Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1999-11-17
2004-03-23
Ton, Dang (Department: 2666)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S389000, C370S394000, C370S474000, C370S476000, C370S509000, C709S232000, C709S250000, C710S030000, C710S052000, C710S305000, C711S171000, C711S172000, C711S173000, C725S134000, C725S142000
Reexamination Certificate
active
06711181
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of communicating packetized data between network node devices. More particularly, the present invention relates to the field of processing packetized data by parsing isochronously received data packets to facilitate data reconstruction operations.
BACKGROUND OF THE INVENTION
International standard IEEE 1394-1995 , “IEEE 1394-1995 Standard For A High Performance Serial Bus,” defines an economical, scalable, high-speed serial bus architecture. This standard provides a universal input/output connection for interconnecting digital devices including, for example, audio-visual equipment and personal computers.
The IEEE 1394-1995 standard defines a peer-to-peer network architecture characterized by point-to-point signaling. A network implemented in accordance with the IEEE 139-1995 standard comprises a plurality of nodes, where each node includes one or more ports. Ports may be linked together via standardized cabling, subject to a restriction that disallows closed loops. In terms of physical topology, the IEEE 1394-1995 standard provides for a non-cyclic network having multiple ports and finite branches.
The IEEE 1394-1995 standard supports both asynchronous and isochronous information transfers. Asynchronous transfers are operations that communicate data from a source node to a destination node and take place as soon as permitted after initiation. Asynchronous transfer operations do not provide a mechanism for maintaining temporal relationships within an information stream between successive data transfers. An example of an application appropriate for asynchronous data transfer is communication of a still image or text document. Control commands can also be sent asynchronously.
Isochronous transfers provide information delivery characterized by predictable, bounded latency; guaranteed bandwidth; and on-time data reception. Time intervals between particular events have essentially the same duration at both the transmitting and receiving applications. Isochronous transfer is particularly advantageous in real-time multimedia applications, such as the real-time transfer of digital audio and video data between a digital video camera and a digital television.
The IEEE 1394-1995 standard defines a structured packet into which information is encapsulated for isochronous transfer upon the bus.
FIG. 1
is a block diagram showing an IEEE 1394-1995 isochronous packet
10
. The IEEE 1394-1995 isochronous packet
10
includes a header field
12
; a header cyclic redundancy check (CRC) field
14
; a payload data field
16
; and a payload data CRC field
18
.
The IEEE 1394-1995 standard does not specify particular formats for the contents of the payload data field
16
. Rather, the organization of payload data in accordance with a particular format and the interpretation of payload data field contents are functions of the transmitting and receiving applications, respectively. In order to facilitate interoperability between a wide range of digital devices, payload data fields
16
should encapsulate data in accordance with a standardized format. One such format that has gained wide acceptance is the Common Isochronous Protocol (CIP).
FIG. 2
is a block diagram showing a CIP packet
20
. The CIP packet
20
includes a CIP header field
22
and a CIP data field
28
. The CIP header field
22
spans a first and a second CIP header quadlet
24
,
26
(i.e., 8 bytes total), while the CIP data field
28
spans 480 bytes. The CIP header field
22
stores source node identification and timing information, plus parameters that define manners in which the information contained in the CIP data field
28
may be interpreted.
A device that receives a stream of IEEE 1394-1995 isochronous packets
10
typically stores the contents of each such packet's payload data field
16
in a receive buffer. Thus, when payload data fields
16
contain CIP packets
20
, a first receive buffer contains a sequence of CIP packets
20
. Once the first receive buffer is full, the receiving device stores subsequent CIP packets
20
in a second receive buffer. Hardware and/or software concurrently processes the CIP packet sequence in the first receive buffer to reconstruct data contained therein in accordance with a format expected by an application program. For example, software may process CIP packet sequences by extracting video data and generating a complete video frame in accordance with a standard format such as Digital Video (DV). A DV frame comprises 120 kilobytes of compressed digital audio and video data, organized as a set of Data in Frame (DIF) sequences. Once constructed, the DV frame may be delivered to an application program for decompression and playback.
Due to timing and data availability considerations, the CIP data field
28
within a particular CIP packet
20
may not contain any information. That is, some CIP packets
20
may contain CIP header information only, being empty in terms of data content. Processing sequential CIP packets
20
under the assumption that data immediately follows CIP header information may therefore produce data reconstruction errors.
The generation of a complete DV frame occasionally requires data from more than one receive buffer. Moreover, the first receive buffer occasionally contains data forming an incomplete DV frame, followed by some or all data necessary to generate a first complete DV frame. Some application programs are incapable of accepting an incomplete DV frame. Hence, processing CIP packets
20
under the assumption that 1) a full DV frame can be generated using a single receive buffer; or 2) a first received CIP packet
20
may be used to begin constructing a first complete DV frame may also produce data reconstruction errors.
SUMMARY OF THE INVENTION
The present invention comprises a system and method for parsing the content of packets received from a source node within a networked node environment. The networked node environment preferably comprises an IEEE 1394-1995 serial bus network that includes the source node and at least one destination node. The source node serves as a data transmission unit that transfers a stream of IEEE 1394-1995 isochronous packets
10
to the data reception unit. Each IEEE 1394-1995 packet
10
contains a CIP packet
20
. The data reception unit parses the CIP packets
20
, and reconstructs data obtained therefrom in accordance with a predetermined format. The source node serves may be, for example, a digital camcorder, a digital videocassette recorder, or a computer system. The destination node is preferably a computer system. The destination node could be essentially any device or system capable of processing a received information stream in accordance with the present invention.
Within the computer system, an IEEE 1394-1995 interface unit receives the stream of IEEE 1394-1995 packets
10
, and transfers the CIP packets
20
contained therein to a first isochronous receive buffer. Upon filling the first isochronous receive buffer, the interface unit begins filling a second isochronous receive buffer, and so on. After the first isochronous receive buffer is full, a parsing state machine locates a CIP header field
22
within a first CIP packet
20
in the first isochronous receive buffer. The parsing state machine determines whether the first CIP header field
22
is immediately followed by a CIP header field
22
within a second CIP packet
20
. If so, the first CIP packet
20
is empty. The parsing state machine then determines whether the second CIP packet
20
is empty, and so on.
Upon finding a CIP header field
22
that is immediately followed by a CIP data field
28
, the parsing state machine transfers DV data within the CIP data field
28
to a user buffer. The parsing state machine transfers CIP data field contents to the user buffer only after finding a non-empty CIP packet
20
that corresponds to the beginning of a DV frame. After transferring DV data to the user buffer, the parsing state machine considers subsequent CIP packets
20
within the first is
Lym Kevin
Shima Hisato
Xue Xin
Haverstock & Owens LLP
Hom Shick
Ton Dang
LandOfFree
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