Multiplex communications – Communication techniques for information carried in plural... – Assembly or disassembly of messages having address headers
Reexamination Certificate
1998-07-28
2003-09-09
Kizou, Hassan (Department: 2662)
Multiplex communications
Communication techniques for information carried in plural...
Assembly or disassembly of messages having address headers
C370S538000
Reexamination Certificate
active
06618396
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a data transmitting device, a data receiving device, and a data recording device and, more particularly to an device which transmits, receives, or records output data of an MPEG (moving picture expert group) 2 encoder or data of an MPEG2 program stream recorded in a recording medium such as an optical disk, through a communication medium (interface) such an IEEE1394 system.
BACKGROUND OF THE INVENTION
In recent years, attention has been focused on the IEEE1394 system as a serial transmission system for data.
The IEEE1394 system uses any of 100 Mbps, 200 Mbps, and 400 Mbps as a base rate of data transmission with a cycle time of 125 &mgr;s (microsecond).
Also, the IEEE1394 system defines two communication methods, namely, an isochronous transfer (synchronous communication) and an asynchronous transfer. In the isochronous transfer, data is transmitted immediately in response to a transmission request, while in the asynchronous transfer, some delay may sometimes occur between generation of a transmission request and data transmission.
The isochronous transfer is a communication method for use by data transmission which must be made in real time, as is typical of transmission of AV (Audio Video) data. In the isochronous transfer, prior to the start of data transmission, a band required for data transmission is obtained. Then, with this band, data of at least one packet is transmitted once in one cycle (125 &mgr;s), which ensures that data transmission is made in real time.
On the other hand, the asynchronous transfer is a communication method for use by data transmission which need not be made in real time, as in the case of transmission of computer data such as commands or still picture data. It is assumed that this is identical to a transmission system such as a conventional SCSI (small computer system interface).
Currently, for transmission of the AV data using the isochronous transfer, a method of transmitting data for digital VCR (Video Cassette Recorder), a method of transmitting MPEG2 transport stream data, and so forth are defined.
Now, a brief description is given of a communication method on a network N by the use of an interface according to the IEEE1394 (hereinafter referred to as 1394I/F).
FIG.
36
(
a
) schematically shows a network to which three terminals are connected through the 1394I/F. Suppose that terminals A, B and C are a digital video camcoder (DVC), a personal computer for outputting the MPEG2 transport stream (TS) as image data, and a receiving device for image data, respectively. Also suppose that the terminal A is a main terminal for outputting cycle start packet per 125 &mgr;s toward the network N, and allocating a frequency band for data transmission to each terminal.
In the 1384I/F, time for the isochronous transfer and time for asynchronous transfer are allocated for one cycle. Of the one cycle, 80% time period is used for the isochronous transfer, and the remaining 20% time period is used for the asynchronous transfer. Each terminal performs data transmission by the isochronous transfer for data which must be transmitted in real time, and performs data transmission by the asynchronous transfer for data which need not be transmitted in real time.
Initially, each of the terminals A-C declares a frequency band required for data transmission to the main terminal A, and requests permission for use of the band. If permitted, each terminal uses the band for data transmission, whereas if not permitted, it tries to request permission for use of reduced band. When the permission is granted, each terminal can transmit packet data by the isochronous transfer at least once in one cycle when it is necessary to perform the isochronous transfer.
Hereinafter, description is given of a case where the terminals A and B perform data transmission by the isochronous transfer, and the terminal C performs data transmission by the asynchronous transfer, with reference to FIG.
36
(
b
).
Referring to FIG.
36
(
b
), the main terminal A outputs cycle start packets St
1
, St
2
, St
3
, . . . , each indicating a head of each cycle in each cycle, and outputs isochronous packets Aiso
1
, Aiso
2
, Aiso
3
, . . . in each cycle.
The terminal B outputs isochronous packets Biso
1
, Biso
2
, Biso
3
, . . . , in each cycle.
The terminal C outputs an asynchronous packet Casyn
1
, subsequently to the isochronous packets Aiso
1
, and Biso
1
, in a cycle between the cycle start packets St
1
and St
2
.
In a case where plural terminals output asynchronous packets, priority of the asynchronous packets is established among them in such a manner that priority decreases in the order in which transmission requests of the corresponding terminals are sent to the main terminal. In this case, asynchronous packets which have not been transmitted in one cycle will be transmitted in a subsequent cycle.
Meanwhile, in DVD (digital versatile disk)-Video standard, a method of recording compressively coded video data or audio data in a DVD disk as a recording medium is defined.
Assume that compressively coded video data or audio data is read from the recording medium such as the DVD, and AV decoding is performed thereto. In this case, in general, data is read from the recording medium at a rotation rate higher than a rotation rate corresponding to normal data processing rate, and data is read intermittently.
As shown in
FIG. 37
, a reproducing device
10
such as a DVD player, includes a buffer
12
at a previous stage of an AV data decoder
13
, for storing read data therein to buffer difference between a data readout rate and a data processing rate. In
FIG. 37
, reference numeral
11
designates an optical head for reading data from the DVD disk
1
, and reference numeral
14
designates a display such as TV (Television Set) which displays image data or outputs audio data on the basis of an output of the AV data decoder
13
.
In the DVD player thus constructed, data transfer from the recording medium
1
to the buffer
12
is controlled according to amount of data stored in the buffer
12
. In response to a request Re from the AV data decoder
13
, data Da is then transferred from the buffer
12
to the AV data decoder
13
.
Here, assume that a digital interface (I/F)
15
is added to the DVD player as shown in FIG.
38
.
At a transmitting end, a transmitting device
10
transfers data from the recording medium
10
a
to the buffer
12
, and then outputs data to the digital interface
15
.
Meanwhile, at a receiving end, a receiving device
20
receives data through a digital interface
21
, and then an AV data decoder
22
decodes received data and outputs decoded data to the TV or the like.
In this case, since data is output from the buffer
12
in response to a request Rq
2
from the AV data decoder
22
of the receiving device
20
, the request Rq
2
must be transmitted through the digital interfaces
21
and
15
at the receiving end and the transmitting end, respectively.
Besides, in another case where plural devices receives data, since operations of the corresponding AV data decoders might differ from each other, it is required that a transmitting device at the transmitting end output data in response to requests from respective receiving devices at the receiving end. Therefore, a transmitting device at the transmitting end must read data from a recording medium at a very high rate.
Data recorded in the DVD is data which takes an MPEG2 program stream format (hereinafter referred to as MEPEG2-PS data). In order to transmit the MEPEG2-PS data through the 1394I/F as the digital interface
15
in FIG.
38
(
a
), that is, to transmit it according to a transmitting method of the conventional MPEG2 transport stream format data (hereinafter referred to as MPEG2-TS data), it is required that the MEPEG2-PS data be converted into the MPEG2-TS data.
Hereinbelow, description is given of problems associated with transmission of the MEPEG2-PS data recorded in the DVD through the 13941/F from the transmitting end to the receiving end with reference to FIG.
Kitaura Hiromu
Kondo Satoshi
Maeda Akiyoshi
Mitui Yoshitaka
Takeda Hidetoshi
Kizou Hassan
Tsegaye Saba
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