Method and apparatus for video coding

• US 10,554,975 B1
• Filed: 11/23/2018
• Issued: 02/04/2020
• Est. Priority Date: 09/30/2018
• Status: Active Grant

• Current Assignee: Tencent America LLC (Tencent Holdings Limited)
• Original Assignee: Tencent America LLC (Tencent Holdings Limited)
• Inventors: Li, Xiang, Xu, Xiaozhong, Liu, Shan
• Primary Examiner(s): Bailey, Frederick D
• Application Number:
  US16/198,966
• Time in Patent Office: 438 Days
• Field of Search: None
• CPC Class Codes: H04N 19/124 Quantisation
• 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 19/197 including determination of the initial value of an encoding parameter H04N19/56 takes precedence
• CPC Class Codes: H04N 19/70 characterised by syntax aspects related to video coding, e.g. related to compression standards
• CPC Class Codes: H04N 19/91 Entropy coding, e.g. variable length coding [VLC] or arithmetic coding

Abstract

Aspects of the disclosure provide method and apparatus for video coding. In some examples, an apparatus includes receiving circuitry and processing circuitry. The processing circuitry decodes, from a coded video bitstream, a syntax element for an adjusted version of an initial quantization parameter (QP) value at a picture level for a picture. The adjusted version is in a range with an upper boundary that is changed with a maximum QP value. Then, the processing circuitry determines the initial QP value of a segment (such as a slice, a tile, a group of tiles and the like) in the picture based on the syntax element and determines a QP value for a block in the segment according to the initial QP value of the segment and adjustments associated with the block. Then, the processing circuitry performs an inverse quantization on quantized data of the block according to the determined QP value.

Claims

1. A method for video decoding in a decoder, comprising:

decoding, from a coded video bitstream, a syntax element for an adjusted version of an initial quantization parameter (QP) value at a picture level for a picture, the adjusted version being in a range with an upper boundary that is changed with a maximum QP value;

recovering, by processing circuitry of the decoder, the initial QP value of a segment in the picture by adding the adjusted version of the initial QP value and an adjustment value calculated based on a half of the maximum QP value, the half of the maximum QP value is calculated according to one of

a right bit-shift of the maximum QP value, and

a right bit-shift of a sum of the maximum QP value and one;

determining a QP value for a block in the segment according to the initial QP value of the segment and an additional adjustment associated with the block; and

performing an inverse quantization on quantized data of the block according to the determined QP value for the block.

2. The method of claim 1, further comprising:

decoding a segment level change for the initial QP value from the coded video bitstream; and

determining the initial QP value for the segment according to the segment level change.

3. The method of claim 1, wherein the syntax element for the adjusted version of the initial QP value is decoded from a picture parameter set of the coded video bitstream.

4. The method of claim 1, wherein the segment is one of a slice, a tile, or a group of tiles.

5. An apparatus for video decoding, comprising:

processing circuitry configured to;

decode, from a coded video bitstream, a syntax element for an adjusted version of an initial quantization parameter (QP) value at a picture level for a picture, the adjusted version being in a range with an upper boundary that is changed with a maximum QP value;

recover the initial QP value of a segment in the picture by adding the adjusted version of the initial QP value and an adjustment value calculated based on a half of the maximum QP value, the half of the maximum QP value is calculated according to one of

a right bit-shift of the maximum QP value, and

a right bit-shift of a sum of the maximum QP value and one;

determine a QP value for a block in the segment according to the initial QP value of the segment and an additional adjustment associated with the block; and

perform an inverse quantization on quantized data of the block according to the determined QP value for the block.

6. The apparatus of claim 5, wherein the processing circuitry is configured to:

decode a segment level change for the initial QP value from the coded video bitstream; and

determine the initial QP value for the segment according to the segment level change.

7. The apparatus of claim 5, wherein the syntax element for the adjusted version of the initial QP value is decoded from a picture parameter set of the coded video bitstream.

8. A non-transitory computer-readable medium storing instructions which when executed by a computer for video decoding cause the computer to perform:

decoding, from a coded video bitstream, a syntax element for an adjusted version of an initial quantization parameter (QP) value at a picture level for a picture, the adjusted version being in a range with an upper boundary that is changed with a maximum QP value;

recovering the initial QP value of a segment in the picture by adding the adjusted version of the initial QP value and an adjustment value calculated based on a half of the maximum QP value, the half of the maximum QP value is calculated according to one of

a right bit-shift of the maximum QP value, and

a right bit-shift of a sum of the maximum QP value and one;

determining a QP value for a block in the segment according to the initial QP value of the segment and an additional adjustment associated with the block; and

performing an inverse quantization on quantized data of the block according to the determined QP value for the block.