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., -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.
