Variable picture rate coding/decoding method and apparatus
First pictures are coded by a variable picture rate coding, the first pictures being set at a predetermined interval, to be used as reference pictures for inter-picture prediction of an incoming moving picture and second pictures different from the first pictures are coded. The first pictures are coded by intra-picture coding or unidirectional inter-picture predictive coding, thus obtaining a first bitstream. A coding picture rate is set in accordance with motion activity of the incoming moving picture. Pictures that have remained after decimation of the second pictures are coded in accordance with the picture rate 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 second bitstream. The first and the second bitstreams and data indicating the picture rate are multiplexed.
1. A moving-picture scanning-type conversion apparatus comprising:
a scanning-type setter to set a scanning type for each frame of a progressive moving picture incoming at a given picture rate, in accordance with motion activity of the incoming moving picture;
a scanning line decimator to decimate scanning lines from the incoming progressive moving picture, thus obtaining an interlaced moving picture at the given picture rate, for each frame;
a frame memory to store the incoming progressive moving picture at the given picture rate and output successive two frames of the same progressive moving picture at the given picture rate;
a line decimator to decimate scanning lines of frames of the incoming progressive moving picture, by separating even and odd scanning lines of the two frames, thus obtaining an interlaced signal that carries a progressive moving picture at a picture rate that is half of the given picture rate; and
a switch to switch the obtained interlaced moving picture and the obtained progressive moving picture carried by the interlaced signal in accordance with the set scanning type, for each frame.
2. A moving-picture scanning-type conversion method comprising the steps of:
setting a scanning type for each frame of a progressive moving picture incoming at a given picture rate, in accordance with motion activity of the incoming moving picture;
decimating scanning lines from the incoming progressive moving picture, thus obtaining an interlaced moving picture at the given picture rate, for each frame;
storing the incoming progressive moving picture at the given picture rate and output successive two frames of the same progressive moving picture at the given picture rate;
decimating scanning lines of frames of the incoming progressive moving picture, by separating even and odd scanning lines of the two frames, thus obtaining an interlaced signal that carries a progressive moving picture at a picture rate that is half of the given picture rate; and
switching the obtained interlaced moving picture and the obtained progressive moving picture carried by the interlaced signal in accordance with the set scanning type, for each frame.
3. The moving-picture scanning-type conversion apparatus according to claim 1 , wherein the scanning-type setter set the scanning type at interlace scanning when an average motion activity of the incoming moving picture is equal to or larger than a predetermined value whereas at progress scanning when the average motion activity is smaller than the predetermined value.
4. The moving-picture scanning-type conversion method according to claim 2 , wherein the scanning type is set at interlace scanning when an average motion activity of the incoming moving picture is equal to or larger than a predetermined value whereas at progress scanning when the average motion activity is smaller than the predetermined value.