Arithmetic encoder for arithmetically encoding and arithmetic decoder for arithmetically decoding a sequence of information values, methods for arithmetically encoding and decoding a sequence of information values and computer program for implementing these methods

Patent metadata

Field	Value
Publication number	US-12413244-B2
Application number	US-202318296055-A
Country	US
Kind code	B2
Filing date	Apr 5, 2023
Priority date	Oct 6, 2020
Publication date	Sep 9, 2025
Grant date	Sep 9, 2025

Abstract

An encoding scheme is provided for arithmetically encoding a sequence of information values into an arithmetic coded bitstream by providing the bitstream with entry point information, allowing for resuming arithmetic decoding of the bitstream from a predetermined entry point onward. A respective decoding scheme is also provided. These encoding and decoding schemes provide more efficient encoding in view of the decoding speed.

First claim

The invention claimed is:

1. An arithmetic encoder for arithmetically encoding a sequence of information values into an arithmetic coded bitstream, configured to:
symbolize the information values into symbol strings so as to acquire a sequence of symbols;
arithmetically encode the sequence of symbols by, for each symbol,
selecting a subinterval out of a plurality of subintervals into which a current interval, which defines a current version of a coding state of the arithmetic encoder, is subdivided according to a probability estimate for the respective symbol, according to a symbol value of the respective symbol so as to acquire an updated version of the coding state of the arithmetic encoder, defined by the selected subinterval, for encoding a next symbol of the sequence of symbols, and
renormalizing encoder-internal parameters which define the coding state under continuing the bitstream,
provide the bitstream with entry point information allowing for resuming arithmetic decoding the bitstream from a predetermined entry point onward.

2. The arithmetic encoder in accordance with claim 1 , wherein the entry point information comprises information on a coding state of an arithmetic decoder, which occurs in the arithmetic decoder when the arithmetic decoder decodes the bitstream until the predetermined entry point.

3. The arithmetic encoder in accordance with claim 2 , wherein the arithmetic encoder is configured to perform the arithmetic decoding the bitstream so as to determine the information on the coding state of the arithmetic decoder.

4. The arithmetic encoder in accordance with claim 2 , wherein the coding state of the arithmetic decoder is defined by decoder-internal parameters comprising an interval width parameter indicating a width of the current interval and a pointer pointing into the current interval and the information on the coding state of the arithmetic decoder comprises a value of the pointer.

5. The arithmetic encoder in accordance with claim 4 , wherein the arithmetic encoder is configured to perform the arithmetic decoding the bitstream and set the value of the pointer comprised by the information on the coding state of the arithmetic decoder to be equal to a current value of the pointer as manifesting itself in the arithmetic decoding the bitstream up to the predetermined entry point.

6. The arithmetic encoder in accordance with claim 2 , wherein the coding state of the arithmetic decoder is defined by decoder-internal parameters comprising an interval width parameter indicating a width of the current interval and a pointer pointing into the current interval and the information on the coding state of the arithmetic decoder comprises a value of the interval width parameter.

7. The arithmetic encoder in accordance with claim 6 , wherein the arithmetic encoder is configured to
perform the arithmetic decoding the bitstream and set the value of the interval width parameter comprised by the information on the coding state of the arithmetic decoder to be equal to a current value of the interval width parameter as manifesting itself in the arithmetic decoding the bitstream up to the predetermined entry point, or set the value of the interval width parameter comprised by the information on the coding state of the arithmetic decoder to be equal to a current value of the interval width parameter as manifesting itself in the arithmetic encoding the sequence of symbols up to the predetermined entry point.

8. The arithmetic encoder in accordance with claim 2 , wherein the coding state of the arithmetic decoder is defined by decoder-internal parameters comprising an interval width parameter indicating a width of the current interval and a pointer pointing into the current interval and the information on the coding state of the arithmetic decoder comprises a value of the pointer [e.g. which value is assumed by the pointer at the predetermined entry point] while being free of a value of the interval width parameter, wherein the arithmetic encoder is configured to set the value of the interval width parameter comprised by the information on the coding state of the arithmetic decoder to be equal to a predetermined value and use the predetermined value for the interval width parameter when resuming the arithmetic encoding the sequence of symbols from the predetermined entry point onwards, or
preliminarily interrupting the arithmetic encoding the sequence of symbols by arithmetically encoding a symbol of a predetermined symbol value immediately ahead the predetermined entry point before resuming the arithmetic encoding the sequence of symbols from the predetermined entry point onwards, and set the value of the interval width parameter comprised by the information on the coding state of the arithmetic decoder to be equal to a current value of the interval width parameter as manifesting itself in the arithmetic encoding the sequence of symbols up to the predetermined entry point, comprising the symbol of the predetermined symbol value.

9. The arithmetic encoder in accordance with claim 2 , wherein the entry point information comprises a bitstream pointer to a predetermined bit in the bitstream, which is up to be read next after the resuming the arithmetic decoding the bitstream from the predetermined entry point onwards.

10. The arithmetic encoder in accordance with claim 1 , wherein the arithmetic encoder is configured to
use context-adaptive arithmetic coding for arithmetically encoding the sequence of symbols, comprising selecting, for a context-adaptively encoded symbol of the sequence of symbols, a context model out of a plurality of context models, each of which has a probability estimate associated therewith, and adapting the probability estimates of the plurality of context models to actual symbol statistics using previously encoded symbols of the sequence of symbols,
wherein the entry point information is indicative of, for each of a set of one or more predetermined context models, a predetermined probability estimate for the respective predetermined context model, and the arithmetic encoder is configured to use the predetermined probability estimate in resuming the adaptation of the probability estimates of the plurality of context models with respect to the respective predetermined context model.

11. The arithmetic encoder in accordance with claim 1 , wherein the arithmetic encoder is configured to
use context-adaptive arithmetic coding for arithmetically encoding the sequence of symbols, comprising selecting, for a context-adaptively encoded symbol of the sequence of symbols, a context model out of a plurality of context models, each of which has a probability estimate associated therewith, and adapting the probability estimates of the plurality of context models to actual symbol statistics using previously encoded symbols of the sequence of symbols,
wherein the arithmetic encoder is configured to, for each of a set of one or more predetermined context models, set the probability estimate for the respective predetermined context model at the predetermined entry point to a default state and the arithmetic encoder is configured to use the default state in resuming the adaptation of the probability estimates of the plurality of context models with respect to the respective predetermined context model, or
wherein the arithmetic encoder is configured to, for each of a set of one or more predetermined context models, set the probability estimate for the respective predetermined context model at the predetermined entry point to a saved state manifesting itself at a predetermined condition during arithmetically encoding the sequence of symbols ahead the predetermined entry point and the arithmetic en

Assignees

• Fraunhofer Ges Forschung

Inventors

• Haase Paul
• Kirchhoffer Heiner
• Mueller Karsten
• Schwarz Heiko
• Marpe Detlev
• Wiegand Thomas

Classifications

• H04N19/625

  using discrete cosine transform [DCT] · CPC title

• H04N19/167

  Position within a video image, e.g. region of interest [ROI] · CPC title

• H03M7/6011

  Encoder aspects · CPC title

• H03M7/6005

  Decoder aspects · CPC title

• H03M7/4018

  Context adapative binary arithmetic codes [CABAC] · CPC title