Image data compression device, encoder, electronic equipment and method of compressing image data

An image data compression device to compress image data, comprising:

• a quantization part quantizing the image data with a quantization step that varies based on a quantization parameter;
• a FIFO buffer part buffering quantized data of a plurality of frames which are quantized by the quantization part;
• a coded data formation part reading out the quantized data from the FIFO buffer part asynchronously with a writing to the FIFO buffer part and generating coded data by encoding the quantized data;
• a rate control part controlling a data size of the coded data by changing the quantization step of the quantization part by frames, calculating a predicted data size of the coded data of a previous frame from a data size of the quantized data of the previous frame and calculating the quantization parameter by using the predicted data size;
• and
• a frame skip part performing a skip process to skip a generation process of the image data supplied to the quantization part and performing the skip process if a complexity, which corresponds to a difference value between the image data that is quantized by the quantization part and the image data of the previous frame, is equal or more than a complexity threshold.

An encoder to perform a compression process to image data, comprising:

• an image input interface performing a first interface process to input the image data;
• a quantization part quantizing the image data with a quantization step that varies based on a quantization parameter;
• a FIFO buffer part buffering quantized data of a plurality of frames which are quantized by the quantization part;
• a host reading out the quantized data from the FIFO buffer part asynchronously with a writing to the FIFO buffer part, calculating a predicted data size of a previous frame from a data size of the quantized data of the previous frame and calculating the quantization parameter by using the predicted data size;
• a host interface performing a second interface process with the host;
• and
• a skip flag register skipping a generation process of the image data and being set if a frame, in which the quantization parameter becomes larger than a skip threshold, appears consecutively in a number of times which is equal or more than the number of a skip succession threshold, wherein the generation process of the image data of a present frame is skipped if the skip flag register is set.

An encoder performing a compression process to image data, comprising:

• an image input interface performing a first interface process to input the image data;
• a quantization part quantizing the image data with a quantization step that varies based on a quantization parameter;
• a FIFO buffer part buffering quantized data of a plurality of frames which are quantized by the quantization part;
• a host reading out the quantized data from the FIFO buffer part asynchronously with a writing to the FIFO buffer part, calculating a predicted data size of a previous frame from a data size of the quantized data of the previous frame and calculating the quantization parameter by using the predicted data size;
• a host interface performing a second interface process with the host;
• and
• a skip flag register skipping a generation process of the image data and being set if a difference value information between the image data quantized by the quantization part and the image data of the previous frame is equal or more than a complexity threshold, wherein the generation process of the image data of a present frame is skipped if the skip flag register is set.