Title: Channel protocol for IEEE 1394 data transmission
Abstract: A system for transmitting and receiving data formatted in IEEE 1394 standard between devices using a same IEEE 1394 broadcast channel includes a CPU interfaced to a bus, a first 1394 interface connected to the bus via a first physical and link layers, and a second 1394 interface connected to the bus via a second physical and link layer. The CPU is configured for 1) receiving data from the bus, prefixing a header to the received data, and retransmitting the received data with the prefixed header onto the bus; and 2) receiving data prefixed with a header, interpreting the header to identify which of the first or second interfaces should receive the data, and transmitting the data over the bus to the identified 1394 interface.
Patent Number: 7,013,354 Issued on 03/14/2006 to Beck, et al.
| Inventors:
|
Beck; Gregory F. (Laguna Hills, CA);
Zhou; Wei (Irvine, CA);
Slick; Royce Earle (Mission Viejo, CA)
|
| Assignee:
|
Canon Kabushiki Kaisha (Tokyo, JP)
|
| Appl. No.:
|
166488 |
| Filed:
|
October 5, 1998 |
| Current U.S. Class: |
710/105; 710/100; 710/105; 710/305; 710/315; 370/351 |
| Current Intern'l Class: |
F06F 13/42 (20060101) |
| Field of Search: |
710/105,100,106,305,306,314,313,319,62,63,64,65, 72,315,379
370/351,389,400
326/86
361/785
709/321
|
References Cited [Referenced By]
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Other References
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|
Primary Examiner: Auve; Glenn A.
Assistant Examiner: King; Justin
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper & Scinto
Claims
What is claimed is:
1. A system for transmitting and receiving data packets formatted in IEEE 1394
standard, comprising:
a controller interfaced to an internal bus;
a first interface connected to the bus;
a first device using a broadcast channel and connected to the first interface:
a second interface connected to the bus; and
a second device using the broadcast channel and connected to the second interface,
wherein the controller is configured for 1) receiving data transmitted from one
of the first and second devices via the bus, attaching an identification (ID) header
to the received data, the ID header including identification information corresponding
to a recipient device determined based at least in part on which of the first and
second devices transmitted the data, and retransmitting the received data with
the ID header onto the bus; and 2) receiving data with the ID header attached thereto,
interpreting the ID header to identify which of the first or second interfaces
should receive the data, and transmitting the data over the bus to the identified
interface,
wherein the ID header is other than a 1394 header formatted in IEEE 1394 standard
and contains information about the data, and
wherein the 1394 header is built based on information contained in the ID header.
2. A system according to claim 1, wherein the first device is a first digital
video camera having a fixed broadcast channel and which transmits/receives digital
video data isochronously through the first interface and the second device is a
second digital video camera having the same fixed broadcast channel as the first
digital video camera and which transmits/receives digital video data isochronously
through the second interface.
3. A system according to claim 2, wherein the digital video data output from
either the first or second video camera includes 1394 header information, data,
and header check and data check information, and wherein a link layer for each
respective interface removes the 1394 header and header check and data check information
prior to transmitting the data over the bus to the controller.
4. A system according to claim 2, further comprising a network controller for
accessing a local area network and for transmitting data with the ID header, wherein
the network controller receives the data and the ID header, attaches a network
header to the data and repackages the data with the ID header and network header
into a network data packet and, upon receiving access to the local area network,
transmits the network packet over the local area network to a receiving side network
controller based on the attached network header.
5. A system according to claim 4, wherein received network data packets are unpackaged,
network headers are removed, and the ID header is interpreted to identify which
interface should receive the data.
6. A system according to claim 5, wherein a link layer of the identified interface
attaches 1394 header and data information to the data and transmits the data through
a physical layer to the identified interface in an isochronous manner and where,
in the case the identified interface connects to the first digital video camera,
the identified interface outputs the data in the isochronous manner to the first
digital video camera and, in the case the identified interface connects to the
second digital video camera, the identified interface outputs the data in the isochronous
manner to the second digital video camera.
7. A system according to claim 6, further comprising a monitor for displaying
analog video data output from either the first or second digital video camera.
8. A system according to claim 1, wherein the ID header identifies the type of
data, the data recipient and amount of data.
9. A system according to claim 1, further comprising a network interface to a
local area network.
10. A system according to claim 1, wherein the bus is a PCI bus.
11. A system for transmitting and receiving data packets formatted in IEEE 1394
standard comprising:
a controller interfaced to an internal bus;
a first interface connected to the bus;
a first device using a broadcast channel and connected to the first interface;
a second interface connected to the bus; and
a second device using the broadcast channel and connected to the second interface,
wherein the controller is configured for receiving data transmitted over the
bus and routing the data to either the first or second interface based on the received
data using an identification (ID) header other than a 1394 header, the ID header
containing information about the data, and identification information corresponding
to one of the first and second devices determined based at least in part on a transmitting
device, and
wherein the 1394 header is built based on information contained in the ID header.
12. A system according to claim 11, wherein the first device is a first digital
video camera having a fixed broadcast channel and which transmits/receives digital
video data isochronously through the first interface and the second device is a
second digital video camera having the same fixed broadcast channel as the first
digital video camera and which transmits/receives digital video data isochronously
through the second interface.
13. A system according to claim 12, wherein the digital video data output from
either the first or second video camera includes 1394 header information, data,
and header and data check information, and wherein a link layer for each respective
interface removes the 1394 header and header data check information prior to transmitting
the data over the bus to the controller.
14. A system according to claim 12, further comprising a network controller for
accessing a local area network and for transmitting data with the ID header, wherein
the network controller receives the data and the ID header, attaches a network
header to the data and repackages the data with the ID header and network header
into a network data packet and, upon receiving access to the local area network,
transmits the network packet over the local area network to a receiving side network
controller based on the attached network header, wherein the ID header is other
than a 1394 header formatted in IEEE 1394 standard.
15. A system according to claim 14, wherein received network data packets are
unpackaged, network headers are removed, and the ID header is interpreted to identify
which interface should receive the data.
16. A system according to claim 15, wherein a link layer of the identified interface
attaches a 1394 header and data information to the data and transmits the data
through a physical layer to the identified interface in an isochronous manner and
where, in the case the identified interface connects to the first digital video
camera, the identified interface outputs the data isochronously to the first digital
video camera and, in the case the identified interface connects to the second digital
video camera, the identified interface outputs the data isochronously to the second
digital video camera.
17. A system according to claim 16, further comprising a monitor for displaying
digital video data output from either the first or second digital video camera.
18. A system according to claim 11, further comprising a network interface to
a local area network.
19. A system according to claim 11, wherein the bus is a PCI bus.
20. A system for transmitting and receiving data packets formatted in IEEE 1394
standard, comprising:
a controller interfaced to an internal bus;
a first interface connected to the bus;
a first device using a broadcast channel and connected to the first interface
a second interface connected to the bus; and
a second device using the broadcast channel and connected to the second interface;
wherein the controller is configured for 1) receiving data transmitted from one
of the first and second devices via the bus, attaching an identification (ID) header
and a subheader to the received data, the ID header including identification information
corresponding to a recipient device determined based at least in part on which
of the first and second devices transmitted the data, and retransmitting the received
data with the ID header and subheader onto the bus; and 2) receiving data with
ID header and subheader attached thereto, interpreting the ID header and subheader
to identify which of the first or second interfaces should receive the data and
which broadcast channel in the identified interface should receive the data, and
transmitting the data over the bus to the identified interface,
wherein the ID header is other than a 1394 header formatted in IEEE 1394 standard
and contains information about the data, and
wherein the 1394 is built based on information contained in the ID header.
21. A system according to claim 20, wherein the first device is a first digital
video camera having a fixed broadcast channel and which transmits/receives digital
video data isochronously through the first interface and the second device is a
second digital video camera having the same fixed broadcast channel as the first
digital video camera and which transmits/receives digital video data isochronously
through the second interface.
22. A system according to claim 21, wherein the digital video data output from
either the first or second video camera includes 1394 header information, data,
and header check and data check information and wherein a link layer for each respective
interface removes the 1394 header and header check and data check information prior
to transmitting the data over the bus to the controller.
23. A system according to claim 21, further comprising a network controller for
accessing a local area network and for transmitting data with the ID header and
subheader, wherein the network controller receives the data and the ID header and
subheader, attaches a network header to the data and repackages the data with the
ID header and subheader and network header into a network data packet and, upon
receiving access to the local area network, transmits the network packet over the
local area network to a receiving side network controller based on the attached
network header.
24. A system according to claim 23, wherein received network data packets are
unpackaged, network headers are removed, and the ID header and subheader are interpreted
to identify which interface and channel in that interface should receive the data.
25. A system according to claim 24, wherein a link layer of the identified interface
attaches a 1394 header and data information to the data and transmits the data
through a physical layer to the identified interface in an isochronous manner and
where, in the case the identified interface connects to the first digital video
camera, the identified interface outputs the data in the isochronous manner to
the first digital video camera and, in the case the identified interface connects
to the second digital video camera, the identified interface outputs the data in
the isochronous manner to the second digital video camera.
26. A system according to claim 25, further comprising a monitor for displaying
analog video data output from either the first or second digital video camera.
27. A system according to claim 20, further comprising a network interface to
a local area network.
28. A system according to claim 20, wherein the bus is a PCI bus.
29. A method for use in a system for transmitting and receiving data packets
formatted in IEEE 1394 standard, the method comprising steps of:
receiving data from an internal bus, which is connected to a first interface
and a second interface, wherein a first device is connected to the first interface
and uses a broadcast channel and a second device is connected to the second interface
and uses the broadcast channel,
attaching an identification (ID) header to the received data;
retransmitting the received data with the ID header onto the bus;
receiving data with the ID header attached thereto;
interpreting the ID header to identify which of the first or second interfaces
should receive the data; and
transmitting the data over the bus to the identified interface, wherein the ID
header is other than a 1394 header formatted in IEEE 1394 standard and contains
information about the data and identification information corresponding to a recipient
device determined based at least in part on a transmitting device; and wherein
the 1394 header is built based on information contained in the ID header.
30. A method for use in a system for transmitting and receiving data packets
formatted in IEEE 1394 standard, the method comprising steps of:
receiving data over an internal bus, which is connected to a first interface
and a second interface, wherein a first device is connected to the first interface
and uses a broadcast channel and a second device is connected to the second interface
and uses the broadcast channel; and
routing the data to either the first or second interface based on the received
data using an identification (ID) header other than a 1394 header, the ID header
containing information about the data and identification information corresponding
to one of the first and second device determined based at least in part on a transmitting
device, and wherein the 1394 header is built based on information contained in
the ID header.
31. A method for use in a system for transmitting and receiving data packets
formatted in IEEE 1394 standard, the method comprising the steps of:
receiving data from an internal bus, which is connected to a first interface
and a second interfaces, wherein a first device is connected to the first interface
and uses a broadcast channel and a second device is connected to the second interface
and uses the broadcast channel,
attaching an identification (ID) header and a subheader to the received data;
retransmitting the received data with the ID header and subheader onto the bus;
receiving data with the ID header and subheader attached thereto;
interpreting the ID header and subheader to identify which of the first or second
interfaces should receive the data and which broadcast channel in the identified
interface should receive the data; and
transmitting the data over the bus to the identified interface, wherein the ID
header is other than a 1394 header formatted in IEEE 1394 standard and contains
information about the data and identification information corresponding to a recipient
device determined based at least in part on a transmitting device; and wherein
the 1394 header is built based on information contained in the ID header.
32. A system for transmitting and receiving data packets formatted in IEEE 1394
standard, comprising:
a controlling means interfaced to a communication means;
a first interface means connected to the communication means;
a first device using a broadcast channel and connected to the first interface
means;
a second interface means connected to the communication means; and
a second device using the broadcast channel and connected to the second interface
means,
wherein the controlling means is configured for 1) receiving data transmitted
from one of the first and second devices via the communication means, attaching
an identification (ID) header to the received data, the ID header including identification
information corresponding to a recipient device determined based at least in part
on which of the first and second devices transmitted the data, and retransmitting
the received data with the ID header onto the communication means; and 2) receiving
data with the ID header attached thereto, interpreting the ID header to identify
which of the first or second interface means should receive the data, and transmitting
the data over the communication means to the identified interface means,
wherein the ID header is other than a 1394 header formatted in IEEE 1394 standard
and contains information about the data, and
wherein the 1394 header is built based on information contained in the ID header.
33. A system for transmitting and receiving data packets formatted in IEEE 1394
standard, comprising:
a controlling means interfaced to a communication means;
a first interface means connected to the communication means;
a first device using a broadcast channel and connected to the first interface
means;
a second interface means connected to the communication means; and
a second device using a broadcast channel and connected to the second interface
means,
wherein the controlling means is configured for receiving data over the communication
means and routing the data to either the first or second interface means based
on the received data using an identification (ID) header other than a 1394 header,
the ID header containing information about the data and identification information
corresponding to one of the first and second devices determined based at least
in part on a device which transmitted the data,
wherein the 1394 header is built based on information contained in the ID header.
34. A system for transmitting and receiving data packets formatted in IEEE 1394
standard, comprising:
a controlling means interfaced to a communication means;
a first interface means connected to the communication means; and
a first device using a broadcast channel and connected to the first interface
means;
a second interface means connected to the communication means; and
a second device using the broadcast channel and connected to the second interface
means,
wherein the controlling means is configured for 1) receiving data transmitted
from one of the first and second devices via the communication means, attaching
an identification (ID) header and a subheader to the received data, the ID header
including identification information corresponding to a recipient device determined
based at least in part on which of the first and second devices transmitted the
data, and retransmitting the received data with the ID header and subheader onto
the communication means; and 2) receiving data with the ID header and subheader
attached thereto, interpreting the ID header and subheader to identify which of
the first or second interface means should receive the data and which broadcast
channel in the identified interface means should receive the data, and transmitting
the data over the communication means to the identified interface means,
wherein the ID header is other than a 1394 header formatted in IEEE standard
and contains information about the data, and
wherein the 1394 header is built based on information contained in the ID header.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for transmitting and receiving data
over a bus in which the data is formatted in IEEE 1394 standard and in which the
data is sent and received over the same IEEE 1394 channel.
2. Incorporation by Reference
This application incorporates by reference commonly assigned U.S. patent application
Ser. No. 09/166,487, entitled "Digital Video Network Interface" (internal reference
No. MOI-328/360), the disclosure of which is herein incorporated by reference,
as if set forth in full.
3. Description of the Prior Art
The IEEE 1394 standard bus (1394 bus) provides for isochronous transmission of
data packets, which are sent and received every 125 microseconds in correspondence
to one cycle. A maximum of 64 isochronous packets can be sent over the bus per
cycle. As a result, any device that uses the IEEE 1394 standard for isochronous
transmission of data, is assigned an isochronous channel, ranging in value from
0 to
63. The channel is assigned to a specific device until it is
released by that device. In this regard, when the 1394 bus is initialized, a node
identifier is automatically assigned to each device (such as a digital video camera)
that uses the bus as a means of identifying each node.
To achieve isochronous transmission on plural channels, the IEEE 1394 specification
(IEEE 1394-1995) reserves one of the plural nodes connected to the bus so that
it is used for isochronous resource management, a function that is supported by
a software layer (to be discussed in greater detail below). This node is known
as the "Isochronous Resource Manager". The Isochronous Resource Manager manages
the channel numbers used for isochronous transmission, and the time remaining in
each cycle that is usable for isochronous transmission. This available remaining
time to transfer additional isochronous data within each cycle is called channel
bandwidth. The Isochronous Resource Manager reserves the channel bandwidth and
channel numbers (
0-
63) needed by 1394 bus nodes for isochronous transmission.
Upon power-up, each device (node) that needs to transmit data isochronously issues
a request to the Isochronous Resource Manager. In particular, a node designed to
transmit isochronous data must first determine if there is an unused channel and
available bandwidth for that purpose. The node typically makes a request to the
Isochronous Resource Manager to determine if there are isochronous channels available
and bandwidth available, in order to obtain a unique channel and bandwidth allocation.
In the case that two or more nodes desire to use the same channel, the first
node
requesting access to an available channel will be assigned that channel. For example,
if two nodes request access to channel
63, only the node whose request reaches
the Isochronous Resource Manager first will be assigned to channel
63. All
other nodes will be locked out from using channel
63 until the device using
channel
63 releases the channel.
The problem of attempting to use the same channel occurs not only when more than
64 devices are attempting to access the 1394 bus, but can also arise even if only
two or more digital video cameras are being used on the same 1394 bus. That is,
many different digital video cameras are designed to transmit over a single preset
channel number, or "broadcast channel" for transmitting digital video data packets
over the 1394 bus. The "broadcast channel" concept is described in U.S. Pat. No.
5,535,208, entitled "Data Transmission System And Method", Kawakami et al, assigned
to Matsushita. This broadcast channel, as defined by this patent, has in practice
become the first available isochronous channel, or channel
63. However,
because the IEEE 1394 standard does not allow more than one node to use the same
isochronous channel at one time, only one of the digital video cameras is permitted
isochronous bandwidth and use of channel
63 to perform transmission of isochronous
data on the bus. As a result of this conflict, two or more digital video cameras
connected to the same 1394 bus cannot be used in a bi-directional video conferencing
configuration, because at the sending and receiving sides, only one camera will
be able to send data per bus.
Therefore, in any configuration where multiple digital video cameras (which
have adopted the "broadcast channel" concept standard of U.S. Pat. No. 5,535,208)
are attempting to transmit isochronous data on a 1394 bus, only one camera will
be able to send isochronous data and all others will be locked out from sending
isochronous data on the bus.
Although the problems with the assignment of channels have been disclosed
with respect to digital video cameras, it should be understood that the same problem
applies in the case of other IEEE 1394 devices, such as scanners, digital video
disks, compact disks, set-top boxes, computers, or any other devices that wish
to isochronously transmit data on conflicting channels. Also, this problem would
apply in the case that all 64 channels have been already assigned and a new device
is attempting to utilize a channel that has already been assigned.
Heretofore, it has not been possible to send/receive data over the same
1394 bus when more than one device is attempting to use a single broadcast channel,
for example, channel
63, of the 1394 bus. Accordingly, it is desirable to
have a system that permits two or more devices to transmit or receive data using
the same channel over a 1394 bus, so that transmitting data over a local data bus
or a local area network by more than one device using the same broadcast channel
becomes possible.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a network interface which
can interface with a local data bus or local area network and at least two peripheral
devices which share identical IEEE 1394 broadcast channels. The present invention
provides an individual 1394 bus for each device using the network interface together
with its own 1394 link layer.
Thus, according to one aspect of the invention, a system for transmitting and
receiving data formatted in IEEE 1394 standard between devices using a same IEEE
1394 broadcast channel includes a controller interfaced to an internal bus, a first
1394 interface connected to the bus via first physical and link layers, a first
device using a broadcast channel and connected to the first interface, a second
1394 interface connected to the bus, and a second device using the broadcast channel
and connected to the second interface. The controller is configured for 1) receiving
data transmitted from one of the first and second devices via the bus, attaching
an identification (ID) header, which includes identification information corresponding
to a recipient device determined based at least in part on which of the first and
second devices transmitted the data, to the received data and retransmitting the
received data with the ID header onto the bus, and 2) receiving data with the ID
header attached thereto, interpreting the ID header to identify which of the first
or second interfaces should receive the data, and transmitting the data over the
bus to the identified 1394 interface. The ID header, which is other than a 1394
interface. The ID header, which is other than a 1394 header, is used to build the
1394 header based on information contained in the ID header.
According to another aspect of the invention, in a system for transmitting
and receiving data formatted in IEEE 1394 standard between devices using a same
IEEE 1394 broadcast channel, the system includes a controller interfaced to a bus,
a first 1394 interface connected to the bus, a first device using a broadcast channel
and connected to the first interface, a second 1394 interface connected to the
bus, and a second device using the broadcast channel and connected to the second
interface. The controller is configured for receiving data transmitted over the
bus and routing the data to either the first or second 1394 interface based on
the received data using an identification (ID) header other than a 1394 header,
the ID header contains information about the data and identification information
corresponding to one of the first and second devices determined based at least
in part on a transmitting device. The 1394 header is built based on information
contained in the ID header.
In yet another aspect of the invention, the present invention provides a system
for transmitting and receiving data packets formatted in IEEE 1394 standard, the
system includes a controller interfaced to an internal bus, a first device using
a broadcast channel and connected to the first interface, a second interface connected
to the bus, and a second device using the broadcast channel and connected to the
second interface. The controller is configured for 1) receiving data transmitted
from one of the first and second devices via the bus, attaching an identification
(ID) header and a subheader to the recieved data, the ID header including identification
information corresponding to a recipient device determined based at least in part
on which of the first and second devices transmitted the data, and retransmitting
the received data with the ID header and subheader onto the bus, and 2) receiving
data with ID header and subheader attached thereto, interpreting the ID header
and subheader to identify which of the first or second interfaces should receive
the data and which broadcast channel in the identified interface should receive
the data, and transmitting the data over the bus to the identified interface. The
ID header, which is other than a 1394 header formatted in IEEE 1394 standard and
contains information about the data, is used to build the 1394 header based on
information contained in the ID header.
These and other features and advantages according to the present invention
will be more readily understood by reference to the following detailed description
of the preferred embodiment taken in conjunction with the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of an IEEE 1394 network interface implemented in a
bi-directional video conferencing system according to the present invention;
FIG. 2 is a block diagram of the 1394 network interface according to the present invention;
FIG. 3, comprising FIGS. 3A-3D, are a IEEE 1394 formatted isochronous data packet,
an 1394 data field, a modified data packet with routing header and ID information,
and a network packet containing network header information, routing information
and data packet, respectively;
FIG. 4, comprising FIGS. 4A and 4B, is a flowchart depicting the transfer and
receipt of video data in the bi-directional video teleconferencing system according
to the present invention;
FIG. 5 is a 1394 network interface system according to a second embodiment of
the present invention;
FIG. 6 is a modified 1394 formatted data packet containing header with ID and
link layer routing information and a subheader which includes additional channel
routing information; and
FIG. 7 is a block diagram of a 1394 network interface according to the second
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram representing a 1394 network interface for transferring
and receiving data across a local area network from devices which send/receive
data over the same IEEE 1394 broadcast channel. The 1394 network interface according
to the present invention, shown in FIG. 1, is implemented within a bi-directional
video conferencing system.
Shown in FIG. 1 is digital video (DV) camera
1, which may be a Canon
Optura digital video camera or the like. In the present example, DV camera
1
is used for transmitting full motion digital video which includes both audio and
video segments. DV camera
1 includes an IEEE 1394 interface connection.
The IEEE 1394 interface connection is connected to a 1394 network interface
3
via an IEEE 1394 serial cable
2. The IEEE 1394 serial cable
2 carries
packets of digital video data to the 1394 network interface
3. The video
conferencing system shown in FIG. 1 also includes DV camera
4 which, in
the present embodiment, receives full motion digital video data, decodes the data,
and transmits the data in analog form to monitor
5 for audio and for display.
Monitor
5 can be any type of monitor or television having an S-Video NTSC
or other connection for receiving analog audio and video.
DV camera
4 receives digital video in data packets via IEEE 1394 cable
6 from 1394 network interface
3. Preferably, the digital video data
which arrive in data packets are received by network interface
3 from local
area network
7. However, it is possible that DV camera
4 could receive
digital video data locally from DV camera
1. Digital video camera
4
decodes the digital video data packets and outputs the analog audio and video data
to monitor
14. Monitor
14 can be any type of monitor or television
which has an S-Video, NTSC or other connection for receiving analog audio and video data.
Depending on their configuration, DV cameras
1 and
4 can
transmit/receive video data via 1394 network interface
3. 1394 network interface
3 has at least two 1394 interface connections for connecting with each 1394
serial cable connected to DV cameras
1 and
4 and has a network interface
connection which connects to local area network
7.
In order to transmit large volumes of data, which is typically needed for transmitting
digital video data, it is preferable that network
7 is a Gigabit Ethernet
network. In this regard, U.S. patent application Ser. No. 09/166,487, entitled
"Digital Video Network Interface", describes the method and system for interfacing
1394 network interface
3 between digital video cameras and a local area
network, such as a Gigabit Ethernet network. Briefly, as described in that application,
each of network interfaces
3 and
8 include send and receive buffers,
which operate to buffer and translate isochronously-timed data to and from the
asynchronously-timed data of the Gigabit Ethernet. The reader is directed to the
disclosure in that document for further detailed explanation regarding communication
between a 1394 network interface according to the present invention and local area
network
7.
In the present embodiment, 1394 network interface
3 is implemented within
a bi-directional video conferencing system. A transmitting DV camera and the receiving
DV camera are connected at each end of local area network
7. This allows
for simultaneous transmission and reception of audio/video from a local location
to a remote location. As mentioned above, a Gigabit Ethernet network is preferably
employed as local area network
7 since the data transfer rate per channel
is very high, typically in a range of 30 Mbits/sec. As will be discussed below
in greater detail with respect to FIG. 2, 1394 network interface
3 provides
for the transmission and reception of data packets for devices that transmit/receive
over the same IEEE 1394 broadcast channel. In the case where each of DV cameras
1 and
10 are set to transmit using channel
63 and cameras
4 and
11 are set to receive using channel
63, the 1394 network
interface
3 resolves the problem of two devices, in the present case, DV
camera
1 and DV camera
4, attempting to send and receive different
data over the same broadcast channel
63 on the same 1394 bus. As will be
discussed below, two separate 1394 buses are implemented to overcome channel conflicts.
Returning to FIG. 1, 1394 network interface
3 transmits/receives
data packets over local area network
7 to/from 1394 network interface
8.
1394 network interface
8, which is at the remote side of local area network
7, acts in a similar fashion to 1394 network interface
3, and includes
at least two IEEE 1394 interface connections and connects to 1394 serial bus cables
9 and
13. Cable
9 is connected with DV camera
10 which,
in the present example, is a transmitting video camera for transmitting digital
video data over the network through 1394 network interface
8. DV camera
11, in the present example, is used as a receiving camera for receiving
and decoding digital video packets which output from 1394 interface network
8
through IEEE 1394 serial cable
13. After decoding each data packet, DV camera
11 outputs digital video in analog format directly to monitor
14
for viewing.
FIG. 2 is a block diagram depicting the internal hardware components of 1394
network interface
3. (1394 network interface
3 and 1394 network interface
8 are identical in hardware and in software and, therefore, a description
of 1394 network interface
8 will not be presented for the purposes of brevity.)
Shown in FIG. 2 is DV camera
1 which is connected through 1394 cable
2 to 1394 network interface
3. According to the present invention,
1394 network interface
3 can be a stand-alone network card or can reside
within a personal computer or the like. 1394 network interface
3 includes
at least two 1394 interface connections for connecting with each of the DV cameras
1 and
4 and also includes a network interface connection for connecting
to the local area network
7. 1394 network interface
3 receives data
from DV camera
1 through its IEEE 1394 interface into 1394 physical layer
20.
Physical layer
20 is an IEEE 1394 hardware connection which provides
electrical and mechanical interaction with 1394 cable
2. Link layer
21,
which is connected to physical layer
20, is an IEEE 1394 interface link
which receives 1394 formatted data, controls access to the 1394 bus, assigns channels
to nodes using the bus (when, as here, the link layer is the isochronous resource
manager), and verifies accuracy of the 1394 data packets. In addition, and under
control of software, link layer
21 interprets the data and routes the data
based on header information in the 1394 data packet. In this regard, the IEEE 1394
standard format for a data packet will be discussed in greater detail with respect
to FIGS. 3A-3D.
After receiving and interpreting the data packet link layer
21 transmits
the data over bus
22 which preferably is a Peripheral Component Interconnect
(PCI) bus. PCI bridge
24 manages the flow of data through PCI bus
22
which connects components together in 1394 network interface
3, such as
all 1394 link layers, CPU (Central Processing Unit)
28, random access memory
(RAM)
29, network controller
30, and other components within 1394
network interface
3. In the present example, data packets that are received
from local area network
7 are routed by PCI bridge
24 to link layer
26 (indirectly, through RAM
29) which outputs the data to physical
layer
25. Physical layer
25 outputs the data packets through its
electrical connection to DV camera
4, via the IEEE 1394 connection and 1394
cable
6. Prior to routing the data packet from RAM
29 through PCI
bridge
24 to link layer
26, CPU
28 interprets information
in the data packets to identify the source and recipient and, based on the information,
routes the data packet to the intended recipient.
Upon receiving the data packet from local area network
7, network controller
30 transfers the data packet through the PCI bus via PCI bridge
24
which routes it to RAM
29. Network driver software, which operates in conjunction
with network controller
30, removes network header information and unpackages
the data from its network protocol format. CPU
28 outputs the data onto
PCI bus
22 via PCI bridge
24, routed to the intended recipient. A
1394 header is added by the link layer to the data packet based on the source of
the data packet and based on the intended recipient of the data packet. In the
present embodiment, since DV camera
4 is the receiving camera, The 1394
header is added by link layer
26.
As mentioned previously, all DV cameras
1,
4,
10 and
11
have the same preset broadcast channel: broadcast channel
63. This causes
a conflict when two or more DV cameras are attempting to transmit over the same
1394 bus. As discussed above, each 1394 link layer controls access to its bus to
transmit and prevents more than one transmitter from using the same broadcast channel
on the bus. In the present invention described with respect to FIG. 2, the conflict
of two or more devices, such as DV cameras, at either side transmitting data over
the same 1394 channel is addressed by providing more than one 1394 physical layer,
1394 link layer, and 1394 bus. Without such a solution, there would be a conflict
between DV cameras attempting to transmit data over the same 1394 bus. In this
regard, each link layer
21 and
26 receives data packets from each
device in an IEEE 1394 standard format. In a videoconferencing environment, only
one camera such as camera
1 transmits while the other camera (camera
4)
receives. The channel
63 conflict occurs because camera
4 is intended
to receive video data from a remote camera, but what it actual
