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Audio: MFCC: Add Voice Activity Detection based on Mel spectrum #10782

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d495cc1
Audio: MFCC: Add Voice Activity Detection based on Mel spectrum
singalsu May 12, 2026
1c5fb79
Audio: MFCC: Add Python script for speech to text with Whisper model
singalsu May 19, 2026
5537875
Audio: MFCC: Add VAD switch control notification to user space
singalsu May 19, 2026
2fa783a
Audio: MFCC: Fix memory leak on reset-prepare cycles
singalsu May 22, 2026
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5 changes: 4 additions & 1 deletion src/audio/mfcc/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -4,5 +4,8 @@ if(CONFIG_COMP_MFCC STREQUAL "m" AND DEFINED CONFIG_LLEXT)
add_subdirectory(llext ${PROJECT_BINARY_DIR}/mfcc_llext)
add_dependencies(app mfcc)
else()
add_local_sources(sof mfcc.c mfcc_setup.c mfcc_common.c mfcc_generic.c mfcc_hifi4.c mfcc_hifi3.c)
add_local_sources(sof mfcc.c mfcc_setup.c mfcc_common.c mfcc_generic.c mfcc_hifi4.c mfcc_hifi3.c mfcc_vad.c)
if(CONFIG_IPC_MAJOR_4)
add_local_sources(sof mfcc_ipc4.c)
endif()
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endif()
56 changes: 25 additions & 31 deletions src/audio/mfcc/mfcc.c
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Expand Up @@ -97,36 +97,14 @@ static int mfcc_free(struct processing_module *mod)
struct mfcc_comp_data *cd = module_get_private_data(mod);

comp_info(mod->dev, "entry");
ipc_msg_free(cd->msg);
cd->msg = NULL;
mod_data_blob_handler_free(mod, cd->model_handler);
mfcc_free_buffers(mod);
mod_free(mod, cd);
return 0;
}

static int mfcc_get_config(struct processing_module *mod,
uint32_t config_id, uint32_t *data_offset_size,
uint8_t *fragment, size_t fragment_size)
{
struct sof_ipc_ctrl_data *cdata = (struct sof_ipc_ctrl_data *)fragment;
struct mfcc_comp_data *cd = module_get_private_data(mod);

comp_info(mod->dev, "entry");

return comp_data_blob_get_cmd(cd->model_handler, cdata, fragment_size);
}

static int mfcc_set_config(struct processing_module *mod, uint32_t config_id,
enum module_cfg_fragment_position pos, uint32_t data_offset_size,
const uint8_t *fragment, size_t fragment_size, uint8_t *response,
size_t response_size)
{
struct mfcc_comp_data *cd = module_get_private_data(mod);

comp_info(mod->dev, "entry");

return comp_data_blob_set(cd->model_handler, pos, data_offset_size,
fragment, fragment_size);
}

static int mfcc_process(struct processing_module *mod,
struct input_stream_buffer *input_buffers, int num_input_buffers,
Expand Down Expand Up @@ -187,22 +165,33 @@ static int mfcc_prepare(struct processing_module *mod,
audio_stream_get_channels(&sourceb->stream));
if (ret < 0) {
comp_err(dev, "setup failed.");
goto err;
return ret;
}
} else {
comp_err(dev, "configuration is missing.");
return -EINVAL;
}

cd->mfcc_func = mfcc_find_func(source_format, sink_format, mfcc_fm, ARRAY_SIZE(mfcc_fm));
if (!cd->mfcc_func) {
comp_err(dev, "No proc func");
ret = -EINVAL;
goto err;
mfcc_free_buffers(mod);
return -EINVAL;
}
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return 0;
/* Initialize VAD switch control notification if enabled */
if (cd->config->enable_vad && cd->config->update_controls) {
if (!cd->msg) {
ret = mfcc_ipc_notification_init(mod);
if (ret < 0) {
mfcc_free_buffers(mod);
return ret;
}
}
}
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err:
comp_set_state(dev, COMP_TRIGGER_RESET);
return ret;
cd->vad_prev = false;
return 0;
}

static int mfcc_reset(struct processing_module *mod)
Expand All @@ -211,6 +200,11 @@ static int mfcc_reset(struct processing_module *mod)

comp_info(mod->dev, "entry");

/* Free MFCC buffers to prevent leaks on reset->prepare cycles.
* mfcc_free_buffers() NULLs the pointers after free.
*/
mfcc_free_buffers(mod);

/* Reset to similar state as init() */
cd->mfcc_func = NULL;
return 0;
Expand Down
110 changes: 79 additions & 31 deletions src/audio/mfcc/mfcc_common.c
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Original file line number Diff line number Diff line change
Expand Up @@ -21,14 +21,17 @@
#include <stddef.h>
#include <stdint.h>

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

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_comp_data *cd)
static int mfcc_stft_process(struct processing_module *mod, struct mfcc_comp_data *cd)
{
const struct comp_dev *dev = mod->dev;
struct sof_mfcc_config *config = cd->config;
struct mfcc_state *state = &cd->state;
struct mfcc_buffer *buf = &state->buf;
Expand Down Expand Up @@ -169,6 +172,32 @@ static int mfcc_stft_process(const struct comp_dev *dev, struct mfcc_comp_data *

cc_count += state->dct.num_out;
}

/* Use hop counter for frame numbering (independent of VAD enable) */
state->header.frame_number = state->hop_count;

/* Run VAD on the mel log spectrum (available in both modes) */
if (config->enable_vad) {
mfcc_vad_update(&cd->vad, state->mel_log_32);

/* Populate data header for this output frame */
state->header.energy = cd->vad.energy;
state->header.noise_energy = cd->vad.noise_energy;
state->header.vad_flag = cd->vad.is_speech ? 1 : 0;
}

/* Increment hop counter at end of hop processing */
state->hop_count++;

/* Send notification when VAD state changes */
if (config->enable_vad && config->update_controls) {
bool vad_now = cd->vad.is_speech;

if (vad_now != cd->vad_prev) {
mfcc_send_vad_notification(mod, vad_now ? 1 : 0);
cd->vad_prev = vad_now;
}
}
}

return cc_count;
Expand Down Expand Up @@ -267,9 +296,8 @@ void mfcc_s16_default(struct processing_module *mod, struct input_stream_buffer
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;
int16_t *w_ptr = audio_stream_get_wptr(sink);
const int num_magic = 2;
const int num_header_s16 = sizeof(state->header) / sizeof(int16_t);
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@lyakh lyakh May 26, 2026

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is the division guaranteed to be exact or you do want rounding-down?

int num_ceps;
int sink_samples;
int to_copy;
Expand All @@ -278,27 +306,35 @@ void mfcc_s16_default(struct processing_module *mod, struct input_stream_buffer
mfcc_source_copy_s16(bsource, buf, &state->emph, frames, state->source_channel);

/* Run STFT and processing after FFT: Mel auditory filter and DCT. */
num_ceps = mfcc_stft_process(mod->dev, cd);
num_ceps = mfcc_stft_process(mod, cd);

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

state->out_remain = num_ceps;
state->magic_pending = true;
state->header_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);
sink_samples -= num_magic;
state->magic_pending = false;
/* Write data header first if pending */
if (state->header_pending) {
if (sink_samples < num_header_s16) {
/* Not enough sink space for header, defer entire frame */
mfcc_sink_copy_zero_s16(sink, w_ptr, sink_samples);
return;
}

w_ptr = mfcc_sink_copy_data_s16(sink, w_ptr, num_header_s16,
(int16_t *)&state->header);
sink_samples -= num_header_s16;
state->header_pending = false;
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}

/* Write cepstral/mel data from scratch buffer */
Expand Down Expand Up @@ -363,9 +399,8 @@ void mfcc_s24_default(struct processing_module *mod, struct input_stream_buffer
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 */
const int num_header_s32 = sizeof(state->header) / sizeof(int32_t);
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@lyakh lyakh May 26, 2026

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same about rounding

int num_ceps;
int sink_samples;
int remain_s32;
Expand All @@ -376,7 +411,7 @@ void mfcc_s24_default(struct processing_module *mod, struct input_stream_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);
num_ceps = mfcc_stft_process(mod, cd);

/* If new output produced, set up pointer into scratch data */
if (num_ceps > 0) {
Expand All @@ -391,17 +426,24 @@ void mfcc_s24_default(struct processing_module *mod, struct input_stream_buffer
}

state->out_remain = num_ceps;
state->magic_pending = true;
state->header_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 data header first if pending */
if (state->header_pending) {
if (sink_samples < num_header_s32) {
/* Not enough sink space for header, defer entire frame */
mfcc_sink_copy_zero_s32(sink, w_ptr, sink_samples);
return;
}

w_ptr = mfcc_sink_copy_data_s32(sink, w_ptr, num_header_s32,
(int32_t *)&state->header);
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@lyakh lyakh May 26, 2026

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it looks like we expect the header size to be a multiple of 4 bytes, so maybe we could add a build-assertion and comments here to make it clear. Can be a follow-up, just checking that this is indeed the case

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@lgirdwood lgirdwood May 26, 2026

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no assertions, return an error.

sink_samples -= num_header_s32;
state->header_pending = false;
}

if (state->mel_only) {
Expand Down Expand Up @@ -443,9 +485,8 @@ void mfcc_s32_default(struct processing_module *mod, struct input_stream_buffer
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 */
const int num_header_s32 = sizeof(state->header) / sizeof(int32_t);
int num_ceps;
int sink_samples;
int remain_s32;
Expand All @@ -455,7 +496,7 @@ void mfcc_s32_default(struct processing_module *mod, struct input_stream_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);
num_ceps = mfcc_stft_process(mod, cd);

/* If new output produced, set up pointer into scratch data */
if (num_ceps > 0) {
Expand All @@ -466,17 +507,24 @@ void mfcc_s32_default(struct processing_module *mod, struct input_stream_buffer
}

state->out_remain = num_ceps;
state->magic_pending = true;
state->header_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 data header first if pending */
if (state->header_pending) {
if (sink_samples < num_header_s32) {
/* Not enough sink space for header, defer entire frame */
mfcc_sink_copy_zero_s32(sink, w_ptr, sink_samples);
return;
}

w_ptr = mfcc_sink_copy_data_s32(sink, w_ptr, num_header_s32,
(int32_t *)&state->header);
sink_samples -= num_header_s32;
state->header_pending = false;
}

if (state->mel_only) {
Expand Down
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