| 摘要 |
<p>The invention concerns a method for an access control transmission of at least an image which has been subjected to a DCT transformation. The invention is characterized in that it consists in: prior to transmission, in partly degrading the quality of the image by scrambling by modifying part of the values of the predefined quantization table (8); swapping the DCT coefficients of a predetermined group (12) of DCT coefficients; transmitting access control data and the modified quantization table with the scrambled image; at reception, retrieving the access control data, and if access is granted; then restoring the predefined quantization table (8); inversely swapping the previously swapped DCT coefficients; otherwise delivering the scrambled image.</p> |
