FreeCalypso > hg > gsm-codec-lib
view libtwamr/g_adapt.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 | 2a265be82195 |
| children |
line wrap: on
line source
/* ******************************************************************************** * * 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 : g_adapt.h * Purpose : gain adaptation for MR795 gain quantization * ******************************************************************************** */ /* ******************************************************************************** * MODULE INCLUDE FILE AND VERSION ID ******************************************************************************** */ #ifndef g_adapt_h #define g_adapt_h "$Id $" /* ******************************************************************************** * INCLUDE FILES ******************************************************************************** */ #include "typedef.h" #define LTPG_MEM_SIZE 5 /* number of stored past LTP coding gains + 1 */ /* ******************************************************************************** * DEFINITION OF DATA TYPES ******************************************************************************** */ typedef struct { Word16 onset; /* onset state, Q0 */ Word16 prev_alpha; /* previous adaptor output, Q15 */ Word16 prev_gc; /* previous code gain, Q1 */ Word16 ltpg_mem[LTPG_MEM_SIZE]; /* LTP coding gain history, Q13 */ /* (ltpg_mem[0] not used for history) */ } GainAdaptState; /* ******************************************************************************** * DECLARATION OF PROTOTYPES ******************************************************************************** */ void gain_adapt_reset (GainAdaptState *st); /* reset of gain adaptor state (i.e. set state memory to zero) returns 0 on success */ /************************************************************************* * * Function: gain_adapt() * Purpose: calculate pitch/codebook gain adaptation factor alpha * (and update the adaptor state) * ************************************************************************** */ void gain_adapt( GainAdaptState *st, /* i : state struct */ Word16 ltpg, /* i : ltp coding gain (log2()), Q */ Word16 gain_cod, /* i : code gain, Q13 */ Word16 *alpha /* o : gain adaptation factor, Q15 */ ); #endif