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Automatic bit-rate control method and image compression apparatus

A bit rate control, automatic technology, applied in the direction of image communication, television, electrical components, etc.

Active Publication Date: 2009-02-04
VIMICRO ELECTRONICS CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0015] The technical problem solved by the present invention is to provide an automatic bit rate control method and an image compression device, so as to correctly predict the next frame during the image compression process when a large change in the Q value between two frames of images is detected. The Q value of the image eliminates the situation of frame loss caused by excessive image compression or insufficient compression, so as to ensure high-quality image compression

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  • Automatic bit-rate control method and image compression apparatus

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Embodiment Construction

[0040] Such as Figure 5 As shown, it is a schematic diagram of the principle of the image compression device according to the embodiment of the present invention. Compared with the existing compression device, this embodiment adds: forced bit rate control (RBRC) module 501, Q value compensation (Q- complement) module 502, and Q-correction module 503. A number of registers are configured in each of the modules, and the parameters required by each are stored.

[0041] Among them, the Q value correction module 503 is used to store the preset difference threshold between the current Q value and the next Q value, and in the image compression process, determine the difference between the current Q value and the predicted next Q value Whether the value exceeds the preset threshold, if it exceeds the preset threshold, adjust the next Q value to further increase the difference between the current Q value and the next Q value, and input the adjusted next Q value into quantization Table gen...

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Abstract

The invention includes procedures: setting up threshold of difference value between current Q value and next time Q value; in procedure of image compression, detecting difference value between Q value utilized by current compression and next time Q value calculated in real time; when the said difference value exceeds threshold of difference value ser up, the method increases difference value, and uses adjusted Q value to compress next frame image; further, resetting condition for detecting compression ratio; when current frame of image is compressed to proportion accorded with detection condition, predicting whether the completed compressed entire image causes overflow of storage space based on current Q value used; if yes, then discarding coefficient of alternating current obtained through discrete cosine transform, and compensating current Q value. The invention better controls image compression distortion in JPEG coding as well as image frame loss caused by not enough compression.

Description

Technical field [0001] The invention relates to an automatic bit rate control method and an image compression device, in particular to an automatic bit rate control method for JPEG encoding and an image compression device. Background technique [0002] In the video chip hardware circuit design, considering that the storage space size is fixed after JPEG compression, the smaller the image compression rate, the smaller the image distortion. Therefore, a fixed image compression rate is selected to maintain the maximum utilization of the storage space. It is very necessary. [0003] In the JPEG encoder, the image compression rate is adjusted by the Q value, and the automatic bit rate control is completed by the adaptive Q value adjuster. The purpose of Q value adjustment is to predict the Q value of the next frame of image, so that the compression rate of the next frame of image can reach expectations. [0004] The principle of JPEG compression is to obtain 1 DC coefficient and 63 AC...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04N7/26H04N7/30H04N19/146H04N19/61
Inventor 郦文其汪源居晓波
Owner VIMICRO ELECTRONICS CORP