Patent ID: 7688891
Filing Date: 2010-03-30
Classification: H04N

Abstract:
1. An image data compression device, comprising: a quantizing section for quantizing image data with a quantization step changing in accordance with a quantization parameter; a FIFO buffer section for buffering the quantized data corresponding to a plurality of frames and quantized by the quantizing section; an encoded data generating section for generating encoded data obtained by encoding the quantized data after reading the quantized data out of the FIFO buffer section asynchronously with writing to the FIFO buffer section; and a rate control section for controlling a data size of the encoded data by changing the quantization step of the quantizing section for each frame, wherein the rate control section finds a predicted data size of the encoded data for the precedent frame from a data size of the quantized data for the precedent frame to the present frame, sets or releases an upper limit threshold of the quantization parameter based on the number of assignable bits assignable to a compressing process in order for maintaining a predetermined bit rate, or the number of remaining frames, or both the number of the assignable bits and the number of the remaining frames, finds the quantization parameter so as to be equal to or less than the upper limit threshold of the quantization parameter using the predicted data size when setting the upper limit threshold of the quantization parameter, and finds the quantization parameter irrespective of the upper limit threshold of the quantization parameter using the predicted data size when releasing the upper limit threshold of the quantization parameter.