Television – Two-way video and voice communication – Transmission control
Reexamination Certificate
1997-03-25
2001-08-14
Chan, Wing F. (Department: 2643)
Television
Two-way video and voice communication
Transmission control
C348S014050, C348S347000
Reexamination Certificate
active
06275252
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related generally to video conferencing systems and, more particularly, to video imaging preprocessing based upon the degree of zoom of a camera lens within such a system.
BACKGROUND
The use of video conferencing systems as a means of conducting meetings, presentations and other matters continues to gain in popularity. Video conferencing systems generally allow users separated geographically to both see and hear one another. A typical video conferencing system is illustrated in FIG.
1
.
Video conferencing system
10
generally includes a local station
12
and a remote station
14
. Each of the local and remote stations
12
and
14
includes a video conference processor
16
, a camera
18
, a monitor
20
, a microphone
22
and a speaker
24
. Certain of these elements may be combined within a single unit. For example, the housing for monitor
20
may also include the video conference processor
16
as well as the microphone
22
and speaker
24
. In such systems, camera
18
may be a separate, stand-alone device or may also be incorporated within the housing of monitor
20
. In other embodiments, each of the elements may be stand-alone devices.
Local station
12
and remote station
14
are connected by a transmission medium
26
. In some cases, transmission medium
26
may be the Public Switched Telephone Network (PSTN) or, in other cases, transmission medium
26
may be an ISDN line or other transmission medium.
In general, during the video conference, video images captured by camera
18
at local station
12
are filtered and encoded by video conference processor
16
prior to transmission to remote station
14
. Similarly, audio signals captured by microphone
22
are filtered and encoded by video conference processor
16
prior to transmission. At remote station
14
, video and audio data received from local station
12
are expanded and processed prior to display on monitor
20
and speaker
24
. Likewise, video and audio signals captured by camera
18
and microphone
22
at remote station
14
are encoded by video conference processor
16
prior to transmission to local station
12
. At local station
12
, this video and audio data are expanded prior to display on monitor
20
and speaker
24
.
FIG. 2
further illustrates the encoding process performed by video conference processor
16
at local and remote stations
12
and
14
. Video signals from camera
18
are passed to video processor
28
. Video processor
28
performs filtering operations on the video images, for example, to remove high frequency components such as noise produced by camera
18
. Filtered images are passed from video processor
28
to video encoder
30
for compression prior to transmission.
During a video conference, a variety of images may be captured and transmitted by a video conference system. For example, as shown in
FIG. 3A
, “long shots” in which a relatively wide angle scene is captured as a image may be transmitted between local station
12
and remote station
14
for display. As shown, the resulting image displayed on monitor
20
at remote station
14
may be such that a user at remote station
14
can view a wide angle presentation or group of people, etc. At various times during the video conference, the user may wish to zoom in on aspects of the presenter or the presentation.
FIG. 3B
illustrates an example where the user has zoomed in on the presenter, for example, during an especially interesting portion of the discussion. To effect this zoom in, the user at remote station
14
transmits zoom commands to the local camera
18
stationed at local station
12
. In response, camera
18
zooms in on the presenter at local station
12
so that the resulting image is displayed. At other times during the presentation, the user at remote station
14
may wish to zoom out so that the entire scene is displayed on his monitor
20
.
At times when the scene to be captured by camera
18
has a relatively wide angle, certain image details may be unimportant and, hence, need not be transmitted to remote station
14
. However, at the same times, motion within the scene, for example gestures by the presenter towards a presentation display, may be important. Accordingly, filtering provided by video processor
28
at local station
12
should be such that accommodates motion within sequential video images but need not be such that a accommodates a great amount of image detail. In contrast, during periods of zoom in, image detail becomes important while motion compensation need not be as important. Thus, at these times video processor
28
should apply filtering to achieve improved image detail.
Typically, video processors such as video processor
28
of video conference processor
16
are incapable of providing different filtering algorithms at different time during a video conference. Accordingly, what is needed is distance adaptive filtering means which achieve optimum performance according to the scene captured by a camera.
SUMMARY OF THE INVENTION
In one embodiment, the present invention provides a method of processing a video image captured by a camera. First, a zoom distance of the camera is determined at a time when the video image is captured. Second, a filtering process is applied to the image based upon the zoom distance. For one embodiment, the process of determining the zoom distance includes establishing a reference focal length of a lens system of the camera and comparing that reference focal length to a measured focal length of the lens system at a time when the video image is captured. Based upon whether the reference focal length is greater than or less than the measured focal length, a filtering process is applied to the image. The filtering process to be applied may be such that when the reference focal length is greater than the measured focal length, the filtering process removes more high frequency components from the image than are removed when the measured focal length is greater than the referenced focal length. That is, when the image is recognized as being that corresponding to a wide angle shot, and hence a lower focal length for the lens system, fewer high frequency components are removed from the image during filtering.
These and other features and advantages of the present invention will be apparent upon review of the specification which follows and the accompanying drawings.
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patent: 5253286 (1993-10-01), Sano et al.
patent: 5424776 (1995-06-01), Hirasawa
patent: 5486860 (1996-01-01), Shiokawa et al.
patent: 5598209 (1997-01-01), Cortjens et al.
patent: 5614951 (1997-03-01), Lee et al.
patent: 5623309 (1997-04-01), Yoshimura et al.
patent: 5680484 (1997-10-01), Ohyama et al.
patent: 5724155 (1998-03-01), Saito
patent: 5838368 (1998-11-01), Masunaga et al.
patent: 5874994 (1999-02-01), Xie et al.
patent: 2312459 (1996-12-01), None
Blakely , Sokoloff, Taylor & Zafman LLP
Chan Wing F.
Eng George
Sony Corporation
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