Methods and apparatuses for encoding and decoding an image or a video

An apparatus, comprising one or more processors, wherein said one or more processors is operable to:

• decode an information for identifying at least one offset from a first initial value of at least one parameter of a context of an entropy coder, the at least one parameter comprising at least one of:
• a size of a window used for updating a probability value after decoding a binary symbol, or a weight used in a weighted average for determining a probability value for decoding a binary symbol,
• the context being associated to at least one binary symbol of a sequence of binary symbols representative of an image or a video,
• determine at least one second initial value of the at least one parameter, using the at least one offset, and
• entropy decode the sequence of binary symbols using the at least one parameter initialized to the second initial value.

A method, comprising:

• obtaining a first initial value of at least one parameter of a context of an entropy coder, the at least one parameter comprising at least one of:
• a size of a window used for updating a probability value after encoding a binary symbol, or a weight used in a weighted average for determining a probability value for encoding a binary symbol, the context being associated to at least one binary symbol of a sequence of binary symbols representative of an image or a video,
• determining a second initial value for the at least one, wherein determining the second initial value is based on a bitrate determination for entropy encoding a set of binary symbols associated to the context,
• encoding an information for identifying at least one offset between the second initial value and the first initial value, and
• entropy encoding the at least one binary symbol using the at least one parameter initialized to the second initial value.

An apparatus, comprising one or more processors, wherein said one or more processors is operable to:

• obtain a first initial value of at least one parameter of a context of an entropy coder, the at least one parameter comprising at least one of:
• a size of a window used for updating a probability value after encoding a binary symbol, or a weight used in a weighted average for determining a probability value for encoding a binary symbol, the context being associated to at least one binary symbol of a sequence of binary symbols representative of an image or a video,
• determine a second initial value for the at least one parameter, wherein determining the second initial value is based on a bitrate determination for entropy encoding a set of binary symbols associated to the context,
• encode an information for identifying at least one offset between the second initial value and the first initial value, and
• entropy encode the at least one binary symbol using the at least one parameter initialized to the second initial value.