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File ns_melspec.c

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Set of mel-scaled spectrogram related utilities. More...

  • #include "am_bsp.h"
  • #include "am_mcu_apollo.h"
  • #include "am_util.h"
  • #include "float.h"
  • #include "ns_ambiqsuite_harness.h"
  • #include "ns_audio_melspec.h"
  • #include <string.h>

Public Attributes

Type Name
arm_cfft_instance_f32 g_melspecRfft

Public Functions

Type Name
void ns_melspec_audio_to_stft (ns_melspec_cfg_t * cfg, const int16_t * audio_in, float32_t * stft_out)
convert the audio samples into a short-time fourier transform
void ns_melspec_init (ns_melspec_cfg_t * cfg)
initialize data structures used for mel spectrogram related functions
void ns_melspec_melspec_to_stft (ns_melspec_cfg_t * cfg, const float32_t * melspec_in, float32_t * stft_out)
Inverts a mel spectrogram back into linear short-time fourier transform.
void ns_melspec_stft_to_audio (ns_melspec_cfg_t * cfg, float32_t * stft_in, int16_t * audio_out)
Inverts short-time fourier transform into a reconstructed audio sample.
void ns_melspec_stft_to_compressed_melspec (ns_melspec_cfg_t * cfg, const float32_t * stft_in, float32_t * melspec_out)
Converts complex valued short-time fourier transform into real-valued, power compressed mel scaled space.

Detailed Description

Author:

Scott Leishman

Version:

0.1

Date:

2022-10-10

Copyright:

Copyright (c) 2022

Public Attributes Documentation

variable g_melspecRfft

arm_cfft_instance_f32 g_melspecRfft;

Public Functions Documentation

function ns_melspec_audio_to_stft

convert the audio samples into a short-time fourier transform 

void ns_melspec_audio_to_stft (
    ns_melspec_cfg_t * cfg,
    const int16_t * audio_in,
    float32_t * stft_out
)

Result is complex valued (containing magnitude and phase info in alternating 32-bit values, so stft_out should be 2*MELSPEC_FRAME_LEN

function ns_melspec_init

void ns_melspec_init (
    ns_melspec_cfg_t * cfg
)

function ns_melspec_melspec_to_stft

void ns_melspec_melspec_to_stft (
    ns_melspec_cfg_t * cfg,
    const float32_t * melspec_in,
    float32_t * stft_out
)

function ns_melspec_stft_to_audio

Inverts short-time fourier transform into a reconstructed audio sample. 

void ns_melspec_stft_to_audio (
    ns_melspec_cfg_t * cfg,
    float32_t * stft_in,
    int16_t * audio_out
)

We assume the stft input is complex valued (containing magnitude and phase info in alternating 32-bit values).

Note that this operation currently modifies the input buffer!

function ns_melspec_stft_to_compressed_melspec

void ns_melspec_stft_to_compressed_melspec (
    ns_melspec_cfg_t * cfg,
    const float32_t * stft_in,
    float32_t * melspec_out
)

The documentation for this class was generated from the following file neuralSPOT/neuralspot/ns-audio/src/ns_melspec.c