FreeCalypso > hg > gsm-codec-lib
view libtwamr/agc.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 | 6b33f3ba4289 |
| 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 : agc.h * Purpose : Scales the postfilter output on a subframe basis * : by automatic control of the subframe gain. * ***************************************************************************** */ #ifndef agc_h #define agc_h "$Id $" /* ***************************************************************************** * INCLUDE FILES ***************************************************************************** */ #include "typedef.h" /* ***************************************************************************** * DEFINITION OF DATA TYPES ***************************************************************************** */ typedef struct { Word16 past_gain; } agcState; /* ***************************************************************************** * DECLARATION OF PROTOTYPES ***************************************************************************** */ /* ************************************************************************** * * Function : agc_reset * Purpose : Reset of agc (i.e. set state memory to 1.0) * Returns : 0 on success * ************************************************************************** */ void agc_reset (agcState *st); /* ************************************************************************** * * Function : agc * Purpose : Scales the postfilter output on a subframe basis * Description : sig_out[n] = sig_out[n] * gain[n]; * where gain[n] is the gain at the nth sample given by * gain[n] = agc_fac * gain[n-1] + (1 - agc_fac) g_in/g_out * g_in/g_out is the square root of the ratio of energy at * the input and output of the postfilter. * ************************************************************************** */ int agc ( agcState *st, /* i/o : agc state */ Word16 *sig_in, /* i : postfilter input signal, (l_trm) */ Word16 *sig_out, /* i/o : postfilter output signal, (l_trm) */ Word16 agc_fac, /* i : AGC factor */ Word16 l_trm /* i : subframe size */ ); /* ************************************************************************** * * Function: agc2 * Purpose: Scales the excitation on a subframe basis * ************************************************************************** */ void agc2 ( Word16 *sig_in, /* i : postfilter input signal */ Word16 *sig_out, /* i/o : postfilter output signal */ Word16 l_trm /* i : subframe size */ ); #endif