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Multi-band spectral audio encoding

  • US 6,968,564 B1
  • Filed: 04/06/2000
  • Issued: 11/22/2005
  • Est. Priority Date: 04/06/2000
  • Status: Expired due to Term
First Claim
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1. A method of inserting an inaudible code into an audio signal comprising:

  • sampling the audio signal to generate a plurality of sub blocks of sampled audio, each of the sub blocks having a duration less than a minimum audibly perceivable signal delay;

    combining the sub blocks into a plurality of partially overlapping short blocks which together comprise a long block;

    individually transforming each of the short blocks into a frequency domain;

    encoding each transformed short block in the frequency domain with a desired code by;

    selecting at least one frequency to encode based on the desired code to insert and a predetermined coding rule;

    setting an amplitude of the at least one frequency based on a masking energy associated with the at least one frequency;

    setting a phase angle of the at least one frequency; and

    transforming the encoded short block into the time domain; and

    constructing an encoded time domain signal from at least two sequential ones of the encoded time domain short blocks, the phase angles of the encoded short blocks are set by setting the phase angle of the at least one frequency of a first short block to a first predetermined value, and incrementing the phase angle of each subsequent short block by a predetermined amount.

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