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/******************************************************************************
*
* Copyright 2022 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
******************************************************************************/
/**
* LC3 - Long Term Postfilter
*
* Reference : Low Complexity Communication Codec (LC3)
* Bluetooth Specification v1.0
*/
#ifndef __LC3_LTPF_H
#define __LC3_LTPF_H
#include "common.h"
#include "bits.h"
/**
* LTPF data
*/
typedef struct lc3_ltpf_data {
bool active;
int pitch_index;
} lc3_ltpf_data_t;
/* ----------------------------------------------------------------------------
* Encoding
* -------------------------------------------------------------------------- */
/**
* LTPF analysis
* dt, sr Duration and samplerate of the frame
* ltpf Context of analysis
* allowed True when activation of LTPF is allowed
* x [-d..-1] Previous, [0..ns-1] Current samples
* data Return bitstream data
* return True when pitch present, False otherwise
*
* The `x` vector is aligned on 32 bits
* The number of previous samples `d` accessed on `x` is :
* d: { 10, 20, 30, 40, 60 } - 1 for samplerates from 8KHz to 48KHz
*/
bool lc3_ltpf_analyse(enum lc3_dt dt, enum lc3_srate sr,
lc3_ltpf_analysis_t *ltpf, const int16_t *x, lc3_ltpf_data_t *data);
/**
* LTPF disable
* data LTPF data, disabled activation on return
*/
void lc3_ltpf_disable(lc3_ltpf_data_t *data);
/**
* Return number of bits coding the bitstream data
* pitch True when pitch present, False otherwise
* return Bit consumption, including the pitch present flag
*/
int lc3_ltpf_get_nbits(bool pitch);
/**
* Put bitstream data
* bits Bitstream context
* data LTPF data
*/
void lc3_ltpf_put_data(lc3_bits_t *bits, const lc3_ltpf_data_t *data);
/* ----------------------------------------------------------------------------
* Decoding
* -------------------------------------------------------------------------- */
/**
* Get bitstream data
* bits Bitstream context
* data Return bitstream data
*/
void lc3_ltpf_get_data(lc3_bits_t *bits, lc3_ltpf_data_t *data);
/**
* LTPF synthesis
* dt, sr Duration and samplerate of the frame
* nbytes Size in bytes of the frame
* ltpf Context of synthesis
* data Bitstream data, NULL when pitch not present
* xr Base address of ring buffer of decoded samples
* x Samples to proceed in the ring buffer, filtered as output
*
* The size of the ring buffer is `nh + ns`.
* The filtering needs an history of at least 18 ms.
*/
void lc3_ltpf_synthesize(enum lc3_dt dt, enum lc3_srate sr, int nbytes,
lc3_ltpf_synthesis_t *ltpf, const lc3_ltpf_data_t *data,
const float *xr, float *x);
#endif /* __LC3_LTPF_H */
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