SKP_int SKP_Silk_init_decoder(
SKP_Silk_decoder_state *psDec /* I/O Decoder state pointer */
)
{
SKP_memset( psDec, 0, sizeof( SKP_Silk_decoder_state ) );
/* Set sampling rate to 24 kHz, and init non-zero values */
SKP_Silk_decoder_set_fs( psDec, 24 );
/* Used to deactivate e.g. LSF interpolation and fluctuation reduction */
psDec->first_frame_after_reset = 1;
psDec->prev_inv_gain_Q16 = 65536;
/* Reset CNG state */
SKP_Silk_CNG_Reset( psDec );
SKP_Silk_PLC_Reset( psDec );
return(0);
}
SKP_int SKP_Silk_decode_frame(
SKP_Silk_decoder_state *psDec, /* I/O Pointer to Silk decoder state */
SKP_int16 pOut[], /* O Pointer to output speech frame */
SKP_int16 *pN, /* O Pointer to size of output frame */
const SKP_uint8 pCode[], /* I Pointer to payload */
const SKP_int nBytes, /* I Payload length */
SKP_int action, /* I Action from Jitter Buffer */
SKP_int *decBytes /* O Used bytes to decode this frame */
)
{
SKP_Silk_decoder_control sDecCtrl;
SKP_int L, fs_Khz_old, ret = 0;
SKP_int Pulses[ MAX_FRAME_LENGTH ];
L = psDec->frame_length;
sDecCtrl.LTP_scale_Q14 = 0;
/* Safety checks */
SKP_assert( L > 0 && L <= MAX_FRAME_LENGTH );
/********************************************/
/* Decode Frame if packet is not lost */
/********************************************/
*decBytes = 0;
if( action == 0 ) {
/********************************************/
/* Initialize arithmetic coder */
/********************************************/
fs_Khz_old = psDec->fs_kHz;
if( psDec->nFramesDecoded == 0 ) {
/* Initialize range decoder state */
SKP_Silk_range_dec_init( &psDec->sRC, pCode, nBytes );
}
/********************************************/
/* Decode parameters and pulse signal */
/********************************************/
SKP_Silk_decode_parameters( psDec, &sDecCtrl, Pulses, 1 );
if( psDec->sRC.error ) {
psDec->nBytesLeft = 0;
action = 1; /* PLC operation */
/* revert fs if changed in decode_parameters */
SKP_Silk_decoder_set_fs( psDec, fs_Khz_old );
/* Avoid crashing */
*decBytes = psDec->sRC.bufferLength;
if( psDec->sRC.error == RANGE_CODER_DEC_PAYLOAD_TOO_LONG ) {
ret = SKP_SILK_DEC_PAYLOAD_TOO_LARGE;
} else {
ret = SKP_SILK_DEC_PAYLOAD_ERROR;
}
} else {
*decBytes = psDec->sRC.bufferLength - psDec->nBytesLeft;
psDec->nFramesDecoded++;
/* Update lengths. Sampling frequency could have changed */
L = psDec->frame_length;
/********************************************************/
/* Run inverse NSQ */
/********************************************************/
SKP_Silk_decode_core( psDec, &sDecCtrl, pOut, Pulses );
/********************************************************/
/* Update PLC state */
/********************************************************/
SKP_Silk_PLC( psDec, &sDecCtrl, pOut, L, action );
psDec->lossCnt = 0;
psDec->prev_sigtype = sDecCtrl.sigtype;
/* A frame has been decoded without errors */
psDec->first_frame_after_reset = 0;
}
}
/*************************************************************/
/* Generate Concealment frame if packet is lost, or corrupt */
/*************************************************************/
if( action == 1 ) {
/* Handle packet loss by extrapolation */
SKP_Silk_PLC( psDec, &sDecCtrl, pOut, L, action );
}
/*************************/
/* Update output buffer. */
/*************************/
SKP_memcpy( psDec->outBuf, pOut, L * sizeof( SKP_int16 ) );
/****************************************************************/
/* Ensure smooth connection of extrapolated and good frames */
/****************************************************************/
SKP_Silk_PLC_glue_frames( psDec, &sDecCtrl, pOut, L );
/************************************************/
/* Comfort noise generation / estimation */
/************************************************/
SKP_Silk_CNG( psDec, &sDecCtrl, pOut , L );
/********************************************/
/* HP filter output */
/********************************************/
SKP_assert( ( ( psDec->fs_kHz == 12 ) && ( L % 3 ) == 0 ) ||
( ( psDec->fs_kHz != 12 ) && ( L % 2 ) == 0 ) );
SKP_Silk_biquad( pOut, psDec->HP_B, psDec->HP_A, psDec->HPState, pOut, L );
/********************************************/
/* set output frame length */
/********************************************/
*pN = ( SKP_int16 )L;
/* Update some decoder state variables */
psDec->lagPrev = sDecCtrl.pitchL[ NB_SUBFR - 1 ];
return ret;
}
