amr.h

#ifndef _OSMO_AMR_H_
#define _OSMO_AMR_H_

#include <osmocom/core/endian.h>

/* As defined by RFC3267: Adaptive Multi-Rate (AMR) */

/*
 *  +----------------+-------------------+----------------
 *  | payload header | table of contents | speech data ...
 *  +----------------+-------------------+----------------
 */

/*
 * 4.4. Octet-aligned Mode:
 *
 * 4.4.1. The Payload Header:
 *
 *   0 1 2 3 4 5 6 7
 *  +-+-+-+-+-+-+-+-+
 *  |  CMR  |X X X X|
 *  +-+-+-+-+-+-+-+-+
 *
 * According to: 3GPP TS 26.201 "AMR Wideband speech codec; Frame Structure",
 * version 5.0.0 (2001-03), 3rd Generation Partnership Project (3GPP):
 *
 * Possible Frame type / CMR values:
 *
 * 0-8 for AMR-WB (from 6.60 kbit/s to 23.85 kbit/s)
 * 9 (SID) confort noise.
 * 10-13 future use.
 * 14 means lost speech frame (only available for AMR-WB)
 * 15 means no data
 *
 * 4.4.2. The table of contents:
 *
 *   0 1 2 3 4 5 6 7
 *  +-+-+-+-+-+-+-+-+
 *  |F|  FT   |Q|X X|
 *  +-+-+-+-+-+-+-+-+
 *
 * X means padding.
 */

struct amr_hdr {
#if OSMO_IS_BIG_ENDIAN
        /* Payload Header */
        uint8_t cmr:4,  /* Codec Mode Request */
                pad1:4;
        /* Table of Contents */
        uint8_t f:1,    /* followed by another speech frame? */
                ft:4,   /* coding mode */
                q:1,    /* OK (not damaged) at origin? */
                pad2:2;
#elif OSMO_IS_LITTLE_ENDIAN
        /* Payload Header */
        uint8_t pad1:4,
                cmr:4;
        /* Table of Contents */
        uint8_t pad2:2,
                q:1,
                ft:4,
                f:1;
#endif
} __attribute__((packed));

static inline void *osmo_amr_get_payload(struct amr_hdr *amrh)
{
        return (uint8_t *)amrh + sizeof(struct amr_hdr);
}

/* AMR voice frame type identifiers
 * See also 3GPP TS 26.101, Table 1a: Interpretation of Frame Type, Mode
 * Indication and Mode Request fields */
#define AMR_FT_0        0       /* 4.75 */
#define AMR_FT_1        1       /* 5.15 */
#define AMR_FT_2        2       /* 5.90 */
#define AMR_FT_3        3       /* 6.70 */
#define AMR_FT_4        4       /* 7.40 */
#define AMR_FT_5        5       /* 7.95 */
#define AMR_FT_6        6       /* 10.2 */
#define AMR_FT_7        7       /* 12.2 */
#define AMR_FT_SID      8       /* SID */
#define AMR_FT_MAX      9

/* AMR voice frame length (in bytes, rounded),
 * See also RFC 3267, chapter 3.6 */
#define AMR_FT_0_LEN    12      /* 4.75 */
#define AMR_FT_1_LEN    13      /* 5.15 */
#define AMR_FT_2_LEN    15      /* 5.90 */
#define AMR_FT_3_LEN    17      /* 6.70 */
#define AMR_FT_4_LEN    19      /* 7.40 */
#define AMR_FT_5_LEN    20      /* 7.95 */
#define AMR_FT_6_LEN    26      /* 10.2 */
#define AMR_FT_7_LEN    31      /* 12.2 */
#define AMR_FT_SID_LEN  5       /* SID */

/* NOTE: the above constant refers to the length of one AMR speech frame-block,
 * not counting CMR, TOC. */

int osmo_amr_ft_valid(uint8_t amr_ft);
size_t osmo_amr_bytes(uint8_t amr_cmr);

bool osmo_amr_is_oa(uint8_t *payload, unsigned int payload_len);
int osmo_amr_oa_to_bwe(uint8_t *payload, unsigned int payload_len);
int osmo_amr_bwe_to_oa(uint8_t *payload, unsigned int payload_len,
                       unsigned int payload_maxlen);

#endif