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view libgsmefr/gsm_efr.h @ 242:f081a6850fb5

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libgsmfrp: new refined implementation The previous implementation exhibited the following defects, which are now fixed: 1) The last received valid SID was cached forever for the purpose of handling future invalid SIDs - we could have received some valid SID ages ago, then lots of speech or NO_DATA, and if we then get an invalid SID, we would resurrect the last valid SID from ancient history - a bad design. In our new design, we handle invalid SID based on the current state, much like BFI. 2) GSM 06.11 spec says clearly that after the second lost SID (received BFI=1 && TAF=1 in CN state) we need to gradually decrease the output level, rather than jump directly to emitting silence frames - we previously failed to implement such logic. 3) Per GSM 06.12 section 5.2, Xmaxc should be the same in all 4 subframes in a SID frame. What should we do if we receive an otherwise valid SID frame with different Xmaxc? Our previous approach would replicate this Xmaxc oddity in every subsequent generated CN frame, which is rather bad. In our new design, the very first CN frame (which can be seen as a transformation of the SID frame itself) retains the original 4 distinct Xmaxc, but all subsequent CN frames are based on the Xmaxc from the last subframe of the most recent SID.
author Mychaela Falconia <falcon@freecalypso.org>
date Tue, 09 May 2023 05:16:31 +0000
parents 88468d5b3590
children 9499d12d315b
line wrap: on
line source

/*
 * This header file is the external public interface to libgsmefr;
 * it should be installed in the same system include directory
 * as <gsm.h> and <gsm_fr_preproc.h> for the older FR codec.
 */

#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);

/* 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);

#endif	/* include guard */