Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-04-07
2003-05-20
Hsu, Alpus H. (Department: 2665)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S465000
Reexamination Certificate
active
06567409
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a data stream converting apparatus which can convert the structure of a data stream, maintaining its content, and more particularly to a data stream converting apparatus which can convert a program stream into a transport stream.
2. Description of the Related Art
The DVD, which has a large amount of capacity compared with some conventional other optical disks, is becoming popular. The DVD uses a data compression technique standardized by MPEG2 (Moving Picture Experts Group 2, ISO13818-1). When recording multiplexed audio and picture information onto the DVD, this information is recorded in the form of a program stream. The program stream (referred to as a “PS”, hereinafter) is a type of data stream standardized by MPEG2.
The PS is suitable for recording a signal program containing audio and picture information onto a recording medium. However, if the audio and picture information is transmitted in communication systems or broadcasting systems, a transport stream is suitably used rather than the program stream. The transport stream (referred to as a “TS”, hereinafter) is also a type of data stream standardized by MPEG2, and it is suitable for transmitting a plurality of programs. For example, a data transmission using the TS may be appropriately used in ATV (Advance Television).
In order to transmit the audio and picture information recorded on the DVD as the program stream to another television directly, it is needed to convert the PS into the TS.
However, the PS and TS are different from each other in structure. Further, both recording using the PS and transmission using the TS require very accurate time management. Therefore, converting the PS into the TS requires accurate and complicated processes.
For example, if the audio and picture information is reproduced by decoding the program stream, and thereafter, the transport stream is newly generated by rearranging the decoded audio and picture information, the TS is finally obtained. However, these processes are very complicated. Further, since the decoding and rearranging are continuously carried out, the quality of sound and picture can be degraded. Further, in rearranging the audio and picture information, it is needed to rewrite time management information, such as a PTS (Presentation Time Stamp) and a DTS (Decoding Time Stamp). The rewriting such time management information requires exact management of the amount of data, accurate measurement of time periods, etc.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a data stream conversion apparatus which can efficiently convert a data stream such as the program stream into a second data stream such as the transport steam without complicated processes.
In accordance with an aspect of the present invention, a first data stream conversion apparatus is an apparatus for converting a first data stream supplied from a first buffer for accumulating the first data stream into a second data stream, and supplying the second data stream to a second buffer for accumulating the second data stream. The first data stream includes a plurality of first data groups. Each of the plurality of first data groups includes significant data. Further, the first data stream includes a plurality of time values. The plurality of time values each indicates a point of time corresponding to a position of respective one of the plurality of first data groups within the first data stream, The transfer rate of the second data stream is higher than that of the first data stream.
The apparatus includes: a first determining device for determining a first amount of the first data stream accumulated in the first buffer on the basis of at least one of the plurality of time values; a second determining device for determining a second amount of the second data stream accumulated in the second buffer on the basis of an amount of the second data stream that is supplied to the second buffer; a calculation device for calculating a difference between the first amount and the second amount by subtracting the first amount from the second amount; a first placing device for placing the significant data extracted from the first data stream supplied from the first buffer, into the second data stream, if the difference is smaller than a predetermined value; and a second placing device for placing an additional data into the second data stream, if the difference is not smaller than the predetermined value.
In this apparatus, the first determining device determines the first amount of the first data stream accumulated in the first buffer on the basis of at least one of the plurality of time values. The second determining device determines the second amount of the second data stream accumulated in the second buffer on the basis of an amount of the second data stream that is supplied to the second buffer. The calculation device calculates the difference between the first amount and the second amount by subtracting the first amount from the second amount.
If the difference is smaller than a predetermined value, the first placing device places the significant data extracted from the first data stream supplied from the first buffer, into the second data stream. That is, if the amount of data accumulated in the second buffer is not sufficiently greater than the amount of data accumulated in the first buffer, the significant data is sent from the first data stream to the second data stream.
On the other hand, if the difference is not smaller than the predetermined value, the second placing device for placing an additional data into the second data stream. That is, if the amount of data accumulated in the second buffer is sufficiently greater than the amount of the data accumulated in the first buffer, the additional data is placed into the second data stream, in stead of placing the significant data. In addition, it is preferable that the amount of the additional data is much smaller than that of the significant data.
If sending the significant data from the first data steam to the second data stream, the amount of the data accumulated in the first buffer decreases, while the amount of the data accumulated in the second buffer increases. If the amount of the data accumulated in the second buffer is not sufficiently greater than that in the first buffer, there is a possibility that lack of data occurs in the second buffer, because the transfer rate of the second data stream is higher than that of the first data stream.
To prevent such a situation, the apparatus observes both the amount of data accumulated in the first buffer and the amount of data accumulated in the second buffer, and then recognizes the difference between these two amounts, and then sends significant data from the first data stream to the second data stream when the amount of data accumulated in the second buffer is not sufficiently greater than that in the first buffer.
Accordingly, the state that the amount of data accumulated in the second buffer is sufficiently greater than that in the first buffer is maintained. Therefore, it is prevented that lack of data occurs in the second buffer. Thus, the first data stream can be converted into the second data stream without occurrence of lack of data in the second buffer. Therefore, it can be prevented that the converting operation is suspended due to occurrence of lack of data in the second buffer.
Further, when the amount of data accumulated in the second buffer is sufficiently greater than that in the first buffer, the additional data is placed into the second data stream. Therefore, the first data stream can be converted into the second data stream without rearranging the data stream or changing the contents of the significant data. If time management information is included in the significant data, it is not necessary to rewrite this. Accordingly, the conversion of data stream can be achieved without complicated processes.
In the apparatus, the first determining device may include: an extraction d
Harada Seiji
Higuchi Masao
Tozaki Akihiro
Hsu Alpus H.
Pioneer Electronics Corporation
Tran Thien
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