FreeCalypso > hg > gsm-codec-lib
view libtwamr/lsp.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 | 550d3594c878 |
| 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 : lsp.h * Purpose : Conversion from A(z) to LSP. Quantization and * interpolation of LSPs. * ******************************************************************************** */ #ifndef lsp_h #define lsp_h "$Id $" /* ******************************************************************************** * INCLUDE FILES ******************************************************************************** */ #include "tw_amr.h" #include "typedef.h" #include "q_plsf.h" /* ******************************************************************************** * LOCAL VARIABLES AND TABLES ******************************************************************************** */ /* ******************************************************************************** * DEFINITION OF DATA TYPES ******************************************************************************** */ typedef struct { /* Past LSPs */ Word16 lsp_old[M]; Word16 lsp_old_q[M]; /* Quantization state */ Q_plsfState qSt; } lspState; /* ******************************************************************************** * DECLARATION OF PROTOTYPES ******************************************************************************** */ /* ************************************************************************** * * Function : lsp_reset * Purpose : Resets state memory * Returns : 0 on success * ************************************************************************** */ void lsp_reset (lspState *st); /* ************************************************************************** * * Function : lsp * Purpose : Conversion from LP coefficients to LSPs. * Quantization of LSPs. * Description : Generates 2 sets of LSPs from 2 sets of * LP coefficients for mode 12.2. For the other * modes 1 set of LSPs is generated from 1 set of * LP coefficients. These LSPs are quantized with * Matrix/Vector quantization (depending on the mode) * and interpolated for the subframes not yet having * their own LSPs. * ************************************************************************** */ int lsp(lspState *st, /* i/o : State struct */ enum Mode req_mode, /* i : requested coder mode */ enum Mode used_mode, /* i : used coder mode */ Word16 az[], /* i/o : interpolated LP parameters Q12 */ Word16 azQ[], /* o : quantization interpol. LP parameters Q12*/ Word16 lsp_new[], /* o : new lsp vector */ Word16 **anap /* o : analysis parameters */ ); #endif