Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1999-03-12
2002-12-10
Ton, Dang (Department: 2732)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S503000
Reexamination Certificate
active
06493362
ABSTRACT:
This Application claims the benefit of Japanese application no. 10-072797 filed on Mar. 20, 1998, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a data recording method and a data recording system, and more particularly, relates to a data recording method and a data recording system for extracting and recording one data out of a plurality of time-division multiplexed data.
2. Description of the Related Art
MPEG 2 standard is an international standard (ISO/IEC 13818-1) proposed by the moving picture expert group (MPEG). It is a coding system for compressing digital video and digital audio signals.
The MPEG 2 standard adopts a time-division multiplexing system using packets. For instance, video and audio signals are divided into streams called packets. The packets have an adequate length for multiplexing the video and audio signals. The packets of the video signal and of the audio signal are then transmitted in a time-division manner while being switched appropriately.
The MPEG 2 standard also adopts a multiplexing and separating system which can accommodate multi-programming in order to transmit a plurality of program data. The use of this system allows not only video and audio signals composing one program data to be transmitted in the time-division manner, but also video and audio signals composing a plurality of programs to be transmitted in the time-division manner.
A system called “transport stream system” is one of such multiplexing and separating systems which can accommodate multi-programming. According to the transport stream system, a packetized elementary stream (PES) packet is divided further into a plurality of packets in order for the system to transmit a plurality of program data in the time-division manner. Each packet has a fixed length which is relatively short, i.e., 188 bytes.
In order to receive and reproduce the program data transmitted in the time-division manner in the transport stream system, it is necessary to synchronize an encoder provided in a transmitter and a decoder provided in a receiver (reproducing unit). In the transport stream system, information for setting and calibrating a clock reference is called a program clock reference (PCR). The PCR is transmitted to synchronize the encoder and the decoder.
It is necessary to control the value of the PCR and the time when the PCR arrives at the decoder accurately in order to synchronize the encoder and the decoder by using the PCR. More specifically, the PCR is data of six bytes and the decoder must set the value of the PCR therein at the time when the final byte of the PCR has arrived. Then, using the PCR arrival time and the value of the PCR, the decoder sets or calibrates a system time clock (STC) which is the basis on which the decoding and reproducing processes within the decoder are performed.
More specifically, the decoder has a phase locked loop (PLL) circuit in which a counter outputting the STC is built in. Every time when the PCR arrives, the PLL circuit calculates a difference between the value of the PCR and the value of the STC, converts its result into a control signal, and performs a feedback control based on this control signal. This creates a STC which coincides completely with the PCR arrival period. Consequently, the encoder provided in the transmitter and the decoder provided in the receiver can be synchronized with a high precision.
A technology for receiving multiplexed data transmitted by using the multi-programming multiplexing and separating system as described above and for recording the received multiplexed data is now being developed. When such technology is established, it becomes possible for a broadcasting station to provide a digital satellite broadcasting service to multiplex and transmit a plurality of movies recorded in digital signals to individual users at home. Also, it becomes possible for individual users to record the movies transmitted from the broadcasting station in the digital signals as received.
Two methods have being proposed for recording the multiplexed data transmitted by using the multi-programming multiplexing and separating system.
A first method is to record all of the transmitted multiplexed data. This method, however, has problems in that the amount of data becomes too large because all of the multiplexed data is recorded including unnecessary program data contained in the multiplexed plurality of program data.
A second method is to extract and record one program data out of the transmitted multiplexed data. This method allows recording of only the necessary and desired program data. Thus, the amount of recorded data is reduced compared to the first method. However, it is difficult to achieve the synchronization by means of the PCR in reproducing the recorded program data.
In other words, when the program data once recorded is to be reproduced, it is necessary to set or calibrate the STC of the reproducing unit based on the reproducing time of the PCR and the value of the PCR in the same manner as the case of receiving and reproducing the multiplexed data transmitted from the transmitter. However, when extracting and recording one program data out of the time-division multiplex signals, the relationship between the reproducing time of the PCR and the value of the PCR is destroyed. As a result, the STC of the reproducing unit cannot be set or be calibrated based on the PCR, and the program data cannot be reproduced.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a data recording method and a data recording system that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a data recording method and a data recording system which allow one specific data to be extracted and recorded out of multiplexed data in which a plurality of data are time-divided. Also, the present invention allows the recorded data to be reproduced with a high precision.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, a data recording method of the present invention performs the function of receiving multiplexed data arranged such that (i) a plurality of program data are time-division multiplexed by packets, (ii) a plurality of time preset values used in synchronizing one program data with a decoder in decoding at least one program data out of the multiplexed plurality of program data by the decoder are provided in advance at predetermined intervals, and (iii) one program data and the decoder are synchronized based on the value of each time preset value received by the decoder every time when it is received, and extracting the respective packets composing at least one program data and recording the extracted respective packets with a predetermined bit rate. The data recording method of the present invention includes the steps of receiving the time preset values disposed in the multiplexed data; generating a new time preset value based on the time preset values received in the receiving step and on the bit rate; and replacing the time preset value disposed in advance with the new time preset value generated in the generating step in recording the packet in which the time preset value has been disposed in advance out of the respective packets composing one program data.
The plurality of program data are time-division multiplexed by packets in the multiplexed data. The program data include sound data, picture data, image data, character data, control data and signal processing data or data
Morgan & Lewis & Bockius, LLP
Pioneer Electronic Corporation
Ton Dang
LandOfFree
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