Moving picture coding apparatus and moving picture decoding apparatus
A video encoder ( 70 ) for coding moving pictures comprising a buffer ( 16 c ) with a plurality of memory areas capable of storing frames composed of top fields and bottom fields, a motion estimation unit ( 19 ) operable to code, field by field, inputted pictures performing moving estimation and moving compensation by referring, field by field, to the picture data stored in a memory area, a motion compensation unit ( 16 d ), a subtractor ( 11 ), a transformation unit ( 13 ) and a quantization unit ( 14 ), a memory management unit ( 71 ) operable to manage, frame by frame, a plurality of memory areas, an inverse quantization unit ( 16 a ) and inverse discrete cosine transform unit ( 16 b ) operable to decode picture data in coded fields and store the picture data in the decoded field in any of the plurality of memory areas under the management by the memory management unit ( 71 ).
1. A picture decoding apparatus which decodes a moving picture, comprising:
a memory having a plurality of memory areas, each memory area being capable of storing picture data of a top field, a bottom field, or a frame comprising one top field and one bottom field;
a decoding unit configured to (1) perform frame-only decoding on input data by referring to only a reference frame stored in one memory area included in the plurality of memory areas, or (2) perform field-only decoding on input data by referring to only a reference field stored in one memory area included in the plurality of memory areas, or (3) perform frame and field decoding on input data by referring to both of the reference frame stored in the one memory area and the reference field stored in the one memory area;
a memory management unit configured to manage each memory area on a frame by frame basis regardless of which one of the following is performed: (1) frame-only decoding on input data; (2) field-only decoding on input data; or (3) frame and field decoding on input data; and
a storing unit configured to store a frame or a field decoded by the decoding unit into one memory area included in the plurality of memory areas under management of the memory management unit,
wherein said memory management unit is further configured to:
(1) set a state corresponding to the one memory area to be “used” when a frame, a top field, or a bottom field, any of which is to be decoded, is stored in the one memory area; and
(2) set a state corresponding to the one memory area to be “unused” when (i) no picture data is stored in the one memory area, (ii) a frame stored in the one memory area is unused for reference, and (iii) both of a top field and a bottom field stored in the one memory area are unused for reference, and
wherein said memory management unit is further configured to:
when a top field is stored in the one memory area for which a state is “unused” and the state corresponding to the one memory area is set to be “used”,
(1) allow a bottom field to be stored in the one memory area and set the state corresponding to the one memory area to be “used” in the case where the bottom field and the top field constitute a same frame; and
(2) prohibit a bottom field from being stored in the one memory area into which the top field is stored and allow the bottom field to be stored in another memory area other than the one memory area and included in the plurality of memory areas and set the state corresponding to the another memory area other than the one memory area to be “used” in the case where the top field and the bottom field do not constitute a same frame.
2. A picture decoding method for decoding a moving picture using a picture decoding apparatus, the picture decoding apparatus including a memory having a plurality of memory areas, each memory area being capable of storing picture data of a top field, a bottom field or a frame comprising one top field and one bottom field, said picture decoding method comprising:
a decoding step of (1) performing frame-only decoding on input data by referring to only a reference frame stored in one memory area included in the plurality of memory areas, or (2) performing field-only decoding on input data by referring to only a reference field stored in one memory area included in the plurality of memory areas, or (3) performing frame and field decoding on input data by referring to both of the reference frame stored in the one memory area and the reference field stored in the one memory area;
a memory management step of managing, using a memory management unit, each memory area on a frame by frame basis regardless of which one of the following is performed: (1) frame-only decoding on input data, (2) field-only decoding on input data, or (3) frame and field decoding on input data; and
a storing step of storing a frame or a field decoded in the decoding step into one memory area included in the plurality of memory areas under management of the memory management step,
wherein said memory management step further includes the steps of:
(1) setting a state corresponding to the one memory area to be “used” when a frame, a top field, or a bottom field, any of which is to be decoded, is stored in the one memory area; and
(2) setting a state corresponding to the one memory area to be “unused” when (i) no picture data is stored in the one memory area, (ii) a frame stored in the one memory area is unused for reference, and (iii) both of a top field and a bottom field stored in the one memory area are unused for reference, and
wherein said memory management step further includes the steps of:
when a top field is stored in the one memory area for which a state is “unused” and the state corresponding to the one memory area is set to be “used”,
(1) allowing a bottom field to be stored in the one memory area and setting the state corresponding to the one memory area to be “used” in the case where the bottom field and the top field constitute a same frame; and
(2) prohibiting a bottom field from being stored in the one memory area into which the top field is stored and allowing the bottom field to be stored in another memory area other than the one memory area and included in the plurality of memory areas and setting the state corresponding to the another memory area other than the one memory area to be “used” in the case where the top field and the bottom field do not constitute a same frame.