# US 2018/0027245 A1 · Speedup Techniques for Rate Distortion Optimized Quantization

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- Number: US 2018/0027245 A1
- Document ID: US20180027245A1
- Status: Published application
- Kind: A1
- Application number: 15/670,965
- Filed: 2017-08-07
- Published: 2018-01-25
- Earliest claimed: 2009-09-10
- Assignees: Dolby Laboratories Licensing Corporation
- Applicants: Dolby Laboratories Licensing Corporation
- Inventors: Alexandros TOURAPIS; Yan YE
- Web page: https://patentgrep.com/patent/US20180027245A1

## CPC

- H04N 19/192: the adaptation method, adaptation tool or adaptation type being iterative or recursive
- H04N 19/103: Selection of coding mode or of prediction mode
- H04N 19/124: Quantisation
- H04N 19/126: Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
- H04N 19/132: Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
- H04N 19/147: according to rate distortion criteria (rate-distortion as a criterion for motion estimation H04N19/567)
- H04N 19/17: the unit being an image region, e.g. an object
- H04N 19/174: the region being a slice, e.g. a line of blocks or a group of blocks
- H04N 19/176: the region being a block, e.g. a macroblock
- H04N 19/19: using optimisation based on Lagrange multipliers
- H04N 19/196: being specially adapted for the computation of encoding parameters, e.g. by averaging previously computed encoding parameters (processing of motion vectors H04N19/513)
- H04N 19/107: between spatial and temporal predictive coding, e.g. picture refresh
- H04N 19/109: among a plurality of temporal predictive coding modes
- H04N 19/11: among a plurality of spatial predictive coding modes
- H04N 19/122: Selection of transform size, e.g. 8x8 or 2x4x8 DCT; Selection of sub-band transforms of varying structure or type
- H04N 19/197: {including determination of the initial value of an encoding parameter (H04N19/56 takes precedence)}
- H04N 19/61: in combination with predictive coding
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

Techniques for selecting a coding mode for an image coding process are described. Coding modes can be selected through a coding mode transition state machine, a re-quantization process, selection of an optimal transform size, by skipping some quantization parameters, or by performing motion search.

## Claims

### Claim 1

A method of selecting a coding mode and a quantization parameter for an image coding unit to be coded and quantized in an image coding process, comprising:
(a) performing a first quantization process having a first type of quantization technique during evaluation of M possible coding modes;
(b) based on the first quantization process, selecting M1 best coding modes according to a predefined coding criterion, wherein M>M1≧1;
(c) after steps (a) and (b) have been performed for each of the M possible coding modes, performing a second quantization process that has a second type of quantization technique for the M1 best coding modes; and
(d) selecting a best coding mode based on the results of the first quantization process and the second quantization process;
wherein the first quantization process has the first type of quantization technique, wherein the first type of quantization technique comprises a faster type of quantization than the second quantization type;
wherein the second quantization process has the second type of quantization technique, which comprises a slower quantization type than the first quantization type; and
wherein the first quantization process and the second quantization process are repeated for each quantization parameter.

### Claim 2 (depends on 1)

The method as recited in claim 1, wherein information about the positions and magnitudes of quantized transform coefficients of one or more quantization parameters is used during the quantization processes of subsequent quantization parameters.

### Claim 3 (depends on 1)

The method as recited in claim 1, wherein the second quantization process is applied to a single best coding mode among the M possible coding modes, or equivalently, M1=1.

### Claim 4 (depends on 1)

The method as recited in claim 1, wherein the best result is selected based on steps that comprise:
comparing i) a value of the predefined coding criterion of a residual, which is quantized with the first quantization process, with ii) a value of the predefined coding criterion of a residual quantized with the second quantization process; and
selecting the residual that offer a better value of the predefined coding criterion.

### Claim 5 (depends on 1)

The method as recited in claim 1, further comprising re-encoding the image coding unit after the optimal coding mode has been selected after the initial encoding process.

### Claim 6 (depends on 5)

The method as recited in claim 5, wherein the second quantization process is performed while re-encoding of the image coding unit.

### Claim 7 (depends on 6)

The method as recited in claim 6, wherein re-encoding comprises evaluating optimal prediction modes.

### Claim 8 (depends on 7)

The method as recited in claim 7, wherein a subset of prediction modes are evaluated during the re-encoding.

### Claim 9 (depends on 8)

The method as recited in claim 8, wherein the subset of prediction modes that is evaluated during the re-encoding process is selected based on the optimal prediction modes, which are chosen after the initial encoding process.

### Claim 10

A system for selecting a coding mode and a quantization parameter for an image coding unit to be coded and quantized in an image coding process, the system comprising:
(a) means for performing a first quantization process having a first type of quantization technique during evaluation of M possible coding modes;
(b) means for selecting, based on the first quantization process, M1 best coding modes according to a predefined coding criterion, wherein M>M1≧1;
(c) means for performing, after a function of means (a) for performing and a function of means (b) for selecting have been performed for each of the M possible coding modes, a second quantization process that has a second type of quantization technique for the M1 best coding modes; and
(d) means for selecting a best coding mode based on the results of the first quantization process and the second quantization process;
wherein the first quantization process has the first type of quantization technique, wherein the first type of quantization technique comprises a faster type of quantization than the second quantization type;
wherein the second quantization process has the second type of quantization technique, which comprises a slower quantization type than the first quantization type; and
wherein the first quantization process and the second quantization process are repeated for each quantization parameter.

### Claim 11 (depends on 10)

The system as recited in claim 10 wherein the system comprises one or more of:
means for performing or executing a computational function; or
means for performing or executing a function that relates to video encoding.

### Claim 12

An apparatus, comprising:
a processor; and
a computer readable storage medium that comprises instructions, which when performed or executed by the processor, cause, control, program or configure the processor to perform a process for selecting a coding mode and a quantization parameter for an image coding unit to be coded and quantized in an image coding process, the process comprising:
(a) performing a first quantization process having a first type of quantization technique during evaluation of M possible coding modes;
(b) based on the first quantization process, selecting M1 best coding modes according to a predefined coding criterion, wherein M>M1≧1;
(c) after steps (a) and (b) have been performed for each of the M possible coding modes, performing a second quantization process that has a second type of quantization technique for the M1 best coding modes; and
(d) selecting a best coding mode based on the results of the first quantization process and the second quantization process;
wherein the first quantization process has the first type of quantization technique, wherein the first type of quantization technique comprises a faster type of quantization than the second quantization type;
wherein the second quantization process has the second type of quantization technique, which comprises a slower quantization type than the first quantization type; and
wherein the first quantization process and the second quantization process are repeated for each quantization parameter.

### Claim 13 (depends on 11)

The apparatus as recited in claim 11 wherein the apparatus comprises one or more of a computer or a video encoder.

### Claim 14

A computer readable storage medium that comprises instructions encoded or stored therewith, which when performed or executed by a processor, cause, control, program or configure the processor to perform, execute or control a process for selecting a coding mode and a quantization parameter for an image coding unit to be coded and quantized in image coding, the process comprising:
(a) performing a first quantization process having a first type of quantization technique during evaluation of M possible coding modes;
(b) based on the first quantization process, selecting M1 best coding modes according to a predefined coding criterion, wherein M>M1≧1;
(c) after steps (a) and (b) have been performed for each of the M possible coding modes, performing a second quantization process that has a second type of quantization technique for the M1 best coding modes; and
(d) selecting a best coding mode based on the results of the first quantization process and the second quantization process;
wherein the first quantization process has the first type of quantization technique, wherein the first type of quantization technique comprises a faster type of quantization than the second quantization type;
wherein the second quantization process has the second type of quantization technique, which comprises a slower quantization type than the first quantization type; and
wherein the first quantization process and the second quantization process are repeated for each quantization parameter.