Sub-bitstream extraction-based image coding device and method for scalability

1 . A method for decoding an image by a decoding apparatus, the method comprising:

obtaining image information from a sub-bitstream;

obtaining information on a target output layer set (OLS) index and information on a highest temporal identifier;

decoding a picture being belonging to a layer included in a target OLS for the target OLS index and being related to the highest temporal identifier; and

outputting the decoded picture,

wherein the sub-bitstream is derived based on sub-bitstream extraction process for a bitstream,

wherein inputs of the sub-bitstream extraction process includes a value related to the target OLS index and a value related to the highest temporal identifier,

wherein the sub-bitstream includes a specific network abstraction layer (NAL) unit including the information on the target OLS index and the information on the highest temporal identifier, and

wherein the specific NAL unit including the information on the target OLS index and the information on the highest temporal identifier is a first NAL unit in an access unit (AU) based on the image information including the AU which contains the specific NAL unit and does not contain an access unit delimiter (AUD) NAL unit.

2 . The method of claim 1 , wherein the sub-bitstream extraction process comprises removing the specific NAL unit including the information on the target OLS index and the information on the highest temporal identifier.

3 . The method of claim 1 , wherein a value of the information on the target OLS index is set based on an input for the sub-bitstream extraction process and a value of the information on the highest temporal identifier is set based on the input for the sub-bitstream extraction process.

4 . The method of claim 1 , wherein the target OLS index is set based on an external means or the information on the target OLS index obtained from the sub-bitstream,

wherein based on the external means being available, the target OLS index is set based on the external means, and

wherein based on the external means not being available, the target OLS index is set based on the information on the target OLS index.

5 . The method of claim 1 , wherein the highest temporal identifier is set based on an external means or the information on the highest temporal identifier obtained based on the sub-bitstream,

wherein based on the external means being available, the highest temporal identifier is set based on the external means, and

wherein based on the external means not being available, the highest temporal identifier is set based on the information on the highest temporal identifier.

6 . The method of claim 1 , wherein the picture is decoded based on a temporal sublayer having a temporal identifier, and

wherein the value of the temporal identifier is smaller than that of the highest temporal identifier.

7 . A method for encoding an image by a encoding apparatus, the method comprising:

obtaining an image;

generating information on a target output layer set (OLS) index and information on a highest temporal identifier;

encoding the image, the information on the target OLS index and the information on the highest temporal identifier; and

outputting a bitstream including image information based on the encoding;

wherein the bitstream includes a specific network abstraction layer (NAL) unit including the information on the target output layer set (OLS) index and the information on the highest temporal identifier,

wherein the specific NAL unit including the information on the target OLS index and the information on the highest temporal identifier is a first NAL unit in an access unit (AU) based on the image information including the AU which contains the specific NAL unit and does not contain an access unit delimiter (AUD) NAL unit.

8 . A non-transitory computer-readable storage medium for storing encoded information generated by the method of claim 7 .

9 . A method for transmitting data for image information, the method comprising:

obtaining a bitstream of the image information; and

transmitting the data comprising the bitstream of the image information,

wherein the bitstream is generated based on:

obtaining an image,

generating information on a target output layer set (OLS) index and information on a highest temporal identifier, and

encoding the image, the information on the target OLS index and the information on the highest temporal identifier,

wherein the bitstream includes a specific network abstraction layer (NAL) unit including the information on the target output layer set (OLS) index and the information on the highest temporal identifier,

wherein the specific NAL unit including the information on the target OLS index and the information on the highest temporal identifier is a first NAL unit in an access unit (AU) based on the image information including the AU which contains the specific NAL unit and does not contain an access unit delimiter (AUD) NAL unit.