Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1999-02-25
2001-08-28
Olms, Douglas (Department: 2661)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S389000
Reexamination Certificate
active
06282209
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention generally relates to a digital broadcasting system in which a plurality of channels are transmitted as a time-division multiplexed data stream, each channel comprising a plurality of continuous or time-series multimedia programs. It relates more particularly to a method of and a system for downloading a segment or the whole of a received continuous program from the data stream with a raised preciseness in such a digital broadcasting system.
2. Description of the Prior Art
Overview of a Conventional Multiplexing Technique
FIG. 1
is a schematic block diagram showing an exemplary arrangement of a conventional digital broadcasting system
1
to which the present invention is applicable. In
FIG. 1
, the broadcasting system
1
comprises at least one broadcasting station
2
, a transmission medium
3
and a multiplicity of receiving terminals
4
.
In a multimedia digital broadcasting system, a video, one or more audio and various data constitute a program. A plurality of such programs for respective channels is multiplexed into a data stream. Coding and multiplexing in most cases is achieved according to a international standard for high efficiency coding and multiplexing, known as MPEG-2 (Motion Picture Experts Group II) (ISO/IEC 13818). For this, the following description will be given in connection with the MPEG-2 standard.
In an MPEG encoder unit
201
of the broadcasting station
2
, a video is coded into a video MPEG-coded bit stream, which is then packetised into video PES (packetised elementary stream) packets (according to ISO/IEC 13818-2). An audio is separately coded into an audio MPEG-coded bit stream, which is packetised into audio PES packets (according to ISO/IEC 13818-3).
FIG. 2
is a diagram showing a structure of a PES packet
900
, wherein a sectioned strip bounded by broken lines fanning out downward form a bold-lined section shows a detailed structure of the bold-lined section and wherein a numeral under each field indicates the length of the field in bits. The PES packets
900
are variable length packets, which are used to synchronize the coded bit streams for a program. Each PES packet
900
comprises a header
901
and PES packet data bytes
902
.
The video and audio PES's (or PES packet streams) that constitute a program are multiplexed into a transport stream (TS), which comprises TS packets shown in FIG.
3
.
FIG. 3
is a diagram showing a structure of a TS packet
910
, wherein a sectioned strip bounded by broken lines fanning out downward form a bold-lined section shows a detailed structure of the bold-lined section. In
FIG. 3
, a TS packet
910
is fixed, i.e., 188 bytes in length and comprises a header
911
and a payload
912
. The header
911
contains information on the contents of the payload
912
, including a 13-bit packet ID (PID)
913
for identifying the contents of the payload
912
.
The multiplexing of the PES packet streams is achieved by dividing and storing each of the PES packets
900
into and in one payload
912
after another of the TS under creation. In this case, the values of the PIDs
913
in the headers
911
of the TS packets
910
are so set that the value of each PID
913
is associated with the PES packet stream a part of which is contained in the corresponding payload
912
. Thus, continuous (or time-series) media materials that constitute a multimedia program are multiplexed into a TS. A plurality of such TSs corresponding to respective channels is further multiplexed into another TS. The operations described so far are executed in the MPEG encoder unit
201
. In order to discriminate the first created TSs from the finally created TS, the former and the latter are referred to as “logical channel TS (LC TS)” and “physical channel TS (PC TS)”, respectively.
The physical channel TS is transmitted by a transmitter
202
into a transmission medium
3
.
On the other hand, a receiving terminal
4
comprises a tuner
210
for receiving a plurality of physical channel TSs and providing a selected physical channel TS, which has been multiplexed in accordance with the MPEG-2 standard; a TS decoder
211
for providing a selected logical channel TS from the received PC TS; a PES decoder
212
for extracting the PES packets
900
from the payloads
912
of the TS packets from the TS decoder
211
and demultiplexing the PES packets
900
into video and audio PES packet streams according to the PIDs
914
in the TS packet headers
911
; and a presentation decoder
213
for restoring video and audio bit streams from the video and audio PES packet streams by MPEG decoding the video and audio PES packet streams separately. The tuner
210
, the TS decoder
211
, the PES decoder
212
and the presentation decoder
213
may be any suitable conventional ones. However, it is noted that the MPEG decoding has to be achieved such that the decoded video and audio bit streams synchronize with each other.
For this purpose, the digital broadcasting system
1
is arranged as follows.
Synchronization Technique
The broadcasting station
2
has a system time clock (STC) generator
203
. The generated STC is a 42-bit number n that is incremented at a frequency of 27 MHz. The STC n is contained in a program clock reference (PCR) field
914
in the header
911
of each TS packet
910
. Also, the broadcasting station
2
is permitted to store a presentation time stamp (PTS) and/or a decode time stamp (DTS) in a PTS
903
and DTS
904
fields in a optional header portion
905
of a PES packet
900
if the PES packet
900
contains the head of an access unit of an MPEG-coded bit steam in its packet data bytes field
902
(An access unit is one frame in case of video bit stream and one audio frame in case of audio bit stream). The PTS and DTS are represented by 33 bits with a precision of 90 KHz. Thus, the receiving terminal
4
can synchronize a plurality of continuous media materials with each other by decoding and presenting the continuous media materials such that the PTSs of the media materials coincide with a corresponding regenerated STC from a STC regenerator
214
. The STC regenerator
214
is a PLL(phase locked loop)-based circuit that provides a regenerated 42-bit STC value n at a frequency of 27 MHz according to the values of the PCR fields
914
of the headers
911
of the TS packets
910
supplied from the TS decoder
211
while keeping the error with respect to the PCR
914
value within a certain range. It is noted that the TS decoder
211
is configured to ensure a high precision of the delay time from input of a TS packet
910
from the tuner
210
to extraction of an STC from the PCR field
914
of the TS packet
910
.
However, since the STC is a clock specific to the broadcasting system
1
and different from ordinary time we use in our daily life, the STC is inconvenient for us to use in operating and programming the receiving terminal
4
. For this, a clock that provides ordinary time is required.
As such a clock, EIT (Event Information Table) and TDT (Time and Date Table) are available which are prescribed in a DVB-SI (Digital video broadcasting—Service Information) standard (ETS 300 468) established by a standardization organization ETS (European Telecommunication Standard). The EIT contains the start and the duration of each event or program. The TDT is a time in which year (y), month (mo), date (d), hour (h), minute (m) and second (s) are expressed in a form known as UTC (Universal Time Co-ordinated) form. The TDT is used for reference to an event or program. (The time according to the TDT is referred to as “reference time”). In Japan, Japanese Standard Time is used as the reference time. The reference time is used in, e.g., displaying a program guide according to EPG (electronic program guide) and programming a VTR (video tape recorder). The broadcasting station
2
preferably has a TDT receiver
204
for receiving the TDT data. The broadcasting station
2
transmits TDT data in the well-known section format.
In order to enable a conversion between a regenerat
Harada Takenosuke
Kataoka Mitsuteru
Lowe Hauptman & Gilman & Berner LLP
Matsushita Electric - Industrial Co., Ltd.
Nguyen Brian
Olms Douglas
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