초록 ▼

A method and apparatus are described for inserting a watermark in the compressed domain. The watermark inserted does not require a reference. An overall watermarking system incorporating the invention combines cleartext, bitstream, and integrated watermarking. In a perceptual coder, the data enters

A method and apparatus are described for inserting a watermark in the compressed domain. The watermark inserted does not require a reference. An overall watermarking system incorporating the invention combines cleartext, bitstream, and integrated watermarking. In a perceptual coder, the data enters a filterbank, where it is processed into multiple separate coefficients. A rate/distortion control module uses noise threshold information from a perceptual coder, together with bit-count information from a noiseless coder, to compute scale factors. The coefficients are multiplied by the scale factors and quantized, then noiseless coded and then output for further processing/transmission. The invention supports three embodiments for inserting a mark into the bitstream imperceptibly. It is assumed that some set of scale factor bands have been selected, into which mark data will be inserted. In one embodiment, a set of multipliers {xi=2Ni: i.epsilon.M} is chosen. Each triple is modified by dividing the scale factor by x,i multiplying the quantized coefficients by {xi}, and adding mark data to the non-zero modified quantized coefficients. In an alternate embodiment, watermark data is represented via two characteristics of the bitstream data. A Huffinan table is selected for encoding the Scale Factor Band receiving watermark data which is not the table that would normally be used. The watermark data bit is set according to any desired scheme, and the quantized coefficients are derived using the alternate Huffinan table. In another embodiment, watermarking is integrated with quantization. The watermark is therefore difficult to remove without perceptible effects. The fact that marking data is present is again indicated by characteristics of the bitstream data. The modification factors {xi} are now all close to unity.

대표청구항 ▼

1. A perceptual coder for encoding at least one compressed audio or video signal to include hidden data, comprising, in combination:means for setting quantization step sizes to obtain a set of integer values after quantization of said at least one compressed signal, said means for setting step sizes

1. A perceptual coder for encoding at least one compressed audio or video signal to include hidden data, comprising, in combination:means for setting quantization step sizes to obtain a set of integer values after quantization of said at least one compressed signal, said means for setting step sizes employing at least one perceptual technique; means for adding the hidden data to said at least one compressed signal; means for quantizing said at least one compressed signal; and means for selecting a set of multipliers during the quantization, said adding of the hidden data occurring during the quantization.