# US 8,542,731 B2 · Method and apparatus for video codec quantization

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- Number: US 8,542,731 B2
- Document ID: US8542731B2
- Status: Granted
- Kind: B2
- Application number: 11/628,825
- Filed: 2005-06-03
- Published: 2008-04-03
- Granted: 2013-09-24
- Earliest claimed: 2004-06-18
- Assignees: Thomson Licensing
- Applicants: Alexandros Michael Tourapis; Jill MacDonald Boyce; Peng Yin
- Inventors: Alexandros Michael Tourapis; Jill MacDonald Boyce; Peng Yin
- Web page: https://patentgrep.com/patent/US8542731B2

## CPC

- H04N 19/192: the adaptation method, adaptation tool or adaptation type being iterative or recursive
- H04N 19/126: Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
- H04N 19/136: Incoming video signal characteristics or properties
- H04N 19/137: Motion inside a coding unit, e.g. average field, frame or block difference
- H04N 19/14: Coding unit complexity, e.g. amount of activity or edge presence estimation (H04N19/146 takes precedence)
- H04N 19/147: according to rate distortion criteria (rate-distortion as a criterion for motion estimation H04N19/567)
- H04N 19/154: Measured or subjectively estimated visual quality after decoding, e.g. measurement of distortion (use of rate-distortion criteria H04N19/147)
- H04N 19/159: Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
- H04N 19/16: for a given display mode, e.g. for interlaced or progressive display mode
- H04N 19/176: the region being a block, e.g. a macroblock
- H04N 19/18: the unit being a set of transform coefficients
- H04N 19/186: the unit being a colour or a chrominance component
- H04N 19/19: using optimisation based on Lagrange multipliers
- H04N 19/61: in combination with predictive coding
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

An encoder, a decoder, and corresponding methods are provided for encoding and decoding video signal data for an image block. The encoder includes a quantizer for receiving transform coefficients for the image block, and for adaptively performing dead-zone quantization based on coefficient positions and coefficient distributions of the transform coefficients.

## Claims

### Claim 1

An encoder for encoding video signal data for an image block, comprising:
a quantizer for receiving transform coefficients for the image block, and for adaptively performing dead-zone quantization based on coefficient positions and coefficient distributions of the transform coefficients to form quantization levels, wherein said quantizer adaptively performs the dead-zone quantization by determining a preliminary quantization level using a fixed dead-zone/rounding control, and repeating the dead-zone quantization based on the preliminary quantization level and using a coefficient quantization level dependent dead-zone/rounding control; and
an inverse quantizer for de-quantizing the quantization levels to generate reconstructed levels, wherein a rounding parameter used for de-quantizing a quantization level of a transform coefficient is determined by the quantization level.

### Claim 2 (depends on 1)

The encoder as defined in claim 1, wherein said quantizer computes the level dependent dead-zone/rounding control based upon a piecewise distribution within a corresponding level.

### Claim 3 (depends on 2)

The encoder as defined in claim 2, wherein said quantizer computes the level dependent dead-zone/rounding control using distribution concentrations with a reconstructed area of the image block.

### Claim 4 (depends on 1)

The encoder as defined in claim 1, wherein said quantizer computes the level dependent dead-zone/rounding control using an arithmetic integral process.

### Claim 5 (depends on 4)

The encoder as defined in claim 4, wherein the arithmetic integral process comprises at least one of a trapezoid approximation process and a simplex approximation process.

### Claim 6 (depends on 1)

The encoder as defined in claim 1, wherein said quantizer computes the level dependent dead-zone/rounding control based on distortion present in the transform coefficients.

### Claim 7 (depends on 1)

The encoder as defined in claim 1, wherein said quantizer forces at least some of the transform coefficients to a higher quantization level to improve subjective quality, when the at least some of the transform coefficients were originally set to a level zero.

### Claim 8 (depends on 7)

The encoder as defined in claim 7, wherein said quantizer determines whether to force the at least some of the transform coefficients to the higher level based on rate distortion optimized criteria.

### Claim 9

A method for encoding video signal data for an image block, comprising the steps of:
receiving transform coefficients for the image block;
adaptively performing dead-zone quantization based on coefficient positions and coefficient distributions of the transform coefficients to form quantization levels, wherein said step of adaptively performing the dead-zone quantization comprises the steps of:
initially performing the dead-zone quantization by determining a preliminary quantization level using a fixed dead-zone/rounding control; and
repeating the dead-zone quantization based on the preliminary quantization level and using a coefficient quantization level dependent dead-zone/rounding control; and
de-quantizing the quantization levels to reconstructed levels, wherein a rounding parameter used for de-quantizing a quantization level of a transform coefficient is determined by the quantization level.

### Claim 10 (depends on 9)

The method as defined in claim 9, further comprising the step of computing the level dependent dead-zone/rounding control based upon a piecewise distribution within a corresponding level.

### Claim 11 (depends on 10)

The method as defined in claim 10, further comprising the step of computing the level dependent dead-zone/rounding control using distribution concentrations with a reconstructed area of the image block.

### Claim 12 (depends on 9)

The method as defined in claim 9, further comprising the step of computing the level dependent dead-zone/rounding control using an arithmetic integral process.

### Claim 13 (depends on 12)

The method as defined in claim 12, wherein the arithmetic integral process comprises at least one of a trapezoid approximation process and a simplex approximation process.

### Claim 14 (depends on 9)

The method as defined in claim 9, further comprising the step of computing the level dependent dead-zone/rounding control based on distortion present in the transform coefficients.

### Claim 15 (depends on 9)

The method as defined in claim 9, further comprising the step of forcing at least some of the transform coefficients to a higher quantization level to improve subjective quality, when the at least some of the transform coefficients were originally set to a level zero.

### Claim 16 (depends on 15)

The method as defined in claim 15, wherein said forcing step comprises the step of determining whether to force the at least some of the transform coefficients to the higher level based on rate distortion optimized criteria.