Picture encoding method, picture encoding apparatus, picture decoding method and picture decoding apparatus

A picture encoding method comprising:

• encoding, by a processor, a luminance component of a picture and a first color difference component of the picture which has a first resolution to generate encoded data of the luminance component and encoded data of the first color difference component;
• generating, by the processor, interpolated data by applying one of a plurality of upsampling filters to data obtained by decoding the encoded data of the first color difference component;
• calculating, by the processor, difference data by obtaining differences in corresponding pixels between the interpolated data and a second color difference component of the picture which has a second resolution higher than the first resolution;
• generating, by the processor, encoded data of the difference data by encoding the difference data;
• and
• generating, by the processor, a stream that contains filter information indicating the applied upsampling filter, the encoded data of the luminance component, the encoded data of the first color difference component, and the encoded data of the difference data.

A picture encoding apparatus comprising:

• a processor configured to:
• encode a luminance component of a picture, a first color difference component of the picture, and difference data for the picture to generate encoded data of the luminance component, encoded data of the first color difference component which has a first resolution, and encoded data of the difference data which has a second resolution higher than the first resolution;
• generate interpolated data by applying one of a plurality of upsampling filters to data obtained by decoding the encoded data of the first color difference component;
• calculate the difference data by obtaining differences in corresponding pixels between the interpolated data and a second color difference component of the picture which has the second resolution;
• and
• generate a stream that contains filter information indicating the applied upsampling filter, the encoded data of the luminance component, the encoded data of the first color difference component, and the encoded data of the difference data.

A non-transitory computer-readable recording medium having recorded thereon a picture decoding program that causes a computer to execute a process comprising:

• decoding a luminance component of a picture, a first color difference component of the picture which has a first resolution, and difference data for the picture from a stream that contains encoded data of the luminance component, encoded data of the first color difference component, filter information indicating an upsampling filter applied to the first color difference component among a plurality of upsampling filters, and encoded data of the difference data which has a second resolution higher than the first resolution;
• generating interpolated data having the second resolution by applying the upsampling filter indicated by the filter information to the decoded first color difference component;
• and
• obtaining a sum of corresponding pixels between the interpolated data and the difference data to decode a second color difference component of the picture which has the second resolution.

A picture decoding method comprising:

• decoding, by a processor, a luminance component of a picture, a first color difference component of the picture which has a first resolution, and difference data for the picture from a stream that contains encoded data of the luminance component, encoded data of the first color difference component, filter information indicating an upsampling filter applied to the first color difference component among a plurality of upsampling filters, and encoded data of the difference data which has a second resolution higher than the first resolution;
• generating, by the processor, interpolated data having the second resolution by applying the upsampling filter indicated by the filter information to the decoded first color difference component;
• and
• obtaining, by the processor, a sum of corresponding pixels between the interpolated data and the difference data to decode a second color difference component of the picture which has the second resolution.

A picture decoding apparatus comprising:

• a processor configured to:
• decode a luminance component of a picture, a first color difference component of the picture which has a first resolution, and difference data for the picture from a stream that contains encoded data of the luminance component, encoded data of the first color difference component, filter information indicating an upsampling filter applied to the first color difference component among a plurality of upsampling filters, and encoded data of the difference data which has a second resolution higher than the first resolution;
• generate interpolated data having the second resolution by applying the upsampling filter indicated by the filter information to the decoded first color difference component;
• and
• obtain a sum of corresponding pixels between the interpolated data and the difference data to decode a second color difference component of the picture which has the second resolution.