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view libgsmefr/gsm_efr.h @ 581:e2d5cad04cbf

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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 f2d0f2f15d5f
children
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/*
 * This header file is the external public interface to libgsmefr:
 * Themyscira Wireless implementation of GSM-EFR speech codec
 * based on the original ETSI code of GSM 06.53, adapted to the
 * RTP frame format of ETSI TS 101 318.
 *
 * This header file should be installed in some system include directory
 * such that it can be included by C sources as <gsm_efr.h>.
 */

#ifndef	__GSM_EFR_H
#define	__GSM_EFR_H

#include <stdint.h>

#define	EFR_RTP_FRAME_LEN	31
#define	EFR_NUM_PARAMS		57

struct EFR_encoder_state;	/* opaque to external users */
struct EFR_decoder_state;	/* ditto */

extern struct EFR_encoder_state *EFR_encoder_create(int dtx);
extern struct EFR_decoder_state *EFR_decoder_create(void);
/* use standard free() call to free both afterward */

/* reset state to initial */
extern void EFR_encoder_reset(struct EFR_encoder_state *st, int dtx);
extern void EFR_decoder_reset(struct EFR_decoder_state *st);

/* encoder public functions */

extern void EFR_encode_params(struct EFR_encoder_state *st, const int16_t *pcm,
			      int16_t *params, int *sp, int *vad);
extern void EFR_encode_frame(struct EFR_encoder_state *st, const int16_t *pcm,
			     uint8_t *frame, int *sp, int *vad);

/* decoder public functions */

extern void EFR_decode_params(struct EFR_decoder_state *st,
			      const int16_t *params, int bfi, int sid, int taf,
			      int16_t *pcm);
extern void EFR_decode_frame(struct EFR_decoder_state *st, const uint8_t *frame,
			     int bfi, int taf, int16_t *pcm);
extern void EFR_decode_bfi_nodata(struct EFR_decoder_state *st, int taf,
				  int16_t *pcm);
extern int EFR_decode_rtp(struct EFR_decoder_state *st, const uint8_t *rtp_pl,
			  unsigned rtp_pl_len, int16_t *pcm);

/* stateless utility functions */

extern int EFR_sid_classify(const uint8_t *frame);
extern void EFR_frame2params(const uint8_t *frame, int16_t *params);
extern void EFR_params2frame(const int16_t *params, uint8_t *frame);
extern void EFR_insert_sid_codeword(uint8_t *frame);

/* public const data item */

extern const uint8_t EFR_decoder_homing_frame[EFR_RTP_FRAME_LEN];

/* sizes of state structures, to support alternative malloc schemes */

extern const unsigned EFR_encoder_state_size;
extern const unsigned EFR_decoder_state_size;

#endif	/* include guard */