Skip to content

Audio: MFCC: Add Mel spectrogram mode via configuration blob #10743

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
singalsu wants to merge 12 commits into
base: main
Choose a base branch
from
Open

Audio: MFCC: Add Mel spectrogram mode via configuration blob #10743

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
12 commits
Select commit Hold shift + click to select a range
551ce88
Audio: MFCC: Improve generic s16 source and sink copy functions
singalsu Apr 28, 2026
0eb5952
Audio: MFCC: Remove unnecessary data copy HiFi3/4 code
singalsu Apr 28, 2026
856d3fc
Audio: MFCC: Add S24 and S32 format support
singalsu Apr 27, 2026
49d80f1
Audio: MFCC: Improve check for input channel select
singalsu May 4, 2026
57731b4
Audio: MFCC: Add Mel log spectra output mode when num_ceps is zero
singalsu Apr 24, 2026
c88c72d
Audio: MFCC: Allow output data to span over single period
singalsu Apr 30, 2026
17dede7
Audio: MFCC: Update user/mfcc.h comment
singalsu Apr 30, 2026
2ee9bed
Audio: MFCC: Add setup of Hann window
singalsu Apr 30, 2026
1c5decd
Audio: MFCC: Add dynamic mmax tracking and configurable mel scaling
singalsu Apr 30, 2026
7119ea4
Audio: MFCC: Update setup_mfcc.m blob export script
singalsu Apr 29, 2026
020de6f
Tools: Topology: Build test topologies for Mel output mode of MFCC
singalsu May 4, 2026
b39cc4e
Audio: MFCC: Update example run script run_mfcc.sh
singalsu Apr 28, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
6 changes: 3 additions & 3 deletions src/audio/mfcc/mfcc.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -38,13 +38,13 @@ SOF_DEFINE_REG_UUID(mfcc);

__cold_rodata const struct mfcc_func_map mfcc_fm[] = {
#if CONFIG_FORMAT_S16LE
{SOF_IPC_FRAME_S16_LE, mfcc_s16_default},
{SOF_IPC_FRAME_S16_LE, mfcc_s16_default},
#endif /* CONFIG_FORMAT_S16LE */
#if CONFIG_FORMAT_S24LE
{SOF_IPC_FRAME_S24_4LE, NULL},
{SOF_IPC_FRAME_S24_4LE, mfcc_s24_default},
#endif /* CONFIG_FORMAT_S24LE */
#if CONFIG_FORMAT_S32LE
{SOF_IPC_FRAME_S32_LE, NULL},
{SOF_IPC_FRAME_S32_LE, mfcc_s32_default},
#endif /* CONFIG_FORMAT_S32LE */
};

Expand Down
311 changes: 288 additions & 23 deletions src/audio/mfcc/mfcc_common.c
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,13 +1,14 @@
// SPDX-License-Identifier: BSD-3-Clause
//
// Copyright(c) 2023 Intel Corporation. All rights reserved.
// Copyright(c) 2023-2026 Intel Corporation.
//
// Author: Andrula Song <andrula.song@intel.com>

#include <sof/audio/mfcc/mfcc_comp.h>

#include <sof/audio/component.h>
#include <sof/audio/audio_stream.h>
#include <sof/audio/format.h>
#include <sof/math/auditory.h>
#include <sof/math/matrix.h>
#include <sof/math/sqrt.h>
Expand Down Expand Up @@ -36,15 +37,21 @@ LOG_MODULE_REGISTER(mfcc_common, CONFIG_SOF_LOG_LEVEL);
* The main processing function for MFCC
*/

static int mfcc_stft_process(const struct comp_dev *dev, struct mfcc_state *state)
static int mfcc_stft_process(const struct comp_dev *dev, struct mfcc_comp_data *cd)
{
struct sof_mfcc_config *config = cd->config;
struct mfcc_state *state = &cd->state;
struct mfcc_buffer *buf = &state->buf;
struct mfcc_fft *fft = &state->fft;
int mel_scale_shift;
int input_shift;
int i;
int m;
int cc_count = 0;
int32_t s;
int16_t mel_value;
int16_t peak;
int16_t clamp_value;

/* Phase 1, wait until whole fft_size is filled with valid data. This way
* first output cepstral coefficients originate from streamed data and not
Expand Down Expand Up @@ -119,16 +126,59 @@ static int mfcc_stft_process(const struct comp_dev *dev, struct mfcc_state *stat
state->mel_spectra->data, mel_scale_shift);
#endif

/* Multiply Mel spectra with DCT matrix to get cepstral coefficients */
mat_init_16b(state->cepstral_coef, 1, state->dct.num_out, 7); /* Q8.7 */
mat_multiply(state->mel_spectra, state->dct.matrix, state->cepstral_coef);
if (state->mel_only) {
/* In Mel-only mode output Mel log spectra directly */
cc_count += state->dct.num_in;

/* Find peak mel value and track state->mmax */
if (config->dynamic_mmax) {
peak = state->mel_spectra->data[0];
for (i = 1; i < state->dct.num_in; i++) {
if (state->mel_spectra->data[i] > peak)
peak = state->mel_spectra->data[i];
}

/* Jump to peak immediately if higher, decay otherwise */
if (peak > state->mmax) {
state->mmax = peak;
} else {
/* Q8.7 * Q1.15, result Q8.7. The coefficient is small so
* no need for saturation.
*/
s = (int32_t)peak - state->mmax;
state->mmax +=
Q_MULTSR_32X32(s, config->mmax_coef, 7, 15, 7);
}
}

/* Clamp Mel values lower than mmax - top_db, add offset, and scale */
clamp_value = state->mmax - config->top_db;
for (i = 0; i < state->dct.num_in; i++) {
mel_value = state->mel_spectra->data[i];
if (mel_value < clamp_value)
mel_value = clamp_value;

/* Q8.7 * Q4.12, result 8.7 */
s = (int32_t)mel_value + config->mel_offset;
state->mel_spectra->data[i] =
sat_int16(Q_MULTSR_32X32(s, config->mel_scale, 7, 12, 7));
}

/* Enable this to check mmax decay */
comp_dbg(dev, "state->mmax = %d", state->mmax);
} else {
/* Multiply Mel spectra with DCT matrix to get cepstral coefficients */
mat_init_16b(state->cepstral_coef, 1, state->dct.num_out, 7); /* Q8.7 */
mat_multiply(state->mel_spectra, state->dct.matrix, state->cepstral_coef);

/* Apply cepstral lifter */
if (state->lifter.cepstral_lifter != 0)
mat_multiply_elementwise(state->cepstral_coef, state->lifter.matrix,
state->cepstral_coef);
/* Apply cepstral lifter */
if (state->lifter.cepstral_lifter != 0) {
mat_multiply_elementwise(state->cepstral_coef, state->lifter.matrix,
state->cepstral_coef);
}

cc_count += state->dct.num_out;
cc_count += state->dct.num_out;
}

/* Output to sink buffer */
}
Expand All @@ -140,6 +190,44 @@ static int mfcc_stft_process(const struct comp_dev *dev, struct mfcc_state *stat
}

#if CONFIG_FORMAT_S16LE
static int16_t *mfcc_sink_copy_zero_s16(const struct audio_stream *sink, int16_t *w_ptr,
int samples)
{
int copied;
int nmax;
int n;

for (copied = 0; copied < samples; copied += n) {
nmax = samples - copied;
n = audio_stream_samples_without_wrap_s16(sink, w_ptr);
n = MIN(n, nmax);
memset(w_ptr, 0, n * sizeof(int16_t));
w_ptr = audio_stream_wrap(sink, w_ptr + n);
}

return w_ptr;
}

static int16_t *mfcc_sink_copy_data_s16(const struct audio_stream *sink, int16_t *w_ptr,
int samples, int16_t *r_ptr)
{
int copied;
int nmax;
int n;

for (copied = 0; copied < samples; copied += n) {
nmax = samples - copied;
n = audio_stream_samples_without_wrap_s16(sink, w_ptr);
n = MIN(n, nmax);
/* Not using memcpy_s() due to speed need */
memcpy(w_ptr, r_ptr, n * sizeof(int16_t));
w_ptr = audio_stream_wrap(sink, w_ptr + n);
r_ptr += n;
}

return w_ptr;
}

void mfcc_s16_default(struct processing_module *mod, struct input_stream_buffer *bsource,
struct output_stream_buffer *bsink, int frames)
{
Expand All @@ -149,35 +237,212 @@ void mfcc_s16_default(struct processing_module *mod, struct input_stream_buffer
struct mfcc_buffer *buf = &cd->state.buf;
uint32_t magic = MFCC_MAGIC;
int16_t *w_ptr = audio_stream_get_wptr(sink);
// int num_magic = sizeof(magic) / sizeof(int16_t);
const int num_magic = 2;
int num_ceps;
int zero_samples;
int sink_samples;
int to_copy;

/* Get samples from source buffer */
mfcc_source_copy_s16(bsource, buf, &state->emph, frames, state->source_channel);

/* Run STFT and processing after FFT: Mel auditory filter and DCT. The sink
* buffer is updated during STDF processing.
*/
num_ceps = mfcc_stft_process(mod->dev, state);
/* Run STFT and processing after FFT: Mel auditory filter and DCT. */
num_ceps = mfcc_stft_process(mod->dev, cd);

/* Done, copy data to sink. This works only if the period has room for magic (2)
* plus num_ceps int16_t samples. TODO: split ceps over multiple periods.
*/
zero_samples = frames * audio_stream_get_channels(sink);
/* If new output produced, set up pointer into scratch data and mark magic pending */
if (num_ceps > 0) {
zero_samples -= num_ceps + num_magic;
if (state->mel_only)
state->out_data_ptr = state->mel_spectra->data;
else
state->out_data_ptr = state->cepstral_coef->data;

state->out_remain = num_ceps;
state->magic_pending = true;
}

/* Write to sink, limited by period size */
sink_samples = frames * audio_stream_get_channels(sink);

/* Write magic word first if pending */
if (state->magic_pending && sink_samples >= num_magic) {
w_ptr = mfcc_sink_copy_data_s16(sink, w_ptr, num_magic, (int16_t *)&magic);
w_ptr = mfcc_sink_copy_data_s16(sink, w_ptr, num_ceps, state->cepstral_coef->data);
sink_samples -= num_magic;
state->magic_pending = false;
}

w_ptr = mfcc_sink_copy_zero_s16(sink, w_ptr, zero_samples);
/* Write cepstral/mel data from scratch buffer */
to_copy = MIN(state->out_remain, sink_samples);
if (to_copy > 0) {
w_ptr = mfcc_sink_copy_data_s16(sink, w_ptr, to_copy, state->out_data_ptr);
state->out_data_ptr += to_copy;
state->out_remain -= to_copy;
sink_samples -= to_copy;
}

/* Zero-fill remaining sink samples */
w_ptr = mfcc_sink_copy_zero_s16(sink, w_ptr, sink_samples);
}
#endif /* CONFIG_FORMAT_S16LE */

#if CONFIG_FORMAT_S24LE || CONFIG_FORMAT_S32LE
static int32_t *mfcc_sink_copy_zero_s32(const struct audio_stream *sink, int32_t *w_ptr,
int samples)
{
int copied;
int nmax;
int n;

for (copied = 0; copied < samples; copied += n) {
nmax = samples - copied;
n = audio_stream_samples_without_wrap_s32(sink, w_ptr);
n = MIN(n, nmax);
memset(w_ptr, 0, n * sizeof(int32_t));
w_ptr = audio_stream_wrap(sink, w_ptr + n);
}

return w_ptr;
}

static int32_t *mfcc_sink_copy_data_s32(const struct audio_stream *sink, int32_t *w_ptr,
int samples, int32_t *r_ptr)
{
int copied;
int nmax;
int n;

for (copied = 0; copied < samples; copied += n) {
nmax = samples - copied;
n = audio_stream_samples_without_wrap_s32(sink, w_ptr);
n = MIN(n, nmax);
/* Not using memcpy_s() due to speed need */
memcpy(w_ptr, r_ptr, n * sizeof(int32_t));
w_ptr = audio_stream_wrap(sink, w_ptr + n);
r_ptr += n;
}

return w_ptr;
}
#endif /* CONFIG_FORMAT_S24LE || CONFIG_FORMAT_S32LE */

#if CONFIG_FORMAT_S24LE
void mfcc_s24_default(struct processing_module *mod, struct input_stream_buffer *bsource,
struct output_stream_buffer *bsink, int frames)
{
struct audio_stream *sink = bsink->data;
struct mfcc_comp_data *cd = module_get_private_data(mod);
struct mfcc_state *state = &cd->state;
struct mfcc_buffer *buf = &cd->state.buf;
uint32_t magic = MFCC_MAGIC;
int32_t *w_ptr = audio_stream_get_wptr(sink);
const int num_magic = 1; /* one int32_t word for magic */
int num_ceps;
int sink_samples;
int remain_s32;
int to_copy;

/* Get samples from source buffer */
mfcc_source_copy_s24(bsource, buf, &state->emph, frames, state->source_channel);

/* Run STFT and processing after FFT */
num_ceps = mfcc_stft_process(mod->dev, cd);

/* If new output produced, set up pointer into scratch data */
if (num_ceps > 0) {
if (state->mel_only)
state->out_data_ptr = state->mel_spectra->data;
else
state->out_data_ptr = state->cepstral_coef->data;

state->out_remain = num_ceps;
state->magic_pending = true;
}

/* Write to sink, limited by period size */
sink_samples = frames * audio_stream_get_channels(sink);

/* Write magic word first if pending */
if (state->magic_pending && sink_samples >= num_magic) {
w_ptr = mfcc_sink_copy_data_s32(sink, w_ptr, num_magic, (int32_t *)&magic);
sink_samples -= num_magic;
state->magic_pending = false;
}

/* Write cepstral/mel data packed as int32_t from scratch buffer */
remain_s32 = (state->out_remain + 1) / 2;
to_copy = MIN(remain_s32, sink_samples);
if (to_copy > 0) {
w_ptr = mfcc_sink_copy_data_s32(sink, w_ptr, to_copy,
(int32_t *)state->out_data_ptr);
state->out_data_ptr += to_copy * 2;
state->out_remain -= to_copy * 2;
if (state->out_remain < 0)
state->out_remain = 0;

sink_samples -= to_copy;
Comment on lines +372 to +380
Copy link
Copy Markdown
Collaborator Author

@singalsu singalsu May 5, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I'll change the Mel values data to 32 bit. It will avoid this issue and improve a lot the accuracy. The normalized log10 Mel values for Whisper in about -1 to +1 range consumed only a part of 16 bit Q9.7 format.

}

/* Zero-fill remaining sink samples */
w_ptr = mfcc_sink_copy_zero_s32(sink, w_ptr, sink_samples);
}
#endif /* CONFIG_FORMAT_S24LE */

#if CONFIG_FORMAT_S32LE
void mfcc_s32_default(struct processing_module *mod, struct input_stream_buffer *bsource,
struct output_stream_buffer *bsink, int frames)
{
struct audio_stream *sink = bsink->data;
struct mfcc_comp_data *cd = module_get_private_data(mod);
struct mfcc_state *state = &cd->state;
struct mfcc_buffer *buf = &cd->state.buf;
uint32_t magic = MFCC_MAGIC;
int32_t *w_ptr = audio_stream_get_wptr(sink);
const int num_magic = 1; /* one int32_t word for magic */
int num_ceps;
int sink_samples;
int remain_s32;
int to_copy;

/* Get samples from source buffer */
mfcc_source_copy_s32(bsource, buf, &state->emph, frames, state->source_channel);

/* Run STFT and processing after FFT */
num_ceps = mfcc_stft_process(mod->dev, cd);

/* If new output produced, set up pointer into scratch data */
if (num_ceps > 0) {
if (state->mel_only)
state->out_data_ptr = state->mel_spectra->data;
else
state->out_data_ptr = state->cepstral_coef->data;

state->out_remain = num_ceps;
state->magic_pending = true;
}

/* Write to sink, limited by period size */
sink_samples = frames * audio_stream_get_channels(sink);

/* Write magic word first if pending */
if (state->magic_pending && sink_samples >= num_magic) {
w_ptr = mfcc_sink_copy_data_s32(sink, w_ptr, num_magic, (int32_t *)&magic);
sink_samples -= num_magic;
state->magic_pending = false;
}

/* Write cepstral/mel data packed as int32_t from scratch buffer */
remain_s32 = (state->out_remain + 1) / 2;
to_copy = MIN(remain_s32, sink_samples);
if (to_copy > 0) {
w_ptr = mfcc_sink_copy_data_s32(sink, w_ptr, to_copy,
(int32_t *)state->out_data_ptr);
state->out_data_ptr += to_copy * 2;
state->out_remain -= to_copy * 2;
if (state->out_remain < 0)
state->out_remain = 0;

Comment on lines +435 to +441
sink_samples -= to_copy;
}

/* Zero-fill remaining sink samples */
w_ptr = mfcc_sink_copy_zero_s32(sink, w_ptr, sink_samples);
}
#endif /* CONFIG_FORMAT_S32LE */
Loading
Loading