Patent ID: 9210483
Filing Date: 2015-12-08
Classification: G10L,H04N

Abstract:
1. A method for watermarking a Digital Audio Compression Standard AC-3 encoded bit stream, said method comprising: partially decoding a Digital Audio Compression Standard AC-3 encoded bit stream, thereby providing original quantized mantissa values and exponent values derived from Modified Discrete Cosine Transform MDCT transform coefficients and AC-3 bit allocation pointer (bap) values for said original quantized mantissa values, and determining the corresponding AC-3 power spectral density PSD values from said exponent values and determining from said PSD values a resulting masking curve; determining from said masking curve and said PSD values truly required bap values denoted as bap_t values; determining from said original quantized mantissa values, said bap values and said bap_t values a maximum allowable mantissa value modification for a current mantissa and, if applicable, limiting a desired mantissa value for said current mantissa by said maximum allowable mantissa value modification, wherein said desired mantissa value is received from a watermarking processing; and changing the AC-3 original quantized mantissa bits for a current mantissa value according to said limited desired mantissa value, wherein: if value ‘Δ’ is a current quantization level distance based on a current bap value and ‘Δ the maximal allowed m