Moving picture coding, coded-moving picture bitstream conversion and coded-moving picture bitstream multiplexing

A bitstream conversion apparatus for converting an incoming first moving-picture bitstream at a first code transfer rate to a second moving-picture bitstream at a second code transfer rate, the incoming first moving-picture bitstream having been obtained by coding first pictures set at a predetermined interval and used as reference pictures for inter-picture prediction of a moving picture to be coded and coding second pictures different from the first pictures, the apparatus comprising:

• a motion amount detector to obtain motion activity on the incoming first moving-picture bitstream;
• a decimation controller to set a decimation rate on the second pictures of the incoming first moving-picture bitstream according to at least the motion activity;
• and
• a bitstream decimator to decimate only bitstreams of the second pictures from the incoming first moving-picture bitstream at another predetermined interval according to the decimation rate.

A bitstream multiplexing apparatus for multiplexing a plurality of incoming first moving-picture bitstreams into a moving-picture bitstream at a bit rate lower than a total bit rate of the incoming first moving-picture bitstreams, each incoming first moving-picture bitstream having first moving-picture bitstreams of first pictures used as reference pictures for inter-picture prediction and bitstreams of second pictures other than the first pictures, the apparatus comprising:

• a decimation controller to set a decimation rate on the second pictures of the incoming first moving-picture bitstreams according to virtual buffer occupancy to the multiplexed moving-picture bitstream;
• a bitstream decimator to decimate the bitstreams of the second pictures from the incoming first moving-picture bitstreams at a predetermined interval according to the decimation rate, thus obtaining second bitstreams;
• a multiplexer to multiplex the second bitstreams to obtain the multiplexed bitstream;
• and
• virtual buffer means for obtaining a code amount of the multiplexed bitstream for each reproduction period as the virtual buffer occupancy.

A method of coding first pictures, that are set at a predetermined interval, to be used as reference pictures for inter-picture prediction of an incoming moving picture and coding second pictures different from the first pictures, the method comprising the steps of:

• encoding the first pictures by intra-picture coding or unidirectional inter-picture predictive coding, and to encode the second pictures by bidirectional inter-picture predictive coding using the first pictures or locally-decoded pictures of the first pictures as the reference pictures, thus obtaining a moving-picture bitstream;
• obtaining motion activity on the incoming moving picture;
• and
• multiplexing the moving-picture bitstream and the information of motion activity.

A method of converting an incoming first moving-picture bitstream at a first code transfer rate to a second moving-picture bitstream at a second code transfer rate, the incoming first moving-picture bitstream having been obtained by coding first pictures set at a predetermined interval and used as reference pictures for inter-picture prediction of a moving picture to be coded and coding second pictures different from the first pictures, the method comprising the steps of:

• obtaining motion activity on the incoming first moving-picture bitstream;
• setting a decimation rate on the second pictures of the incoming first moving-picture bitstream according to at least the motion activity;
• and
• decimating only bitstreams of the second pictures from the incoming first moving-picture bitstream at another predetermined interval according to the decimation rate.

A method of multiplexing a plurality of incoming first moving-picture bitstreams into a moving-picture bitstream at a bit rate lower than a total bit rate of the incoming first moving-picture bitstreams, each incoming first moving-picture bitstream having first moving-picture bitstreams of first pictures used as reference pictures for inter-picture prediction and bitstreams of second pictures other than the first pictures, the method comprising the steps of:

• obtaining a code amount of the multiplexed bitstream for each reproduction period as virtual buffer occupancy;
• setting a decimation rate on the second pictures of the incoming first moving-picture bitstreams according to the virtual buffer occupancy;
• decimating the bitstreams of the second pictures from the incoming first moving-picture bitstreams at a predetermined interval according to the decimation rate, thus obtaining second bitstreams;
• and
• multiplexing the second bitstreams to obtain the multiplexed bitstream.