CN1710960A

CN1710960A - Continuous image compressing method with difference judgement

Info

Publication number: CN1710960A
Application number: CN 200510085650
Authority: CN
Inventors: 吴坤荣; 陈俊文
Original assignee: Chunghwa Telecom Co Ltd
Current assignee: Chunghwa Telecom Co Ltd
Priority date: 2005-07-21
Filing date: 2005-07-21
Publication date: 2005-12-21

Abstract

Using result determined by difference between image frames before compression decides content of next piece of image frame to be compressed. Determining difference between image frames before carrying out JPEG encoding image flame, the method decides whether a high similar part in image frame is needed to output based on result determined by difference between image frames. Cooperated with characteristics of JPEG encoding method, the method reduces quantity of data generated at encoding operation. The invention is applicable to monitoring system needed for encoding compressed video steam or a series of image frames in order to reach maximal efficiency in saving operation time and storing quantity of data

Description

The continuous image compressing method that tool difference is judged

Technical field

The continuous image compressing method that the present invention judges about a kind of tool difference, especially refer to that a kind of image-type digital supervision, road vehicle monitoring, the monitoring of gate inhibition gateway, family or other public place of can be applicable to need be with online program or the system that carries out the digital video crossfire of world-wide web, or the environment and the occasion that need supervise in real time or record a video with the digital video crossfire.

Background technology

It is many with motion jpeg (motion JPEG) or the MPEG algorithm carries out video coding and compression to be applied to the video streams of image-type digital supervision at present; Use the benefit of motion jpeg image coding to be to have no lag characteristic, and do not need to do the computing of correlation between continuous two pictures, algorithm complexity is lower, demand when encoding on hardware usefulness is lower, because be the characteristic of carrying out absolute coding at each picture, if have when several image contents are identical continuously, identical data will repeat output or transmission; Mpeg encoded is when compressing consecutive identical picture, solved the problem of data burden, MPEG in coding except to the single picture coding, also can carry out and be close to the computing of correlation between picture, if with in the contiguous image content same or analogous part is arranged, will produce motion-vector (motion vector) and represent a small amount of data of otherness to save data quantity, but the computing of motion-vector makes the MPEG algorithm comparatively complicated between continuous pictures, need higher hardware usefulness requirement when encoding, and mpeg encoded is with picture group (GOP, group of pictures) be unit, the frame numbers among the picture group can have influence on the picture length of time of delay.

Summary of the invention

The continuous image compressing method that purpose of the present invention promptly is to provide the tool difference of a kind of low usefulness demand and low data quantity to judge, be be applied to image-type digital supervision, road vehicle monitoring, the monitoring of gate inhibition gateway, family or other public place need be with online program or the system that carries out the digital video crossfire of world-wide web, as digital supervision and video streams mechanism, and reduce world-wide web volume of transmitted data and the fluency of promoting video pictures.

The continuous image compressing method that tool difference of the present invention is judged, based on the JPEG compiling method, but earlier to carry out diversity ratio right with last picture Fi-1 content for picture Fi before coding, only the bigger part of otherness in the picture is encoded then, the method of carrying out is: before picture Fi will carry out the JPEG coding, at first being cut into nonoverlapping is the block of unit with 8 * 8 pixels, this moment each block to make diversity ratio right with the same position block of last picture Fi-1 separately, if the similarity subcritical value of these two blocks, two pictures have produced otherness before and after just being considered as in this block of 8 * 8, so this block that just keeps among the picture Fi carries out next code; If the similarity of these two blocks is higher than a critical value, two pictures are same or analogous before and after just being considered as in this block of 8 * 8, just do not keep the content of this block among the picture Fi this moment, and the block that does not keep is in order to obtain bigger compression ratio, so all the elements in this block all are set at fixed numbers 0 or 255 in the JPEG coding; Picture Fi is carried out obtaining difference picture Δ Fi after the above-mentioned otherness comparison, then picture Δ Fi is carried out the JPEG coding; The block part that in picture Fi, does not have reservation, in order to react to the trickle variation of brightness in the continuous pictures, so picture Fi is calculated average brightness value Mi, last picture Fi-1 calculated average brightness value Mi-1, then Mi is deducted Mi-1 and obtain brightness changing value Δ Mi, the block that does not quite upgrade because of otherness in picture only need add that brightness changing value Δ Mi upgrades and becomes new picture and get final product.

After receiving coded data, promptly deciphers receiving terminal, among the difference picture Δ Fi that separates out, if content all is 0 in 8 * 8 blocks, just must obtain the block content of last picture Fi-1 same position earlier, obtain new picture block after adding brightness changing value Δ Mi, and then continue the decoding flow process; Be not 0 value if having in 8 * 8 blocks, just representing this block is complete picture, and can directly replace becomes new picture.

The continuous image compressing method that the tool difference that provided of invention is judged mutually relatively the time, has more following advantage with existing:

One, coding side uses the jpeg algorithm encoding compression, and is lower on the demand of hardware usefulness when encoding because of algorithm complexity is low than the MPEG algorithm, and do not have lag characteristic, meets the required of most of digitized video supervisory control system reality.

Two, elder generation compares the otherness of two pictures in front and back and rejects the high part of similitude before picture is encoded, and can strengthen the compression ratio of JPEG coding and save data quantity.

Three, when the same block content of continuous two pictures is same or similar, the brightness that only needs to see through in the brightness changing value modified block changes, and both can react to the trickle variation of brightness in the continuous pictures, can also save the data quantity that transmits or store.

Description of drawings

Below in conjunction with the drawings and specific embodiments the present invention is described in further details.

Fig. 1 is the coding side operation workflow embodiment of the continuous image compressing method of tool difference judgement of the present invention;

Fig. 2 is the decoding end operation workflow embodiment of the continuous image compressing method of this tool difference judgement.

Embodiment

As shown in Figure 1, the continuous image compressing method coding side operation workflow embodiment that tool difference provided by the present invention is judged, picture Fi at first is cut into the block of nonoverlapping 8 * 8 pixels, to make diversity ratio right with the same position block of last picture Fi-1 separately for each block, if the similarity subcritical value of these two blocks, two pictures have produced otherness before and after just being considered as in this block of 8 * 8, carry out next code (ash color part in the upper left corner among the difference picture Δ Fi) so just keep this block, but wherein above-mentioned critical value can be used a fixed numbers or the numerical value of a random fluctuation, and the critical value that wherein can change numerical value is to see through correction of image numerical value obtained between each block to calculate alternately and get; If the similarity of these two blocks is higher than a critical value, two pictures are same or analogous before and after just being considered as in this block of 8 * 8, just do not keep the content (upper right corner blockage part among the difference picture Δ Fi) of this block among the picture Fi this moment, and the block that does not keep is in order to obtain bigger compression ratio, so all the elements in this block all are set at 0 (or other fixed numbers) in the JPEG coding; Picture Fi is carried out obtaining difference picture Δ Fi after the above-mentioned otherness comparison, then picture Δ Fi is carried out the JPEG coding; The block part that in picture Fi, does not have reservation, in order to react to the trickle variation of brightness in the continuous pictures, so picture Fi is calculated average brightness value Mi, last picture Fi-1 calculated average brightness value Mi-1, then Mi is deducted Mi-1 and obtain brightness changing value Δ Mi; After obtaining Δ Fi and Δ Mi, can be merged into the data behind the coding.

As shown in Figure 2, the continuous image compressing method decoding end operation workflow embodiment that tool difference provided by the present invention is judged, after receiving coded data, promptly deciphers at the decoding end, can obtain difference picture Δ Fi and brightness changing value Δ Mi after the decoding, after difference picture Δ Fi is divided into the block of nonoverlapping 8 * 8 pixels, if content all is 0 (upper right corner blockage part among the difference picture Δ Fi) in 8 * 8 blocks, just must obtain the block content (upper right corner blockage part among last the picture Fi-1) of last picture Fi-1 same position earlier, obtain new picture block (blockage part in the upper right corner among the picture Fi) after adding brightness changing value Δ Mi; Be not 0 value (ash color part in the upper left corner among the difference picture Δ Fi) if having in 8 * 8 blocks, just representing this block is complete picture, and can directly replace becomes new picture (ash color part in the upper left corner among the picture Fi).

Claims

1, the continuous image compressing method that a kind of tool difference is judged, it is characterized in that: this method cuts into picture Fi the block of nonoverlapping 8 * 8 pixels earlier before picture carries out the JPEG coding, it is right that the same position block that each block cuts into not overlapping 8 * 8 block of pixels with last picture Fi-1 is separately made diversity ratio, and according to the result of picture differences judgement, when among the difference picture Δ Fi that separates out, if content all is 0 in 8 * 8 blocks, just must obtain the block content of last picture Fi-1 same position earlier, obtain new picture block after adding brightness changing value Δ Mi, and then continue the decoding flow process.

2, the continuous image compressing method of judging as tool difference as claimed in claim 1 is characterized in that: wherein have not to be 0 value in 8 * 8 blocks, just representing this block is complete picture, and can directly replace becomes new picture.

3, the continuous image compressing method of tool difference judgement as claimed in claim 1, it is characterized in that: when wherein the block that at first is cut into nonoverlapping 8 * 8 pixels as picture Fi is separately with the right similarity subcritical value of the same position block diversity ratio of last picture Fi-1, two pictures have produced otherness before and after just being considered as in this block of 8 * 8, so this block that just keeps among the picture Fi carries out next code.

4, the continuous image compressing method of tool difference judgement as claimed in claim 1, it is characterized in that: when wherein the block that at first is cut into nonoverlapping 8 * 8 pixels as picture Fi is higher than a critical value with the right similarity of the same position block diversity ratio of last picture Fi-1 separately, two pictures are same or analogous before and after just being considered as in this block of 8 * 8, just do not keep the content of this block among the picture Fi this moment.

5, as the continuous image compressing method of claim 3 or 4 described tool differences judgements, it is characterized in that: but wherein this critical value is a fixed numbers or the numerical value of a random fluctuation.

6, the continuous image compressing method of tool difference judgement as claimed in claim 4, it is characterized in that: wherein in the block that does not keep in order in JPEG coding, to obtain bigger compression ratio, so all the elements in this block all are set at fixed numbers 0 or 255.

7, the continuous image compressing method of tool difference judgement as claimed in claim 4, it is characterized in that: the block part that does not wherein have reservation, in order to react to the trickle variation of brightness in the continuous pictures, so picture Fi is calculated average brightness value Mi, last picture Fi-1 calculated average brightness value Mi-1, then Mi is deducted Mi-1 and obtain brightness changing value Δ Mi, the block that does not quite upgrade because of otherness in picture only need add that brightness changing value Δ Mi upgrades and becomes new picture and get final product.