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Claims  |
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I claim:
1. A video camera apparatus comprising:
a video camera comprising a lens, and for generating the video signals comprising a plurality of video images;
a camera control system for causing adjustment of the video camera, the camera control system comprising means for generating an adjustment indication signal indicative of adjustment of the video camera by the camera control system;
compression means effecting a degree of compression processing on the video signals, said compression means comprising: means for effecting a degree of spatial compression processing on the video signals; and means for effecting a degree of
temporal compression processing on the video signals including means for generating motion vectors in response to the adjustment indication signal;
a processor for outputting to the compression means, an instruction to vary the degree of compression processing in response to the adjustment indication signal, said instruction to vary the degree of compression processing comprising
instructions to vary the degree of spatial compression processing and the degree of temporal compression processing in response to the adjustment indication signal.
2. The video camera apparatus of claim 1 wherein the means for effecting a degree of spatial compression comprises a quantizer for effecting a degree of quantization of the video signals and wherein the instruction to vary the degree of spatial
compression processing in response to the adjustment indication signal comprises an instruction to the compression means to vary the degree of quantization of the video signals by the quantizer.
3. The video camera apparatus of claim 1 wherein the means for effecting a degree of spatial compression comprises at least one compression filter having a filter length and wherein the instruction to vary the degree of spatial compression in
response to the adjustment indication signal comprises an instruction to vary the filter length.
4. The video camera apparatus of claim 1 wherein the means for effecting a degree of spatial compression comprises a filter having a plurality of filter coefficients and wherein the instruction to vary the degree of spatial compression in
response to the adjustment indication signal comprises an instruction to vary at least one of the filter coefficients.
5. The video camera apparatus of claim 1 wherein the means for effecting a degree of spatial compression comprises a compression filter having a filter shape and wherein the instruction to vary the degree of spatial compression in response to
the adjustment indication signal comprises an instruction to vary the filter shape.
6. The video camera apparatus of claim 1 wherein the camera control system comprises a remote controller.
7. The video camera of claim 6 wherein the remote controller comprises means for generating a control signal for causing adjustment of the video camera, wherein the control signal is provided to the means for generating an adjustment indication
signal and wherein the means for generating an adjustment indication signal generates the adjustment indication signal in response to the control signal.
8. The video camera apparatus of claim 1 wherein the camera control system comprises a transducer for detecting the adjustment of the video camera and generating the adjustment indication signal in response to detection of the adjustment of the
video camera.
9. The video camera apparatus of claim 1 wherein the processor outputs an instruction to the compression means to increase the degree of spatial compression processing on commencement of the adjustment of the video camera.
10. The video camera apparatus of claim 1 wherein the processor outputs an instruction to the compression means to decrease the degree of spatial compression processing on cessation of the adjustment of the video camera.
11. The video camera apparatus of claim 1 wherein the processor outputs an instruction to the compression means to vary the degree of spatial compression processing in proportion to the adjustment of the video camera.
12. The video camera apparatus of claim 1 wherein said motion vectors comprise information relating to frame to frame changes in the video images.
13. The video camera apparatus of claim 1 further comprising means for analyzing the video images to determine whether the video images are moving and for generating motion vectors if the picture video images are moving, the motion vectors
comprising information relating to movement of the video images.
14. The video camera apparatus of claim 1 wherein the adjust indication signal indicates palming of the video camera.
15. The video camera apparatus of claim 1 wherein the adjustment indication signal indicates tilting of the video camera.
16. The video camera apparatus of claim 1 wherein the adjustment indication signal indicates zooming of the lens.
17. The video camera apparatus of claim 1 wherein the adjustment indication signal indicates focusing of the lens.
18. The video camera apparatus of claim 1 further comprising means for storing the video signals on a storage medium and wherein the instruction to vary the degree of compression processing is stored on the storage medium.
19. The video camera apparatus of claim 18 further comprising means for storing the video signals on a storage medium and wherein the instruction to vary the degree of temporal compression processing is stored on the storage medium.
20. The video camera apparatus of claim 1 wherein if the adjustment of the video camera is such that the video images move, the degree of spatial compression processing is decreased and the degree of temporal compression is increased.
21. A video surveillance system for surveillance of a remote location, the system comprising:
a video camera module at the remote location, the video camera module comprising:
a video camera for generating video signals;
a first network interface connecting the video camera module to a communications network, such that with the video camera module connected to the communications network, the video camera module can communicate with a monitoring station over the
communications network;
a camera control system for causing adjustment of the video camera, the camera control system comprising means for generating an adjustment indication signal indicative of adjustment of the video camera by the camera control system;
compression means effecting a degree of compression processing on the video signals, said compression means comprising: means for effecting a decree of spatial compression processing on the video signals; and means for effecting a degree of
temporal compression processing on the video signals including means for generating motion vectors in response to the adjustment indication signal:
a processor for outputting to the compression means, an instruction to vary the degree of compression processing in response to the adjustment indication signal, said instruction to vary the degree of compression processing comprising
instructions to vary the degree of spatial compression processing and the degree of temporal compression processing in response to the adjustment indication signal.
22. The video surveillance system of claim 21 further comprising a monitoring station comprising a second network interface for connection to the network.
23. The video surveillance system of claim 21 further comprising means for analyzing the video images to determine whether the video images are moving and for generating motion vectors if the picture video images are moving, the motion vectors
comprising information relating to movement of the video images.
24. The video surveillance system of claim 21 wherein the adjustment indication signal indicates panning of the video camera.
25. The video surveillance system of claim 21 wherein the adjustment indication signal indicates tilting of the video camera.
26. The video surveillance system of claim 21 wherein the adjustment indication signal indicates zooming of the lens.
27. The video surveillance system of claim 22 wherein the adjustment indication signal indicates focusing of the lens.
28. The video surveillance system of claim 21 further comprising means for storing the video signals on a storage medium and wherein the instruction to vary the degree of compression processing is stored on the storage medium.
29. The video camera apparatus of claim 19 further comprising means for storing the video signals on a storage medium and wherein the instruction to vary the degree of temporal compression processing is stored on the storage medium.
30. The video camera apparatus of claim 21 further comprising means for storing the video signals on a storage medium and wherein the instruction to vary the degree of spatial compression processing is stored on the storage medium.
31. A video camera apparatus comprising:
a video camera comprising a lens and for generating video signals comprising a plurality of video images comprising picture elements;
a camera control system for causing adjustment of the video camera, the camera control system comprising means for generating an adjustment indication signal indicative of adjustment of the video camera by the camera control system;
compression means effecting a degree of compression processing on the video signals, said compression means comprising: means for effecting a degree of spatial compression processing on the video signals; and means for effecting a degree of
temporal compression processing on the video signals including means for generating motion vectors in response to the adjustment indication signal;
a processor for outputting to the compression means, an instruction to vary the degree of compression processing in response to the adjustment indication signal, said instruction to vary the degree of compression processing comprising
instructions to vary the degree of spatial compression processing and the degree of temporal compression processing in response to the adjustment indication signal; and
means for storing the video signals on a storage medium and wherein the instruction to vary the degree of compression processing is stored on the storage medium.
32. For use in a video camera system comprising an adjustable video camera and a controller for adjusting the video camera, the method comprising the steps of:
generating the video signals comprising a plurality of video images;
adjusting the video camera and generating an adjustment indication signal indicative of adjustment of the video camera;
effecting a degree of compression processing on the video signals, thereby generating compressed video signals, said effecting the degree of compression processing comprising: effecting the degree of spatial compression processing on the video
signals: and effecting the degree of temporal compression processing on the video signals including generating motion vectors in response to the adjustment indication signal;
outputting to the compression means, an instruction to vary the degree of compression processing in response to the adjustment indication signal, said instruction to vary the degree of compression processing comprising instructions to vary the
degree of spatial compression processing and the degree of temporal compression processing in response to the adjustment indication signal.
33. The method of claim 22 wherein the step of effecting a degree of further compression processing comprises the step of effecting a degree of temporal compression of the video signals and herein the processor further outputs an instruction to
the compression means to vary the degree of temporal compression in response to the adjustment indication signal.
34. A video camera apparatus comprising:
a video camera comprising a lens, and for generating video signals comprising a plurality of video images;
a camera control system for causing adjustment of the video camera, the camera control system comprising: a remote controller including means for generating a control signal for causing adjustment of the video camera; and means for receiving
said control signal and generating an adjustment indication signal indicative of adjustment of the video camera by the camera control system in response to the received control signal;
compression means effecting a degree of compression processing on the video signals, said compression means comprising: means for effecting a degree of spatial compression processing on the video signals: and means for effecting a degree of
temporal compression processing on the video signals including means for generating motion vectors in response to the adjustment indication signal;
a processor for outputting to the compression means, an instruction to vary the degree of compression processing in response to the adjustment indication signal, said instruction to vary the degree of compression processing comprising
instructions to vary the degree of spatial compression processing and the degree of temporal compression processing in response to the adjustment indication signal. |
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Description |
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BACKGROUND
The present invention relates generally to the field of video compression. More specifically, it relates to a system for using knowledge of the adjustment of a video camera to optimize the use of resources for compressing a video signal
generated by the video camera.
Video surveillance cameras are commonly used to monitor premises for security purposes. Typically one or more video cameras are placed at various locations to be monitored. The output of the cameras may be viewed or recorded at a central
station. It is also possible to have a number of video cameras distributed at locations which are remote from the central station. For example, cameras may be placed in several stores at various locations in a city and monitored from a central station. Remote cameras could also be placed at outlying parts of an airport and monitored centrally.
In such systems, it is necessary to transmit the information acquired by the video cameras to the central monitoring location. For this reason, it is often desirable to compress the video data so that it can be transmitted over a communications
channel having a relatively narrow bandwidth.
Known video compression systems involve two basic forms of compression processing spatial and temporal. Spatial processing compresses information by transforming the picture elements within a particular frame of a video signal in accordance with
a compression algorithm, thereby reducing the amount of information required for reproduction of the frame. In contrast, temporal processing takes into account the way in which information is changing with time. It therefore reduces the amount of
information required for reproduction of a frame by taking into account changes in the picture which occur from frame to frame. These changes are reflected in motion vectors which are generated and transmitted instead of the actual contents of the video
frames. A description of an implementation of spatial and temporal processing can be found in the MPEG compression recommendation ISO/IEC 1172-2 (referred to herein as the MPEG Standard).
The MPEG Standard is one of several well known standards for video processing. Conventional MPEG encoders allow the degree of spatial processing to be varied, for example to conserve memory by adjusting the quantization of information in a
particular frame. Such encoders also have the facility to detect motion of the picture from frame to frame and adjust the degree of temporal processing (i.e. adjust the motion vectors).
Within a scene being monitored by a video camera, motion can occur due to movement of the subject (e.g. a person traversing the field of view of the camera), or as a result of movement of the camera (i.e. due to the panning, tilting, zooming or
focusing of the camera). When the picture moves, the movement information must be extracted in order to generate motion vectors. Systems of the prior art (e.g. systems using MPEG-type compression) which perform temporal processing to convey motion
information require relatively large amounts of memory space and computational power.
The present invention is directed to the use of known information about the movement of the video picture caused by movement due to the camera to reduce the computational and memory overhead required for compression of video data. Specifically,
it uses information generated as a result of adjustments to the camera to adjust and thus trade off spatial processing against temporal processing. Rather than extracting the information from the video pictures, it obtains the information from the means
by which the camera is actually being controlled.
SUMMARY OF THE INVENTION
The present invention is a video camera apparatus with compression processing and a method used with such an apparatus. The apparatus includes an adjustable video camera. The camera generates video signals made up of a plurality of video
images. A degree of compression processing of the video signals is brought about by compression means, thus generating compressed video signal- A camera control system causes adjustment of the video camera. The camera control system comprises means for
generating an adjustment indication signal indicative of adjustment of the video camera by the camera control system A processor outputs to the compression means, an instruction to vary the degree of compression processing in response to the adjustment
indication signal produced by the control system. This a priori knowledge of the adjustment of the camera derived from the control system is thus used to vary the degree of compression processing.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a first embodiment of the video camera apparatus of the invention;
FIG. 2 is a block diagram of a second embodiment of the video camera apparatus of the invention.
FIG. 3 is a block diagram of a third embodiment of the video camera apparatus of the invention;
FIG. 4 is a block diagram of a video surveillance system of the invention; an&
FIG. 5 is a flow chart showing the method of operation of the video surveillance system of the invention.
DETAILED DESCRIPTION
The following is a detailed description of the invention. It is intended to be illustrative, and not limiting of the invention, the fill scope of which is to be determined by the appended claims.
Video camera apparatus 1 shown in FIG. 1 is made up of pan-tilt-zoom video camera 10 having A/ID color space converter 20 and pan-tilt-zoom ("PTZ") unit 18, control panel 30 with user input 32, control interpreter 40 (a suitably programmed
microprocessor with associated memory) and a compression unit 50. Camera 10 produces a video signal 19 (made up of video images comprising picture elements) which is fed into color space converter 20, which in turn outputs digital chrominance and
luminance signals Cr, Cb and Y at output 52. Camera 10 has zoom lens 12 having focus control mechanism 14 and zoom control mechanism 16. PTZ mechanism 18 enables camera 10 to pan, tilt and zoom on instructions input at control panel 30. Control panel
30 and control interpreter 40 are preferably included in a single microprocessor based unit available from Sensormatic Electronics Corp. of Deerfield Beach, Fla. under the name "Touchtracker." Camera 10, with its associated lens and PTZ unit 18 and
color space converter 20 are preferably included in a self-contained "dome" available form Sensormatic Electronics Corp. under the name "SpeedDome."
Compression unit 50 is a conventional video compression unit comprising hardware and software which implements a compression algorithm--preferably the well-known MPEG system as described in the MPEG Standard. The MPEG Standard describes a system
which effects a degree of compression processing (including spatial and temporal compression). Any compression system where the degree of compression processing can be varied can be used. For example, known systems having compression filters (having
predetermined filter length, shape and coefficients) in which the degree of spatial compression is varied by adjusting filter length, adjusting filter coefficients or adjusting filter shape can be used and are considered to be equivalents represented by
compression unit 50. Since the video compression hardware and software are well known to persons of ordinary skill in the art, only the aspects which are germane to this invention will be described.
Compression unit 50 has an input 53 connected to output 52 of color space converter 20 for receiving digitized chrominance signals Cr and Cb and luminance signal Y. It also has an input 55 for receiving motion vectors produced by control
interpreter 40 at output 54. The generation and purpose of these motion vectors will be described below. Input 57 of compression unit 50 receives instructions as to the degree of spatial processing from output 56 of control interpreter 40, the details
of which will be described below. Compression unit 50 has an output 58 for outputting a compressed video signal to multiplexer 80 for transmission over a communication channel.
The basic components of the preferred compression unit 50 are as follows: subtractor 60, discrete cosine transform unit 62, quantizer 64, variable length coder 66, de-quantizer 68, inverse discrete cosine transform unit 70, summing point 72 and
picture store predictor 74. Quantizer 64 quantizes the discrete cosine transformed signal supplied by discrete cosine transform unit 62. The degree to which quantizer 64 effects spatial compression processing of the supplied signal is variable. To
that end, quantizer 64 has at least two quantization matrices, each of which causes a different degree of spatial compression processing. Writing a variable into register 65 via input 57 causes one of the quantization matrices to be selected. All of
these components are well known to persons of ordinary skill in the art, being described in detail in the MPEG manual.
As discussed above, the MPEG standard, as well as other compression systems, includes two modes of compression processing--spatial and temporal In the spatial compression processing mode, compression unit 50 compresses information within a video
frame generated by video camera 10. Each video frame carries images made up of a large number of picture elements. In the temporal compression processing mode, motion vectors are generated to describe changes in a picture from one frame to another.
The motion vectors thus are an indication of the motion of the images carried by the video frames.
When camera 10 is stationary, the differences from frame to frame of the video signal it produces are less significant than when the camera is panning, tilting, zooming or focusing. Further, when the camera is stationary, the human eye is more
able to discern picture details than when the camera is in motion. Therefore, the compression operation must convey greater detail within each frame when the camera is stationary than when it is in motion- That is to say, when the camera is stationary,
the degree of spatial processing must be low In the case of the preferred processing system described herein, this corresponds to a low degree of quantization.
When the camera is in motion, zooming or focusing, in order for the signal to be accurately reconstructed, the compression operation must convey more information as to how the picture is changing. This requires greater bandwidth than when the
camera is stationary. Increasing the degree of spatial compression (i.e. increasing the spatial quantization) frees bandwidth for temporal compression processing (i.e. the generation of motion vectors) in response to panning, tilting, zooming or
focusing. However, this results in less detail appearing when the compressed signal is reconstructed. Nevertheless, this is an acceptable solution because the human eye is less sensitive to detail in a moving object than in a still one.
When camera 10 is stationary, focused and lens 12 is not being zoomed, control interpreter 40 does not perform temporal compression processing (i.e., it does produce motion vectors). The degree of spatial compression is low. That is to say, a
quantization matrix giving a low quantization is selected by writing an appropriate value into register 65. This results in a high degree of detail being conveyed in the compressed signal at output 58.
The video signals at output 52 which are fed into compression unit 50 at input 53 are compressed in accordance with the MPEG algorithm using the degree of spatial compression processing set by control interpreter 40 and made available as a
compressed video signal at output 58. This signal is passed to output 82 by multiplexer 80 for transmission over a communications channel or to a storage device.
Control panel 30, control interpreter 40 and PTZ unit 18 make up a camera control system When the user inducts camera 10 to pan, tilt, zoom or focus by means of user input 32, control panel 30 produces a control signal at output 31. This is fed
into control interpreter 40 at input 41. In response, control interpreter 40 generates an adjustment indication signal at output 42 which is provided to input 43 of PTZ unit 18 to cause camera 10 to pan, tilt, zoom, or focus. In response to the
adjustment indication signal, control interpreter 40 generates a series of motion vectors. The motion vectors describe how the picture produced by camera 10 is changing due to the instruction received from the user. The motion vectors are output in a
format dictated by the MPEG Standard, thus effecting temporal compression processing. The motion vectors are stored in a look up table in the memory of control interpreter 40. Thus, for any particular degree of panning, tilting, zooming or focusing,
there is a particular set of motion vectors in the look up table. Vectors indicative of combined panning, tiling, zooming or focusing are obtained by multiplying each of the vectors associated with the particular degree of panning, tilting, zooming or
focusing by each other. The motion vectors are fed into multiplexer 80 and multiplexed with the compressed signal produced as a result of the spatial compression.
When the camera control system causes camera 10 to be adjusted (panned, tilted, zoomed or focused), control interpreter 40 outputs an instruction to compression unit to increase the degree of spatial compression processing. In the preferred
embodiment, control interpreter instructs quantizer 64 to select the quantization matrix to produce a higher degree of spatial compression by causing an appropriate value to be written into register 65. As panning, tilting, zooming and focusing
increases or decreases, so control interpreter 40 outputs instructions to compression unit 40 to increase or decrease the degree of spatial compression processing in appropriate proportion. Thus, when camera is caused to move relative to its
surroundings or to zoom or focus, the compression operation is weighted towards the frame to frame changes in the picture (temporal compression processing), rather than towards the details of each frame (spatial compression processing).
When the panning, tilting, zooming and focusing have stopped, control interpreter 40 stops producing the motion vectors. It also causes the degree of spatial compression processing to be adjusted back to an appropriate lower level. The system
just described allows the degree of compression processing to be varied depending on adjustment of the video camera. This allows a tradeoff between the degree spatial and temporal processing on the basis of a priori knowledge of whether the camera is
panning, tiling, zooming or focusing. The system has been described by reference to a system in which the degree of spatial compression processing is varied by adjusting the quantization of an MPEG-type compression processing system. A person of
ordinary ski in the art will recognize that the principles of the preferred embodiment of this invention are equally applicable to systems which use different forms of compression processing and in which the degree of compression processing can be
varied.
The system can also have the capability to record the video images produced by camera 10. The instructions to vary the degree of compression processing are provided to video cassette recorder 90 and stored on the video tape between frames of the
video signal That is to say, the instructions output by control interpreter 50 and/or the motion vectors are stored on the video tape. Thus, when the video tape is replayed into a compression unit 50, the instructions to vary the degree of spatial
and/or temporal compression and the motion vectors are extracted from the recorded signal and used in the manner described above.
In a second embodiment of the invention shown in FIG. 2, the adjustment indication signals are produced by transducers which detect the state of panning, tilting, zooming or focusing, rather than control signals produced by the control panel.
Transducer 118 detects the stat | | |
