Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
2000-09-11
2004-02-03
Rao, Andy (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C348S461000, C348S462000
Reexamination Certificate
active
06687305
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a digital broadcast receiver for receiving a digital broadcast signal in which a compressed video signal, a compressed audio signal, and a data signal in association with the compressed video and audio signals are multiplexed, as well as a CPU and a decoder used for the digital broadcast.
FIG. 9
shows a typical configuration of a conventional digital broadcast receiver for receiving digitally compressed digital broadcast that is defined by the ISO/IEC 13818 standard and usually abbreviated as MPEG
2
.
The digital broadcast receiver shown in the figure comprises a tuner/FEC (Forward Error Correctioner)
10
, an antenna
11
, a demultiplexer
20
, a CPU
30
, a memory
40
, a decoder buffer
50
, a video decoder
60
, data selectors
70
and
90
, an audio decoder
80
, a CPU interface
100
, a display
110
, a speaker
120
, and a data bus
130
.
The electric waves of digital broadcast received by the antenna
11
are amplified and detected by a tuner in the tuner/FEC
10
, and then subjected to FEC (Forward Error Correction), so that the electric waves of the digital broadcast are converted into a digital signal. The digital signal is sent to the demultiplexer
20
. The demultiplexer
20
separates a digital broadcast signal obtained from the tuner/FEC
10
, in which signal a compressed video signal, a compressed audio signal, and a data signal are multiplexed, to supply the compressed video signal and the compressed audio signal to the decoder buffer
50
and supply the data signal to the memory
40
via the data bus
130
.
The decoder buffer
50
retains the compressed video signal and the compressed audio signal. The video decoder
60
reads the compressed video signal from the decoder buffer
50
, decodes the signal according to a PTS (Presentation Time Stamp), and sends the result of signal decoding to the selector
70
. The audio decoder
80
reads the compressed audio signal from the decoder buffer
50
, decodes the signal according to a PTS, and sends the result of signal decoding to the selector
90
. The memory
40
accumulates the data signal mentioned above, and also stores programs to be executed by the CPU
30
, which will be described below. The CPU
30
executes, by time division, a plurality of programs such as a data decoder
42
, an OSD (On Screen Display)
43
, a system control
44
, and the like extracted to an execution program area
41
of the memory
40
, and accordingly supplies a data signal to the data bus
130
, which will be described later. The data decoder
42
analyzes the header portion of the data signal, and decodes the data signal according to the type of data indicated in the header portion of the data signal. The OSD
43
performs calculations for image rendering necessary for OSD display. The system control
44
controls the entire digital broadcast receiver.
The CPU interface
100
obtains from the data bus
130
a video signal and an audio signal decoded by the data decoder
42
, a program executed by the CPU
30
. The CPU interface
100
then supplies the video signal and the audio signal to the selector
70
or the selector
90
according to the signal type obtained, and sends a control signal to the selector
70
or the selector
90
. According to the control signal from the CPU
30
, the selector
70
selects the output of the video decoder
60
when broadcast, the main signal, is to be outputted, and selects the video signal supplied from the CPU interface
100
and supplies the video signal to the display
110
, which will be described below, when the video signal included in the data signal is to be outputted. According to the control signal from the CPU
30
, the selector
90
selects the output of the audio decoder
80
when broadcast, the main signal, is to be outputted, and selects the audio signal supplied from the CPU interface
100
and supplies the audio signal to the speaker
120
, which will be described below, when the audio signal included in the data signal is to be outputted. The display
110
displays the video signal supplied from the selector
70
. The speaker
120
outputs the audio signal supplied from the selector
90
. The data bus
130
is a path for transmitting the data signal processed by the CPU
30
to each part in the digital broadcast receiver.
According to the configuration described above, if a data signal is multiplexed in a digital broadcast signal, a display and an audio output can be obtained by subjecting the data signal to software decoding by the data decoder
42
.
Incidentally, there is disclosed in Japanese Patent Laid-open No. Hei 07-264562 an example of a digital broadcast receiver that decodes a digital broadcast signal in which a compressed video signal, a compressed audio signal, and an accompanying data signal are multiplexed.
SUMMARY OF THE INVENTION
As digital compression technology has been improved, the proportion of a transmission line for digital broadcast occupied by a compressed video/audio signal has been reduced. Thus, it has been possible to transmit a greater amount of data signal.
Therefore, it has been possible to transmit not only conventional data, which is mostly text data, but also video and audio data such as video clips and effect sound. As a result, more various data can be transmitted.
When video and audio data for digital broadcast is to be transmitted, it is possible to transmit the data without compressing it. However, more data can be transmitted if the data is compressed, as is a video and audio signal for digital broadcast, and transmitted as a data signal.
Now, in a conventional digital broadcast receiver as shown in
FIG. 9
, all of the data signal is decoded by a data decoder
42
. Thus, after analyzing the data signal, the data decoder
42
needs to decode the data signal in the same manner as a video decoder
60
and an audio decoder
80
do even if the data transmitted is compressed by the same method as that used for a compressed video signal or a compressed audio signal multiplexed in digital broadcast. In addition, in cases where a compressed still image is transmitted, it is more efficient if the video decoder decodes it as a compressed video signal.
Moreover, as digital compression technology has been improved, the process of decoding a compressed video signal or a compressed audio signal has become more complex, and therefore the processing load on a CPU
30
when the data decoder
42
is used has been increased. Since the CPU
30
executes, by time division, other programs such as OSD
43
and system control
44
, the increase in the processing load on the data decoder
42
affects the operation of the entire digital broadcast receiver. Specific examples of the operation affected include image rendering by the OSD
43
. When the decoding of a data signal is started, the priority of the image rendering process of the OSD
43
is lowered, and therefore it will take more time for switching in the OSD screen than before. For example, if data broadcast is selected from a menu displayed by the OSD, the operation of the OSD becomes slower on starting the decoding of the data signal. Thus, this problem greatly affects the user.
In the meantime, the results of signal decoding by the video decoder
60
and the audio decoder
80
are not selected at selectors
70
and
90
respectively during the decoding of the data signal. Therefore, decoding is performed but the result of decoding is not outputted.
Thus, when a compressed video signal or a compressed audio signal included in a data signal is to be decoded and outputted, the load on the CPU
30
becomes heavier, while the results of decoding by the video decoder
60
and the audio decoder
80
are not outputted. Therefore, the efficiency of utilization in the entire digital broadcast receiver is poor.
An object of the present invention is to provide a digital broadcast receiver that makes it possible in decoding a data signal to relieve the increasing processing load on the CPU, which increase results when a compressed video signal and a com
Fujii Yukio
Katsumata Kenji
Koreeda Hiroyuki
Nakamura Taku
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