Video encoding and decoding apparatus

A video decoding apparatus comprising:

• input means for temporarily holding data generated by encoding an input video signal in one of an intra-encoding mode and an inter-encoding mode;
• decoding means for decoding the data temporarily held in said input means;
• memory means for storing a reference picture signal which is used to decode the data generated by encoding the input video signal in the inter-encoding mode;
• and
• rewriting means for rewriting the reference picture signal stored in the memory means, on the basis of a video signal obtained by said decoding means by decoding the data encoded in the intra-encoding mode,
• wherein said rewriting means determines a state of the data for each frame on the basis of the number of bits of the data temporarily held in said input means and the number of bits of one frame of the data, and when the frame is found to have errors, the rewriting means is inhibited from rewriting the reference picture signal on the basis of the frame, until said decoding means generates a video signal from data which has been encoded in the intra-encoding mode and which represents a frame having no errors.

A video encoding apparatus comprising:

• encoding means having an intra-encoding mode to intra-encode an input video signal, a first motion compensation mode to compensate for motion of a frame and inter-encode the frame, and a second motion compensation mode to compensate for motions of parts of the frame and inter-encode the parts of the frame;
• and
• selection means for selecting one of the intra-encoding mode, the first motion compensation mode and the second motion compensation mode for each specified domain of a picture represented by the input video signal,
• wherein said selection means causes said encoding means to periodically set an intra-encoding domain in the frame represented by the input video signal and to refresh the specified domain so as to move the intra-encoding domain in the frame, and selects one of the intra-encoding mode and the second motion compensation mode for a domain of the picture whose motion vector needs to be limited in order to refresh the input video signal before the domain of the picture is inter-encoded.

A video encoding method comprising the steps of:

• preparing an intra-encoding mode to intra-encode an input video signal and an inter-encoding mode to inter-encode an input video signal;
• selecting one of the inter-encoding mode and the intra-encoding mode for each specified domain of a picture represented by the input video signal;
• and
• determining whether said each specified domain of the picture is one of a motion domain and a stationary domain, on the basis of the input video signal and a video signal representing a frame immediately preceding a frame represented by the input video signal,
• wherein said selecting step includes periodically setting an intra-encoding domain in the frame represented by the input video signal, refreshing the specified domain so as to move the intra-encoding domain in the frame, and making a cycle of refreshing a signal for the stationary domain longer than a cycle of refreshing a signal for the motion domain.

A video decoding method comprising the steps of:

• temporarily holding data generated by encoding an input video signal in one of an intra-encoding mode and an inter-encoding mode;
• decoding the data temporarily held in said temporarily holding step;
• storing a reference picture signal which is used to decode the data generated by encoding the input video signal in the inter-encoding mode;
• and
• rewriting the reference picture signal stored in the storing step, on the basis of a video signal obtained by said decoding step by decoding the data encoded in the intra-encoding mode,
• wherein said rewriting step includes determining a state of the data for each frame on the basis of the number of bits of the data temporarily held in the temporarily holding step and the number of bits of one frame of the data, and when the frame is found to have errors, inhibiting rewriting the reference picture signal on the basis of the frame having errors, until a video signal is generated which has been encoded in the intra-encoding mode and which represents a frame having no errors.

A video encoding method comprising the steps of:

• preparing an intra-encoding mode to intra-encode an input video signal, a first motion compensation mode to compensate for motion of a frame and inter-encode the frame, and a second motion compensation mode to compensate for motions of parts of the frame and inter-encode the parts of the frame;
• and
• selecting one of the intra-encoding mode, the first motion compensation mode and the second motion compensation mode for each specified domain of a picture represented by the input video signal,
• wherein said selecting step includes periodically setting an intra-encoding domain in the frame represented by the input video signal, refreshing the specified domain so as to move the intra-encoding domain in the frame, and inhibiting selecting the first motion compensation mode for a domain of the picture whose motion vector needs to be limited in order to refresh the input video signal before the domain of the picture is inter-encoded.