Image coding apparatus and method

An image coding method for converting first coded data coded in a first coding scheme into second coded data coded in a second coding scheme, said method comprising:

• decoding the first coded data to generate a decoded picture and decoding information containing motion vectors;
• coding, in the second coding scheme, the decoded picture generated in said decoding of the first coded data, to generate the second coded data including a coded picture and coding information containing motion vectors;
• holding the decoding information generated in said decoding of the first coded data;
• holding the coding information generated in said coding of the decoded picture;
• and
• selecting either the decoding information or the coding information based on a coding condition indicating a picture type of a current decoded picture to be coded in said coding of the decoded picture, to generate, from the selected information, basic motion information to be used in said coding of the decoded picture for estimating motion vectors,
• wherein in said coding of the decoded picture, (i) a search range is determined according to the basic motion information generated in said selecting, (ii) motion vectors of the current decoded picture are estimated in the determined search range, and (iii) the second coded data including the coded picture and coding information containing the estimated motion vectors is generated.

A program for coding an image by converting first coded data coded in a first coding scheme into second coded data coded in a second coding scheme, said program causing a computer to execute:

• decoding the first coded data to generate a decoded picture and decoding information containing motion vectors;
• coding, in the second coding scheme, the decoded picture generated in the decoding of the first coded data, to generate the second coded data including a coded picture and coding information containing motion vectors;
• holding the decoding information generated in the decoding of the first coded data;
• holding the coding information generated in the coding of the decoded picture;
• and
• selecting either the decoding information or the coding information based on a coding condition indicating a picture type of a current decoded picture to be coded in the coding of the decoded picture, to generate, from the selected information, basic motion information to be used in the coding of the decoded picture for estimating motion vectors,
• wherein in the coding of the decoded picture, (i) a search range is determined according to the basic motion information generated in the selecting, (ii) motion vectors of the current decoded picture are estimated in the determined search range, and (iii) the second coded data including the coded picture and coding information containing the estimated motion vectors is generated.

An integrated circuit which codes an image by converting first coded data coded in a first coding scheme into second coded data coded in a second coding scheme, said integrated circuit comprising:

• a decoding unit configured to decode the first coded data to generate a decoded picture and decoding information containing motion vectors;
• a coding unit configured to code, in the second coding scheme, the decoded picture generated by said decoding unit, to generate the second coded data including a coded picture and coding information containing motion vectors;
• a decoding information holding unit configured to hold the decoding information generated by said decoding unit;
• a coding information holding unit configured to hold the coding information generated by said coding unit;
• and
• a basic motion information generating unit configured to select either the decoding information or the coding information based on a coding condition indicating a picture type of a current decoded picture to be coded by said coding unit, and to generate, from the selected information, basic motion information to be used by said coding unit for estimating motion vectors,
• wherein said coding unit is configured to (i) determine a search range according to the basic motion information generated by said basic motion information generating unit, (ii) estimate motion vectors of the current decoded picture in the determined search range, and (iii) generate the second coded data including the coded picture and coding information containing the estimated motion vectors.