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90 lines
3.7 KiB
C
90 lines
3.7 KiB
C
#pragma once
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#include "esp_speech_features.h"
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#include <stdint.h>
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/*
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This describes an interface for a MFCC runner, that is, some kind of implementation that can be
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fed sample chunks and returns the MFCC cepstrum of those samples. This is an abstracted interface so
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multiple implementations can be used.
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*/
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typedef struct esp_mfcc_data_t esp_mfcc_data_t;
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// Options for the mfcc algorithm itself. These more-or-less match the parameters of csf_mfcc (from c_speech_features),
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// please refer to its documentation for details.
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typedef struct {
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int winstep_ms; // The step between successive windows in ms. (10)
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int winlen_ms; // The length of the analysis window in ms. (25)
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int nch; // The number of input channel
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int numcep; // The number of cepstrum to return
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int nfilter; // The number of filters in the filterbank
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int nfft; // The FFT size
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int samp_freq; // The sample-rate of the signal.
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int low_freq; // The lowest band edge of mel filters, in hz. (e.g. 0)
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int high_freq; // The highest band edge of mel filters, in hz. Must not be higher than samp_freq
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float preemph; // Preemphasis filter coefficient. 0 is no filter. (e.g. 0.97)
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char *win_type; // Analysis window type to apply to each frame， "hanning","hamming","sine","rectangular","povey"
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bool append_energy; // If true, the zeroth cepstral coefficient is replaced with the log of the total frame energy
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bool use_power; // If true, use power of fft spectrum, else use magnitude of fft spectrum
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int use_log_fbank; // 0: return fbank, 1: return log(x+log_epsilon), 2: return log(max(x, log_epsilon))
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float log_epsilon; // log epsilon. (e.g. 1e-7)
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bool psram_first; // Alloc memory from PSRAM first
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bool remove_dc_offset; // Whether to subtract mean of wave before FFT
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} esp_mfcc_opts_t;
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/**
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* @brief Un-initialize and free a mfcc runner
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*
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* Function to free a previously allocated mfcc runner.
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*
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* @param r Runner object to destroy
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*/
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typedef void (*esp_mfcc_op_destroy_t)(esp_mfcc_data_t *r);
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/**
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* @brief Initialize parameters for a mfcc runner.
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*
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* After creation, a mfcc runner needs to be initialized first; this is usually done
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* in the initialization routine of a speech recognition algorithm. This provides
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* a pointer to do this for a specific mfcc runner.
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*
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* @param opt Options for the mfcc process
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* @return True if success, false on error.
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*/
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typedef esp_mfcc_data_t *(*esp_mfcc_op_create_t)(const esp_mfcc_opts_t *opt);
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/**
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* @brief Run a mfcc iteration on frame by frame
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*
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* This will take a set of samples and return a ceptrum. Note that this may be pipelined:
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* an initial call to this function may return NULL and subsequent calls may return the
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* cepstrum of previous calls.
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*
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* @param r The mfcc runner
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* @param samp An array of signed 16-bit samples. The amount of samples should be sampfreq/(winstep_ms/1000).
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* @return A set of cepstral values, or NULL if no such values are available yet. Free using the free_cepbuf function
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* when done with this buffer. Note that some implementations require the buffer to be freed before another call
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* to this function is done.
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*/
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typedef float *(*esp_mfcc_op_run_step_t)(esp_mfcc_data_t *r, int16_t *samp, int16_t nch);
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typedef void (*esp_mfcc_op_run_step_s16_t)(esp_mfcc_data_t *r, int16_t *samp, int16_t *fbank);
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/**
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* @brief Clean all state of mfcc handle
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*
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* @param r The mfcc runner
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*/
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typedef void (*esp_mfcc_op_clean_t)(esp_mfcc_data_t *r);
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/**
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* @brief Operations possible on a mfcc runner
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*/
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typedef struct {
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esp_mfcc_op_destroy_t destroy;
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esp_mfcc_op_create_t create;
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esp_mfcc_op_run_step_t run_step;
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esp_mfcc_op_run_step_s16_t run_step_s16;
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esp_mfcc_op_clean_t clean;
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} esp_mfcc_iface_t;
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