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