sample_rate_converter.h

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/*
 * Copyright (c) 2023 Nordic Semiconductor ASA
 *
 * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
 */
 
#ifndef _SAMPLE_RATE_CONVERTER_H_
#define _SAMPLE_RATE_CONVERTER_H_
 
#ifdef CONFIG_SAMPLE_RATE_CONVERTER
#include <zephyr/sys/ring_buffer.h>
#include <dsp/filtering_functions.h>
#endif /* CONFIG_SAMPLE_RATE_CONVERTER */
 
#define SAMPLE_RATE_CONVERTER_STATE_BUFFER_SIZE                                                    \
        (CONFIG_SAMPLE_RATE_CONVERTER_BLOCK_SIZE_MAX +                                             \
         CONFIG_SAMPLE_RATE_CONVERTER_MAX_FILTER_SIZE - 1)
 
enum sample_rate_converter_filter {
        SAMPLE_RATE_FILTER_TEST = 1,
        SAMPLE_RATE_FILTER_SIMPLE
};
 
#define SAMPLE_RATE_CONVERTER_INPUT_BUFFER_NUMBER_OVERFLOW_SAMPLES 2
 
#define SAMPLE_RATE_CONVERTER_OUTPUT_BUFFER_NUMBER_OVERFLOW_SAMPLES 6
 
#ifdef CONFIG_SAMPLE_RATE_CONVERTER_BIT_DEPTH_16
#define SAMPLE_RATE_CONVERTER_INPUT_BUF_SIZE                                                       \
        (SAMPLE_RATE_CONVERTER_INPUT_BUFFER_NUMBER_OVERFLOW_SAMPLES * sizeof(uint16_t))
#define SAMPLE_RATE_CONVERTER_RINGBUF_SIZE                                                         \
        ((CONFIG_SAMPLE_RATE_CONVERTER_BLOCK_SIZE_MAX +                                            \
          SAMPLE_RATE_CONVERTER_OUTPUT_BUFFER_NUMBER_OVERFLOW_SAMPLES) *                           \
         sizeof(uint16_t))
#elif CONFIG_SAMPLE_RATE_CONVERTER_BIT_DEPTH_32
#define SAMPLE_RATE_CONVERTER_INPUT_BUF_SIZE                                                       \
        (SAMPLE_RATE_CONVERTER_INPUT_BUFFER_NUMBER_OVERFLOW_SAMPLES * sizeof(uint32_t))
#define SAMPLE_RATE_CONVERTER_RINGBUF_SIZE                                                         \
        ((CONFIG_SAMPLE_RATE_CONVERTER_BLOCK_SIZE_MAX +                                            \
          SAMPLE_RATE_CONVERTER_OUTPUT_BUFFER_NUMBER_OVERFLOW_SAMPLES) *                           \
         sizeof(uint32_t))
#else
#define SAMPLE_RATE_CONVERTER_INPUT_BUF_SIZE 0
#define SAMPLE_RATE_CONVERTER_RINGBUF_SIZE   0
#endif
 
struct buf_ctx {
        uint8_t buf[SAMPLE_RATE_CONVERTER_INPUT_BUF_SIZE];
        size_t bytes_in_buf;
};
 
struct sample_rate_converter_ctx {
        /* Input and output sample rate to be used for the conversion. */
        uint32_t sample_rate_input;
        uint32_t sample_rate_output;
 
        /* The ratio for the current conversion. When the conversion is upsampling the ratio is
         * positive and negative when downsampling.
         */
        int conversion_ratio;
 
        /* Filter type to be used for the conversion. */
        enum sample_rate_converter_filter filter_type;
 
        /* Buffer used to store input samples between process calls. */
        struct buf_ctx input_buf;
 
        /* Ring buffer used to store output samples between process calls. */
        struct ring_buf output_ringbuf;
        uint8_t output_ringbuf_data[SAMPLE_RATE_CONVERTER_RINGBUF_SIZE];
 
        /* Contexts for the CMSIS DSP filter functions. */
        union {
#ifdef CONFIG_SAMPLE_RATE_CONVERTER_BIT_DEPTH_16
                arm_fir_interpolate_instance_q15 fir_interpolate_q15;
                arm_fir_decimate_instance_q15 fir_decimate_q15;
#elif CONFIG_SAMPLE_RATE_CONVERTER_BIT_DEPTH_32
                arm_fir_interpolate_instance_q31 fir_interpolate_q31;
                arm_fir_decimate_instance_q31 fir_decimate_q31;
#endif
        };
 
        /* State buffers used by the CMSIS DSP filters to keep history of the stream between process
         * calls.
         */
#ifdef CONFIG_SAMPLE_RATE_CONVERTER_BIT_DEPTH_16
        q15_t state_buf_15[SAMPLE_RATE_CONVERTER_STATE_BUFFER_SIZE];
#elif CONFIG_SAMPLE_RATE_CONVERTER_BIT_DEPTH_32
        q31_t state_buf_31[SAMPLE_RATE_CONVERTER_STATE_BUFFER_SIZE];
#endif
};
 
int sample_rate_converter_open(struct sample_rate_converter_ctx *ctx);
 
int sample_rate_converter_process(struct sample_rate_converter_ctx *ctx,
                                  enum sample_rate_converter_filter filter, void const *const input,
                                  size_t input_size, uint32_t input_sample_rate, void *const output,
                                  size_t output_size, size_t *output_written,
                                  uint32_t output_sample_rate);
 
#endif /* _SAMPLE_RATE_CONVERTER_H_ */