Multiplex communications – Communication techniques for information carried in plural... – Byte assembly and formatting
Reexamination Certificate
2000-04-26
2004-10-12
Duong, Frank (Department: 2666)
Multiplex communications
Communication techniques for information carried in plural...
Byte assembly and formatting
C370S535000, C370S487000, C725S139000
Reexamination Certificate
active
06804259
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a digital broadcast receiving apparatus for receiving stream data of a plurality of channels in a digital broadcast system such as digital satellite broadcast system or cable television system.
2. Description of the Related Art
When handling video data and audio data in digital satellite broadcast system cable TV system and the like, compression coding is widely used to compress the amount of information by reducing information redundancy of an enormous amount of data. As this compression coding method, for example, MPEG2 (Moving Picture Experts Group-2) standards defined in ISO/IEC 13818 and so on have been well known.
In the MPEG2 standards, not only the compression coding method of video data and audio data, but also the multiplexing method of coded data is standardized in “ISO/IEC 13818-1: 1994 Information technology Coding of moving pictures and associated audio Part 1: Systems” (MPEG2 system).
By using this multiplexing technique, video data and audio data compressed in amount of information by using the compression coding method are subjected to time division multiplexing. As a result, it is possible to Multiplex a plurality of sets (programs) of video data and audio data associated therewith in one carrier (one channel) and transmit the multiplexed data (program multiplexing).
In such an MPEG2 system, a program stream (PS) system and a transport stream (TS) system are defined as a technique for packet multiplexing.
In each of these systems, video data or audio data subjected to compression coding are packetized into PS (Program Stream) packets or TS (Transport Stream) packets, and these packets are then multiplexed. Typically, in a broadcasting system, a TS system capable of multi-program has been used.
There has been disclosed a device for receiving video data, audio data, and added value service data from a bit stream formed of a plurality of programs in Japanese Patent Application Unexamined Publication No. 8-275147. More specifically, this conventional receiving device is provided with data selection means for selecting a coded stream, multiplexed data, and added value information corresponding to one channel from a multiplexed data stream, and demultiplexes desired TS packets to extract video data, audio data, and added data.
Packet-multiplexed data are inputted in a bit stream form, from a transmission medium of digital satellite broadcasting or cable TV system. This bit stream has been obtained by adding error correction codes to TS packets of the MPEG2 standards and applying transmission path modulation to resultant TS packets. The inputted bit stream is demodulated and subjected to error correction processing, and supplied as TS system data to a packet demultiplexer. In order to obtain desired video and/or audio data from program-multiplexed TS packets, the packet demultiplexer separates and extracts desired TS packets and sends them to a subsequent stage.
The format of a TS packet will be described briefly by referring to
FIGS. 9A
,
9
B and
9
C, before describing a conventional digital broadcast receiver.
In
FIG. 9A
, each TS packet has a fixed length of
188
bytes. TS packets and 16-byte error correction codes are arranged alternately. Each TS packet is basically formed of a 4-byte transport stream header (TS header) and a payload including data to be transmitted. As necessary, an extension header called adaptation field is inserted between the TS header and the payload. Within the TS header, a packet ID (PID) which is an identifier indicating the attribute of the TS packet is represented by 13 bits. Data included In the payload is classified into two types as shown in FIG.
9
B and
FIG. 9C
, according to information to be transmitted.
FIG. 9B
shows the case where a part of a PES (Packetized Elementary Stream) packet is included in a payload. This PES packet includes a PES header and coded video data or coded audio data, which is an element of contents of a program to be transmitted. The PES header includes the kind of an element included within the PES packet and a PES packet length. This PES packet is divided into payloads of TS packets provided with different PIDs according to kinds of elements included within the PES packet. Resultant payloads are carried by TS packets.
FIG. 9C
shows the case where a payload includes program specific information (PSI) which is specific information for system control and service information (SI) which is information specific to service such as program information. Hereafter, the information PSI and the information SI are referred to collectively as “PSI/SI data.”
The PSI/SI data is tabulated every unit called “section.” In the same way as the case of PES, the PSI/SI data is divided into payloads of TS packets respectively provided with different PIDs, according to included information contents and resultant payloads are stored in TS packets. Besides the PSI/SI data which is the contents of the section, each section includes a section header at its head. In the section header, a table ID representing the table kind of the section and a section length indicating the section length are described At the end of the section, cyclic redundancy check (CRC) bits are included.
The PSI data has the structure of a hierarchical table. For each program (set of video and audio data), the PSI data includes a program map table (PMT) describing correspondence between elements with PIDs (packet IDs) and a program association table (PAT) describing corresponding between the PMTs with PIDS.
Further, in the case where transmitted TS packets are encrypted (scrambled), key information for solving the encrypted data is needed. In such a case, however, the PSI includes an entitlement control message (ECM) representing descramble information of each program and an entitlement management message (EMM) representing key information of each contracting subscriber.
Further, in the case where a plurality of scramble systems, relations between ECMs and EMMs corresponding to these scramble systems are described by using a conditional access table (CAT).
In this way, each TS packet has a payload including an element as shown in
FIG. 9B
or a payload including information (system control data) for system control as shown in FIG.
9
C. These can be distinguished by the PID. In a TS packet having system control data, the contents of each section can be distinguished by the section header.
FIG. 1
shows an example of a conventional digital broadcast receiving apparatus comprised of a demodulator
101
, a packet demultiplexer
102
, a CPU
103
, a ROM
140
, and a RAM
105
. In the packet demultiplexer
102
, the PID of a TS packet storing a desired program is stored in a PID table
112
. Upon receiving program-multiplexed TS packets from the demodulator
101
, a PID filter
111
compares the PID of a TS packet received from the demodulator
101
with the PIDs stored in the PID table
112
and extracts a TS packet matching one of the PIDs of the PID table
112
. A plurality of necessary PIDs are previously written by the CPU
103
into the PID table
112
via a data bus and a bus I/F
114
.
The ROM
104
stores a system control program for controlling the operations of the digital broadcast receiving apparatus by running on the CPU
103
. The CPU
103
operates in accordance with the system control program.
Among TS packets extracted by the PID filter
111
, TS packets including elementary data such as video data or audio data are successively supplied to a decoder I/F
113
, subjected to removal (demultiplexing) of TS header and adaptation field, and are then sent to the outside through an elementary output port.
ATS packet Including PSI/SI data in Its payload, which has been extracted by the PID filter
111
, is once stored in a packet storage area of the RAM
105
via the bus I/F
114
and subjected to section reconfiguration in the CPU
103
. Out of the reconfigured section, only information required for system control is processed by the CPU
103
, and the recon
Duong Frank
Harper Kevin C.
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