Dynamic video focus control

• US 6,314,140 B1
• Filed: 12/28/1995
• Issued: 11/06/2001
• Est. Priority Date: 12/28/1995
• Status: Expired due to Term

• Current Assignee: Alcatel-Lucent USA, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Shelby, Kevin A.
• Primary Examiner(s): RAO, ANAND SHASHIKANT
• Application Number:
  US08/581,640
• Time in Patent Office: 2,140 Days
• Field of Search: 348/14, 348/27, 348/401, 348/405, 348/409, 348/411, 348/419, 348/420, 348/700, 348/169, 348/170, 375/240.25, 375/240.26, 375/240.02
• US Class Current: 375/240.26
• CPC Class Codes: H04N 19/107 between spatial and temporal predictive coding, e.g. picture refresh
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/137 Motion inside a coding unit, e.g. average field, frame or block difference
• CPC Class Codes: H04N 19/152 by measuring the fullness of the transmission buffer
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/527 Global motion vector estimation
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 7/148 Interfacing a video terminal to a particular transmission medium, e.g. ISDN

Abstract

In a video camera the effects of global motion of a subject being photographed are accommodated by varying the pixel definition or focus of a digitally transmitted video image in response to frame-to-frame changes falling outside of a predetermined range. Specifically this is accomplished by sensing changes in the image content between successive images, determining whether the extent of that change lies within the predetermined range, and adjusting the pixel definition when the extent of change lies outside the range, and maintaining a given pixel definition when the extent of change remains within a predetermined range.

Claims

1. A method of digitally transmitting video images in blocks, comprising:

setting a focus and a coordinated frame rate to a data stream of video images on the basis of available channel capacity;

said data stream having a plurality of successive frames, each frame having a multiplicity of blocks corresponding to blocks on the successive frames;

sensing changes by means of structural components, beyond a given difference, in image content between corresponding blocks of successive image frames; and

softening, by means of the components and in the absence of manual intervention, the focus in response to the changes, beyond a given difference between corresponding blocks in successive frames, occurring in a number of blocks above a first predetermined number of blocks.

2. A method as in claim 1, wherein the frame rate is increased in response to the focus being softened, by means of the components and in the absence of manual intervention, and the frame rate is decreased and the focus is sharpened in response to the changes, beyond a given difference between corresponding blocks in successive frames, occurring in a number of blocks below a second predetermined number of blocks less than the first predetermined number of blocks.

3. A method as in claim 1, wherein the focus is a function of the bit rate per pixel.

4. A method as in claim 1, wherein each of said blocks contains an image content that constitutes a portion of the image content of the frame.

5. A method as in claim 4, wherein the step of softening the focus includes counting the number of blocks in each frame having changes, beyond a given difference in the image content from corresponding blocks of the previous image frames, and the step of softening the focus further includes softening the focus in response to the number of blocks having changes, beyond a given difference above a given number spread.

6. A method as in claim 5, wherein the step of sensing changes, beyond a given difference in image content between corresponding blocks, includes saving one image and comparing the blocks of one image with blocks of a successive image, by means of the components and in the absence of manual intervention,.

7. A method as in claim 1, further comprising transmitting a data stream on the basis of the frame rate and on the basis of the focus.

8. A method as in claim 4, further comprising transmitting a data stream on the basis of the frame rate and of a focus.

9. A method as in claim 5, wherein the first predetermined number of blocks is manually variable.

10. A method as in claim 5, wherein the transmitting step includes transmitting signals indicating no change from block to block in successive frames as a definition of the number of bits per pixel in blocks which having no changes, beyond a given difference, in successive images.

11. A system for digitally transmitting video images in blocks, comprising:

a coder responsive to a data stream of video images and having a given channel capacity for setting a focus and a coordinated frame rate on the basis of available channel capacity, and for dividing each frame into blocks corresponding to blocks on successive frames;

a comparator responsive, in the absence of manual intervention, to changes, beyond a given difference, in corresponding blocks of successive image frames;

a global motion control responsive, in the absence of manual intervention, to the number of blocks in a frame having changes, beyond a given difference between corresponding blocks of successive frames, lying above a predetermined number of blocks, for softening the focus.

12. A system as in claim 11, wherein the global motion control includes means, in the absence of manual intervention, for increasing the frame rate while softening the focus and decreasing the frame rate and sharpening the focus in response to the changes, beyond a given difference between corresponding blocks in successive frames, occurring in a number of blocks below a second predetermined number of blocks less than the first predetermined number of blocks.

13. A system as in claim 11, wherein the focus is a function of the bit rate per pixel.

14. A system as in claim 11, wherein each of said blocks contains an image content that constitutes a portion of the image content of the frame.

15. A system as in claim 14, wherein the global motion control, in the absence of manual intervention, counts the number of blocks in each frame having changes, beyond a given difference, in the image content from corresponding blocks of the previous image frames, and softens the focus in response to the number of blocks having changes, beyond a given difference, above a given number spread.

16. A system as in claim 15, wherein the comparator includes means for saving one image and comparing the blocks of one image with blocks of a successive image.

17. A system as in claim 11, further comprising means for transmitting a data stream on the basis of the frame rate and on the basis of the focus.

18. A system as in claim 14, further comprising means for transmitting a data stream on the basis of the frame rate and on the basis of a focus.

19. A system as in claim 15, wherein the first predetermined number of blocks is manually variable.

20. A system as in claim 15, wherein the transmitting means includes transmitting signals indicating no change from block to block in successive frames as a definition of the number of bits per pixel in blocks which having no changes, beyond a given difference, in successive images.