Image coding apparatus and method for converting first coded data coded into second coded data based on picture type

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 image coding method comprising:

• decoding the first coded data to generate a decoded picture and to generate decoding information containing motion vectors;
• coding, in the second coding scheme, the decoded picture generated in said decoding of the first coded data, so as to generate the second coded data including a coded picture and coding information containing motion vectors;
• holding, in a memory, the decoding information generated in said decoding of the first coded data;
• holding, in a memory, the coding information generated in said coding of the decoded picture;
• and
• a basic motion information generation step of (i) generating the basic motion information to be used in said coding of the decoded picture to estimate the motion vectors contained in the coding information, the basic motion information being generated using motion information obtained from the decoding information generated by said decoding when generating a currently decoded picture, when a picture type to be used by said coding of the decoded picture to re-code the currently decoded picture is a P picture, and (ii) generating the basic motion information using motion information obtained from the coding information generated by said coding when generating the second coded picture using a previously decoded picture previously decoded by said decoding and that has already been re-coded by said coding, when the picture type to be used in said coding of the decoded picture to re-code the currently decoded picture is a B picture,
• wherein, in said coding of the decoded picture, (i) a search range is determined according to the basic motion information generated in said basic motion information generation step, (ii) the motion vectors of the currently decoded picture are estimated in the determined search range, and (iii) the second coded data including the coded picture and the coding information containing the estimated motion vectors is generated.

A non-transitory computer-readable recording medium having a program recorded thereon, the 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, and the program causing a computer to execute a method comprising:

• decoding the first coded data to generate a decoded picture and to generate decoding information containing motion vectors;
• coding, in the second coding scheme, the decoded picture generated in the decoding of the first coded data, so as to generate the second coded data including a coded picture and coding information containing motion vectors;
• holding, in a memory, the decoding information generated in the decoding of the first coded data;
• holding, in a memory, the coding information generated in the coding of the decoded picture;
• and
• a basic motion information generation step of (i) generating the basic motion information to be used in said coding of the decoded picture to estimate the motion vectors contained in the coding information, the basic motion information being generated using motion information obtained from the decoding information generated by said decoding when generating a currently decoded picture, when a picture type to be used by said coding of the decoded picture to re-code the currently decoded picture is a P picture, and (ii) generating the basic motion information using motion information obtained from the coding information generated by said coding when generating the second coded picture using a previously decoded picture previously decoded by said decoding and that has already been re-coded by said coding, when the picture type to be used in said coding of the decoded picture to re-code the currently decoded picture is a B picture,
• wherein, in said coding of the decoded picture, (i) a search range is determined according to the basic motion information generated in said basic motion information generation step, (ii) the motion vectors of the currently decoded picture are estimated in the determined search range, and (iii) the second coded data including the coded picture and the 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 to generate decoding information containing motion vectors;
• a coding unit configured to code, in the second coding scheme, the decoded picture generated by said decoding unit, so as 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 (i) generate basic motion information to be used by said coding unit to estimate the motion vectors contained in the coding information, the basic motion information being generated using motion information obtained from the decoding information generated by said decoding unit when generating a currently decoded picture, when a picture type to be used by said coding unit to re-code the currently decoded picture is a P picture, and (ii) generate the basic motion information using motion information obtained from the coding information generated by said coding unit when generating the second coded picture using a previously decoded picture previously decoded by said decoding unit and that has already been re-coded by said coding unit when the picture type to be used by said coding unit to re-code the currently decoded picture is a B picture,
• 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 the motion vectors of the currently decoded picture in the determined search range, and (iii) generate the second coded data including the coded picture and the coding information containing the estimated motion vectors.