Adaptive quantization within the JPEG sequential mode

• US 5,157,488 A
• Filed: 05/17/1991
• Issued: 10/20/1992
• Est. Priority Date: 05/17/1991
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Pennebaker, William B.
• Primary Examiner(s): Kostak, Victor R.
• Application Number:
  US07/702,904
• Time in Patent Office: 522 Days
• Field of Search: 358/13, 358/133, 358/135, 358/136, 341/200
• US Class Current: 375/240.04
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/126 Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
• CPC Class Codes: H04N 19/30 using hierarchical techniques, e.g. scalability H04N19/63 takes precedence
• CPC Class Codes: H04N 19/593 involving spatial prediction techniques
• CPC Class Codes: H04N 19/60 using transform coding

Abstract

A system and method for masking adaptive quantization during compressed image data transmission by defining a scaling factor for the quantization tables of the multiple image components, wherein the scaling factor signals changes in quantization for successive blocks of the image data. The scaling factor is transmitted as a further component together with the image components to thereby signal adaptive quantization of the image data.

Claims

1. A method for masking adaptive quantization during compressed image data transmission in a system for transmitting blocks of data representing multiple components of an image, comprising the steps of:

generating a quantization table for each of the multiple image components;

defining a common scaling factor for a portion of said quantization tables of the multiple image components; and

signaling changes in quantization for successive blocks of the image data by transmitting said common scaling factor as a further component together with the image components to thereby signal adaptive quantization of the image data.

2. A method according to claim 1, further comprising the steps of:

defining a separate scaling factor for each value in a portion of said quantization tables of the multiple image components; and

transmitting said separate scaling factors as said further component together with the image components to thereby signal adaptive quantization of the image data.

3. A method according to claim 1, wherein said defining is done by coding changes in scaling such that said common scaling factor is the DC coefficients in a further image component.

4. A method according to claim 2, wherein said defining is done by coding changes in each separate scaling factor such that said differences in scaling factors are the corresponding AC coefficients in a further image component.

5. A method according to claim 2, wherein said defining is done by coding in each separate scaling factor such that it is a corresponding AC coefficient in a further image component.

6. A method for masking adaptive quantization during compressed image data transmission in a system for transmitting blocks of data representing luminance-chrominance components of an image, comprising the steps of:

generating a quantization table for each of the luminance-chrominance image components;

defining a common scaling factor for a portion of said quantization tables of the luminance-chrominance image components; and

signaling changes in quantization for successive blocks of the image data by transmitting said common scaling factor as a further component together with the luminance-chrominance components to thereby signal adaptive quantization of the image data.

7. A method according to claim 6, further comprising the steps of:

defining a separate scaling factor for each value in portions of each of said quantization tables of the luminance-chrominance image components; and

transmitting said separate scaling factors as said further component together with the luminance-chrominance components to thereby signal adaptive quantization of the image data.

8. A method according to claim 7, further comprising the steps of:

defining a first scaling factor for a portion of a Y quantization table of the luminance-chrominance image components;

defining a second scaling factor for a portion of a Cr quantization table of the luminance-chrominance image components;

defining a third scaling factor for a portion of a Cb quantization table of the luminance-chrominance image components; and

transmitting said first through third scaling factors as a further component together with the luminance-chrominance components to thereby signal adaptive quantization of the image data.

9. A method according to claim 8, wherein said defining is done by coding changes in scaling such that the common scaling factor is the DC coefficients in a further image component.

10. A system for masking adaptive quantization during compressed image data transmission of blocks of data representing multiple components of an image, comprising:

first means for generating a quantization table for each of the multiple image components;

second means for defining a common scaling factor for a portion of said quantization tables of the multiple image components, said common scaling factor signaling changes in quantization for successive blocks of the image data; and

third means for transmitting said scaling factor as a further component together with the image components to thereby signal adaptive quantization of the image data.

11. A system according to claim 10, wherein:

said second means defines a separate scaling factor for each value in portions of each of said quantization tables of the multiple image components; and

said third means transmits said separate scaling factors as said further component together with the image components to thereby signal adaptive quantization of the image data.

12. A system according to claim 10, wherein said second means defines coding changes in each separate scaling factor such that said differences in scaling factors are the corresponding AC coefficients in a further image component.

13. A system according to claim 10, wherein said second means defines coding in each separate scaling factor such that it is a corresponding AC coefficient in a further image component.

14. A system according to claim 10, wherein:

said scaling factors signal changes in quantization for successive blocks of luminance-chrominance image data.

15. A system according to claim 14, further comprising:

fourth means for defining a first common scaling factor for a portion of a Y quantization table of the luminance-chrominance image components;

fifth means for defining a second common scaling factor for a portion of a Cr quantization table of the luminance-chrominance image components; and

sixth means for defining a third common scaling factor for a portion of a Cb quantization table of the luminance-chrominance image components;

wherein said transmitting means transmits said first through third scaling factors as a further component together with the luminance-chrominance components to thereby signal adaptive quantization of the image data.

16. A system according to claim 15, wherein:

said fourth through sixth means define a separate scaling factor for each value in portions of each of said quantization tables of the multiple image components; and

said third means transmits said separate scaling factors as said further component together with the image components to thereby signal adaptive quantization of the image data.

17. A system according to claim 16, wherein said fourth through sixth means use coding changes in scaling such that said common scaling factor is the DC coefficients in a further image component.