FreeCalypso > hg > gsm-codec-lib
view libtwamr/d_plsf.h @ 581:e2d5cad04cbf
libgsmhr1 RxFE: store CN R0+LPC separately from speech
In the original GSM 06.06 code the ECU for speech mode is entirely
separate from the CN generator, maintaining separate state. (The
main intertie between them is the speech vs CN state variable,
distinguishing between speech and CN BFIs, in addition to the
CN-specific function of distinguishing between initial and update
SIDs.)
In the present RxFE implementation I initially thought that we could
use the same saved_frame buffer for both ECU and CN, overwriting
just the first 4 params (R0 and LPC) when a valid SID comes in.
However, I now realize it was a bad idea: the original code has a
corner case (long sequence of speech-mode BFIs to put the ECU in
state 6, then SID and CN-mode BFIs, then a good speech frame) that
would be broken by that buffer reuse approach. We could eliminate
this corner case by resetting the ECU state when passing through
a CN insertion period, but doing so would needlessly increase
the behavioral diffs between GSM 06.06 and our version.
Solution: use a separate CN-specific buffer for CN R0+LPC parameters,
and match the behavior of GSM 06.06 code in this regard.
| author | Mychaela Falconia <falcon@freecalypso.org> |
|---|---|
| date | Thu, 13 Feb 2025 10:02:45 +0000 |
| parents | 3f574255c3aa |
| children |
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/* ******************************************************************************** * * GSM AMR-NB speech codec R98 Version 7.6.0 December 12, 2001 * R99 Version 3.3.0 * REL-4 Version 4.1.0 * ******************************************************************************** * * File : d_plsf.h * Purpose : common part (init, exit, reset) of LSF decoder * module (rest in d_plsf_3.c and d_plsf_5.c) * ******************************************************************************** */ #ifndef d_plsf_h #define d_plsf_h "$Id $" /* ******************************************************************************** * INCLUDE FILES ******************************************************************************** */ #include "tw_amr.h" #include "typedef.h" #include "cnst.h" /* ******************************************************************************** * LOCAL VARIABLES AND TABLES ******************************************************************************** */ /* *--------------------------------------------------* * Constants (defined in cnst.h) * *--------------------------------------------------* * M : LPC Order * *--------------------------------------------------* */ /* ******************************************************************************** * DEFINITION OF DATA TYPES ******************************************************************************** */ typedef struct { Word16 past_r_q[M]; /* Past quantized prediction error, Q15 */ Word16 past_lsf_q[M]; /* Past dequantized lsfs, Q15 */ } D_plsfState; /* ******************************************************************************** * DECLARATION OF PROTOTYPES ******************************************************************************** */ /* ************************************************************************** * * Function : D_plsf_reset * Purpose : Resets state memory * Returns : 0 on success * ************************************************************************** */ void D_plsf_reset (D_plsfState *st); /* ************************************************************************** * * Function : D_plsf_5 * Purpose : Decodes the 2 sets of LSP parameters in a frame * using the received quantization indices. * Description : The two sets of LSFs are quantized using split by * 5 matrix quantization (split-MQ) with 1st order MA * prediction. * See "q_plsf_5.c" for more details about the * quantization procedure * Returns : 0 * ************************************************************************** */ int D_plsf_5 ( D_plsfState *st, /* i/o: State variables */ Word16 bfi, /* i : bad frame indicator (set to 1 if a bad frame is received) */ Word16 *indice, /* i : quantization indices of 5 submatrices, Q0 */ Word16 *lsp1_q, /* o : quantized 1st LSP vector (M) Q15 */ Word16 *lsp2_q /* o : quantized 2nd LSP vector (M) Q15 */ ); /************************************************************************* * * FUNCTION: D_plsf_3() * * PURPOSE: Decodes the LSP parameters using the received quantization * indices.1st order MA prediction and split by 3 matrix * quantization (split-MQ) * *************************************************************************/ void D_plsf_3( D_plsfState *st, /* i/o: State struct */ enum Mode mode, /* i : coder mode */ Word16 bfi, /* i : bad frame indicator (set to 1 if a */ /* bad frame is received) */ Word16 * indice, /* i : quantization indices of 3 submatrices, Q0 */ Word16 * lsp1_q /* o : quantized 1st LSP vector, Q15 */ ); /************************************************************************* * * FUNCTION: Init_D_plsf_3() * * PURPOSE: Set the past_r_q[M] vector to one of the eight * past_rq_init vectors. * *************************************************************************/ void Init_D_plsf_3(D_plsfState *st, /* i/o: State struct */ Word16 index /* i : past_rq_init[] index [0, 7] */ ); #endif