Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1998-12-21
2002-11-05
Diep, Nhon (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C375S240200
Reexamination Certificate
active
06477204
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a video image signal decoding method and apparatus for decoding a plurality of decoded video image signals simultaneously.
BACKGROUND OF THE INVENTION
Conventionally, in the system for transmitting the moving picture or the audio such as the television broadcast, the television conference system or the television telephone, or the system for recording the moving picture or the audio signal in the magnetic disc, the optical disc or the magnetic tape, and for reproducing the recorded signal, the high efficiency coding is performed then the transmission efficiency enhanced, in order to use the transmission channel or the recording medium effectively.
Also in recent years, a digital satellite broadcast via a broadcast satellite or communications satellite starts in order to solve the channel insufficiency of the analog ground wave television broadcasts or to develop new multi-channel services. Also, there are moves of digitizing the cable television (CATV) transmitted through a communication channel of coaxial cables or optical fiber cables or the ground wave broadcast.
Since in the digital broadcast the digitized video image signal or audio signal are high efficiency compressed through the use of the compression technique such as the MPEG system or the AC-3 system it is possible to secure channels by six to eight times larger than that in a conventional analog broadcast system in the same band width, so as to enhance a variety of services.
There is an MPEG-2 (MPEG stands for Moving Picture Expert Group) as a typical high efficiency coding system. The MPEG-2 is a coding standard which has been fostered standardization as the ISO/IEC 13818 which is the JTC (Joint Technical Committee) of the ISO (International Organization for Standardization) and the IEC (International Electro-Technical Commission).
MPEG-2 defines not only the coding, but also the multiplexing of the video or the audio data streams in order to make use of data streams of encoded video and/or audio data for a wide range of applications. This standard is called the MPEG-2 standard, and there are two kinds according to the use of data stream, i.e., the transport stream (TS: Transport Stream) for the broadcast and communicating, and the program stream (PS: Program Stream) for the storing and recording.
The transport stream is considered to transmit a plurality of programs in one stream, which will be supplied to many broadcast or communicating in the future.
On the other hand, it has been possible to decode the MPEG compression video image signal in the DSP (Digital Signal Processor). Since the processing faculty of the hardware in the DSP or the IC motion speed are improved, it is also possible to decode a plurality of video image signals or audio signals contained in the MPEG streams.
In the digital broadcast system, at the transmitter side, a plurality of MPEG-encoded video image data (TS packets) are multiplexed into one transport system, and the transport stream and other transport streams generated in the similar manner are transmitted to the transponder such as the satellite by carrier waved with different frequencies, and in receivers a plurality of transport streams which are transmitted in conjunction with carrier waves with the different frequencies are decoded in the decoder different for each frequency (containing the tuner), and from each decoded transport stream one selected video image data is MPEG-decoded, so that the decoded video image signals are displayed on the multiple screen of the display device such as the cathode lay tube (CRT), or a MPEG-decoded video images are displayed on different display devices.
When such a digital TV broadcast is received, in order to make it simple for viewer to select a desired channel, the video image signals in a plurality of channels are decoded simultaneously, a TV screen is divided into a plurality of small screens, so as to provide the multi screen display function to display these decoded channel video image signals on the respective small screens simultaneously.
That is, it is assumed that the MPEG transport system in which a plural channel of encoded TV signals are multiplexed is received, and each channels is simultaneously decoded and the combined together so as to be displayed in multi-windows on a TV screen. In this case, as shown in
FIG. 1
, the transport stream is demultiplexed into each TV channels in a demultiplexer (DEMUX)
101
, then each of the TV channels are stored in each of the input buffer memories
201
through
204
.
Here the circuit of
FIG. 1
represents a related art imagined by Inventors for reference purposes to make the understanding of the present invention as described later easy, wherein a plurality of basic low circuits each comprised of one conventional decoder are coupled in parallel. Then, these video image signal streams are decoded separately in the decoders
115
through
118
, and each of the decoded video image signals is stored in each of the output buffer memories
205
through
208
.
Then, as shown in
FIG. 2
, the video signal in each channel is decoded according to the decode starting information contained in the video image signal stream in each channel. Further, in these video image signal streams to be decoded a video image signal to be assigned to a master video image signal is selected, and the decoded video image signals stored in the output buffer memories
205
through
208
are read out by the use of a synchronizing signal reproduced from the data which are used when the video signal assigned to the master video image signal is displayed, then these decoded video image signals are displayed on one screen after synchronized with each other in a synchronizer
119
.
However in the conventional apparatus mentioned above, in order to match the Synchronization for combining the decoded video image signals the output buffer memory for storing the decoded video image signal is required.
Further, through the use of that of the video image signal to be assigned to a master video image signal for the vertical synchronizing signal of the display, the synchronizing signal is changed every when the mater is changed, as shown in
FIG. 2
, so that the phase of the vertical synchronizing signal is also changed simultaneously. Accordingly there had been a problem that the displayed video image is disturbed at the master changing time.
FIG. 3
is a block diagram showing the conventional MPEG decoder for processing a plurality of video image data. Here, it will be explained that the two video image data selected from each two transport streams are supplied to each first and the second video decoders
10
and
20
as the two input streams. The two input streams are supplied to the input terminals
11
and
21
of the first and the second video decoders, respectively. The video streams supplied to the input terminals
11
and
21
are supplied to the MPEG decoders
12
and
22
inside the first and the second video decoders so as to output the MPEG-decoded video image signals to the output terminals
13
and
23
.
To the MPEG decoders
12
and
22
, the clock counting values from the STC counters
15
and
25
(STC stands for the System Time Clock meaning the reference synchronizing signal), and the synchronizing signals from the synchronizing signal generators
18
and
28
based on the clock counting value are supplied.
In the PCR detectors
14
and
24
the PCR (Program Clock Reference: the program time reference value) which are the reference time information of the video image signals are extracted from each streams supplied to the input terminals
11
and
21
. Each video decoders
10
and
20
are provided with each separated generators
17
and
27
. Here, the PCR is contained in the input stream at a specific cycle (for instance, the cycle of 100 ms), which is used for setting or correcting the counts of the STC counters
15
and
25
to the desired counts intended at the MPEG encoder side by periodically comparing and consulting with the PCR.
The clock
Abe Shuji
Fukushima Michihiro
Yamada Masahiro
Kabushiki Kaisha Toshiba
Pillsbury & Winthrop LLP
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