IMAGE CODING APPARATUS, IMAGE CODING METHOD, AND IMAGE CODING PROGRAM FOR CODING AT LEAST ONE STILL FRAME WITH STILL FRAME CODING HAVING A HIGHER QUALITY THAN NORMAL FRAME CODING OF OTHER FRAMES

• US 20090010556A1
• Filed: 09/05/2008
• Published: 01/08/2009
• Est. Priority Date: 01/16/2002
• Status: Active Grant

• Current Assignee: Sovereign Peak Ventures, LLC (Dominion Harbor Enterprises, LLC)
• Original Assignee: Kyoko Uchibayashi, Makoto Hagai
• Inventors: UCHIBAYASHI, Kyoko, HAGAI, Makoto
• Granted Patent: US 7,869,661 B2
• Time in Patent Office: Days
• US Class Current: 382/239
• CPC Class Codes: H04N 19/105 Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction
• CPC Class Codes: H04N 19/107 between spatial and temporal predictive coding, e.g. picture refresh
• CPC Class Codes: H04N 19/132 Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
• CPC Class Codes: H04N 19/149 by estimating the code amount by means of a model, e.g. mathematical model or statistical model
• CPC Class Codes: H04N 19/159 Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/196 being specially adapted for the computation of encoding parameters, e.g. by averaging previously computed encoding parameters processing of motion vectors H04N19/513
• CPC Class Codes: H04N 19/197 including determination of the initial value of an encoding parameter H04N19/56 takes precedence
• CPC Class Codes: H04N 19/503 involving temporal prediction adaptive coding with adaptive selection between spatial and temporal predictive coding H04N19/107; adaptive coding with adaptive selection among a plurality of temporal predictive coding modes H04N19/109
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

An image coding apparatus includes a still frame coding judgement unit for judging whether a target frame to be coded is a still frame or not from a difference value between the target frame and an immediately previous reference frame, and a quantization parameter control unit for performing control of a quantization parameter value to be used for coding, on an initial one frame at which an image starts to come into a standstill, wherein the initial frame is subjected to coding with less coding error as compared with coding for other frames.

Claims

1. An image coding method for dividing a target frame to be coded into macroblocks as processing units, obtaining a difference value between the target frame and a reference frame, and coding the difference value, said method including:

a still frame judgement step of judging whether or not the target frame to be coded is a still frame that is standing still; and

a high image quality coding step of subjecting at least one frame among plural frames which are judged as still frames in the still frame judgement step, to still frame coding which realizes higher image quality as compared with coding of other frames,

wherein said still frame judgement step performs the judgement on the basis of the difference value between the target frame and the reference frame.

2. An image coding method for dividing a target frame to be coded into macroblocks as processing units, obtaining a difference value between the target frame and a reference frame, and coding the difference value, said method including:

a still frame judgement step of judging whether or not the target frame to be coded is a still frame that is standing still; and

a high image quality coding step of subjecting at least one frame among plural frames which are judged as still frames in the still frame judgement step, to still frame coding which realizes higher image quality as compared with coding of other frames, wherein said high image quality coding step includes;

a still frame coding judgement step of judging whether the target frame which is judged as a still frame should be subjected to still frame coding or normal frame coding;

a quantization parameter value control step of controlling a quantization scale of an externally inputted quantization parameter, on the basis of the coding method determined in the still frame coding judgement step;

a skip macroblock judgement step of judging whether each macroblock in the target frame is a skip macroblock or not, using the quantization parameter controlled in the quantization parameter value control step, and the difference value; and

a coding step of coding the target frame on the basis of the results of judgements performed on the respective macroblocks in the target frame, which are obtained in the skip macroblock judgement step.

3. An image coding method for dividing a target frame to be coded into macroblocks as processing units, obtaining a difference value between the target frame and a reference frame, and coding the difference value, said method including:

a still frame judgement step of judging whether or not the target frame to be coded is a still frame that is standing still; and

a high image quality coding step of subjecting at least one frame among plural frames which are judged as still frames in the still frame judgement step, to still frame coding which realizes higher image quality as compared with coding of other frames, wherein said high image quality coding step includes;

a still frame coding judgement step of judging whether the target frame which is judged as a still frame should be subjected to still frame coding or normal frame coding;

a skip macroblock judgement step of

judging whether each macroblock in the target frame is a skip macroblock or not, by using the difference value between the target frame and the reference frame, and a prescribed threshold value, when the target frame is judged as a frame not to be subjected to still frame coding, in the still frame coding judgement step, and

controlling the prescribed threshold value to reduce it, and judging whether each macroblock in the target frame is a skip macroblock or not, using the controlled threshold value, and the difference value between the target frame and the reference frame, when the target frame is judged as a frame to be subjected to still frame coding, in the still frame coding judgement step; and

a coding step of coding the target frame on the basis of the results of judgements performed on the respective macroblocks in the target frame, which are obtained in the skip macroblock judgement step.

4. An image coding method for dividing a target frame to be coded into macroblocks as processing units, obtaining a difference value between the target frame and a reference frame, and coding the difference value, said method including:

a still frame judgement step of judging whether or not the target frame to be coded is a still frame that is standing still;

a high image quality coding step of subjecting at least one frame among plural frames which are judged as still frames in the still frame judgement step, to still frame coding which realizes higher image quality as compared with coding of other frames,

a still frame coding judgement step of judging whether a frame next to the target frame is a frame to be subjected to still frame coding or a frame to be subjected to normal frame coding, on the basis of coding information of the target frame that is determined in coding a frame previous to the target frame;

a quantization parameter value control step of controlling a quantization scale of an externally inputted quantization parameter, on the basis of the coding method determined in the still frame judgement step;

a skip macroblock judgement step of judging whether each macroblock in the target frame is a skip macroblock or not, by using the quantization parameter controlled in the quantization parameter value control step, and the difference value; and

a coding step of determining a coding method for the next frame on the basis of the result of judgement performed in the still frame coding judgement step, and coding the target frame on the basis of coding information that is determined in coding the previous frame.

5. An image coding method for dividing a target frame to be coded into macroblocks as processing units, obtaining a difference value between the target frame and a reference frame, and coding the difference value, said method including:

a still frame judgement step of judging whether or not the target frame to be coded is a still frame that is standing still; and

a high image quality coding step of subjecting at least one frame among plural frames which are judged as still frames in the still frame judgement step, to still frame coding which realizes higher image quality as compared with coding of other frames, and

wherein said still frame judgement step is carried out on the basis of a coding type which is possessed by each macroblock in the reference frame and indicates a coding method for the macroblock.

6. An image coding method as defined in claim 5, wherein

the coding type of each macroblock is indicated by three values of flags comprising a first flag indicating whether the target macroblock is a skip macroblock or not, and a second and a third flags indicating, when the target macroblock is a skip macroblock, whether the target frame should be subjected to still frame coding or not;

and

the flag of the target macroblock is updated according to the flag value of a macroblock which is referred to by the target macroblock.

7. An image coding method for dividing a target frame to be coded into macroblocks as processing units, obtaining a difference value between the target frame and a reference frame, and coding the difference value, said method including:

a still macroblock judgement step of performing intra-frame prediction as to whether each macroblock in the target frame is standing still or not; and

a macroblock coding step of coding a macroblock which is judged as a still macroblock in the still macroblock judgement step, with a higher image quality as compared with coding of other macroblocks.

8. An image coding method for dividing a target frame to be coded into macroblocks as processing units, obtaining a difference value between the target frame and a reference frame, and coding the difference value, said method including:

a still frame judgement step of judging whether or not the target frame to be coded is a still frame that is standing still; and

a high image quality coding step of subjecting at least one frame among plural frames which are judged as still frames in the still frame judgement step, to still frame coding which realizes higher image quality as compared with coding of other frames, and

wherein said high image quality coding step includes;

a still macroblock judgement step of judging whether each macroblock is standing still or not in the target frame which is judged as a still frame; and

a macroblock coding step of coding a macroblock which is judged as a still macroblock in the still macroblock judgement step, with a higher image quality as compared with coding of other macroblocks.

9. An image coding apparatus for dividing a target frame to be coded into macroblocks as processing units, obtaining a difference value between the target frame and a reference frame, and coding the target frame on the basis of the difference value, said apparatus including:

a still frame coding judgement unit for judging whether the target frame is a still frame or not on the basis of the difference value, and judging whether the target frame which is judged as a still frame is a frame to be subjected to still frame coding for coding the target frame with a higher image quality as compared with coding of other frames, or a frame to be subjected to normal frame coding;

a quantization parameter value control unit for controlling a quantization scale of an externally inputted quantization parameter, on the basis of an output signal from the still frame coding judgement unit;

a skip macroblock judgement unit for judging whether each macroblock in the target frame is a skip macroblock or not, using the quantization parameter controlled by the quantization parameter value control unit, and the difference value; and

a coding unit for coding the target frame on the basis of an output from the skip macroblock judgement unit.

10. An image coding apparatus as defined in claim 9, wherein said coding unit performs the coding by using the quantization parameter that is controlled by the quantization parameter value control unit.

11. An image coding apparatus for dividing a target frame to be coded into macroblocks as processing units, obtaining a difference value between the target frame and an already-coded reference frame, and coding the target frame on the basis of the difference value, said apparatus including:

a still frame coding judgement unit for judging whether the target frame is a still frame or not on the basis of the difference value, and judging whether the target frame that is judged as a still frame is a frame to be subjected to still frame coding for coding the target frame with a higher image quality as compared with coding of other frames, or a frame to be subjected to normal frame coding;

a skip macroblock judgement unit for judging whether each macroblock in the target frame is a skip macroblock or not, using an output from the still frame coding judgement unit and the difference value; and

a coding unit for coding the target frame on the basis of an output from the skip macroblock judgement unit.

12. An image coding apparatus as defined in claim 11 further including:

a quantization parameter value control unit for controlling a quantization scale of an externally inputted quantization parameter, on the basis of an output signal from the still frame coding judgement unit; and

said coding unit coding the target frame by using the quantization parameter that is controlled by the quantization parameter value control unit.

13. An image coding apparatus for dividing a target frame to be coded into macroblocks as processing units, obtaining a difference value between the target frame and a reference frame, and coding the target frame on the basis of the difference value, said apparatus including:

a skip macroblock judgement unit for performing intra-frame prediction as to whether each macroblock in the target frame is standing still or not, and judging that a target macroblock is a still macroblock when macroblocks in the vicinity of the target macroblock are skip macroblocks;

a quantization parameter value control unit for controlling a quantization parameter value of the target macroblock which is judged as a still macroblock by the skip macroblock judgement unit so that the quantization parameter value becomes smaller than an externally inputted quantization parameter value; and

a coding unit for coding the macroblock which is judged as a still macroblock, with a high image quantity as compared with coding of other macroblocks, by using the quantization parameter controlled by the quantization parameter value control unit.

14. A program for making a computer execute a process of dividing a target frame to be coded into macroblocks as processing units, obtaining a difference value between the target frame and a reference frame, and coding the difference frame,

said program making the computer execute a high image quality coding process comprising:

judging whether the target frame to be coded is a still frame or not; and

coding at least one frame among plural frames which are judged as still frames as the results of judgement, with a higher image quality as compared with coding of other frames.