ilbc/ilbc.h

/*
 * iLBC - a library for the iLBC codec
 *
 * ilbc.h - The iLBC low bit rate speech codec.
 *
 * Adapted by Steve Underwood <steveu@coppice.org> from the reference
 * iLBC code supplied in RFC3951.
 *
 * Copyright (C) The Internet Society (2004).
 * All Rights Reserved.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * $Id: ilbc.h,v 1.2 2008/10/02 12:00:56 steveu Exp $
 */

#if !defined(_ILBC_ILBC_H_)
#define _ILBC_ILBC_H_

#define ILBC_BLOCK_LEN_20MS     160
#define ILBC_BLOCK_LEN_30MS     240
#define ILBC_BLOCK_LEN_MAX      240

#define ILBC_NO_OF_BYTES_20MS   38
#define ILBC_NO_OF_BYTES_30MS   50
#define ILBC_NO_OF_BYTES_MAX    50

#define ILBC_NUM_SUB_MAX        6

#define SUBL                    40

#define ENH_BLOCKL              80  /* block length */
#define ENH_NBLOCKS_TOT         8   /* ENH_NBLOCKS + ENH_NBLOCKS_EXTRA */
#define ENH_BUFL                (ENH_NBLOCKS_TOT*ENH_BLOCKL)

#define ILBC_LPC_FILTERORDER    10
#define LPC_LOOKBACK            60

#define CB_NSTAGES              3

#define STATE_BITS              3
#define BYTE_LEN                8
#define ILBC_ULP_CLASSES        3

typedef struct
{
    int lsf_bits[6][ILBC_ULP_CLASSES + 2];
    int start_bits[ILBC_ULP_CLASSES + 2];
    int startfirst_bits[ILBC_ULP_CLASSES + 2];
    int scale_bits[ILBC_ULP_CLASSES + 2];
    int state_bits[ILBC_ULP_CLASSES + 2];
    int extra_cb_index[CB_NSTAGES][ILBC_ULP_CLASSES + 2];
    int extra_cb_gain[CB_NSTAGES][ILBC_ULP_CLASSES + 2];
    int cb_index[ILBC_NUM_SUB_MAX][CB_NSTAGES][ILBC_ULP_CLASSES + 2];
    int cb_gain[ILBC_NUM_SUB_MAX][CB_NSTAGES][ILBC_ULP_CLASSES + 2];
} ilbc_ulp_inst_t;

/* Type definition encoder instance */
typedef struct
{
    /* flag for frame size mode */
    int mode;

    /* basic parameters for different frame sizes */
    int blockl;
    int nsub;
    int nasub;
    int no_of_bytes;
    int lpc_n;
    int state_short_len;
    const ilbc_ulp_inst_t *ULP_inst;

    /* analysis filter state */
    float anaMem[ILBC_LPC_FILTERORDER];

    /* old lsf parameters for interpolation */
    float lsfold[ILBC_LPC_FILTERORDER];
    float lsfdeqold[ILBC_LPC_FILTERORDER];

    /* signal buffer for LP analysis */
    float lpc_buffer[LPC_LOOKBACK + ILBC_BLOCK_LEN_MAX];

    /* state of input HP filter */
    float hpimem[4];
} ilbc_encode_state_t;

/* Type definition decoder instance */
typedef struct
{
    /* Flag for frame size mode */
    int mode;

    /* Basic parameters for different frame sizes */
    int blockl;
    int nsub;
    int nasub;
    int no_of_bytes;
    int lpc_n;
    int state_short_len;
    const ilbc_ulp_inst_t *ULP_inst;

    /* Synthesis filter state */
    float syntMem[ILBC_LPC_FILTERORDER];

    /* Old LSF for interpolation */
    float lsfdeqold[ILBC_LPC_FILTERORDER];

    /* Pitch lag estimated in enhancer and used in PLC */
    int last_lag;

    /* PLC state information */
    int prevLag, consPLICount, prevPLI, prev_enh_pl;
    float prevLpc[ILBC_LPC_FILTERORDER + 1];
    float prevResidual[ILBC_NUM_SUB_MAX*SUBL];
    float per;
    unsigned long seed;

    /* Previous synthesis filter parameters */
    float old_syntdenum[(ILBC_LPC_FILTERORDER + 1)*ILBC_NUM_SUB_MAX];

    /* State of output HP filter */
    float hpomem[4];

    /* Enhancer state information */
    int use_enhancer;
    float enh_buf[ENH_BUFL];
    float enh_period[ENH_NBLOCKS_TOT];
} ilbc_decode_state_t;

#if defined(__cplusplus)
extern "C"
{
#endif

/*! Initialise an iLBC encode context.
    \param s The iLBC encode context.
    \param mode The frame size.
    \return A pointer to the iLBC encode context, or NULL for error. */
ilbc_encode_state_t *ilbc_encode_init(ilbc_encode_state_t *s,
                                      int mode);

int ilbc_encode_release(ilbc_encode_state_t *s);

/*! Encode a buffer of linear PCM data to iLBC
    \param s The iLBC encode context.
    \param bytes The iLBC data produced.
    \param amp The audio sample buffer.
    \param len The number of samples in the buffer.
    \return The number of bytes of iLBC data produced. */
int ilbc_encode(ilbc_encode_state_t *s,
                uint8_t bytes[],
                const int16_t amp[],
                int len);

/*! Initialise an iLBC decode context.
    \param s The iLBC decode context.
    \param mode The frame size.
    \param use_enhancer TRUE to use the audio enhancer option.
    \return A pointer to the iLBC decode context, or NULL for error. */
ilbc_decode_state_t *ilbc_decode_init(ilbc_decode_state_t *s,
                                      int mode,
                                      int use_enhancer);

int ilbc_decode_release(ilbc_decode_state_t *s);

/*! Decode a buffer of iLBC data to linear PCM.
    \param s The iLBC deocde context.
    \param amp The audio sample buffer.
    \param bytes The excoded data.
    \param len The length of the encoded data, in bytes.
    \return The number of samples returned. */
int ilbc_decode(ilbc_decode_state_t *s,
                int16_t amp[],
                const uint8_t bytes[],
                int len);

/*! Produce linear PCM data to fill in where received iLBC data is missing.
    \param s The iLBC context.
    \param amp The audio sample buffer.
    \param len
    \return The number of samples returned. */
int ilbc_fillin(ilbc_decode_state_t *s,
                int16_t amp[],
                int len);

#if defined(__cplusplus)
}
#endif

#endif
/*- End of file ------------------------------------------------------------*/