Television – Image signal processing circuitry specific to television – Special effects
Reexamination Certificate
1999-10-13
2002-11-26
Miller, John (Department: 2614)
Television
Image signal processing circuitry specific to television
Special effects
C348S423100, C348S584000, C348S598000
Reexamination Certificate
active
06486922
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an image decoding apparatus such as a personal computer, for example, that receives digital broadcast signals where image-compressed moving pictures and program information are multiplexed, and decodes selected moving pictures to display them.
BACKGROUND ART
Apparatuses that capture television broadcasts and display them include an apparatus that digitizes analog television broadcasts and displays moving pictures on a personal computer.
FIG. 10
shows an example of the structure of a personal computer for receiving analog broadcasts. Reference numeral
101
represents an input high-frequency signal. Reference numeral
102
represents a tuner. Reference numeral
103
represents A/D converting means. Reference numeral
104
represents a digital video signal which is a digitized video signal. Reference numeral
10
represents graphic generating means. Reference numeral
11
represents a graphic signal. Reference numeral
12
represents overlaying means. Reference numeral
13
represents a memory. Reference numeral
14
represents memory control means. Reference numeral
22
represents a memory data signal. Reference numeral
107
represents a overlaid digital video signal. Reference numeral
16
represents D/A converting means. Reference numeral
108
represents an analog video signal. Reference numeral
18
represents display means such as a CRT display. Reference numeral
105
represents timing generating means. Reference numeral
106
represents a clock for D/A conversion.
Here, the graphic signal
11
is a signal for causing graphics such as so-called icons and window frames to be displayed on the display screen of the personal computer.
In
FIG. 10
, the input high-frequency signal
101
is channel-selected by the tuner
102
and is digitized by the A/D converting means
103
, the digitized video signal
104
is overlaid on the graphic signal
11
by the overlaying means
12
, and the overlaid digital video signal
107
is supplied to the D/A converting means
16
and is output as the analog video signal
108
.
The timing generating means
105
generates a display reference clock
106
, which is supplied to the memory control means
14
so as to be used as a reading reference clock for reading the overlaid digital video signal from the memory and is supplied to the D/A converting means
16
so as to be used as a D/A conversion reference clock.
However, in this conventional image display apparatus, the overlaid digital video signal
107
is read out from the memory means
13
based on the display reference clock
106
that is most suitable for display of a personal computer. For this reason, the timing of the reading and the timing of writing of the digital video signal
104
to the memory means
13
are asynchronous to each other, so that a problem arises that in the digital video signal
104
, after the D/A conversion, disturbances in displayed images such as tearing artifacts of display frames and missing frames are caused on the display means
18
.
This problem similarly arises when digitally compressed video signals such as MPEG-compressed video signals are captured by a personal computer in order to support digital broadcasts which will emerge in the future.
DISCLOSURE OF THE INVENTION
In view of this conventional problem, an object of the present invention is to provide an image decoding apparatus in which disturbances in digital video images are'substantially not caused even when digitally compressed image signals are used and overlaid on graphic signals and the overlaid image is displayed.
The first present invention(corresponding to the invention of claim
1
) is an image decoding apparatus for decoding an image from a digital transport stream obtained by multiplexing a digital video bit stream being frame-coded or field-coded, and a time stamp signal, comprising:
de-multiplexing means for extracting the digital video bit stream and the time stamp signal from the digital transport stream;
first clock reproducing means for reproducing a first clock signal from the time stamp signal;
decoding means for decoding the digital video bit stream and outputting a first digital video signal having a first frame frequency and synchronizing with the first clock signal;
graphic generating means for generating a graphic signal;
overlaying means for overlaying the first digital video signal and the graphic signal and outputting a first overlaid digital signal synchronizing with the first clock signal;
memory means for storing at least the first digital video signal; and
digital-to-analog converting means for converting the first overlaid digital signal into a first analog signal in synchronization with the first clock signal.
The second present invention(corresponding to the invention of claim
2
) is an image decoding apparatus for decoding an image from a digital transport stream obtained by multiplexing a digital video bit stream being frame-coded or field-coded, and a time stamp signal, comprising:
de-multiplexing means for extracting the digital video bit stream and the time stamp signal from the digital transport stream;
first clock reproducing means for reproducing a first clock signal from the time stamp signal;
second clock reproducing means for reproducing a second clock signal from the first clock signal;
decoding means for decoding the digital video bit stream and outputting a first digital video signal having a first frame frequency and synchronizing with the first clock signal;
graphic generating means for generating a graphic signal;
overlaying means for overlaying the first digital video signal and the graphic signal and outputting a second overlaid digital signal synchronizing with the second clock signal and having a second frame frequency;
memory means for storing at least the first digital video signal; and
digital-to-analog converting means for converting the second overlaid digital signal into a second analog signal in synchronization with the second clock signal.
The third present invention(corresponding to the invention of claim
3
) is an image decoding apparatus for decoding an image from a digital transport stream obtained by multiplexing a digital video bit stream being frame-coded or field-coded, and a time stamp signal, comprising:
de-multiplexing means for extracting the digital video bit stream and the time stamp signal from the digital transport stream;
first clock reproducing means for reproducing a first clock signal from the time stamp signal;
second clock reproducing means for reproducing a second clock signal from the first clock signal;
decoding means for decoding the digital video bit stream and outputting a first digital video signal having a first frame frequency and synchronizing with the first clock signal;
graphic generating means for generating a graphic signal;
interpolating means for outputting a second digital video signal obtained by increasing a spatial resolution of the first digital video signal;
overlaying means for overlaying the second digital video signal and the graphic signal and outputting a third overlaid digital signal synchronizing with the second clock signal;
memory means for storing at least the second digital video signal; and
digital-to-analog converting means for converting the third overlaid digital signal into a third analog signal in synchronization with the second clock signal.
The fourth present invention(corresponding to the invention of claim
4
) is an image decoding apparatus for decoding an image from a digital transport stream obtained by multiplexing a digital video bit stream being frame-coded or field-coded, and a time stamp signal, comprising:
de-multiplexing means for extracting the digital video bit stream and the time stamp signal from the digital transport stream;
first clock reproducing means for reproducing a first clock signal from the time stamp signal;
second clock reproducing means for reproducing a second clock signal from the first clock signal;
decoding means for decoding the digital video bit stream and outputting a first digital
Miller John
Yenke Brian
LandOfFree
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