Method and apparatus for coding an input signal based on characteristics of the input signal

• US 5,579,051 A
• Filed: 12/14/1994
• Issued: 11/26/1996
• Est. Priority Date: 12/25/1992
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation), Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Murakami, Tokumichi, Kato, Yoshiaki, Shimada, Toshiaki
• Primary Examiner(s): Tran, Thai Q.
• Assistant Examiner(s): LEE, RICHARD J
• Application Number:
  US08/355,659
• Time in Patent Office: 713 Days
• Field of Search: 348/384, 348/390, 348/400, 348/401, 348/402, 348/409, 348/412, 348/415, 348/403, 348/405, 348/419, 348/438
• US Class Current: 348/409.1
• CPC Class Codes: H04N 19/107 between spatial and temporal predictive coding, e.g. picture refresh
• CPC Class Codes: H04N 19/112 according to a given display mode, e.g. for interlaced or progressive display mode
• CPC Class Codes: H04N 19/117 Filters, e.g. for pre-processing or post-processing sub-band filter banks H04N19/635
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/146 Data rate or code amount at the encoder output
• 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 19/172 the region being a picture, frame or field
• 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 19/527 Global motion vector estimation
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/80 Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation H04N19/635, H04N19/86 take precedence
• CPC Class Codes: H04N 19/82 involving filtering within a prediction loop
• CPC Class Codes: H04N 19/86 involving reduction of coding artifacts, e.g. of blockiness

Abstract

An interframe coding system which eliminates higher frequency components contained in an image signal effectively and adaptively with an adaptive filter provided in a coding loop. The adaptive filter eliminates the higher frequency components with the optimal filtering intensity for an image signal specified with a filtering coefficient which is decided by a filter controller. The filtering coefficient is decided by normalization of the difference between an input image signal and a predictive signal from a frame memory by the "Activity" of the input image signal or the predictive signal. The "Activity" can be based upon the sum of the absolute or squared difference values based upon the mean value of luminance intensity of pixels of the image signal.

Claims

1. A coding system comprising:

an encoder, responsive to a control signal, that selectively chooses a quantization step size of the encoder and that encodes an input signal into a coded signal using the quantization step size;

a frame memory that stores a previous signal and provides a predicative signal corresponding to a difference between the input signal and the previous signal;

means for generating a predictive error signal corresponding to a difference between the input signal and the predictive signal;

a filter, having an input coupled to the frame memory to receive the predictive signal, having a control input coupled to a filter control signal, and having an output coupled to an input of the means for generating a predictive error signal, that receives and filters the predictive signal, and that outputs a filtered signal to the means for generating a predictive error signal; and

a filter controller, having an output coupled to the control input of the filter, that is responsive to the input signal and the predictive signal, and that generates the filter control signal to control the filter; and

coding controller, responsive to the input signal and the predictive error signal, that calculates characteristics of the input signal and the predictive error signal and that generates the coding control signal the encoder based on the characteristics of the input signal and the predictive error signal.

2. The coding system of claim 1, wherein the coding controller includes means for generating the coding control signal based on the coded signal output by the encoder.

3. The coding system of claim 1, wherein the input signal comprises an intraframe signal and the predictive error signal comprises an interframe signal, and wherein the coding controller includes:

means for determining characteristics of the interframe signal and the intraframe signal;

means for comparing the characteristics of the interframe signal and the intraframe signal to produce a comparison result; and

means for generating the coding control signal based on the comparison result.

4. The coding system of claim 3, wherein the comparing means includes means for weighting the characteristics of the interframe signal and the intraframe signal.

5. The coding system of claim 3, wherein the means for determining characteristics determines a difference between maximum and minimum values of the signal.

6. The coding system of claim 3, wherein the means for determining characteristics determines a sum of absolute difference values between individual values of a signal and a mean value of the signal.

7. The coding system of claim 3 wherein the means for determining characteristics determines a sum of squared difference values between individual values of a signal and a mean value of a signal.

8. The coding system of claim 1 wherein the coding controller receives a first interframe signal based on the filtered signal, a second interframe signal based on the predictive signal, and an interframe signal corresponding to the input signal, the coding controller comprising;

means for determining characteristics of the first and second interframe signals and the intraframe signal;

means for comparing the characteristics of the first interframe signal, the characteristics of the second interframe signal, and the characteristics of the interframe signal to produce a comparison result; and

means for generating the coding control signal based on the comparison results.

9. The coding system of claim 8, wherein the comparing means includes means for weighting at least one of the characteristics of at least one of the first interframe signal, the second interframe signal, and the intraframe signal.

10. The coding system of claim 8, wherein the means for determining characteristics determines a difference between maximum and minimum values of the signal.

11. The coding system of claim 8, wherein the means for determining characteristics determines a sum of absolute difference values between individual values of a signal and a mean value of the signal.

12. The coding system of claim 8 wherein the means for determining characteristics determines a sum of squared difference values between individual values of a signal and a mean value of the signal.

13. The coding system of claim 1 wherein the coding controller receives an intraframe signal corresponding to the input signal and an interframe signal based on the filtered signal and wherein the coding controller comprises:

means for determining characteristics of the intraframe signal and characteristics of the intraframe signal;

means for comparing the characteristics of the interframe signal with the characteristics of the intraframe signal to provide a comparison result; and

means for generating the coding control signal based on the comparison result.

14. The coding system of claim 13, wherein the comparing means includes means for weighting at least one of the characteristics of at least one of the interframe signal and the intraframe signal.

15. The coding system of claim 13, wherein the means for determining characteristics determines a difference between maximum and minimum values of a signal.

16. The coding system of claim 13, wherein the means for determining characteristics determines a sum of absolute difference values between individual values of a signal and a mean value.

17. The coding system of claim 13 wherein the means for determining characteristics determines a sum of squared difference values between individual values of the signal and a mean value.