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view libtwamr/tw_amr.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 fa0652115168
children
line wrap: on
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/*
 * This header file is the external public interface to libtwamr;
 * it should be installed in the same system include directory
 * as <tw_gsmfr.h> and <gsm_efr.h> for more classic GSM codecs.
 */

#ifndef	__THEMWI_AMR_H
#define	__THEMWI_AMR_H

#include <stdint.h>

/* AMR definitions that matter for the public interface */

#define	AMR_MAX_PRM		57	/* max. num. of params      */
#define	AMR_IETF_MAX_PL		32	/* max bytes in RFC 4867 frame */
#define	AMR_IETF_HDR_LEN	6	/* .amr file header bytes */
#define	AMR_COD_WORDS		250	/* # of words in 3GPP test seq format */

enum RXFrameType {
	RX_SPEECH_GOOD = 0,
	RX_SPEECH_DEGRADED,
	RX_ONSET,
	RX_SPEECH_BAD,
	RX_SID_FIRST,
	RX_SID_UPDATE,
	RX_SID_BAD,
	RX_NO_DATA,
	RX_N_FRAMETYPES		/* number of frame types */
};

enum TXFrameType {
	TX_SPEECH_GOOD = 0,
	TX_SID_FIRST,
	TX_SID_UPDATE,
	TX_NO_DATA,
	TX_SPEECH_DEGRADED,
	TX_SPEECH_BAD,
	TX_SID_BAD,
	TX_ONSET,
	TX_N_FRAMETYPES		/* number of frame types */
};

enum Mode {
	MR475 = 0,
	MR515,
	MR59,
	MR67,
	MR74,
	MR795,
	MR102,
	MR122,
	MRDTX
};

#define	AMR_FT_NODATA		15

/* libtwamr encoder and decoder state */

struct amr_encoder_state;	/* opaque to external users */
struct amr_decoder_state;	/* ditto */

struct amr_encoder_state *amr_encoder_create(int dtx, int use_vad2);
struct amr_decoder_state *amr_decoder_create(void);

/* reset state to initial */
void amr_encoder_reset(struct amr_encoder_state *st, int dtx, int use_vad2);
void amr_decoder_reset(struct amr_decoder_state *st);

/* interface structure for passing frames of codec parameters */

struct amr_param_frame {
	uint8_t	type;
	uint8_t	mode;
	int16_t	param[AMR_MAX_PRM];
};

/* encoder and decoder main functions */

void amr_encode_frame(struct amr_encoder_state *st, enum Mode mode,
			const int16_t *pcm, struct amr_param_frame *frame);

void amr_decode_frame(struct amr_decoder_state *st,
			const struct amr_param_frame *frame, int16_t *pcm);

/* stateless utility functions: format conversions */

int amr_txtype_to_rxtype(enum TXFrameType tx_type, enum RXFrameType *rx_type);

unsigned amr_frame_to_ietf(const struct amr_param_frame *frame, uint8_t *bytes);
int amr_frame_from_ietf(const uint8_t *bytes, struct amr_param_frame *frame);
int amr_ietf_grok_first_octet(uint8_t fo);

void amr_frame_to_tseq(const struct amr_param_frame *frame, uint16_t *cod);
int amr_frame_from_tseq(const uint16_t *cod, int use_rxtype,
			struct amr_param_frame *frame);

/* stateless function and const data for DHF detection */

int amr_check_dhf(const struct amr_param_frame *frame, int first_sub_only);

extern const int16_t amr_dhf_mr475[AMR_MAX_PRM];
extern const int16_t amr_dhf_mr515[AMR_MAX_PRM];
extern const int16_t amr_dhf_mr59[AMR_MAX_PRM];
extern const int16_t amr_dhf_mr67[AMR_MAX_PRM];
extern const int16_t amr_dhf_mr74[AMR_MAX_PRM];
extern const int16_t amr_dhf_mr795[AMR_MAX_PRM];
extern const int16_t amr_dhf_mr102[AMR_MAX_PRM];
extern const int16_t amr_dhf_mr122[AMR_MAX_PRM];
extern const int16_t amr_dhf_gsmefr[AMR_MAX_PRM];

/* DHF transformation on encoder output, for AMR-EFR emulation */

void amr_dhf_subst_efr(struct amr_param_frame *frame);
void amr_dhf_subst_efr2(struct amr_param_frame *frame, const int16_t *pcm);

/* public const datum: RFC 4867 file header */

extern const uint8_t amr_file_header_magic[AMR_IETF_HDR_LEN];

#endif	/* include guard */