Clock conversion apparatus and method

Details Clock conversion apparatus and method Clock conversion apparatus and method

1997-07-07

2002-03-19

Chin, Wellington (Department: 2664)

Multiplex communications

Communication techniques for information carried in plural...

Combining or distributing information via time channels

C370S517000, C375S354000, C348S423100

Reexamination Certificate

active

06359910

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a multiplexed data producing apparatus, an encoded data reproducing apparatus, a clock conversion apparatus, an encoded data recording medium, an encoded data transmission medium, a multiplexed data producing method, an encoded data reproducing method, and a clock conversion method More particularly, the present invention relates to production of multiplexed data and synchronization/reproduction of encoded data when digital video, audio, or digital data is multiplexed to be transmitted or to be stored.
BACKGROUND OF THE INVENTION
Recently, with progresses of digitization of data and compression technique, applications of digital images and digital sounds have been developed in broadcasting, CATV or the like. Merits of using digitized data in broadcasting are as follows. i) Since various data including video, sounds, characters or the like may be handled collectedly, integration of services can be provided. ii) By utilizing compression technique in transmitting/receiving data, a great deal of broadcasting of high quality can be performed utilizing a limited transmission bandwidth. iii) Uniform services can be provided using an error correcting technique. iv) High techniques may be utilized with ease as an encryption technique for limited receive.
Packetization is generally employed for transmitting/receiving digitized data or compressed/encoded data. A packet represents an unit of data with entire data divided into a given size. Transmitting/receiving data as a packet allows high efficiency and precision in data communications. For example, in the case of performing exchange of packets in a computer network, respective separate packets are sent to transfer destination at varied timings through a network and reconstructed into original data in the transfer destination, so that information as to the transfer destination, transmission origin or order of packets is added to respective packets.
In the case of handling digital data, use of a packetization technique allows various data such as video, sounds, and character information-additional information to be packetized and combined to make multiplexed data, which is transmitted/received as a transport stream (TS) for transmission. Accordingly, both the compression technique and a multiplexing method of data are important in transmitting the data.
International standards of the multiplexing method of data includes MPEG
2
(ISO/IEC 13818-1: Information technology-Generic coding of moving pictures and associated audio: Systems”, 1996.4). A description is given of production of multiplexed data according to the MPEG
2
standard and reproduction of the produced multiplexed data in the prior art.
FIGS.
19
(
a
) to
19
(
c
) and
20
(
a
) to
20
(
e
) are diagrams for explaining multiplexed data which is produced according to the MPEG
2
in the prior art, wherein FIG.
19
(
a
) to
19
(
c
) illustrate TS for use in transmission of digitized data and FIG.
20
(
a
) to
20
(
e
) illustrate packets constituting TS. A description is given of production of multiplexed data in the prior art with reference to FIGS.
19
(
a
) to
19
(
c
) and FIGS.
20
(
a
) to
20
(
e
).
Video data is compressed/encoded for each frame corresponding to a screen and audio data is compressed/encoded every given sample number such as
1024
, and one or a plurality of frames are collected into packets which are refereed to as PES (packetized elementary stream) packets. It should be noted that the given sample number of the audio data represents a frame in the MPEG. FIG.
20
(
a
) to
20
(
c
) schematically show formats of TS packets as packets constituting PES. The PES packet includes a header, and the header includes types of subsequent data areas, i.e., a stream ID indicating video data, audio data or the other data, DTS (decoding time stamp) and PTS (presentation time stamp) as time information for synchronization video with audio to be reproduced. The PES packet is divided into a plurality of TS packets of
188
byte length, respectively, to be transmitted or to be stored.
FIGS.
20
(
d
) and
20
(
e
) schematically illustrate formats of TS packets comprising an adaptation field in which various information is included. As shown in figures, the adaptation field includes PCR (program clock reference). The PCR has a time base for encoding data such as video data or audio data, and has the same time base as PTS and DTS.
FIGS.
19
(
a
) to
19
(
c
) schematically show formats of TS packets The TS packets have numbers inherent in packets, respectively, which are called PIDs (packet identifiers). For example, the same PES packet has the same PID. The TS packets comprise a header, an adaptation field or data part subsequent to the header as shown in FIG.
19
(
b
). The PID of the TS packet is given as a part of the header as shown in FIG.
19
(
c
).
In FIGS.
19
(
a
) to
19
(
c
), a data region of the TS packet may include information as to program selection which is called PSI (program specific information) other than the PES. In the PSI, a number of a program and the PID of the TS packet including video data PES, audio data PES and data PES packets are described. Multiplexed data of a specific program is decoded and reproduced to obtain original images, referring to the PSI.
According to the prior art, the PES packet or the TS packet is produced by adding various information to various data of video data or audio data, resulting in a TS, which is recorded and stored or transmitted.
A description is given of a prior art multiplexed data reproducing apparatus wherein data multiplexed in the MPEG
2
data multiplexing system is decoded/reproduced.
FIG. 21
is a block diagram illustrating the prior art reproducing apparatus. In the figure, a separating means
2101
is for separating required portion from multiplexed data for each packet, comprising a first buffer
2111
and a CPU
2112
. A control means
2102
is for controlling of decoding, comprising a second buffer
2121
and a CPU
2122
A video decoder
2105
is for decoding video data. An audio decoder
2106
is for decoding audio data.
FIG. 22
is a flowchart illustrating a procedure of control of the control means
2102
. A description is given of an operation of the prior art MPEG
2
multiplexed data reproducing apparatus constructed above.
As shown in
FIG. 21
, multiplexed data is input from a recording medium
2107
or a transmission medium
2108
to the buffer
2111
, the multiplexed data being stored temporarily therein. The CPU
2112
extracts video PES and audio PES corresponding to a desired program number based on a correspondence between a program and a PID which is obtained from separated/extracted PSI and outputs the video PES and the audio PES to a video decoder
2105
and an audio decoder
2106
, respectively.
Each decoder performs decoding processing, directed by the control means
2102
.
FIG. 22
is a flowchart illustrating a processing procedure of control of the control means
2102
. A description is given of control procedure of the control means
2102
, following a flow in FIG.
22
. In step
2201
, an STC (system time clock) is obtained as a time base of the decoding apparatus on the basis of PCR in the TS packet. By obtaining the STC, a time base of reproducing apparatus matches a time base of an encoding apparatus. In step
2202
, the video decoder
2105
performs decoding to obtain PTS or DTS. Similarly in step
2203
, the audio decoder
2106
performs decoding to obtain DTS.
In step
2204
, it is decided that whether the video decoder
2105
has started decoding or not and whether the PTS or the DTS which is obtained in step
2202
matches the STC. When it is decided that the video decoder
2105
has not started processing and the PTS or the DTS matches the STC, step
2206
is performed and the video decoder
2105
starts decoding. Similarly, in step
2205
, it is decided whether the audio decoder
2106
has started decoding or not and whether the DTS which is obtained in step
2203
matches the STC or not. When it is decided th

Affiliated with

Also associated with

Rating

Clock conversion apparatus and method does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Clock conversion apparatus and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Clock conversion apparatus and method will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2852394