| 摘要 |
<p>Described is a transmission system (10) comprising a transmitter (12) for transmitting a narrowband audio signal to a receiver (14) via a transmission channel (16). The receiver (14) comprises a frequency domain bandwidth extender (18) for extending a bandwidth of the received narrowband audio signal by complementing the received narrowband audio signal with a highband extension thereof. The bandwidth extender (18) comprises an amplitude extender (24) for extending the bandwidth of an amplitude spectrum of the received narrowband audio signal by mapping narrowband amplitudes onto highband amplitudes. The bandwidth extender (18) further comprises a phase extender (26) for extending the bandwidth of a phase spectrum of the received narrowband signal and a combiner (28) for combining the extended amplitude spectrum and the extended phase spectrum into a bandwidth extended audio signal. The transmission system (10) is characterized in that the amplitude extender (24) comprises an amplitude mapper (42) and first and second frequency scale transformers (40,44). The first frequency scale transformer (40) is arranged for transforming a linear frequency scale of the amplitude spectrum into a logarithmic frequency scale, e.g. the Bark scale. The amplitude mapper (42) is arranged for mapping according to the logarithmic frequency scale the narrowband amplitudes onto the highband amplitudes. The second frequency scale transformer (44) is arranged for transforming the logarithmic frequency scale of the extended amplitude spectrum into the linear frequency scale.</p> |
