Method for dual-standard coding of very low data-rate images and coder- decoder for implementing this method

摘要

A method for dual-standard coding of very low data-rate images and a coder-decoder system for implementing the method, wherein images can be transmitted with low spatial "Quarter of Common Intermediate Format" (QCIF) resolution and with high time resolution according to a first standard, or with high spatial "Common Intermediate Format" (CIF) resolution and low time resolution according to a second standard. In the method and system, the coding of the images includes calculating the mean value of the quantification steps used by a quantifier circuit, comparing the calculated mean value with a first predetermined threshold value and with a second predetermined threshold value higher than the first threshold value, and, chronologically, coding the images in the first standard when the mean value of the quantification steps is lower than the first predetermined threshold value, then coding the images in the first standard as long as the mean value of the quantification steps is lower than the second predetermined threshold value, then coding the images in the second standard as long as the mean value of the quantification steps is higher than the second predetermined threshold value, then coding the images in the first standard when the mean value of the quantification steps is lower than the first predetermined threshold value.