view libgsmefr/enc_main.c @ 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 035424a6ca83
children
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/*
 * This module contains our GSM EFR encoder main function, EFR_encode_params(),
 * that stands at the boundary between our public interface and the guts of
 * ETSI-based codec.
 */

#include "gsm_efr.h"
#include "typedef.h"
#include "namespace.h"
#include "basic_op.h"
#include "cnst.h"
#include "codec.h"
#include "sig_proc.h"
#include "memops.h"
#include "enc_state.h"
#include "e_homing.h"
#include "dtx.h"

void EFR_encode_params(struct EFR_encoder_state *st, const int16_t *pcm_in,
			int16_t *params, int *sp_out, int *vad_out)
{
	Word16 *new_speech = st->old_speech + L_TOTAL - L_FRAME;
	Word16 syn[L_FRAME];
	Word16 reset_flag;
	Word16 i;

        /* Check whether this frame is an encoder homing frame */
        reset_flag = encoder_homing_frame_test (pcm_in);

        for (i = 0; i < L_FRAME; i++)   /* Delete the 3 LSBs (13-bit input) */
        {
            new_speech[i] = pcm_in[i] & 0xfff8;
        }

        Pre_Process (st, new_speech, L_FRAME);       /* filter + downscaling */

        Coder_12k2 (st, params, syn);    /* Find speech parameters   */

        if ((st->txdtx_ctrl & TX_SP_FLAG) == 0)
        {
            /* Write comfort noise parameters into the parameter frame.
            Use old parameters in case SID frame is not to be updated */
            CN_encoding (st, params, st->txdtx_ctrl);
        }

        /* VAD and SP flag outputs */
        if (vad_out)
            *vad_out = ((st->txdtx_ctrl & TX_VAD_FLAG) != 0);

        if (sp_out)
            *sp_out = ((st->txdtx_ctrl & TX_SP_FLAG) != 0);

        if (reset_flag != 0)
        {
            /* Bring the encoder, VAD and DTX to the home state */
            EFR_encoder_reset(st, st->dtx_mode);
        }
}