Television – Synchronization – Sync generation
Reexamination Certificate
1999-08-27
2003-02-18
Lee, Michael H. (Department: 2714)
Television
Synchronization
Sync generation
C348S521000
Reexamination Certificate
active
06522364
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a clock frequency generator for generating a clock of an unified frequency in the case of converting the format of the video signal of the television receiver, in order to obtain the horizontal and the vertical synchronizing signals for the video signal after converting the format, without changing the field frequency and the scanning lines of the standard video signal.
BACKGROUND OF THE INVENTION
Recently, in the television broadcasting the digital broadcasting service has been started besides the conventional analogue broadcasting service. In the United States, the digital broadcasting by the surface wave has been started since 1998. In Japan, a digital BS broadcast for mainly servicing a high definition video signal will start in 2000.
There are a variety of standards for signal formats which are employed for the digital television broadcast service. For instance, there are an interlace scanning system signal comprising 525 scanning lines and 858 pixels and a progressive scanning system signal comprising the same 525 scanning lines and the same 858 pixels (these two signals will be referred to SD format signals, hereinafter), a progressive scanning system signal comprising 750 scanning lines and 1650 pixels, and a progressing scanning system signal comprising 1125 scanning lines and 2200 pixels (these two signals will be referred to HD format signals, hereinafter).
In the television receiver compatible with the digital broadcasting, a display format will vary in wider ways, such as a way of supplying the various video signals as mentioned above and away of mixing the HD format signal and SD format signal, a way of displaying by using the synchronizing signal for the HD format signal, or a way of adjusting the screen size to display the graphics or character information on the free space.
In order to comply with the various display formats as mentioned above, it is necessary to convert the format of the video signals between the SD format signal and the HD format signal.
However, if it is considered the number of the scanning lines of each signal formats or the field frequencies (59.94 Hz or 60 Hz), it is difficult to convert the format of the signals as described above by using the standard value. An example of it will be shown below.
First, the horizontal synchronizing signal frequency fH and the clock signal CK of the SD format interlacing scanning signal comprised of 858 pixels and 525 scanning lines are given as follows:
FH
(
SD
)
=
(
field
frequency
)
×
(
number
of
scanning
lines
in
1
field
)
=
59.94
×
525
/
2
=
15.734
(
KHz
)
CK
(
SD
)
=
(
1
)
×
(
number
of
pixels
)
=
15.734
×
858
=
13.499
(
MH
)
(
1
)
This is a case in that the field frequency is 59.94 Hz.
Next, the horizontal synchronizing signal frequency fH and the clock frequency CK of the HD format interlace scanning signal comprised of 2200 pixels and 1125 scanning lines are given as follows:
FH
(
HD
)
=
(
field
frequency
)
×
(
number
of
scanning
lines
in
1
field
)
=
59.94
×
1125
/
2
=
33.716
(
KHz
)
CK
(
HD
)
=
(
2
)
×
(
number
of
pixels
)
=
33.716
×
2200
=
74.175
(
MHz
)
This is a case in that the field frequency is 59.94 Hz.
By the values of each signal formats as shown above, it is difficult to convert the format of the signal from SD format signal to HD format signal without changing the original field frequency and the number of the scanning lines. However, in the television receiver which is possible to input both SD format signal and HD format signal, it had displayed the image without converting the format of the video signal in the case of being input the HD format signal. On the other hand, in the case of being input the SD format interlace scanning signal, it had displayed the image by converting the format of the video signal into that of the SD format progressive scanning signal. Here, the conversion to the progressive scanning signal is explained in detail in the Laied-open Japanese patent Application Tokkai-Hei 4-157886.
Here, the horizontal synchronizing frequency of the SD format progressive scanning signal differs from that of the HD format signal.
That is, the horizontal synchronizing frequency of the SD format progressive scanning signal is 31.468 KHz, and that if the HD format signal is 33.716 KHz as shown in the above Equation (2). For instance, in the television receiver using the cathode ray tube, it is possible display any video signals as mentioned above by controlling the difference of the horizontal synchronizing frequency by deflection system. However, in the television receiver which does not equipped with the deflection system such as the liquid crystal projection television, it needs the video signal processing to display the images by the same horizontal frequency.
In the conventional television receiver which converts the format of the video signal, it was needed a generator for generating a clock in order to obtain the video signal field frequency and the scanning lines which comply with every formats.
SUMMARY OF THE INVENTION
So, the present invention has an object to provide the clock frequency generator for generating a clock of an unified frequency, so as to obtain the horizontal and the vertical synchronizing signals for the video signal after converting the format without changing the field frequency and the number of the scanning lines of the standard video signal.
According to a first aspect of the present invention, a clock frequency generator for a television receiver capable of converting a signal format from that of an interlace scanning signal comprising 525 scanning lines into that comprising 1125 scanning lines, comprising:
a multiplier for multiplying by a factor of 4740 a horizontal synchronizing signal for the interlace scanning signal comprising 525 scanning lines;
a frequency divider for dividing by a factor of 2212 the frequency of the signal obtained in the multiplier, in order to obtain a horizontal synchronizing signal for the interlace scanning signal comprising 1125 scanning lines; and
a clock generator for generating a clock which is used for generating the horizontal and the vertical synchronizing signals for the interlace scanning signal comprising 1125 scanning lines from the horizontal synchronizing signal for the interlace scanning signal comprising 525 scanning lines in the multiplier.
According to a second aspect of the present invention, a clock frequency generator for a television receiver capable of converting a signal format from that of an interlace scanning signal comprising 525 scanning lines into a progressive scanning signal comprising 750 scanning lines, comprising:
a multiplier for multiplying by a factor of 4740 a horizontal synchronizing signal for the interlace scanning signal comprising 525 scanning lines;
a frequency divider for dividing by a factor of 659 the frequency of the signal obtained in the multiplier, in order to obtain a horizontal synchronizing signal for the progressive scanning signal comprising 750 scanning lines; and
a clock generator for generating a clock which is used for generating the horizontal and the vertical synchronizing signals for the progressive scanning signal comprising 750 scanning lines from the horizontal synchronizing signal for the interlace scanning signal comprising 525 scanning lines in the multiplier.
According to a third aspect of the present invention, a clock frequency generator for a television receiver capable of converting a signal format from that of
Sato Koichi
Suzuki Takashi
Kabushiki Kaisha Toshiba
Lee Michael H.
Pillsbury & Winthrop LLP
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