Computer graphics processing and selective visual display system – Computer graphic processing system – Integrated circuit
Reexamination Certificate
1997-08-20
2001-11-13
Bayerl, Raymond J. (Department: 2173)
Computer graphics processing and selective visual display system
Computer graphic processing system
Integrated circuit
C345S504000, C345S519000, C345S205000
Reexamination Certificate
active
06317134
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a computer system having a shared system memory, and more particularly to system software in a computer system having a shared system memory.
2. Related Art
FIG. 1
is a block diagram of a conventional computer system
102
. The computer system
102
is “bus centric,” in that all components are connected to and communicate with each other via a bus
116
. In particular, a CPU
104
(central processing unit), system memory
106
, graphics rendering hardware
108
, and an I/O (input/output) interface
118
are connected to a bus
116
, and communicate with each other via the bus
116
.
The system memory
106
is the main memory in the computer system
102
, and it is implemented as random access memory (RAM). However, the system memory
106
is not the only RAM in the computer system
102
. The computer system
102
also includes a frame buffer
110
in a graphics memory
109
, which is implemented using VRAM (video random access memory). The graphics memory
109
and the frame buffer
110
located therein are dedicated for use by the rendering hardware
108
. In operation, the rendering hardware
108
performs graphical operations and renders a graphical image to the frame buffer
110
. A graphics back end (GBE)
112
displays the graphical image on a graphics monitor
114
.
The computer system
102
also includes a video buffer RAM
122
that is used for direct communication of video data to the compression module
124
(which may represent a video compression computer card, for example). There is also a compression RAM
123
that is used for compression operations. In operation, a video source
120
(such as a video camera) generates a video signal. The bandwidth of the video signal is approximately 20 Mbytes/second. Typically, “consumers” or “users” of the video signal have a smaller bandwidth. For example, the storage device
126
(such as a disk drive) usually has a bandwidth of 2-4 Mbytes/second. A communication network (not shown) usually has a bandwidth of approximately 1 Mbyte/second. Thus, it is necessary to compress the video signal.
Accordingly, the video signal is stored in the video buffer RAM
122
. The compression module
124
compresses the video data stored in the video buffer RAM
122
using the compression RAM
123
to hold compression task state information such as inter-frame reference data, and then transfers the compressed video data to the I/O interface
118
. The I/O interface
118
sends the compressed video data to an external device, such as a storage device
126
or to a destination over a communication network (not shown). In other systems, data is transferred directly from the compression module
124
to the storage device
126
or other external device.
Thus, the computer system
102
has multiple RAMS: the system memory
106
, the graphics memory
109
, the video buffer RAM
122
, and the compression RAM
123
. It is costly to have multiple RAMS. This cost manifests itself in increased system cost (since more RAMs cost more money) and increased system size (since more RAMs take up more space). Thus, the conventional computer system
102
is not ideal since it requires multiple RAMS.
The system memory
106
is general purpose, but the graphics memory
109
, the video buffer RAM
122
, and the compression RAM
123
are dedicated to specific functions. The graphics memory
109
can be used only for graphics operations, and the video buffer RAM
122
and compression RAM
123
can be used only for compression operations. Thus, a significant portion of the RAM in the computer system
102
can be used only for particular functions. Accordingly, the conventional computer system
102
is not ideal because its RAMs are not flexible.
The inflexibility of the compression RAM
122
extends to the entire video compression path. The compression module
124
and compression RAM
122
that comprise the video compression path are capable of opening with a single video signal. Thus, the compression path of the conventional computer system
102
is inflexible because it cannot simultaneously work with multiple video signals.
Also, the compression module
124
and compression RAM
122
can only work with one video signal type. The type of video signal that the compression module
124
and compression RAM
122
can work with is determined when the computer system
102
is manufactured. Thus, the compression path of the conventional computer system
102
is inflexible because it cannot work with multiple types of video signals.
This latter inflexibility of the compression path, and the inflexibility of the computer system
102
as a whole, results from its manner of operation. As shown in
FIG. 2
, processing of a video signal by the conventional computer system
102
is performed entirely by hardware
208
(the hardware
208
includes the video buffer RAM
122
, the compression RAM
123
, compression module
124
, and I/O interface
118
). Such processing is represented by path
212
, which does not extend into the operating system layer
206
or the user application layer
204
. Since it is performed entirely by hardware
208
, video compression functionalities and capabilities are essentially “hardwired” into the computer system
102
. Thus, the compression device
124
and other related hardware have limited applicability because they are hardwired to and embedded in the video input/output path.
This inflexibility can be alleviated somewhat by enabling user applications in the user application layer
204
, and executing in the CPU
104
, to manipulate the video signal. To do this, graphical data representative of the video signal must be copied from the graphics memory
109
into the system memory
106
. A user application can then manipulate the graphical data while it is stored in the system memory
106
(note that the user application does not have access to data stored in the graphics memory
109
). In order to display the graphical data, the graphical data must be copied from the system memory
106
back to the graphics memory
109
(in particular, back to the frame buffer
110
in the graphics memory
109
).
Thus, in order to obtain some level of flexibility in the system
102
of
FIG. 1
, it is necessary to copy and/or move data from one memory component to another memory component, such as from the graphics memory
109
to the system memory
106
, and vice versa. These copy and move operations degrade system performance because they are time consuming and resource intensive. Accordingly, any flexibility in the conventional system
102
of
FIG. 1
is achieved only at the cost of significant system performance.
SUMMARY OF THE INVENTION
Briefly stated, the present invention is directed to a computer system having a shared system memory, and to system software in the computer system. One or more user applications execute in the computer system. Each user application has one or more device contexts.
The computer system has a general purpose, shared system memory that is used for all processing, including video input/output operations and image conversion operations. The computer system also has a multimedia access and control module (MACM), which is the input/output interface between the computer system and the external world In operation, the MACM receives, at one of its video input ports, video data comprising a video image (such as a frame or a field). The MACM stores the video image in a first buffer contained in a first buffer pool of the system memory. The first buffer pool was previously created by a user application. The user application previously associated the first buffer pool with the MACM's video input port.
A video imaging and compression module (VICM) performs image conversion operations. Each user application creates one or more converter contexts of the VICM. Each converter context is capable of performing an image conversion operation. In operation, a converter context of the VICM performs an image conversion operation on the video image
Beach Brian
Carpenter John Wiltse
Crane Terrence
Hagemark Bent
Lai Angela
Bayerl Raymond J.
Luu Sy D.
Silicon Graphics Inc.
Sterne Kessler Goldstein & Fox PLLC
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