Intra-macroblock DC and AC coefficient prediction for interlaced digital video

• US 5,974,184 A
• Filed: 10/24/1997
• Issued: 10/26/1999
• Est. Priority Date: 03/07/1997
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: General Instrument Corporation (CommScope Holding Company, Inc.)
• Inventors: Chen, Xuemin, Luthra, Ajay, Eifrig, Robert O.
• Primary Examiner(s): Tadayon, Bijan
• Application Number:
  US08/957,511
• Time in Patent Office: 732 Days
• Field of Search: 711/202, 711/220, 345/502, 345/202, 345/203, 345/418, 348/721, 348/402, 348/403, 348/407, 348/408, 348/409, 348/413, 348/415, 348/416, 348/699, 348/399, 386/68, 386/67, 360/70, 360/75, 382/232, 382/233, 382/234, 382/235, 382/236, 382/238, 382/239, 382/240, 382/243, 382/244, 382/248, 382/250, 382/251, 382/252, 382/253, 395/114, 395/376, 712/1
• US Class Current: 382/236
• 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 19/112 according to a given display mode, e.g. for interlaced or progressive display mode
• CPC Class Codes: H04N 19/137 Motion inside a coding unit, e.g. average field, frame or block difference
• CPC Class Codes: H04N 19/186 the unit being a colour or a chrominance component
• CPC Class Codes: H04N 19/51 Motion estimation or motion compensation
• CPC Class Codes: H04N 19/517 by encoding
• CPC Class Codes: H04N 19/56 Motion estimation with initialisation of the vector search, e.g. estimating a good candidate to initiate a search
• CPC Class Codes: H04N 19/563 Motion estimation with padding, i.e. with filling of non-object values in an arbitrarily shaped picture block or region for estimation purposes
• CPC Class Codes: H04N 19/583 Motion compensation with overlapping blocks
• CPC Class Codes: H04N 19/593 involving spatial prediction techniques
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/63 using sub-band based transform, e.g. wavelets
• CPC Class Codes: H04N 19/649 the transform being applied to non rectangular image segments

Abstract

DC and AC DCT transform coefficients of an INTRA coded block are differentially encoded by selecting predictor DC and AC coefficients from a left-hand neighboring block and a top neighboring block. Each block is coded according to a frame mode, a reordered field mode, and a non-reordered field mode. The AC predictor block is selected according to the respective coding modes of the blocks, and the block in which a DC predictor resides. The top block is selected as an AC predictor when the top block and current block are both reordered field mode, or both frame mode and/or non-reordered field mode, and the DC predictor resides in the top block. Zeroed AC spatial transform coefficients are used in place of the AC spatial transform coefficients from the selected block when the selected block is not INTRA coded, or does not reside in the same Video Object Plane (VOP) as the current block. DC coefficients may be non-linearly quantized.

Claims

1. A method for coding spatial transform coefficients of a current, INTRA coded block in a digital video image, comprising the steps of:

identifying an adjacent left-hand block, an adjacent top block, and a top, left block which is adjacent to said left-hand block and said top block;

said left-hand block, top block, and top, left block each having a DC spatial transform coefficient and a plurality of AC spatial transform coefficients;

each of said blocks being coded in a coding mode according to one of a frame mode, a reordered field mode, and a non-reordered field mode; and

selecting AC spatial transform coefficients from one of said left-hand block and said top block for use in differentially encoding respective AC spatial transform coefficients of said current block;

said selecting step being responsive to the coding mode of said current block and said top block.

2. The method of claim 1, comprising the further step of:

selecting the AC spatial transform coefficients from said left-hand block when said top block is coded according to one of the frame mode and the non-reordered field mode, and said current block is coded according to the reordered field mode.

3. The method of claim 1, comprising the further step of:

selecting the AC spatial transform coefficients from said left-hand block when said current block is coded according to one of the frame mode and the non-reordered field mode, and said top block is coded according to the reordered field mode.

4. The method of claim 1, comprising the further step of:

selecting a DC spatial transform coefficient for use in differentially encoding the DC spatial transform coefficient of said current block from one of said left-hand block and said top block according to (a) a gradient between the DC spatial transform coefficients of said left block and said top, left block, and (b) a gradient between the DC spatial transform coefficients of said top block and said top, left block.

5. The method of claim 4, comprising the further step of:

selecting AC spatial transform coefficients for use in the differential encoding from one of said left-hand block and said top block according to the selected DC spatial transform coefficient.

6. The method of claim 4, comprising the further step of:

selecting AC spatial transform coefficients for use in the differential encoding from said top block when the DC spatial transform coefficient is selected from said top block, and said current block is coded according to the frame mode or the non-reordered field mode, and said top block is coded according to the frame mode or the non-reordered field mode.

7. The method of claim 4, comprising the further step of:

selecting AC spatial transform coefficients for use in the differential encoding from said top block when the DC spatial transform coefficient is selected from said top block, and said current block and said top block are both coded according to the reordered field mode.

8. The method of claim 1, comprising the further step of:

using zeroed AC spatial transform coefficients in place of the AC spatial transform coefficients from the selected block when the selected block is not INTRA coded.

9. The method of claim 1, wherein said current block resides in a current video object plane (VOP), comprising the further step of:

using zeroed AC spatial transform coefficients in place of the AC spatial transform coefficients from the selected block when the selected block does not reside in said current VOP.

10. The method of claim 4, comprising the further step of:

non-linearly quantizing the DC spatial transform coefficient of the current block.

11. A method for decoding differentially encoded spatial transform coefficients of a current, INTRA coded block in a digital video image which is transmitted in a digital bitstream to recover corresponding full AC spatial transform coefficients of said current block, comprising the steps of:

recovering said digital bitstream;

said digital bitstream comprising data from an adjacent left-hand block, an adjacent top block, and a top, left block which is adjacent to said left-hand block and said top block;

said left-hand block, top block, and top, left block each having a DC spatial transform coefficient and a plurality of AC spatial transform coefficients;

each of said blocks being coded in a coding mode according to one of a frame mode, a reordered field mode, and a non-reordered field mode;

selecting AC spatial transform coefficients from one of said left-hand block and said top block; and

summing said selected AC spatial transform coefficients with said corresponding differentially encoded AC spatial transform coefficients of said current block to recover said full AC spatial transform coefficients of said current block;

said selecting step being responsive to the coding mode of said current block and said top block.

12. The method of claim 11, comprising the further step of:

selecting AC spatial transform coefficients for said summing step from said left-hand block when said top block is coded according to one of the frame mode and the non-reordered field mode, and said current block is coded according to the reordered field mode.

13. The method of claim 11, comprising the further step of:

selecting AC spatial transform coefficients for said summing step from said left-hand block when said current block is coded according to one of the frame mode and the non-reordered field mode, and said top block is coded according to the reordered field mode.

14. The method of claim 11, wherein the DC spatial transform coefficient of said current block is differentially encoded prior to transmission in the digital bitstream using the DC spatial transform coefficient from one of said left-hand block and said top block according to (a) a first gradient between the DC spatial transform coefficients of said left block and said top, left block, and (b) a second gradient between the DC spatial transform coefficients of said top block and said top, left block, comprising the further steps of:

determining said first and second gradients; and

selecting the DC spatial transform coefficient which was used in differentially encoding the DC spatial transform coefficient of said current block from one of said left-hand block and said top block according to the determined gradients.

15. The method of claim 14, comprising the further step of:

selecting AC spatial transform coefficients for said summing step from one of said left-hand block and said top block according to the selected DC spatial transform coefficient.

16. The method of claim 14, comprising the further step of:

selecting AC spatial transform coefficients for said summing step from said top block when the DC spatial transform coefficient is selected from said top block, and said current block is coded according to the frame mode or the non-reordered field mode, and said top block is coded according to the frame mode or the non-reordered field mode.

17. The method of claim 14, comprising the further step of:

selecting AC spatial transform coefficients for said summing step from said top block when the DC spatial transform coefficient is selected from said top block, and said current block and said top block are both coded according to the reordered field mode.

18. The method of claim 11, comprising the further step of:

using zeroed AC spatial transform coefficients in place of the AC spatial transform coefficients from the selected block when the selected block is not INTRA coded.

19. The method of claim 11, wherein said current block resides in a current video object plane (VOP), comprising the further step of:

using zeroed AC spatial transform coefficients in place of the AC spatial transform coefficients from the selected block when the selected block does not reside in said current VOP.

20. The method of claim 11, wherein:

said selecting step is responsive to a codeword provided in said digital bitstream which designates the AC spatial transform coefficients from one of said left-hand block and said top block.

21. The method of claim 14, wherein the DC spatial transform coefficient of the current block is non-linearly quantized, comprising the further steps of:

recovering data from said digital bitstream indicative of the respective quantization levels of the selected block and the current block; and

scaling the DC spatial transform coefficient of the current block according to the respective quantization levels of the selected block and the current block to recover a scaled DC spatial transform coefficient.

22. An apparatus for coding spatial transform coefficients of a current, INTRA coded block in a digital video image, comprising:

means for identifying an adjacent left-hand block, an adjacent top block, and a top, left block which is adjacent to said left-hand block and said top block;

said left-hand block, top block, and top, left block each having a DC spatial transform coefficient and a plurality of AC spatial transform coefficients;

each of said blocks being coded in a coding mode according to one of a frame mode, a reordered field mode, and a non-reordered field mode; and

means for selecting AC spatial transform coefficients from one of said left-hand block and said top block for use in differentially encoding respective AC spatial transform coefficients of said current block;

said means for selecting being responsive to the coding mode of said current block and said top block.

23. The apparatus of claim 22, wherein:

said means for selecting selects the AC spatial transform coefficients from said left-hand block when said top block is coded according to one of the frame mode and the non-reordered field mode, and said current block is coded according to the reordered field mode.

24. The apparatus of claim 22, wherein:

said means for selecting selects the AC spatial transform coefficients from said left-hand block when said current block is coded according to one of the frame mode and the non-reordered field mode, and said top block is coded according to the reordered field mode.

25. The apparatus of claim 22, wherein:

said means for selecting selects a DC spatial transform coefficient for use in differentially encoding the DC spatial transform coefficient of said current block from one of said left-hand block and said top block according to (a) a gradient between the DC spatial transform coefficients of said left block and said top, left block, and (b) a gradient between the DC spatial transform coefficients of said top block and said top, left block.

26. The apparatus of claim 25, wherein:

said means for selecting selects AC spatial transform coefficients for use in the differential encoding from one of said left-hand block and said top block according to the selected DC spatial transform coefficient.

27. The apparatus of claim 25, wherein:

said means for selecting selects AC spatial transform coefficients for use in the differential encoding from said top block when the DC spatial transform coefficient is selected from said top block, and said current block is coded according to the frame mode or the non-reordered field mode, and said top block is coded according to the frame mode or the non-reordered field mode.

28. The apparatus of claim 25, wherein:

said means for selecting selects AC spatial transform coefficients for use in the differential encoding from said top block when the DC spatial transform coefficient is selected from said top block, and said current block and said top block are both coded according to the reordered field mode.

29. The apparatus of claim 22, further comprising:

means for using zeroed AC spatial transform coefficients in place of the AC spatial transform coefficients from the selected block when the selected block is not INTRA coded.

30. The apparatus of claim 22, wherein said current block resides in a current video object plane (VOP), further comprising:

means for using zeroed AC spatial transform coefficients in place of the AC spatial transform coefficients from the selected block when the selected block does not reside in said current VOP.

31. The apparatus of claim 25, further comprising:

means for non-linearly quantizing the DC spatial transform coefficient of the current block.

32. An apparatus for decoding differentially encoded spatial transform coefficients of a current, INTRA coded block in a digital video image which is transmitted in a digital bitstream to recover corresponding full AC spatial transform coefficients of said current block, comprising:

means for recovering said digital bitstream;

said digital bitstream comprising data from an adjacent left-hand block, an adjacent top block, and a top, left block which is adjacent to said left-hand block and said top block;

said left-hand block, top block, and top, left block each having a DC spatial transform coefficient and a plurality of AC spatial transform coefficients;

each of said blocks being coded in a coding mode according to one of a frame mode, a reordered field mode, and a non-reordered field mode;

first means for selecting AC spatial transform coefficients from one of said left-hand block and said top block; and

means for summing said selected AC spatial transform coefficients with said corresponding differentially encoded AC spatial transform coefficients of said current block to recover said full AC spatial transform coefficients of said current block;

said first means for selecting being responsive to the coding mode of said current block and said top block.

33. The apparatus of claim 32, wherein:

said first means for selecting selects AC spatial transform coefficients for use by the summing means from said left-hand block when said top block is coded according to one of the frame mode and the non-reordered field mode, and said current block is coded according to the reordered field mode.

34. The apparatus of claim 32, wherein:

said first means for selecting selects AC spatial transform coefficients for use by the summing means from said left-hand block when said current block is coded according to one of the frame mode and the non-reordered field mode, and said top block is coded according to the reordered field mode.

35. The apparatus of claim 32, wherein the DC spatial transform coefficient of said current block is differentially encoded prior to transmission in the digital bitstream using the DC spatial transform coefficient from one of said left-hand block and said top block according to (a) a first gradient between the DC spatial transform coefficients of said left block and said top, left block, and (b) a second gradient between the DC spatial transform coefficients of said top block and said top, left block, further comprising:

means for determining said first and second gradients; and

second means for selecting the DC spatial transform coefficient which was used in differentially encoding the DC spatial transform coefficient of said current block from one of said left-hand block and said top block according to the determined gradients.

36. The apparatus of claim 35, wherein:

said first means for selecting selects AC spatial transform coefficients for use by the summing means from one of said left-hand block and said top block according to the selected DC spatial transform coefficient.

37. The apparatus of claim 35, wherein:

said first means for selecting selects AC spatial transform coefficients for use by the summing means from said top block when the DC spatial transform coefficient is selected from said top block, and said current block is coded according to the frame mode or the non-reordered field mode, and said top block is coded according to the frame mode or the non-reordered field mode.

38. The apparatus of claim 35, wherein:

said first means for selecting selects AC spatial transform coefficients for use by the summing means from said top block when the DC spatial transform coefficient is selected from said top block, and said current block and said top block are both coded according to the reordered field mode.

39. The apparatus of claim 32, further comprising:

means for using zeroed AC spatial transform coefficients in place of the AC spatial transform coefficients from the selected block when the selected block is not INTRA coded.

40. The apparatus of claim 32, wherein said current block resides in a current video object plane (VOP), further comprising:

means for using zeroed AC spatial transform coefficients in place of the AC spatial transform coefficients from the selected block when the selected block does not reside in said current VOP.

41. The apparatus of claim 32, wherein:

said first means for selecting is responsive to a codeword provided in said digital bitstream which designates the AC spatial transform coefficients from one of said left-hand block and said top block.

42. The apparatus of claim 35, wherein the DC spatial transform coefficient of the current block is non-linearly quantized, further comprising:

means for recovering data from said digital bitstream indicative of the respective quantization levels of the selected block and the current block; and

means for scaling the DC spatial transform coefficient of the current block according to the respective quantization levels of the selected block and the current block to recover a scaled DC spatial transform coefficient.