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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a data reproducing device for reproducing music
data and image data which are recorded on a data carrier.
2. Description of the Prior Art
As shown in the signal format illustrated in FIG. 3, in addition to music
data, a series of digital data called "sub-codes" are recorded on a
compact disc in which music data are recorded in the form of digital data.
Each sub-code is made up of eight (8) bits. Of the eight bits, two
higher-order bits correspond to a P signal and a Q signal, and the
remaining six bits are used as image data. The sub-code is so determined
that ninety-eight image words correspond to one frame of the sub-code. The
P signal indicates the top of a piece of music, and it is raised to "1" at
the top of the piece of music and held at "0" at the other positions. The
Q signals are used to record a music number, data concerning the length of
time for a piece of music (hereinafter referred to as "music time lapse
data", when applicable), and data concerning the total time from the start
(hereinafter referred to as "total time data", when applicable).
For the image data, ninety-eight words each consisting of six bits are
provided as shown in FIG. 4(A). Of the ninety-eight words, the first and
second are used as a synchronizing signal, and the remaining words are
used as image data. The ninety-six words of image data are made up of four
groups of unitary image data in which twenty-four words is a minimum unit.
In the unitary image data, as shown in FIG. 4(B), the record mode is
recorded in the first word an image processing instruction is recorded in
the second word, and error correction signs for the first and second words
are recorded in the third and fourth words.
As for the record mode, a line graphics mode and a TV graphics mode are
provided. As for the image processing instruction, an instruction for
covering a screen with a color, an instruction for applying two different
colors to a screen forming units (fonts) to draw a figure, an instruction
for moving an entire screen vertically or horizontally, and so forth are
available.
A channel number and color data for specifying picture color are recorded
in the fifth and sixth words. Position data for indicating a data display
position in the picture are recorded in the seventh and eight words, and
data and error correction signs are recorded in the last sixteen words
(i.e., the ninth through twenty-fourth words).
FIG. 5 is a block diagram showing a conventional data reproducing device
for playing a disc in which music data and image data including sub-codes
have been recorded.
The data reproducing device, as shown in FIG. 5, comprises; a player 1; a
sound generating unit 2 including an amplifier and a loudspeaker: a
display unit 3; and a data processing unit 4. The player 1 reads music
data, sub-codes, etc. from the disc D to apply a reproduction signal to
the data processing unit 4. The unit 4 extracts the music data and image
data from the output reproduction signal of the player 1, to control the
sound generating unit 2 and the display unit 3.
The output reproduction signal of the player 5 is first applied to a
decoder 5 in the data processing unit 4, where it is subjected to
deinterleaving and error correction, and the music data is applied through
a processing circuit (not shown) to the sound generating unit 2 while the
image data is applied to an instruction discriminating circuit 6. The
instruction discriminating circuit 6 determines whether or not an image
processing instruction is recorded in the second word (FIG. 4(B)) of the
sub-code and outputs a detection signal when an image processing
instruction is present. An instruction analyzing circuit 7 operates to
analyze an image processing instruction, to thereby provide data which
specify the colors of the picture elements of the picture according to the
image data recorded in the sub-code. In response to the output data of the
instruction analyzing circuit 7 and the output detection signal of the
instruction discriminating circuit 6, a display control circuit 8 forms
video signals including color signals and synchronizing signals, so that
the image data is displayed on the display unit 3.
In the case where, with the conventional data reproducing device, the music
data recorded in the disc D is manually searched with the player 1 by fast
forwarding or fast reversing, the player 1 performs a sequential operation
where data at discontinuous parts of the disc D are reproduced
sequentially. As for the music data, even when sound reproduction is made
with data obtained from separate parts of the disc, we hear it naturally.
On the other hand, the image data recorded in the sub-code is a sequential
data train. Therefore, if a discontinuous reproduction is produced, for
instance, by manual search, the continuity of the image data is lost. As a
result, the displayed picture is missing parts over the entire screen,
suffers from double writing, or is abnormal in coloration. That is, the
reproduction is unsatisfactory. Thus, the conventional data reproducing
device is unreliable, and the user may find the resultant picture
disagreeable.
SUMMARY OF THE INVENTION
Accordingly, an object of this invention is to provide a data reproducing
device in which the reproduced picture is free from the defects which
otherwise may occur with the discontinuous reproduction of image data,
whereby the user can observe the resultant picture at ease.
According to the present invention a data reproducing device is provided
which, as shown in FIG. 1, comprises: reading means 1 for reading
digitally recorded music data and image data from a data carrier D and
data processing means 4 for forming a music signal and an image signal
according to the music data and image data thus read, and applying the
music signal and image signal to a sound generating means 2 and display
means 3, respectively, wherein the data processing means 4 monitors time
data recorded in the record carrier D, and suspends the image reproduction
by the display means upon detection of a discontinuity of the time data.
The music data and image data recorded in the carrier D are read out by the
reading means 1 and then are applied to the data processing means 4. The
data processing means 4 produces the music signal and the image signal
according to the music data and image data thus read out. The music signal
and the image signal are applied to the sound generating means 2 and the
display means 3, respectively.
The data processing means 4 monitors the time data which represents the
lapse of time in the performance of a piece of music recorded in the data
carrier D. Upon detection of a discontinuous change of the time data, the
data processing means 4 determines therefrom that a manual search
(discontinuous reproduction), such as a quick forwarding operation or
quick reversing operation, has been carried out, and causes the display
means 3 to suspend the image reproduction, thereby pliminating the
irregularities which otherwise may occur with the reproduced image in the
discontinuous reproduction.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram for a description of the principle of a data
reproducing device according to this invention.
FIG. 2 is a block diagram showing one example of the data reproducing
device according to the invention.
FIG. 3 is an explanatory diagram showing a format for signals recorded in a
compact disc.
FIG. 4A and 4B is an explanatory diagram sowing a sub-code format.
FIG. 5 is a block diagram showing a conventional data reproducing device.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
FIG. 2 is a block diagram showing one example of a data reproducing device
according to this invention. In FIG. 2, those components which have been
previously described with reference to FIG. 5 are therefore designated by
the same reference numerals or characters.
In the device of FIG. 2, a disc player 2 reads music data and sub-codes
from a disc D and applies them to a data processing circuit 4. The data
processing circuit 4 extracts image data from the sub-code thus read, so
that an image is displayed on a display unit 3.
The data processing circuit 4 comprises a series circuit which includes a
decoder 5 to which the output reproduction signal of the player 1 is
applied, an instruction discriminating circuit 6, an instruction analyzing
circuit 7, and a display control circuit 8. The output of the circuit 8 is
supplied to the display unit 3. The data processing circuit 4 further
comprises a series circuit of a Q signal extracting circuit 9 to which the
output signal of the decoder 5 is applied, a Q signal discriminating
circuit 10, and an interrupt processing circuit 11. The interrupt
processing circuit 11 is designed to issue an interrupt instruction to the
display control circuit 8.
In the data reproducing device thus organized, the music data and sub-code
data read by the player 1 are applied to the decoder 5, where they are
subjected to deinterleaving and error correction. As a result, the music
data is applied through a processing circuit (not shown) to a sound
generating unit, 2 such as a loudspeaker system. From the sub-code data,
the image data is supplied to the instruction discriminating circuit 6 to
determine whether or not the image processing instruction is recorded in
the second word of each unitary image data. If an image processing
instruction is recorded, the circuit 6 applies a detection signal to the
instruction analyzing circuit 7. In response to the detection signal, the
instruction analyzing circuit 7 forms image data. The display control
circuit 8 forms a video signal according to the image data thus formed, so
that a picture is displayed on the display unit 3.
The decoder 5 operates to extract the Q signal from the sub-code and
outputs the same. The Q signal, as was described before, is one bit of the
sub-code which consists of eight (8) bits per image word, and the unitary
data consists of ninety-eight (98) frames (corresponding to one frame of
the sub-code). The Q signal covers a 2-bit synchronizing signal, 4-bit
control code, 4-bit address code, 72-bit data, and 16-bit error detecting
code; i.e., ninety-eight (98) bits in total. The 72-bit data includes time
data such as the above-described total time data and music time lapse
data.
The Q signal extracting circuit 9 decodes the time data from the Q signal
and applies it to the Q signal discriminating circuit 10. The Q signal
discriminating circuit 10 determines whether or not the time data
increases or decreases regularly. During ordinary reproduction, the time
data will increase with a predetermined regularity for every frame of the
sub-code, however, the regularity is affected by fast-forwarding and
fast-rewinding operations. The Q signal discriminating circuit 10 detects
this condition to apply the detection signal to the interrupt processing
circuit 11, whereupon the interrupt processing circuit 11 suspends the
image display carried out under the control of the display control circuit
8, and erases the displayed picture. Sometimes the Q signal discriminating
circuit 10 cannot reproduce the time data because of scratches or the like
on the disc D. Therefore, the resulting discontinuity in the time data is
detected utilizing a certain width, to perform the picture erase control.
When during the reproduction of the music data and image data from the
carrier, discontinuous reproduction is performed, for instance, by the
manual search, according to the invention the discontinuity in the time
data indicating the music performance time is detected to thereby detect
the discontinuous reproduction whereby the displayed picture is erased.
Therefore, with the data reproducing device of the invention, the picture
can be erased before it is affected by the manual search. Thus, the data
reproducing device of the invention is reliable at all times.
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