Patent ID: 9546924
Date: 2017-01-17
CPC Classifications: G01L,G10L

Claim:
1. A method in a transform audio encoder for encoding a time segment of an audio signal, the method comprising: receiving the time segment of the audio signal at the transform audio encoder; deriving an indicator, z, of the position in a frequency scale of a residual vector of a segment of a transform vector associated with the time segment of the audio signal; deriving a measure, Φ, related to the distribution of energy over frequency of the residual vector; estimating whether a change of sign of at least some of the non-zero coefficients of the residual vector would be audible after reconstruction of the time segment of the audio signal, based on determining whether a predefined criterion involving the measure Φ, the indicator z and a predefined threshold Θ, is fulfilled; encoding the amplitude of the coefficients of the residual vector to form an encoded audio signal time segment; encoding the sign of the coefficients of the residual vector into the encoded audio signal time segment only when it is determined that the criterion is fulfilled, and thus that a change of sign would be audible; and outputting the encoded audio signal time segment from the transform audio encoder.