| 摘要 |
An analogue signal coder suitable for use in a speech codec for digital radio system comprises means (12) for digitising the analogue signal, means (22) for deriving a long term correlation coefficient for the analogue signal and means (24) for deriving a number of short term coefficients. The coder also includes means for deriving an excitation sequence which can be used to synthesise an approximation to the analogue signal. The means (22) for deriving a long term coefficient derives a plurality of sums of products of samples of the digitised signal and means for interpolating the sums of products. The long term correlation coefficient is derived from the interpolated plurality of sums of products with fractional resolution and reduced computational complexity. |
