Converting an audio signal between data compression formats

摘要

A first audio signal in a first data compression format (for example MPEG 1 Layer II), in which a frame includes subband data, is converted into a second audio signal in a second data compression format (for example MPEG 1 Layer III). The subband data is used directly or indirectly so that the audio signal is not fully decoded prior to encoding in the second data compression format. The subband data is the 32 subband analysis coefficients that are output from a filterbank or transform which generates 32 subband representations of an input audio stream. Additional data such as the change in scale factors or the related change in the subband coefficients may be used to estimate a psycho acoustic entropy for the second audio signal which is in turn used to determine window switching for the second audio signal. The signal to mask ratio applied to the first audio signal is used to estimate the signal to mask ratio required for the second audio signal.