Moving picture coding apparatus
AssigneeSharp Kabushiki Kaisha
InventorHiroyuki Okada
Life of this patent
Estimating the term…
Abstract
The coding mode determining section, when receiving the information as to occurrence of a scene change from the scene change detector, outputs a piece of mode control information to the coding controller. The coding controller, based on the amount of coding in the coder and the mode control information, controls the quantizer by setting up a quantization stepsize so that the current frame will have the target amount of coding. In this way, the quantization and coding are controlled by three stages, i.e., immediately after a scene change, from the scene change to the stabilization of the amount of coding, and after the stabilization of the amount of coding, to thereby prevent degradation of picture quality.
Claims5
A moving picture coding apparatus comprising:
- a motion detecting means for detecting motion vectors by dividing the input picture into blocks of N×M pixels (N and M are natural numbers) and determining the interframe difference for each block between the current frame and the previous frame;
- a motion compensation predicting means for determining motion compensated prediction values from the motion vectors to select interframe prediction or interframe prediction;
- an orthogonal transforming means for obtaining transform coefficients by performing an orthogonal transform of the difference between the input picture and the motion compensated prediction values;
- a quantizing means for quantizing the transform coefficients;
- a coding means for coding the quantized transform coefficients to generate coded information;
- a block skip determining means for determining blocks to skipped without coding, based on the interframe difference, determined by the motion detecting means, between the current frame and the previous frame and based on the determined result of the motion compensated prediction obtained from the motion compensation predicting means;
- a specific area extracting means for extracting specific area from the input picture;
- a scene change detecting means for detecting a scene change based on the interframe difference;
- a coding mode determining means which, when the scene change detecting means has detected a scene change, determines which mode the current state is in among three modes, the scene change frame mode for coding the scene change frame, the post-scene change mode for coding a predetermined number of frames after the occurrence of the scene change, and the specific area mode in which frames downstream are coded to improve the quality of picture of the specific area which has been extracted by the specific area extracting means;
- and
- a coding control means which, based on the mode determined by the coding mode determining means, controls the quantization in a manner such that a scene change frame and a predetermined number of frames downstream are quantized by setting up a quantization stepsize at the quantizing means and by using the quantization stepsize which allows no discrimination between the specific area and the area other than the specific area whilst thinning frames;
- and frames after the predetermined number of frames are quantized setting up a quantization stepsize at the quantizing means for increasing the coding amount of the specific area whilst restoring the original frame rate, wherein the coded information is transmitted at a predetermined frame rate by making the system capacity match the transmission rate of the network.
Dependencies are inferred from the claim text.