Methods, encoder and decoder for linear predictive encoding and decoding of sound signals upon transition between frames having different sampling rates
Methods, an encoder and a decoder are configured for transition between frames with different internal sampling rates. Linear predictive (LP) filter parameters are converted from a sampling rate S 1 to a sampling rate S 2 . A power spectrum of a LP synthesis filter is computed, at the sampling rate S 1 , using the LP filter parameters. The power spectrum of the LP synthesis filter is modified to convert it from the sampling rate S 1 to the sampling rate S 2 . The modified power spectrum of the LP synthesis filter is inverse transformed to determine autocorrelations of the LP synthesis filter at the sampling rate S 2 . The autocorrelations are used to compute the LP filter parameters at the sampling rate S 2.
1. A method for interpolating LP filter parameters in a current sound signal processing frame following a previous sound signal processing frame, the previous frame using an internal sampling rate S 1 and the current frame using an internal sampling rate S 2 and defining a number of subframes, comprising:
providing LP filter parameters from the previous frame at the internal sampling rate S 1 ;
providing LP filter parameters from the current frame at the internal sampling rate S 2 ;
converting the LP filter parameters from the previous frame from the internal sampling rate S 1 to the internal sampling rate S 2 ;
transforming the LP filter parameters to a quantization and interpolation domain; and
computing LP filter parameters of at least one of the subframes of the current frame using a weighted sum of the LP filter parameters from the current frame at the internal sampling rate S 2 and the LP filter parameters from the previous frame at the internal sampling rate S 2 .
2. The method of claim 1 , wherein the LP filter parameters are quantized LP filter parameters.
3. The method of claim 1 , wherein the quantization and interpolation domain is a line spectrum frequencies domain.
4. A device for interpolating LP filter parameters in a current sound signal processing frame following a previous sound signal processing frame, the previous frame using an internal sampling rate S 1 and the current frame using an internal sampling rate S 2 and defining a number of subframes, comprising:
at least one processor; and
a memory coupled to the processor and storing non-transitory instructions that when executed cause the processor to:
provide LP filter parameters from the previous frame at the internal sampling rate S 1 ;
provide LP filter parameters from the current frame at the internal sampling rate S 2 ;
convert the LP filter parameters from the previous frame from the internal sampling rate S 1 to the internal sampling rate S 2 ;
transform the LP filter parameters to a quantization and interpolation domain; and
compute LP filter parameters of at least one of the subframes of the current frame using a weighted sum of the LP filter parameters from the current frame at the internal sampling rate S 2 and the LP filter parameters from the previous frame at the internal sampling rate S 2 .
5. The device of claim 4 , wherein the LP filter parameters are quantized LP filter parameters.
6. The device of claim 4 , wherein the quantization and interpolation domain is a line spectrum frequencies domain.