FreeCalypso > hg > gsm-codec-lib
view libgsmefr/int_lpc.c @ 120:bd832a456339
gsmefr-rec2etsi usage msg: call it input.gsmx instead of input.rec
author | Mychaela Falconia <falcon@freecalypso.org> |
---|---|
date | Sat, 10 Dec 2022 02:56:02 +0000 |
parents | a0a1e8de4b46 |
children |
line wrap: on
line source
/************************************************************************* * * FUNCTION: Int_lpc() * * PURPOSE: Interpolates the LSPs and converts to LPC parameters to get * a different LP filter in each subframe. * * DESCRIPTION: * The 20 ms speech frame is divided into 4 subframes. * The LSPs are quantized and transmitted at the 2nd and 4th subframes * (twice per frame) and interpolated at the 1st and 3rd subframe. * * |------|------|------|------| * sf1 sf2 sf3 sf4 * F0 Fm F1 * * sf1: 1/2 Fm + 1/2 F0 sf3: 1/2 F1 + 1/2 Fm * sf2: Fm sf4: F1 * *************************************************************************/ #include "gsm_efr.h" #include "typedef.h" #include "namespace.h" #include "basic_op.h" #include "no_count.h" #include "sig_proc.h" #include "codec.h" #define M 10 /* LP order */ #define MP1 11 /* M+1 */ void Int_lpc ( Word16 lsp_old[], /* input : LSP vector at the 4th subframe of past frame */ Word16 lsp_mid[], /* input : LSP vector at the 2nd subframe of present frame */ Word16 lsp_new[], /* input : LSP vector at the 4th subframe of present frame */ Word16 Az[] /* output: interpolated LP parameters in all subframes */ ) { Word16 i; Word16 lsp[M]; /* lsp[i] = lsp_mid[i] * 0.5 + lsp_old[i] * 0.5 */ for (i = 0; i < M; i++) { lsp[i] = add (shr (lsp_mid[i], 1), shr (lsp_old[i], 1)); move16 (); } Lsp_Az (lsp, Az); /* Subframe 1 */ Az += MP1; move16 (); Lsp_Az (lsp_mid, Az); /* Subframe 2 */ Az += MP1; move16 (); for (i = 0; i < M; i++) { lsp[i] = add (shr (lsp_mid[i], 1), shr (lsp_new[i], 1)); move16 (); } Lsp_Az (lsp, Az); /* Subframe 3 */ Az += MP1; move16 (); Lsp_Az (lsp_new, Az); /* Subframe 4 */ return; } /*----------------------------------------------------------------------* * Function Int_lpc2() * * ~~~~~~~~~~~~~~~~~~ * * Interpolation of the LPC parameters. * * Same as the previous function but we do not recompute Az() for * * subframe 2 and 4 because it is already available. * *----------------------------------------------------------------------*/ void Int_lpc2 ( Word16 lsp_old[], /* input : LSP vector at the 4th subframe of past frame */ Word16 lsp_mid[], /* input : LSP vector at the 2nd subframe of present frame */ Word16 lsp_new[], /* input : LSP vector at the 4th subframe of present frame */ Word16 Az[] /* output: interpolated LP parameters in subframes 1 and 3 */ ) { Word16 i; Word16 lsp[M]; /* lsp[i] = lsp_mid[i] * 0.5 + lsp_old[i] * 0.5 */ for (i = 0; i < M; i++) { lsp[i] = add (shr (lsp_mid[i], 1), shr (lsp_old[i], 1)); move16 (); } Lsp_Az (lsp, Az); /* Subframe 1 */ Az += MP1 * 2; move16 (); for (i = 0; i < M; i++) { lsp[i] = add (shr (lsp_mid[i], 1), shr (lsp_new[i], 1)); move16 (); } Lsp_Az (lsp, Az); /* Subframe 3 */ return; }