Data multiplexer and data multiplexing method

Details Data multiplexer and data multiplexing method Data multiplexer and data multiplexing method

1998-12-08

2003-01-07

Ngo, Ricky (Department: 2664)

Multiplex communications

Communication techniques for information carried in plural...

Combining or distributing information via time channels

C370S242000

Reexamination Certificate

active

06504855

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a data multiplexer and a multiplexing method and more particularly, is suitably applied to a data multiplexer of a digital broadcasting system.
2. Description of the Related Art
Various compression-encoding methods are recently proposed as methods of reducing the information quantity of pictures and sounds and Moving Picture Experts Group Phase 2 (MPEG2) is the typical one of the compression-encoding methods.
The MPEG2 method is standardized (e.g. Recommendation H.222.0) by an organization such as International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) and specified in order to compression-encode, multiplex and transmit picture data and sound data.
Actually, the MPEG2 method specifies a data format referred to as a program stream (hereafter, referred to as a PS data format) and a data format referred to as a transport stream (hereafter, referred to as a TS data format) as data formats for multiplexing compression-encoded picture data and sound data.
The PS data format is used to accumulate multiplexed picture data and sound data in a predetermined digital accumulation medium, and the TS data format is used to transmit multiplexed picture data and sound data. Moreover, streams having the PS data format and TS data format can be mutually converted with a variable-length Packetized Elementary Stream (PES) packet as a basic element.
In the case of the PS data format, for example, it is specified that compression-encoded picture data and sound data are respectively formed into a PES packet every predetermined unit (e.g. every picture), to form a PS packet string (so-called, a program stream) by time-dividing and multiplexing each of the resultant PES packets.
FIG. 1
shows a transmitter
100
of a digital broadcasting system. The transmitter
100
supplies picture data D
1
A and D
1
B corresponding to respective television broadcast programs to corresponding encoders
101
A and
101
B from data output sections (not illustrated) corresponding to plural channels, compression-encodes the picture data D
1
A and D
1
B in accordance with the MPEG2 method in the corresponding encoders
101
A and
101
B, and successively forms encoded data thus obtained into a PES packet every picture, in order to form and supply encoded data streams D
31
A and D
31
B to a multiplexer
102
.
To multiplex the encoded data streams D
31
A and D
31
B supplied from the respective encoders
101
A and
101
B, the multiplexer
102
stores and temporarily accumulates plural PES packets included in the encoded data streams D
31
A and D
31
B in corresponding buffers
103
A and
103
B in arriving order and then, reads out and transmits the PES packets from the buffers to a multiplexing section
104
in accordance with the first-in first-out method.
In this case, the buffers
103
A and
103
B respectively supply the amount of data accumulated in the PES packets to a multiplexing control section
105
as data accumulation signals S
2
A and S
2
B and thereby, the multiplexing control section
105
respectively detects the amount of data accumulated in the buffers
103
A and
103
B, based on the data accumulation signals S
2
A and S
2
B.
The multiplexing control section
105
transmits buffer output control signals S
3
A and S
3
B to the respective buffers
103
A and
103
B based on the detection result before the amount of data exceed the maximum data accumulation capacities of the buffers
103
A and
103
B. Thereby, the section
105
can read out the PES packets from the buffers
103
A and
103
B in accordance with the first-in first-out method and thus, it is possible to prevent the buffers
103
A and
103
B from being broken down due to excessive data accumulation.
Then, the multiplexing section
104
receives the encoded data streams D
31
A and D
31
B from the respective buffers
103
A and
103
B and moreover, receives a multiplexing control signal S
4
from the multiplexing control section
105
and then, successively forms plural PES packets included in the respective encoded data streams D
31
A and D
31
B into a packet (hereafter, referred to as transport stream “TS” packet) every predetermined unit (e.g. every 188-byte data) and thereafter, forms a transport stream (TS stream) comprising one TS packet string D
32
by time-dividing and multiplexing the resultant TS packets.
Then, the TS stream D
32
is modulated by a not-illustrated modulator in accordance with a predetermined method and the resultant transmission signal is transmitted toward a broadcasting satellite (not illustrated) through an antenna. In this way, the transmitter
100
can broadcast television programs for plural channels through the broadcasting satellite.
In the case of the transmitter
100
, the encoders
101
A and
101
B supply the respective compression-encoded picture data (encoded data streams D
31
A and D
31
B) to a multiplexer at a fixed bit rate. In this case, when patterns of input picture data D
1
A and D
1
B are flat, the amount of encoded data successively generated by the encoders
101
A and
101
B are reduced due to the fact that the amount of picture information of the picture data D
1
A and D
1
B are extremely small.
Therefore, when the encoders
101
A and
101
B form successively generated encoded data into a PES packet every picture, they keep the transmission rates of the encoded data streams D
31
A and D
31
B comprising the PES packet strings constant by adding dummy data originally unnecessary for encoding (hereafter, referred to as invalid data) to valid data in bytes.
The transmission rates of significant information in the encoded data streams D
31
A and D
31
B have a problem of being reduced by a value equivalent to added invalid data because the encoders
101
A and
101
B respectively output encoded data streams D
31
A and D
31
B to which invalid data is added.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of this invention is to provide a data multiplexer in which multiplexing efficiency can be improved by effectively using the data transmission rate of a transmission system.
The foregoing object and other objects of the invention have been achieved by the provision of a data multiplexer which detects and extracts invalid data assigned to an inputted data stream and multiplexes and outputs the data stream from which the invalid data is extracted. Thereby, it is possible to improve multiplexing efficiency for invalid data.
Moreover, by detecting the amount of extracted invalid data and multiplexing a predetermined data stream onto the data stream from which invalid data is extracted in accordance with the amount of detected invalid data, it is possible to improve multiplexing efficiency by a value equivalent to the multiplexed predetermined data stream instead of the invalid data.


REFERENCES:
patent: 5657325 (1997-08-01), Lou et al.
patent: 5710756 (1998-01-01), Pasternak et al.
patent: 5761209 (1998-06-01), Murakami
patent: 5801781 (1998-09-01), Hiroshima et al.
patent: 5878045 (1999-03-01), Timbs
patent: 6185526 (2001-02-01), Kato et al.

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