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114 lines
4.4 KiB
C
114 lines
4.4 KiB
C
/*
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* Copyright (C) 2023 BlueKitchen GmbH
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the copyright holders nor the names of
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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* 4. Any redistribution, use, or modification is done solely for
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* personal benefit and not for any commercial purpose or for
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* monetary gain.
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*
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* THIS SOFTWARE IS PROVIDED BY BLUEKITCHEN GMBH AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL BLUEKITCHEN
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* GMBH OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
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* THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* Please inquire about commercial licensing options at
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* contact@bluekitchen-gmbh.com
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*
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*/
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/**
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* @title Sample rate compensation
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*
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* Prevents buffer over/under-run at the audio receiver by compensating for varying/different playback/receiving sample rates.
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*
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* Intended to measure the L2CAP packet sample rate and with the provided playback sample rate calculates a compensation ratio
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* which compensates for drift between playback and reception.
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*
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* Requires the audio interface to provide the current playback sample rate.
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*
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*/
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#ifndef BTSTACK_SAMPLE_RATE_COMPENSATION_H_
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#define BTSTACK_SAMPLE_RATE_COMPENSATION_H_
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#include <stdint.h>
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#if defined __cplusplus
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extern "C" {
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#endif
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/* API_START */
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#define FLOAT_TO_Q15(a) ((signed)((a)*(UINT16_C(1)<<15)+0.5f))
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#define FLOAT_TO_Q8(a) ((signed)((a)*(UINT16_C(1)<<8)+0.5f))
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#define FLOAT_TO_Q7(a) ((signed)((a)*(UINT16_C(1)<<7)+0.5f))
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#define Q16_TO_FLOAT(a) ((float)(a)/(UINT32_C(1)<<16))
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#define Q15_TO_FLOAT(a) ((float)(a)/(UINT32_C(1)<<15))
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#define Q8_TO_FLOAT(a) ((float)(a)/(UINT32_C(1)<<8))
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#define Q7_TO_FLOAT(a) ((float)(a)/(UINT32_C(1)<<7))
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//#define DEBUG_RATIO_CALCULATION
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typedef struct {
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uint32_t count; // 17bit are usable to count samples, recommended for max 96kHz
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uint32_t last; // time stamp of last measurement
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uint32_t rate_state; // unsigned Q17.8
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uint32_t ratio_state; // unsigned Q16.16
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uint32_t constant_playback_sample_rate; // playback sample rate if no real one is available
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#ifdef DEBUG_RATIO_CALCULATION
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double sample_rate;
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double ratio;
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#endif
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} btstack_sample_rate_compensation_t;
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/**
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* @brief Initialize sample rate compensation
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* @param self pointer to current instance
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* @param time stamp at which to start sample rate measurement
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*/
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void btstack_sample_rate_compensation_init( btstack_sample_rate_compensation_t *self, uint32_t timestamp_ms, uint32_t sample_rate, uint32_t ratioQ15 );
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/**
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* @brief reset sample rate compensation
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* @param self pointer to current instance
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* @param time stamp at which to start sample rate measurement
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*/
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void btstack_sample_rate_compensation_reset( btstack_sample_rate_compensation_t *self, uint32_t timestamp_ms );
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/**
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* @brief update sample rate compensation with the current playback sample rate decoded samples
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* @param self pointer to current instance
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* @param time stamp for current samples
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* @param samples for current time stamp
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* @param playback sample rate
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*/
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uint32_t btstack_sample_rate_compensation_update( btstack_sample_rate_compensation_t *self, uint32_t timestamp_ms, uint32_t samples, uint32_t playback_sample_rate );
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/* API_END */
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#if defined __cplusplus
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}
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#endif
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#endif /* BTSTACK_SAMPLE_RATE_COMPENSATION_H_ */
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