Transmitting system and transmitting apparatus

Details Transmitting system and transmitting apparatus Transmitting system and transmitting apparatus

1999-01-22

2003-06-10

Tran, Thai (Department: 2615)

Motion video signal processing for recording or reproducing

Local trick play processing

With randomly accessible medium

C348S423100

Reexamination Certificate

active

06577813

ABSTRACT:

FIELD OF THE INVENTION
The present, invention relates to a transmitting system, apparatus, a recording and reproducing apparatus, and a recording apparatus, for transmitting/recording a stream comprising plural packets according to MPEG (Moving Picture Experts Group)2.
BACKGROUND OF THF INVENTION
It has been well known that a TS (transport stream) according to MPEG2 i , a stream comprising compressed digital video, compressed digital audio, and the like. The TS is used in digital broadcasting, and contains multiplexed plural programs. Hereinafter, “TS” always refers to the TS according to MPEG2 (MPEG2 TS). MPEG2 is defined in ITU-T H.222.0 (ISO/IEC 13818-1) “Generic Coding of Moving Pictures And Associated Audio Information”.
FIGS.
3
(
a
) and
3
(
b
) show the TS. Shown in FIG.
3
(
a
) are TS packets. The TS comprises a set of TS packets which are fixed in length (188 byte). The TS packets each includes plural fields, i.e., 8-bit Sync Byte, a 13-bit PID (Packet identifier), a 4-bit CC (Continuity Counter), an AF (Adaptation Field) (0-184 bytes), and a payload (0-184 bytes), and so forth. Information irrelevant to the present invention is not discussed herein. Information in respective fields of the TS packet will be discussed below.
The Sync Byte (8 bits) is positioned at the head of the TS packet, and is 0x47 (0x: Hexadecimal numeral), which is used for detecting the head of the packet.
The PID (13 bits) is used for identifying payload data. According to plural PIDs, plural programs contained in one TS can be identified PID-0x
1
fff indicates that the corresponding TS racket is an ineffective (null) packet.
The CC (4 bit) increases ore by one among the TS packets of the same PID. In some cases, neighboring TS packets of the same PID take the same CC value. They are called a “Duplicated Packet”. When the Duplicated Packet is transmitted, two TS packets of the same content are sequentially transmitted.
The AF (0-184 bytes) is used for storing additional information.
The Payload (0∝184 bytes) is used for storing actual data, the length of which is determined by the length of the AF.
In addition, the TS contains PCRs (Program Clock References) inserted at regular intervals. The PCR is information which a decoder at a receiving end uses so as to set the value of a reference time STC (System Time Clock) to the value intended by a transmitting end. Therefore, it is required that the PCR arrive at the receiving and at a timing as intended by the transmitting end.
When the TS is used in the digital broadcasting, as shown in FIG.
3
(
b
), an error correction code is some times added after the TS packet. The typical code length of the error correction code is 16 bytes, and the TS packet and the error correction code (204 bytes in total) is transmitted as a unit. In some cases, the error correction code (16 byte) is dummy data.
A description will be given of a prior art transmitting system which transmits the TS described above.
One example of the prior art transmitting system is a system which adopts an adaptive clock system using an ATM (Asynchronous Transfer Mode). This is described in detail in Practical MPEG Text (P218-221), published by Aski Publishing Company
FIG. 8
shows this prior art transmitting system. In
FIG. 8
, reference numerals
81
,
82
,
83
,
821
,
822
, and
823
designate a transmitting apparatus, a receiving apparatus, a transmission line, receiving means, storage means, and PLL (phase-locked loop), respectively. The MPEG2 TS is input to the transmitting apparatus
81
, the transmitting means
811
which transmits the input data to the transmission line
83
. The transmission line
83
is an ATM network. When transmitting input data on the transmission line
83
, some variance of delay occurs. The receiving means
821
of the receiving apparatus
82
receives data on the transmission line
83
. The receiving means
821
stores the received data in the storage means
822
. The storage means
822
is an FIFO (first-in, first-out) memory, and outputs the input data in synchronization with the output clock. The PLL
823
adjusts the speed of the output clock so that the amount of data stored in the storage means
822
is kept constant. To be specific, when the amount of stored data is larger than a predetermined value, the PLL
823
makes the speed of the output clock higher, while when the amount is smaller than the predetermined value, the PLL
823
makes the speed lower.
As described above, in the prior art transmitting system, although some variance of delay occurs on the transmission line
83
, the PLL
823
and the storage means
822
of the receiving apparatus
82
make it possible to decode the data correctly
However, in the prior art method, all the packets (programs) contained in the input data are transmitted even for the case where only a part of them needs to be transmitted. This makes it impossible to realize effective use of the band of the transmission line.
The similar problem occurs in the recording and reproducing apparatus.
SUMMARY OF THF INVENTION:
It is an object of the present invention to provide a transmitting system which is capable of transmitting data in such a manner that data to be transmitted on a transmission line can be reduced and a stream can be reproduced correctly when it is received.
It is another object of the present invention to provide a recording and reproducing apparatus which is capable of recording and reproducing data in such a manner that data to by recorded in a recording medium can be reduced and the stream ran be reproduced correctly when it is reproduced.
Other objects and advantages of the invention will become apparent from the detailed description that follows. The detailed description and specific embodiments described are provided only for illustration since various additions and modifications within the spirit and scope of the invention will be apparent to those skill in the art from the detailed description.
According to a first aspect of the present invention, in a transmitting system which comprises a transmission line, a transmitting apparatus connected to the transmission line, and a receiving apparatus connected to the transmission line, and transmits data between the transmitting apparatus and the receiving apparatus, the transmitting apparatus comprises: packet compressing means which receives input data comprising plural packers having identifiers as an input, identifies packets to be discarded and effective packets according to the identifiers, and outputs compression information indicating the number of continuously discarded packets and the effective packets to the transmission line, and the receiving apparatus comprises: packet restoring means which receives the compression information and the effective packets which have been output from the transmitting apparatus generates ineffective packets which are as many as the discarded packets, and outputs the ineffective packets and the effective packets. Therefore, it is possible to realize a transmitting system which is capable of reducing data to be transmitted on the transmission line and reproducing the stream correctly when it is received.
According to a second aspect of the present invention, in the transmitting system of the first aspect, the transmitting apparatus further comprises: identifying means which receives, a fixed clock and the input data synchronized with the fixed clock as inputs, identifies the packets to be discarded and the effective packets according to the identifiers, and outputs identification signals each indicating that a packet is either the effective, packet or the packet to be discarded; and counting means for counting the number of continuously discarded packets from the identification signals.
According to a third aspect of the present invention, in the transmitting system of the second aspect, the input data to the transmitting apparatus is a transport stream according to MPEG2, and the identification signals each indicates that the packet is either the packet to be discarded or the effective packet accord

Affiliated with

Also associated with

Rating

Transmitting system and transmitting apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.

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

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3088002