Adaptive resolution system and method for providing efficient low bit rate transmission of image data for distributed applications
First Claim
1. A method for encoding image data for transmission over a communication channel, comprising the steps of:
- receiving image data;
encoding the image data using an adaptive log-polar mapping protocol that generates a log-polar representation of the image data comprising a fovea region and periphery region, wherein the encoding comprises selecting encoding parameters for the log-polar mapping based on either the size of the fovea region, the channel bandwidth, or both, to modify the resolution of the image data within the periphery region; and
transmitting the image data within the fovea region at full resolution and the image data within the periphery region at the modified resolution.
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Accused Products
Abstract
A client-server system and method that enables efficient, low bit rate transmission of image data over a network from an image server (e.g., active cameras) to a client for, e.g., distributed surveillance. A detection and tracking module detects a human presence within an observation area and provides 2-dimensional face coordinates and its estimated scale to a video transmission module. The captured video is then efficiently encoded in log-polar coordinates using an adaptive log-polar mapping, with a foveation point centered on the face. A fovea region, which covers the target object (face), is uniformly sampled and transmitted at full resolution to the client. The periphery region (background) is sampled according to a log-polar grid. To compensate for bit rate variations due to the changes in the scale of the target object and/or bandwidth of the communication channel, the resolution of the periphery region is modified through an adaptive log-polar mapping process, so as to maintain a virtually constant transmission rate from the server to the client. The high resolution of the data in the fovea region enables efficient recognition and/or identification of the transmitted video.
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Citations
20 Claims
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1. A method for encoding image data for transmission over a communication channel, comprising the steps of:
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receiving image data;
encoding the image data using an adaptive log-polar mapping protocol that generates a log-polar representation of the image data comprising a fovea region and periphery region, wherein the encoding comprises selecting encoding parameters for the log-polar mapping based on either the size of the fovea region, the channel bandwidth, or both, to modify the resolution of the image data within the periphery region; and
transmitting the image data within the fovea region at full resolution and the image data within the periphery region at the modified resolution. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps for encoding image data for transmission over a communication channel, the method steps comprising:
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receiving image data;
encoding the image data using an adaptive log-polar mapping protocol that generates a log-polar representation of the image data comprising a fovea region and periphery region, wherein the encoding comprises selecting encoding parameters for the log-polar mapping based on either the size of the fovea region, the channel bandwidth, or both, to modify the resolution of the image data within the periphery region; and
transmitting the image data within the fovea region at full resolution and the image data within the periphery region at the modified resolution. - View Dependent Claims (8, 9, 10, 11, 12, 14, 15, 16, 18, 19, 20)
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13. A method for providing distributed surveillance over a communications network, comprising the steps of:
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detecting the presence of an individual in a predetermined field of view;
tracking the face of the individual within the field of view;
generating image data, the image data comprising two-dimensional coordinates and estimated scale of the individual'"'"'s face being tracked;
filtering and sampling the image data using a log-polar mapping to generate encoded image data comprising a fovea region and periphery region, the fovea region being centered on the face of the individual; and
transmitting the encoded image data over a communication channel at a predetermined transmission bit rate, the fovea region being transmitted at full resolution;
wherein the log-polar mapping of the periphery region is adapted based on scale and locations changes of the fovea region to substantially maintain the predetermined transmission bit rate.
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17. A client/server system, comprising:
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an image sever, operatively interfaced to a camera, the image server comprising an encoder for filtering and sampling image data received from the camera using a log-polar mapping to generate encoded image data comprising a fovea region and periphery region, the fovea region being centered on a target of interest in the image; and
a communication stack for transmitting the encoded image data over a communication channel at a predetermined bit rate, wherein the fovea region is transmitted at full resolution, and wherein the log-polar mapping of the periphery region is adapted based on scale and locations changes of the fovea region to substantially maintain the predetermined transmission bit rate; and
a client for receiving the encoded image data transmitted from the image server and decoding the encoded image data for identification of the target of interest.
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Specification