Method and apparatus for processing image data

• US 20060013495A1
• Filed: 01/24/2005
• Published: 01/19/2006
• Est. Priority Date: 07/25/2001
• Status: Abandoned Application

• Current Assignee: Agency For Science Technology and Research (Government of Singapore), Vislog Technology Pte Limited
• Original Assignee: Agency For Science Technology and Research (Government of Singapore), Vislog Technology Pte Limited of Singapore
• Inventors: Zhao, Lei, Guo, Chun Biao, Tang, Juel Hoi, Quian, Guo Yu, Duan, Ling Yu, Zhou, Ruowei
• Application Number:
  US11/039,883
• Publication Number:
  US 20060013495A1
• Time in Patent Office: Days
• US Class Current: 382/235
• CPC Class Codes: G06T 7/254 involving subtraction of images
• CPC Class Codes: G06T 9/00 Image coding bandwidth or redundancy reduction for static pictures H04N1/41; coding or decoding of static colour picture signals H04N1/64; methods or arrangements for coding, decoding, compressing or decompressing digital video signals H04N19/00
• CPC Class Codes: G06T 9/007 Transform coding, e.g. discrete cosine transform
• CPC Class Codes: G06V 10/28 Quantising the image, e.g. histogram thresholding for discrimination between background and foreground patterns
• CPC Class Codes: H04N 19/115 Selection of the code volume for a coding unit prior to coding
• CPC Class Codes: H04N 19/136 Incoming video signal characteristics or properties
• CPC Class Codes: H04N 19/137 Motion inside a coding unit, e.g. average field, frame or block difference
• CPC Class Codes: H04N 19/164 Feedback from the receiver or from the transmission channel
• CPC Class Codes: H04N 19/17 the unit being an image region, e.g. an object
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/59 involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution

Abstract

A network camera apparatus is disclosed including an image requisition unit which obtains an analog signal of an image and converts this into digital format; an image compression unit which utilizes standard image compression techniques (JPEG, MJPEG) to decrease the data size; an image processing unit which analyzes the compressed data of each image, detects motion from compressed data, and identifies background and foreground regions for each image; a data storage unit which stores the image data processed by the image processing unit; a traffic detection unit which detects the traffic amount of the network and decides the frame rates of the image data to be transmitted; and a communication unit which communicates with the network to transmit the image data and other signals.

Claims

1. A method of processing image data comprising the steps of taking a compressed version of an image and determining from the compressed version if a change in the image compared to previously obtained image data has occurred and identifying the changed portion of the compressed image.

2. A method as claimed in claim 1, wherein the change is indicative of motion.

3. A method as claimed in claim 1, wherein the identifying step comprises identifying a foreground and/or a background region, the foreground region comprising moving object(s) and the background region comprising stationary object(s).

4. A method as claimed in claim 1, wherein the determining step is performed upon Direct Cosine Transformation coefficients of the compressed image.

5. A method as claimed in claim 4, wherein the coefficients are quantized or dequantized.

6. A method as claimed in claim 1, wherein a mask is formed of the identified portions.

7. A method as claimed in claim 6, wherein the mask is subject to segmentation and morphological processing.

8. A method as claimed in claim 1, further comprising the step of transmitting the compressed image or part thereof to a storage location.

9. A method as claimed in claim 8, wherein, if the image contains a changed portion, only the changed portion is transmitted and if the image does not contain a changed portion, the whole compressed image is transmitted.

10. A method as claimed in claim 9, wherein if consecutive images do not contain a changed portion, not all the unchanged images are transmitted.

11. A method as claimed in claim 10, wherein the number of consecutive unchanged compressed images that are not transmitted is determined by an adjustable parameter.

12. A method as claimed in claim 9, wherein the changed image portion and the unchanged image are transmitted at different rates.

13. A method as claimed in claim 1, wherein the previously obtained compressed image data comprises a previous compressed image.

14. A method as claimed in claim 1, wherein the previously obtained compressed image data comprises a stored background frame.

15. A method as claimed in claim 14, wherein the background frame is updated by background learning.

16. A method as claimed in claim 1, wherein the compressed version of the image uses JPEG or MJPEG compression.

17. A method as claimed in claim 1, wherein at least one step of a compression process used to form the compressed version is reversed prior to making said determination.

18. A method as claimed in claim 17, wherein the step comprises a coding step.

19. A method as claimed in claim 17, wherein the step is a vector-forming step.

21. An image processor arranged to perform the method of claim 1.

22. A camera including an image processor as claimed in claim 21.

23. A network camera holding an image processor as claimed in claim 21.

24. Network camera apparatus including an image processor as claimed in claim 21 and further comprising an image acquisition means arranged to acquire an image in digital form, an image compressor arranged to compress the image and pass this to the image processor, data storage arranged to store image data from the image processor and communication means arranged to communicate with the network.

26. Apparatus as claimed in claim 24, wherein the recited elements of the apparatus are software programs or circuits.

27. Surveillance apparatus including a camera as claimed in claim 22.

20. A method of processing compressed data derived from an original image, the data being organized as a set of blocks, each block comprising a string of bits corresponding to an area of the original image, Direct Cosine Transformation (DCT) coefficients for each block being derived by decoding each string of bits, the differences between the DCT coefficients of the current frame and the DCT coefficients of a previous frame or a background frame being thresholded for each frame to produce an initial mask indicating changed blocks, applying segmentation and morphological techniques to the initial mask to filter out noise and find regions of movement, if no moving region is found, regarding the current frame as a background frame, otherwise identifying the blocks in the moving regions as foreground blocks and extracting the foreground blocks to form a foreground frame.

25. Network camera apparatus comprising an image requisition unit arranged to capture an image and converts the image into digital format;

an image compression unit arranged to decrease the data size;

an image processing unit arranged to analyze the compressed data of each image, detect motion from the compressed data, and identify background and foreground regions for each image;

a data storage unit arranged to store the image data processed by the image processing unit;

a traffic detection unit arranged to detect network traffic and set the frame rates of the image data to be transmitted; and

a communication unit arranged to communicate with the network to transmit the image data.

28. A method of transmitting image data where the data has been split into foreground data and background data wherein the foreground and background data are transmitted at different bit rates.

29. A method as claimed in claim 28, wherein the bit rates are adjustable in dependence upon traffic over the transmission medium.

30. A method of forming a changed image from a previous image data and current image data identifying a change in the portion of the previous image comprising replacing a corresponding portion of the previous image data with the current image data to form the changed image.

31. A method as claimed in claim 30, wherein the previous image data is a previous image.

32. A method as claimed in claim 30, wherein the previous image data is a background image.