Multimedia adaptive scrambling system (MASS)
View Patent ↗A system ( 300, 500 ) for scrambling digital samples ( 115, 200, 250, 260, 270 ) of multimedia data, including audio and video data samples, such that the content of the samples is degraded but still recognizable, or otherwise provided at a desired quality level. The samples may be in any conceivable compressed or uncompressed digital format, including Pulse Code Modulation (PCM) samples, samples in floating point representation, samples in companding schemes (e.g., μ-law and A-law), and other compressed bit streams. The quality level may be associated with a particular signal to noise ratio, or quality level that is determined by objective and/or subjective tests, for example. A number of LSBs can be scrambled in successive samples in successive frames (FRAME A, FRAME B, FRAME C). Moreover, the parameters for scrambling may change from frame to frame. Furthermore, all or part of the scrambling key ( 310 ) can be embedded ( 340 ) in the scrambled data and recovered at a decoder ( 400, 600 ) to be used in descrambling. After descrambling, the scramble key is no longer recoverable because the scramble key itself is scrambled by the descrambler.
1. A method for protecting digital samples of content from illicit use by scrambling the content, wherein each sample includes a plurality of bits, ranging from least significant bits (LSBs) to most significant bits (MSBs), comprising the steps of:
determining a dynamic range defined by a most significant non-zero data bit of each sample; and
adaptively selecting a number of LSBs to be scrambled in each sample according to the dynamic range determined therefor;
scrambling the selected number of LSBs in each sample according to a scrambling key, while preserving a number of MSBs in each sample, to provide corresponding scrambled samples; wherein:
the selected number of LSBs is scrambled in each sample such that the scrambled samples are degraded but still recognizable.
2. The method of claim 1 , wherein the samples are provided in successive frames, comprising the further step of:
adaptively selecting the number of LSBs to be scrambled in each sample according to the frame thereof.
3. The method of claim 1 , wherein:
said scrambling key is a pseudo-random scrambling key.
4. The method of claim 1 , wherein:
in said scrambling step, the number of LSBs are scrambled within the same sample using intra-sample scrambling.
5. A method for protecting digital samples of content from illicit use by scrambling the content, wherein each sample includes a plurality of bits, ranging from least significant bits (LSBs) to most significant bits (MSBs), comprising the steps of:
determining a dynamic range defined by a most significant non-zero data bit of each sample; and
adaptively selecting a number of LSBs to be scrambled in each sample according to the dynamic range determined therefor;
scrambling the selected number of LSBs in each sample according to a scrambling key, while preserving a number of MSBs in each sample, to provide corresponding scrambled samples; wherein:
the selected number of LSBs is scrambled in each sample such that the scrambled samples are degraded but still recognizable; and
in said scrambling step, the selected number of LSBs are scrambled between different samples, and within the same sample, using inter-sample and intra-sample scrambling, respectively.
6. A method for protecting digital samples of content from illicit use by scrambling the content, wherein each sample includes a plurality of bits, ranging from least significant bits (LSBs) to most significant bits (MSBs), comprising the steps of:
determining a dynamic range defined by a most significant non-zero data bit of each sample; and
adaptively selecting a number of LSBs to be scrambled in each sample according to the dynamic range determined therefor;
scrambling the selected number of LSBs in each sample according to a scrambling key, while preserving a number of MSBs in each sample, to provide corresponding scrambled samples; wherein:
the selected number of LSBs is scrambled in each sample such that the scrambled samples are degraded but still recognizable; and
in said scrambling step, the selected number of LSBs are scrambled between different samples using horizontal inter-sample scrambling by interchanging bits having the same weight.
7. The method of claim 1 , comprising the further step of:
embedding the scrambling key, at least in part, into the scrambled samples for use at a decoder in descrambling the scrambled samples.
8. The method of claim 7 , wherein:
the scrambling key for a current frame of scrambled samples is embedded, at least in part, into a previous frame of samples.
9. The method of claim 7 , wherein:
the scrambling key for a current frame of scrambled samples is embedded, at least in part, into a current frame of samples.
10. A method for descrambling previously scrambled digital samples of content, wherein each sample includes a plurality of bits, ranging from least significant bits (LSBs) to most significant bits (MSBs), comprising the steps of:
determining a dynamic range defined by a most significant non-zero data bit of each sample; and
adaptively selecting a number of LSBs to be descrambled in each sample according to the dynamic range determined therefor;
descrambling the selected number of LSBs in each sample according to a scrambling key, while preserving a number of MSBs in each sample, to provide corresponding descrambled samples; wherein:
the selected number of LSBs is scrambled in each sample such that the scrambled samples are degraded but still recognizable.
11. The method of claim 10 , wherein the samples are provided in successive frames, comprising the further step of:
adaptively selecting the number of LSBs to be descrambled in each sample according to the frame thereof.
12. The method of claim 10 , wherein:
said scrambling key is a pseudo-random scrambling key.
13. The method of claim 10 , wherein:
in said descrambling step, the number of LSBs are descrambled within the same sample using intra-sample descrambling.
14. A method for descrambling previously scrambled digital samples of content, wherein each sample includes a plurality of bits, ranging from least significant bits (LSBs) to most significant bits (MSBs), comprising the steps of:
determining a dynamic range defined by a most significant non-zero data bit of each sample; and
adaptively selecting a number of LSBs to be descrambled in each sample according to the dynamic range determined therefor;
descrambling the selected number of LSBs in each sample according to a scrambling key, while preserving a number of MSBs in each sample, to provide corresponding descrambled samples; wherein:
the selected number of LSBs is scrambled in each sample such that the scrambled samples are degraded but still recognizable; and
in said descrambling step, the selected number of LSBs are descrambled between different samples, and within the same sample, using inter-sample and intra-sample descrambling, respectively.
15. A method for descrambling previously scrambled digital samples of content, wherein each sample includes a plurality of bits, ranging from least significant bits (LSBs) to most significant bits (MSBs), comprising the steps of:
determining a dynamic range defined by a most significant non-zero data bit of each sample; and
adaptively selecting a number of LSBs to be descrambled in each sample according to the dynamic range determined therefor;
descrambling the selected number of LSBs in each sample according to a scrambling key, while preserving a number of MSBs in each sample, to provide corresponding descrambled samples; wherein:
the selected number of LSBs is scrambled in each sample such that the scrambled samples are degraded but still recognizable; and
in said descrambling step, the selected number of LSBs are descrambled between different samples using horizontal inter-sample descrambling by interchanging bits having the same weight.
16. The method of claim 10 , wherein the scrambling key is embedded into the scrambled samples, comprising the further step of:
recovering the scrambling key from the scrambled samples for use in said descrambling step.
17. The method of claim 16 , wherein:
the scrambling key for a current frame of scrambled samples is embedded into a previous frame of samples.
18. The method of claim 10 , comprising the further steps of:
scrambling the scrambling key after descrambling the scrambled sample in said descrambling step.
19. An apparatus for protecting digital samples of content from illicit use by scrambling the content, wherein each sample includes a plurality of bits, ranging from least significant bits (LSBs) to most significant bits (MSBs), comprising:
a range detector/mask generator for determining a dynamic range defined by a most significant non-zero data bit of each sample and adaptively selecting a number of LSBs to be scrambled in each sample according to the dynamic range thereof;
a scrambler for scrambling the selected number of LSBs in each sample according to a scrambling key, while preserving a number of MSBs in each sample, to provide corresponding scrambled samples; wherein:
the selected number of LSBs is scrambled in each sample such that the scrambled samples are degraded but still recognizable.
20. An apparatus for descrambling previously scrambled digital samples of content, wherein each sample includes a plurality of bits, ranging from least significant bits (LSBs) to most significant bits (MSBs), comprising:
a range detector/mask generator for determining a dynamic range defined by a most significant non-zero data bit of each sample and adaptively selecting a number of LSBs to be descrambled in each sample according to the dynamic range thereof;
a descrambler for descrambling the selected number of LSBs in each sample according to a scrambling key, while preserving a number of MSBS in each sample, to provide corresponding descrambled samples; wherein:
the selected number of LSBs is scrambled in each sample such that the scrambled samples are degraded but still recognizable.
21. A method in accordance with claim 1 , wherein:
in said scrambling step, the number of LSBs are scrambled between different samples using inter-sample scrambling.
22. A method in accordance with claim 10 , wherein:
in said descrambling step, the number of LSBs are descrambled between different samples using inter-sample descrambling.