Pulse or digital communications – Synchronizers
Reexamination Certificate
1999-10-01
2003-04-22
Chin, Stephen (Department: 2634)
Pulse or digital communications
Synchronizers
C386S349000
Reexamination Certificate
active
06553086
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for recording and transferring time information for digital data streams. A digital data stream is recorded on a recording medium along with the time information thereof and thus every packet stream unit has the time information of its own. The time information is used for searching the recording medium for a specific packet stream unit requested by a user and maintaining a precise timing for transferring packet stream units through a digital interface to an external apparatus.
2. Description of the Related Art
In conventional analog television broadcast, video signals are transmitted over the air or through cables after being AM or FM modulated. With the recent rapid advance of digital technologies such as digital image compression or digital modulation/demodulation, standardization for digital television broadcast is in rapid progress. Based upon the Moving Picture Experts Group (MPEG) format, satellite and cable broadcast industry also moves towards digital broadcast.
Digital broadcast offers several advantages that its analog counterpart cannot provide. For example, digital broadcast is capable of providing services with far more improved video/audio quality, transmitting several different programs within a fixed bandwidth, and offering enhanced compatibility with digital communication media or digital storage media.
In digital broadcast, a plurality of programs encoded based upon the MPEG format are multiplexed into a transport stream before transmitted. The transmitted transport stream is received by a set top box at the receiver and demultiplexed into a plurality of programs. If a program is chosen from among the demultiplexed programs, the chosen program is decoded by a decoder in the set top box and original audio and video signals are retrieved. The retrieved audio and video signals can be presented by an A/V output apparatus such as a TV.
It is also possible to store the received digital broadcast signals on a storage medium instead of directly outputting the received broadcast signals to A/V output devices. The stored digital broadcast signals can be edited and presented afterwards. For example, a digital data stream received by a set top box can be stored in a streamer such as a digital video disk (DVD) through communication interfaces like an IEEE-1394 serial bus. Later, the stored digital data stream can be edited and transmitted back to the set top box so that the original digital audio and video data can be presented.
When recording the digital data stream of a single program in a streamer, the basic recording unit is the stream object (SOB) comprising a series of stream object units (SOBUs). To record received digital broadcast signals in a streamer and reproduce the recorded signals afterwards, it is necessary to explore how to group and record stream objects (SOBs) and stream object units (SOBUs) and how to create search information for managing and searching for the recorded stream objects (SOBS) and stream object units (SOBUs). Also, it is required to investigate how to search a specific data stream corresponding to a search time requested by a user.
A conventional method for recording digital data streams and creating and recording navigation information will now be explained with reference to the accompanying drawings.
FIG. 1
depicts a block diagram of an apparatus in which the conventional method for creating and recording the navigation information of a digital data stream can be employed.
FIG. 2
depicts the process of recording the digital data stream and creating the navigation information in the system shown in FIG.
1
. The system comprises a set top box
100
, a communication interface (IEEE-1394), and a streamer
200
. Set top box
100
receives transport streams encoded by system encoders and broadcast by a plurality of broadcast stations and demultiplexes the received transport streams. After a decoder
120
decodes the transport stream of a program tuned by a tuning unit
110
, a control unit
140
outputs the decoded transport stream to an A/V output apparatus or to streamer
200
through an IEEE-1394 communication interface
130
and
210
so that the transmitted program can be recorded in streamer
200
, depending upon a user's request. When requested by a user, streamer
200
retrieves the recorded program and transmits the retrieved program through the IEEE-1394 communication interface back to set top box
100
. In set top box
100
, the received program is decoded by decoder
120
and outputted to an A/V output apparatus so that the recorded program can be presented.
A control unit
250
in streamer
200
controls the data stream transmitted from set top box
100
to be recorded as shown in
FIG. 2
on a recording medium
230
by a recording stream processing unit
220
. The received data stream consisting of transport stream packets is recorded on the recording medium along with the packet arrival time (PAT) of each transport stream packet, wherein the packet arrival time will be used as a time reference for transmitting the associated transport packet in playback. In streamer
200
, the transport stream packets with packet arrival times are organized in sectors with each sector having a predetermined size. A predetermined number of sectors, for example 32 sectors, are grouped into a stream object unit (SOBU). If the recording process is stopped or suspended by a user, the recorded stream object units (SOBUs) are organized into a stream object (SOB). Additionally, navigation data such as the stream start application packet arrival time (S_S_APAT) and incremental application packet arrival time (IAPAT) for searching for and managing the stream object (SOB) and stream object units (SOBUs) is recorded together on the recording medium.
FIG. 3
shows the way the received digital data stream is recorded in streamer
200
. An application packet and a packet arrival time (PAT or time stamp) constitute a transport stream packet (TSP). A plurality of transport stream packets (TSPs) and a header are organized into a sector and a predetermined number of sectors, for example 32 sectors, constitute a stream object unit (SOBU). A series of stream object units (SOBUs) constitutes a stream object (SOB). Meanwhile, the stream object information (SOBI), which is the navigation data for managing and searching for the recorded stream objects (SOBs), comprises a stream object general information (SOB_GI) and a mapping list (MAPL) for managing stream object units (SOBUs), as shown in
FIGS. 4 and 5
. The stream object general information (SOB_GI) includes the stream start application packet arrival time (S_S_APAT) indicative of the start time of the associated stream object (SOB). As shown in
FIG. 2
, the incremental packet arrival time (IAPAT), which is a count value counted at constant time intervals (x) between two consecutive stream object units (SOUBs), is included in the mapping list (MAPL) and used as information for searching for the stream object (SOB) and stream object units (SOBUs) afterwards.
The stream start packet arrival time (S_S_APAT) contained in the stream object general information (SOB_GI) is recorded as a 6-byte packet arrival time (PAT) comprising a 9-bit packet arrival time extension (PAT_ext) and 39-bit packet arrival time base (PAT_base), as shown in FIG.
6
A. The packet arrival time extension (PAT_ext) is a modulo-300 counter that is incremented at a rate of 27 MHz, whereas the packet arrival time base (PAT_base) is incremented at a rate of 90 kHz. Unlike format of the stream start application packet arrival time (S_S_APAT), the time stamp recorded along with the application packet shown in
FIG. 3
is recorded as a 4-byte packet arrival time (PAT), shown in
FIG. 6B
, that is incremented at a rate of 27 MHz and can represent from 0 s up to 159 s (=232/27 MHz).
The method for searching a digital data stream corresponding to a requested search time using the navigation and time information regarding the str
Kim Byung-Jin
Seo Kang-Soo
Yoo Jea-Yong
Chin Stephen
LG Electronics Inc.
Williams Lawrence
LandOfFree
Method and apparatus for recording time information for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for recording time information for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for recording time information for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3048440