Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1999-05-20
2003-06-24
Luther, William A. (Department: 2664)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S395400, C370S395600, C370S503000, C348S423100, C348S518000
Reexamination Certificate
active
06584120
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a data multiplexing apparatus and method for assembling a plurality of programs of coded video and audio data into packets and multiplexing the packets into a single bit stream.
2. Description of Related Art
Recently, the digital satellite broadcasting systems have been prevailing in which a transmitting side uses the techniques of information compression and multiplexing as in the MPEG (Moving Picture coding Experts Group) 2 or the like to code and multiplex a plurality of programs of quality video and audio information into a single bit stream within in a limited transmission band and transmit the bit stream to a receiving side which disassembles and decode the received bit stream.
At the transmitting side, the video and audio information is coded as in the MPEG2, the digital coded data is multiplexed into a bit stream, the bit stream is subjected to an error correction and modulation, and then transmitted towards a communication satellite from a transmission antenna.
The multiplexer used at the transmitting side is configured as schematically shown in FIG.
1
. Briefly, the multiplexer disassembles an elementary stream packetized by an encoder provided upstream thereof, namely, a packetized elementary stream (will be referred to as “PES” hereinunder)
101
into transport packets in relatively short transmission units of 188 bytes, and connects a plurality of transport packets by time-division multiplexing to provide a transport stream (will be referred to as “TS” hereinunder)
120
.
Three PES streams
101
, for example, supplied from three encoders are stored into an input controller
103
. The input controller
103
supplies three multiplex buffers
102
1
,
102
2
and
102
3
with three input PES streams
101
, respectively, acquire information of PES headers and ES headers of video and audio data, and supplies a channel selection controller
116
with a synchronization control information.
The multiplex buffers
102
1
,
102
2
and
102
3
are each of an FIFO type to provisionally store three PES streams
101
, respectively. In these multiplex buffers
102
1
,
102
2
and
102
3
, the three PES streams
101
are packetized as transport packets (will be referred to as “TP” hereinunder) and kept there until they are multiplexed.
The multiplexer includes also a control data generator
105
which generates and packetizes program specific information (will be referred to as “PSI” hereinunder) necessary for selection and decoding of a program at the receiving side and service information (will be referred to as “SI” hereinunder) on the whole or a part of a program. In some cases, the control data generator
105
uses a system time generated from a basic clock inside the multiplexer to generate a program clock reference (will be referred to as “PCR” hereinunder) peculiar to each program and which is used as a reference. A transmission period is managed for each control data, a multiplex request for each control data is sent to the channel selection controller
113
at a time when a control data has to be transmitted while a TP packets for the control data are kept in an output register included in the control data generator
105
The multiplexer further includes a null packet generator
106
which generates, at a time when it is not necessary to multiplex the PES and control data, a TP packet as a code which is meaningless as a data but fills voids in the bit stream.
A TP header generator
109
is also provided in the multiplexer to generate a TP header which has to be multiplexed before the three PES streams
101
are read from the multiplex buffers
102
1
102
2
and
102
3
for multiplexing.
The channel selection controller
113
determines which code should be selected for one of the channels to the control data generator
105
, multiplex buffers
102
1
,
102
2
and
102
3
and null packet generator
106
, and sends a selection signal to a switch
114
to control the multiplex channels. When any one of the multiplex buffers
102
1
,
102
2
and
102
3
is selected, the switch
114
is controlled to read from the TP header generator
109
before reading from the multiplex buffers
102
1
,
102
2
and
102
3
. For reading from the TP header generator
109
, the switch
114
is provided with a one of parameters stated in the TP header and which varies depending upon a channel over which the reading is to be done and a timing at which the reading is to be done. The parameters thus delivered to the switch
114
include a packet ID (will be referred to as “PID” hereinunder), adaptation field control signal, etc. A code multiplexed by the switch
114
is delivered as a TP code to a presentation time stamp (will be referred to as “PTS” hereinunder)/decoding time stamp (will be referred to as “DTS” hereinunder) controller
116
also included in the multiplexer.
The PTS/DTS controller
116
swaps a PTS and DTS of a program being multiplexing between them when the PTS and DTS are not suitable for the PCR for the program, and sends it to an output controller
119
also included in the multiplexer. For example, when a PCR is generated from a value of a system time the multiplexer has, the input controller
103
acquires an elementary stream clock reference (will be referred to as “ESCR” hereinunder) along with a PTS and DTS, clarifies the topological relation with the ESCR, and replaces it with the PTS and DTS having a correct topological relation with a PCR which is actually sent.
The output controller
119
reads and delivers a TS stream
120
at a time based on the system clock the multiplexer has.
The TS stream
120
should be a bit stream with which all code buffers the decoders have can operate successfully or without failure. Normally, the encoder to implement the coding as in the MPEG2 generates a bit stream with which all the buffers in a transport stream system target decoder (will be referred to as “T-STD” hereinunder) can work without failure.
However, in the multiplexer shown in
FIG. 1
, namely, in the multiplexer disassembling a PES stream
101
into TP packets in relatively short transmission units of 188 bytes, and connecting a plurality of TP packets by time-division multiplexing to provide a TS
120
, each buffer of the T-STD is not completely assured for normal operation. If the delay in a multiplex buffer
102
for a certain channel, for example, is larger for any reason, the virtual buffer in the T-STD is likely to fail.
If a code topological relation an input stream inherently has and which is appropriate for the synchronization control is broken when the content of the input stream is subjected to some bit manipulation such as invalid code removal, etc., the above-mentioned method cannot assure the normal operation of the virtual buffer of the T-STD.
SUMMARY OF THE INVENTION
Also, when a certain integrated receiver decoder (IRD) is used to simulate each buffer of the T-STD by an IRD for actual operation of the buffer at the transmitting side, it is difficult to have the buffer operate as specified for a memory configuration, inter-memory transfer rate and inter-memory transfer delay.
Accordingly, the present invention has an object to overcome the above-mentioned drawbacks of the prior art by providing a multiplexing apparatus and method adapted to assure the normal operation of decoder and code buffer and normal reproduction of decoder.
The above object can be attained by providing a data multiplexer for multiplexing a number n of coded stream data, comprising, according to the present invention:
a number n of means for provisionally storing the number n of coded stream data;
a selection controlling means for retrieving a data occupancy in the number
17
of storage means to select any one of the storage means;
means for switching and delivering the coded stream data from the storage means selected by the selection controlling means;
an output means for multiplexing the switched output from the switching means; and
a virtual storage means for simulating the write and read, fo
Kugumiya Mamoru
Shiomoto Shoji
Bell Boyd & Lloyd LLC
Luther William A.
Sony Corporation
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