process determines that the abnormal condition
occurs if the probability that no control information is detected is
higher than or equal to a predetermined threshold in a period to record or
reproduce the amount of information corresponding to the maximum amount of
information to be error-corrected at a time while the main information is
reproduced.
According to this aspect, the abnormal condition can be detected soon. and
an error correction at the time of reproduction is rightly executed.
In another aspect of the method of detecting an abnormal condition at the
time of recording or reproducing information on information recording
medium, said information recording medium is an optical disc rotated at a
constant linear velocity, and said control information is recorded every
predetermined amount for the main information on the information recording
medium in advance and includes at least address information indicating a
recording position of the main information on the information recording
medium
According to this aspect, the presence or absence of the occurrence of the
abnormal condition can be accurately detected.
In another aspect of the method of detecting an abnormal condition at the
time of recording or reproducing information on information recording
medium, said abnormal condition is detected as a track skipping that a
irradiated position by a light beam to be irradiated on an optical disc is
unexpectedly skipped from a position of the track to be correctly
irradiated to a different position.
According to this aspect, the presence or absence of the occurrence of the
track skipping, which is likely to cause an abnormal of detection at the
time of detecting the main information, can be accurately detected.
In another aspect of the method of detecting an abnormal condition at the
time of recording or reproducing information on information recording
medium, said control information is used for controlling a recording of
the main information on the information recording medium, and the method
further comprises a controlling process of controlling the recording of
the main information on the information recording medium on the basis of
the result of the determination by the determining process.
According to this aspect, the occurrence of the abnormal condition at the
time of recording the main information can be promptly and accurately
detected, and it is prevented that the recording of the main information
is executed so that the abnormal condition occurs at the time of
reproducing the main information.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view illustrating the structure of DVD-R;
FIG. 2 is a diagram illustrating the recording format of the DVD-R;
FIG. 3 is a block diagram illustrating the outline structure of the
information recording apparatus;
FIG. 4 is a flow diagram illustrating the operation of the information
recording apparatus;
FIG. 5 is a block diagram illustrating the outline structure of a sync
detector;
FIG. 6 is a timing chart illustrating the operation of the sync detector;
FIG. 7 is a block diagram illustrating the outline structure of a gate
signal generator;
FIG. 8 is a timing chart illustrating the operation of the gate signal
generator;
FIG. 9 is a block diagram illustrating the outline structure of a
determination timing generator;
FIG. 10 is a block diagram illustrating the outline structure of an error
rate calculator;
FIG. 11 is a timing chart illustrating the operation of the error rate
calculator;
FIG. 12 is a flow diagram illustrating the operation by a sub CPU; and
FIG. 13 is a flow diagram illustrating the operation by a CPU.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the accompanying drawings, an embodiment of the present
invention will be explained.
In the embodiment, the present invention is adapted for an audio
information outputting device for playing tunes in a place like the
nightclub. Further the device includes a mixer which combines tunes
outputted from a plurality of players and composes a tune for play.
(I) DVD-R
First, an embodiment of the DVD-R will be described with reference to FIGS.
1 and 2. The DVD-R is a storage medium on which the pre-pits corresponding
to the pre-information are formed and the synchronization signal is
recorded by forming the groove tracks wobbled at a predetermined
frequency.
FIG. 1 is a perspective view showing the structure of the DVD-R. FIG. 2 is
an example of recording format of the DVD-R.
First, the structure of the DVD-R according to the present invention will
be described with referring to FIG. 1. In FIG. 1, the DVD-R is a
write-once type dye DVD-R having the dye film 5, and is formed with the
groove tracks 2 on which the recording information should be recorded and
the land tracks 3 for guiding the laser beam B for recording and
reproduction along the groove tracks 2. The DVD-R is conducted so as to
obtain a constant linear velocity.
The DVD-R is further provided with the protection film 7 for protecting the
groove tracks 2 and the land tracks 3, and the gold-deposition surface 6
for reflecting the light beam B at the time of reproducing the recorded
information. The land track 3 are formed with the pre-pits 4 corresponding
to the pre-information. The pre-pits 4 are formed before the DVD-R 1 is
put on the market.
On the DVD-R 1, the groove tracks 2 are wobbled at the frequency
corresponding to the rotation rate of the DVD-R 1. The recording of the
synchronization signal for the rotation control of the DVD-R 1, by
wobbling the groove track 2, is carried out before the DVD-R is put on the
market, like the formation of the pre-pits 4.
When recording the main information (such as video and/or audio information
to be recorded, other than the pre-information and the synchronization
signal. The term "main information" will be used hereinafter for this
meaning through this specification.), the information recording apparatus,
described later in detail, detects the wobbling. frequency of the groove
tracks 2 to obtain the synchronization signal, thereby controlling the
rotation of the DVD-R at the given rotation rate. Simultaneously, the
information recording apparatus detects the pre-pits 4 to obtain the
pre-information previously and sets the optimum output power of the light
beam B based on the pre-information thus obtained, and obtains the address
information indicated of the position on the DVD-R 1 where the main
information is to be recorded. Thereafter, the information recording
apparatus records the main information on the appropriate position on the
DVD-R 1 based on the address information thus obtained.
The main information is recorded in such a manner that the light beam B is
moved to trace, by its beam center, the center of the groove tracks 2 to
form the information pits corresponding to the main information on the
groove track 2.
As shown in FIG. 1, the size of the light spot B is determined so that the
light spot 8 covers not only the groove tracks 2 but partially the land
tracks 3. Using the reflected portion of the light spot 8 from the land
tracks 3 with the push-pull method, the pre-information is detected from
the pre-pits 4. In this case, the above push-pull method uses the
photodetectors divided by the diving lines parallel to the rotation
direction of the DVD-R 1, and this method will be referred to as radial
push-pull method. Further, from the reflected portion of the light spot 8
from the groove track 2, the wobbling signal is detected to obtain the
clock signal (such as the synchronization signal) used for the rotation
control.
Next, the recording format of the pre-information and the information of
the rotation control and the main information recorded beforehand on the
DVD-R 1 according to the present invention will be described with
reference to FIG. 2.
In FIG. 2, the upper part of the illustration represents the recording
format of the main information, and the lower part of illustration in the
form of the waveform represents the wobbling state of the groove track 2
(plan view of the groove track 2) on which the main information is to be
recorded. The upward arrows between the main information and the wobbling
state of the groove track 2 schematically represent the positions where
the pre-pits 4 are formed.
It is noted that, in FIG. 2, the wobbling state of the groove track 2 is
illustrated to have larger magnitude than it really is, to assist the
understanding of the reader. The main information is recorded on the
center line of the groove track 2.
As shown in FIG. 2, the main information to be recorded on the DVD-R is
divided, in advance, into a plurality of sync frames. Twenty six sync
frames constitute one recording sector which serves as a unit information,
and sixteen recording sectors constitute one ECC (Error Correction Code)
block which serves as a unit of error correction at the time of
reproduction.
One sync frame has a length (i.e., 1488T) of 1488 times longer than a unit
length T which corresponds to the bit interval prescribed by the recording
format in recording the main information. The sync frame includes the sync
information SY, having the length of 14 T at its leading portion, which is
used for establishing the synchronization of the respective sync frames.
The pre-information, recorded on the DVD-R 1 according to the present
invention, is recorded in every sync frame. When recording the
pre-information in the form of pre-pits 4, one pre-pit 4 indicating the
sync signal in the pre-information (the sync signal is hereinafter called
a sync code to distinguish it from the sync signal for the rotation
control of the DVD-R) is necessarily formed on the land track 3 adjacent
to the area of each sync frame in the main information where the sync
information SY is recorded. Further, one or two additional pre-pits 4 are
formed on the land track 3 at the position adjacent to the leading portion
of the sync frame other than the sync information SY, so as to indicate
the contents (address information)of the pre-information to be recorded.
It is noted that, in some cases, no pre-pit 4 may be recorded at the front
half portion of the sync frame except for the sync information SY,
depending of the contents of the pre-information to be recorded. In the
first sync frame (EVEN frame as mentioned below) in one recording sector,
three pre-pits 4 are consequently formed at the front half portion of the
sync frame.
In the DVD-R of the present invention, the pre-pits 4 may be formed only in
one of the even numbered sync frames (hereinafter referred to as "EVEN
frame") and the odd numbered sync frames (hereinafter referred to as "ODD
frame") to record pre-information. In this embodiment, the pre-pits 4 are
formed in the EVEN frames (as shown by the solid arrows in FIG. 2), but no
pre-pits 4 is formed in the ODD frames adjacent thereto (as shown by the
broken arrows in FIG. 2).
Further, the pre-pit 4 is formed in the position that the amplitude of the
wobbling becomes maximum.
The relationship between the position that the pre-pit 4 is formed and the
contents of the pre-information in the pre-pit 4 will be specifically
explained. In the following explanation, the pre-pit 4 formed on the land
track 3 which is next to the area the synchronous information SY is
recorded is indicated as "pre-pit B2". The pre-pits 4 formed on the land
track 3 which is next to the front side of the sync frame other than the
the synchronous information SY are indicated as "pre-pit B1" and "pre-pit
B0" in order of the arrangement from the head.
As shown in the following table, all pre-pits B2 to B0 are formed at the
position corresponding to the sync code in the EVEN frame which is located
at the head of the one recording sector. Further, only the pre-pit B2 and
B1 are formed at the position corresponding to the sync code in the ODD
frame. Moreover, only the pre-pits B2 and B0 are formed at the position
corresponding to data "1" as the pre-information other than the sync code.
Furthermore, only the pre-pit B2 is formed at the position corresponding
to data "0" as the pre-information other than the sync code.
TABLE 1
pre-pit
contents B2 B1 B0
sync code of EVEN 1 1 1
frame
sync code of ODD 1 0 0
frame
pre-information 1 0 1
data "1"
pre-information 1 0 0
data "0"
The groove track 2 is wobbled at the constant wobbling frequency of about
140 kHz, which is determined such that one sync frame corresponds to 8
waves of varying wave forms of the groove track 2. The above mentioned
information recording apparatus detects the wobbling signal having the
constant wobbling frequency thereby to detect the signal used for the
rotation control of the spindle motor.
(II) Configuration and Operation of the Information Recording Apparatus
An embodiment of the information recording apparatus of the present
invention will be described with reference to FIGS. 3 to 13. The
information recording apparatus records the main information on the DVD-R
having the above-mentioned feature.
First, the whole structure of the information recording apparatus of the
present invention will be described with reference to FIG. 3. FIG. 3 is a
block diagram showing the whole structure of the information recording
apparatus of the present invention.
As shown in FIG. 3, the information recording apparatus S according to this
embodiment includes a pickup 10, a pre-pit detector 11, a DVD encoder 15,
a strategy circuit 16, a wobbling detector 18, a spindle motor 19, a sync
detector 20, a gate signal generating circuit 21, a determination timing
generator 22, a pre-pit gate circuit 23, an error rate counter 24, a CPU
25, a spindle servo circuit 44, a wobbling PLL (Phase Locked Loop) WP and
a spindle controller SP.
The wobbling PLL WP includes dividers 30 and 31, a phase comparator 32, an
equalizer 33 and VCO (Voltage Controlled Oscillator) 34.
The spindle controller SP includes a reference signal generator 40, a
divider 41, a phase comparator 42 and an equalizer 43.
Next, the whole operation of the information recording apparatus S will be
described with reference to FIGS. 3 and 4. FIG. 4 is a flow diagram
showing the whole operation.
The recording data Sr serving as the main information is supplied from an
external device to the DVD encoder 15. Then the recording data Sr is
modulated under the eight to sixteen modulation scheme based on a clock
signal, which is not shown in FIG. 3, and the below-mentioned control
signal Sct by the DVD encoder 15, and supplied to the strategy circuit 16
as a modulation signal Sec. Further, a waveform of the modulation signal
Sec is converted into that of a recording signal Srr by the strategy
circuit 16 in order to adjust a form of a recording pit formed on the
DVD-R 1 based on the clock signal. Then the recording signal Srr is
supplied to the pickup 10.
The pickup 10 irradiates the light beam B whose intensity is modulated by
the recording signal Srr on the groove track 2 where the recording pit is
to be formed corresponding to the recording signal Sr.
The pickup 10 irradiates the light beam B as shown in FIG. 1 in advance of
forming the recording pit corresponding to the recording signal Sr. Then
the pickup 10 receives the reflected light of the light beam B modulated
based on the pre-pits 4 and the wobbling of the groove track 2, and
generates a detection signal Sp including the information of the pre-pits
4 and the wobbling of the groove track 2. Then the pickup 10 outputs the
detecting signal Sp to the pre-pit detector 11 and the wobbling detector
18.
The detecting signal Sp has a frequency (about 140 kHz) corresponding to
the wobbling of the groove track 2 as shown in the top part of FIG. 4, and
has a waveform like an impulse indicated by (4) in FIG. 4 at the timing
which the pre-pit 4 is formed.
The wobbling detector 18 generates a wobbling detecting signal Swp (shown
in the second part from the top of the FIG. 4) corresponding to the
wobbling of the groove track 2 based on the detecting signal Sp, and
outputs the wobbling detecting signal Swp to the divider 30 in the
wobbling PLL WP and the phase comparator 42 in the spindle controller SP.
The wobbling signal Swp can be have no pulse at the timing which the pulse
is to be detected under the influence of a surface flaw of the DVD-R 1 as
shown by a dotted line in the second part from the top of FIG. 4.
The wobbling PLL WP, where the wobbling detecting signal Swp is supplied,
generates a clock signal Scl based on the wobbling detecting signal Swp,
which is synchronized with the wobbling frequency of the groove track 2
and has a frequency corresponding to an inverse number of the "T". Then
the wobbling PLL WP outputs the clock signal Scl to the gate signal
generating circuit 21 and the determination timing generator 22 and
outputs the clock signal Scl to the divider 31 again for feedback.
In the wobbling PLL WP, the phase comparator 32 compares the phase between
the signal divided the clock signal Scl into by the divider 31 and the
signal divided the wobbling signal Swp into by the divider 30. The former
signal has the frequency which accurately equals to an original wobbling
frequency, and hereinafter is called a wobbling signal Sw as shown in the
third part of FIG. 4. Then in the wobbling PLL WP a frequency of the
signal obtained by the comparison is regulated by the equalizer 33, and
the VCO 34 is driven by using the signal. Then the VCO 34 generates the
clock signal Scl. According to the above-mentioned operation of the
wobbling PLL WP, if there are some missing pulses in the wobbling
detecting signal Swp as shown by dotted lines in the second part from the
top of FIG. 4, The wobbling signal Sw and the clock signal Scl are
generated as signals compensated for the missing pulses as shown in the
third part from the top of FIG. 4.
Further, the wobbling signal Sw is supplied to the sync detector 20 in
addition to the phase comparator 32.
The spindle controller SP, where the wobbling detecting signal is supplied,
generates a drive control signal Sdc used for controlling the number of
revolutions of the spindle motor 19 based on the wobbling detecting signal
Swp, and outputs the drive control signal Sdc to the spindle servo circuit
44. Then the spindle servo circuit 44 generates a drive signal Sd used for
activating the spindle motor 19 so that the DVD-R rotates at a constant
linear velocity, and outputs drive signal Sd to the spindle motor 19.
In the spindle controller SP, a reference signal for activating the spindle
motor 19 generated by the reference signal generator 40 is divided by the
divider 41. Then the phase comparator 42 compares the phase between the
divided signal and the wobbling detecting signal Swp. The equalizer 43
regulates a frequency response of the signal obtained by the comparison,
and generates the drive control signal Sdc.
The pre-pit detector 11 extracts a pre-pit signal Spp, which corresponding
to the pre-pit 4 included in the detecting signal Sp as shown the second
part of the bottom of FIG. 4, according to radial push-pull method, and
outputs the pre-pit signal Spp to the pre-pit gate circuit 23 and the sync
detector 20.
The sync detector 20 generate a position signal Spsp by the below-mentioned
operation, and outputs the position signal Spsp to the gate signal
generate circuit 21 by using the supplied pre-pit signal and wobbling
signal, and the determination timing generator 22. The position signal
Spsp, indicating the timing of the sync code in each sync frame as shown
in the fourth part from the top of FIG. 4, is used for generating a gate
signal Sgt by the gate signal generating circuit 21. The gate signal Sgt
indicates the timing when the pre-pit signal Spp corresponding to the lead
pre-pit 4 in each sync frame, is duly generated. The lead pre-pit 4
corresponds to the pre-pit B2 in the table 1.
The gate signal generating circuit 21 generates the gate signal Sgt
according to the below-mentioned operation by using the clock signal Scl
and the position signal Sps as shown in the third part from the bottom of
FIG. 4, and outputs the gate signal Sgt to the pre-pit gate circuit 23.
The pre-pit gate circuit 23 applies the supplied gate signal Sgt to the
pre-pit signal Spp, and generates a pre-pit gate signal Spg serving as an
impulse signal as shown in the bottom part of FIG. 4 in the case that the
pre-pit signal Spp corresponding to the pre-pit 132 is supplied to the
pre-pit gate circuit 23 while the gate signal Sgt indicates high level.
Further, the pre-pit gate circuit 23 outputs the pre-pit gate signal Spg
to the error rate counter 24.
The pre-pit gate signal Spg is generated only when the pre-pit signal Spp
corresponding to the pre-pit B2 is normally detected (i.e., the pre-pit
signal Spp is detected while the gate signal Sgt indicates high level.).
Therefore if the pre-pit signal Spp is generated at the different timing
from the regular timing, the pre-pit gate signal Spg is not generated.
The determination timing generator 22, where the clock signal Scl and the
position signal Spsp are supplied, generates a determination timing signal
Sjt according to the below-mentioned operation, which indicates the timing
of determining whether the pre-pit signal Spp is normally detected in the
below-mentioned error rate counter 24 by using the clock signal Scl and
the position signal Spsp, and outputs the determination timing signal Sjt
to the error rate counter 24.
The error rate counter 24 generates an error rate signal Ser indicating the
rate of the detection of the pre-pit signal Spp at the incorrect timing
(i.e., the rate of occurrence of the track-skipping) according to the
below-mentioned operation by using the pre-pit gate signal Spg and the
determination timing signal Sjt, and outputs the error rate signal Ser to
the CPU 25.
The CPU 25 determines whether the track-skipping occurs according to the
below-mentioned operation based on the rate indicated by the error rate
signal Ser, and generates the control signal Sct for controlling the DVD
encoder 15 so that the output of the modulation signal Sec from the DVD
encoder 15 is stopped if the track-skipping occurs. If the recording is
carried on in that case, recording is done on the incorrect groove track
other than the correct groove track to be recorded. The CPU 25 outputs the
control signal Sct to the DVD encoder 15.
Therefore the occurrence of the abnormal condition of the reproduction at
the time of the reproduction, caused by recording the main information on
incorrect groove track 2 which is not to be used for recording in the case
that the above-mentioned track-skipping occurs, is avoided.
Next, the detail configuration and operation of the sync detector 20 will
be described with reference to FIGS. 5 and 6.
FIG. 5 is a block diagram showing the outline structure of the sync
detector 20. FIG. 6 is a timing diagram showing the operation of the sync
detector 20.
As shown in FIG. 5, the sync detector 20 includes a rising edge generating
circuit 50, a falling edge generating circuit 51, D-type flip-flop
circuits 52, 53, 54, 55, and 57, an AND circuit 56 and a position signal
generator 58.
Next, the operation will be described with reference to FIG. 6.
Three pre-pits 4 corresponding to the sync code of the first EVEN frame in
one recording sector are consequently formed at the position where the
amplitude of wobbling of groove track 2 becomes maximum. Therefore the
sync detector 20 detects the pre-pit 4 indicating the sync code of the
EVEN frame by finding the three pre-pits 4 formed consequently, and
generates the position signal Spsp indicating the timing of the sync code.
In the sync detector 20, the rising timing of the wobbling signal Sw
supplied by the rising edge generating circuit 50 is detected by the
rising edge generating circuit 50, and supplied to a clear terminal of the
flip-flop circuit 52 as a rising signal S.sub.1 as shown in the third part
of top of FIG. 6.
Paralleling that operation, the falling timing of the wobbling signal Sw
supplied to the falling edge generating circuit 51 is detected by the
falling edge generating circuit 51, and supplied to clock terminals of the
flip-flop circuits 53, 54, and 55 as a falling signal S.sub.2 as shown in
the fourth part from the top of FIG. 6.
The output of the flip-flop circuit 52 where the pre-pit signal Spp is
supplied becomes HIGH when the pre-pit signal Spp is supplied, and
maintains HIGH until the next rising signal S.sub.1 is supplied.
Accordingly, a timing signal S.sub.3 including three | | |
