ADAPTATION OF SCAN ORDER FOR ENTROPY CODING

• US 20190313101A1
• Filed: 06/10/2019
• Published: 10/10/2019
• Est. Priority Date: 05/30/2017
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google LLC (Alphabet Inc.)
• Inventors: He, Dake
• Granted Patent: US 10,757,411 B2
• Time in Patent Office: Days
• CPC Class Codes: H04N 19/129 Scanning of coding units, e.g. zig-zag scan of transform coefficients or flexible macroblock ordering [FMO]
• 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 19/18 the unit being a set of transform coefficients
• CPC Class Codes: H04N 19/182 the unit being a pixel
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

Apparatuses and methods are disclosed for adapting scan order of a transform block. An apparatus for decoding coefficients of a transform block includes a processor. The processor is configured to decode, from a compressed bitstream, first coefficients of at least one row of the transform block; decode, from the compressed bitstream, second coefficients of at least one column of the transform block, where the transform block consists of the first coefficients, the second coefficients, and remaining coefficients; select, using the first coefficients and the second coefficients, a scan order for decoding the remaining coefficients; and decode the remaining coefficients of the transform block using the scan order.

Claims

1. An apparatus for decoding coefficients of a transform block, comprising:

a processor, the processor is configured to;

decode, from a compressed bitstream, first coefficients of at least one row of the transform block;

decode, from the compressed bitstream, second coefficients of at least one column of the transform block, the transform block consisting of the first coefficients, the second coefficients, and remaining coefficients;

select, using the first coefficients and the second coefficients, a scan order for decoding the remaining coefficients; and

decode the remaining coefficients of the transform block using the scan order.

2. The apparatus of claim 1, wherein to select, using the first coefficients and the second coefficients, the scan order for decoding the remaining coefficients comprises to:

select, using first magnitudes of the first coefficients and second magnitudes of the second coefficients, the scan order for decoding the remaining coefficients.

3. The apparatus of claim 1, wherein to select, using the first coefficients and the second coefficients, the scan order for decoding the remaining coefficients comprises to:

select, using first count of non-zero coefficients in the first coefficients and second count of non-zero coefficients in the second coefficients, the scan order for decoding the remaining coefficients.

4. The apparatus of claim 1, wherein to select, using the first coefficients and the second coefficients, the scan order for decoding the remaining coefficients comprises to:

in response to determining that a right half of the at least one row includes at least one non-zero coefficient and a bottom half of the at least one column does not include non-zero coefficients, select a vertical scan order as the scan order.

5. The apparatus of claim 1, wherein to select, using the first coefficients and the second coefficients, the scan order for decoding the remaining coefficients comprises to:

in response to determining that a right half of the at least one row does not include non-zero coefficients and a bottom half of the at least one column includes at least one non-zero coefficient, select a horizontal scan order as the scan order.

6. The apparatus of claim 1, wherein to select, using the first coefficients and the second coefficients, the scan order for decoding the remaining coefficients comprises to:

in response to determining that a first condition is not satisfied and a second condition is not satisfied, select a zig-zag, diagonal scan order as the scan order,

wherein the first condition comprises that a right half of the at least one row includes at least one non-zero coefficient and that a bottom half of the at least one column does not include non-zero coefficients, and

wherein the second condition comprises that the right half of the at least one row does not include non-zero coefficients and that the bottom half of the at least one column includes at least one non-zero coefficient.

7. The apparatus of claim 1, wherein the at least one row consists of a top-most row of the transform block.

8. The apparatus of claim 1, wherein the at least one column consists of a left-most column of the transform block.

9. The apparatus of claim 1, wherein the processor is further configured to:

determine, based on the first coefficients and the second coefficients, a category, wherein the category is one of horizontal, vertical, or other;

determine a context using the category; and

decode, using the context, an intra-prediction mode from the compressed bitstream.

10. A method for decoding coefficients of a transform block, comprising:

decoding, from a compressed bitstream, first coefficients of at least one row of the transform block;

decoding, from the compressed bitstream, second coefficients of at least one column of the transform block, the transform block consisting of the first coefficients, the second coefficients, and remaining coefficients;

selecting, using the first coefficients and the second coefficients, a scan order for decoding the remaining coefficients; and

decoding the remaining coefficients of the transform block using the scan order.

11. The method of claim 10, wherein selecting, using the first coefficients and the second coefficients, the scan order for decoding the remaining coefficients comprises:

selecting, using first magnitudes of the first coefficients and second magnitudes of the second coefficients, the scan order for decoding the remaining coefficients.

12. The method of claim 10, wherein selecting, using the first coefficients and the second coefficients, the scan order for decoding the remaining coefficients comprises to:

selecting, using first count of non-zero coefficients in the first coefficients and second count of non-zero coefficients in the second coefficients, the scan order for decoding the remaining coefficients.

13. The method of claim 10, wherein selecting, using the first coefficients and the second coefficients, the scan order for decoding the remaining coefficients comprises:

in response to determining that a right half of the at least one row includes at least one non-zero coefficient and that a bottom half of the at least one column does not include non-zero coefficients, selecting a vertical scan order as the scan order.

14. The method of claim 10, wherein to select, using the first coefficients and the second coefficients, the scan order for decoding the remaining coefficients comprises to:

in response to determining that a right half of the at least one row does not include non-zero coefficients and that a bottom half of the at least one column includes at least one non-zero coefficient, selecting a horizontal scan order as the scan order.

15. The method of claim 10, wherein to select, using the first coefficients and the second coefficients, the scan order for decoding the remaining coefficients comprises to:

in response to determining that a first condition is not satisfied and a second condition is not satisfied, selecting a zig-zag, diagonal scan order as the scan order,

wherein the first condition comprises that a right half of the at least one row includes at least one non-zero coefficient and that a bottom half of the at least one column does not include non-zero coefficients, and

wherein the second condition comprises that the right half of the at least one row does not include non-zero coefficients and that the bottom half of the at least one column includes at least one non-zero coefficient.

16. The method of claim 10, wherein the at least one row consists of a top-most row of the transform block.

17. The method of claim 10, wherein the at least one column consists of a left-most column of the transform block.

18. The method of claim 10, further comprising:

determining, based on the first coefficients and the second coefficients, a category, wherein the category is one of horizontal, vertical, and other;

determining a context using the category; and

decoding, using the context, an intra-prediction mode from the compressed bitstream.

19. An apparatus for encoding coefficients of a transform block, comprising:

a processor, the processor is configured to;

encode, in a compressed bitstream, first coefficients of at least one row of the transform block;

encode, in the compressed bitstream, second coefficients of at least one column of the transform block, the transform block consisting of the first coefficients, the second coefficients, and remaining coefficients;

select, using the first coefficients and the second coefficients, a scan order for encoding the remaining coefficients; and

encoding the remaining coefficients of the transform block using the scan order.

20. The apparatus of claim 19, wherein to select, using the first coefficients and the second coefficients, the scan order for encoding the remaining coefficients comprises to:

in response to determining that a first condition is satisfied, select a vertical scan order as the scan order, wherein the first condition comprises that a right half of the at least one row includes at least one non-zero coefficient and that a bottom half of the at least one column does not include non-zero coefficients;

in response to determining that a second condition is satisfied, select a horizontal scan order as the scan order, wherein the second condition comprises that the right half of the at least one row does not include non-zero coefficients and that the bottom half of the at least one column includes at least one non-zero coefficient; and

in response to determining that the first condition is not satisfied and the second condition is not satisfied, select a zig-zag, diagonal scan order as the scan order.