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[i2s_audio] Optimize software volume control (#16278)

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This commit is contained in:
Kevin Ahrendt
2026-05-06 12:57:03 -04:00
committed by GitHub
parent a4a57a540d
commit fc25ab0246
2 changed files with 17 additions and 36 deletions
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51
esphome/components/i2s_audio/speaker/i2s_audio_speaker.cpp
View File

@@ -13,22 +13,16 @@
#include "esp_timer.h"
// esp-audio-libs
#include <gain.h>
namespace esphome::i2s_audio {
static const char *const TAG = "i2s_audio.speaker";
// Lists the Q15 fixed point scaling factor for volume reduction.
// Has 100 values representing silence and a reduction [49, 48.5, ... 0.5, 0] dB.
// dB to PCM scaling factor formula: floating_point_scale_factor = 2^(-db/6.014)
// float to Q15 fixed point formula: q15_scale_factor = floating_point_scale_factor * 2^(15)
static const std::vector<int16_t> Q15_VOLUME_SCALING_FACTORS = {
0, 116, 122, 130, 137, 146, 154, 163, 173, 183, 194, 206, 218, 231, 244,
259, 274, 291, 308, 326, 345, 366, 388, 411, 435, 461, 488, 517, 548, 580,
615, 651, 690, 731, 774, 820, 868, 920, 974, 1032, 1094, 1158, 1227, 1300, 1377,
1459, 1545, 1637, 1734, 1837, 1946, 2061, 2184, 2313, 2450, 2596, 2750, 2913, 3085, 3269,
3462, 3668, 3885, 4116, 4360, 4619, 4893, 5183, 5490, 5816, 6161, 6527, 6914, 7324, 7758,
8218, 8706, 9222, 9770, 10349, 10963, 11613, 12302, 13032, 13805, 14624, 15491, 16410, 17384, 18415,
19508, 20665, 21891, 23189, 24565, 26022, 27566, 29201, 30933, 32767};
// Software volume control maps the user-facing [0.0, 1.0] range to a Q31 scale factor.
// Volumes in (0.0, 1.0) map linearly to a dB reduction in [-49.0, 0.0] dB.
static constexpr float SOFTWARE_VOLUME_MIN_DB = -49.0f;
void I2SAudioSpeakerBase::setup() {
this->event_group_ = xEventGroupCreate();
@@ -147,14 +141,16 @@ void I2SAudioSpeakerBase::set_volume(float volume) {
} else
#endif // USE_AUDIO_DAC
{
// Fallback to software volume control by using a Q15 fixed point scaling factor.
// At maximum volume (1.0), set to INT16_MAX to completely bypass volume processing
// Fallback to software volume control by using a Q31 fixed point scaling factor.
// At maximum volume (1.0), set to INT32_MAX to bypass volume processing entirely
// and avoid any floating-point precision issues that could cause slight volume reduction.
if (volume >= 1.0f) {
this->q15_volume_factor_ = INT16_MAX;
this->q31_volume_factor_ = INT32_MAX;
} else if (volume <= 0.0f) {
this->q31_volume_factor_ = 0;
} else {
ssize_t decibel_index = remap<ssize_t, float>(volume, 0.0f, 1.0f, 0, Q15_VOLUME_SCALING_FACTORS.size() - 1);
this->q15_volume_factor_ = Q15_VOLUME_SCALING_FACTORS[decibel_index];
this->q31_volume_factor_ =
esp_audio_libs::gain::db_to_q31(remap<float, float>(volume, 0.0f, 1.0f, SOFTWARE_VOLUME_MIN_DB, 0.0f));
}
}
}
@@ -173,7 +169,7 @@ void I2SAudioSpeakerBase::set_mute_state(bool mute_state) {
{
if (mute_state) {
// Fallback to software volume control and scale by 0
this->q15_volume_factor_ = 0;
this->q31_volume_factor_ = 0;
} else {
// Revert to previous volume when unmuting
this->set_volume(this->volume_);
@@ -309,29 +305,14 @@ bool IRAM_ATTR I2SAudioSpeakerBase::i2s_on_sent_cb(i2s_chan_handle_t handle, i2s
}
void I2SAudioSpeakerBase::apply_software_volume_(uint8_t *data, size_t bytes_read) {
if (this->q15_volume_factor_ >= INT16_MAX) {
if (this->q31_volume_factor_ == INT32_MAX) {
return; // Max volume, no processing needed
}
const size_t bytes_per_sample = this->current_stream_info_.samples_to_bytes(1);
const uint32_t len = bytes_read / bytes_per_sample;
// Use Q16 for samples with 1 or 2 bytes: shifted_sample * gain_factor is Q16 * Q15 -> Q31
int32_t shift = 15; // Q31 -> Q16
int32_t gain_factor = this->q15_volume_factor_; // Q15
if (bytes_per_sample >= 3) {
// Use Q23 for samples with 3 or 4 bytes: shifted_sample * gain_factor is Q23 * Q8 -> Q31
shift = 8; // Q31 -> Q23
gain_factor >>= 7; // Q15 -> Q8
}
for (uint32_t i = 0; i < len; ++i) {
int32_t sample = audio::unpack_audio_sample_to_q31(&data[i * bytes_per_sample], bytes_per_sample); // Q31
sample >>= shift;
sample *= gain_factor; // Q31
audio::pack_q31_as_audio_sample(sample, &data[i * bytes_per_sample], bytes_per_sample);
}
esp_audio_libs::gain::apply(data, data, this->q31_volume_factor_, len, bytes_per_sample);
}
void I2SAudioSpeakerBase::swap_esp32_mono_samples_(uint8_t *data, size_t bytes_read) {

2
esphome/components/i2s_audio/speaker/i2s_audio_speaker.h
View File

@@ -151,7 +151,7 @@ class I2SAudioSpeakerBase : public I2SAudioOut, public speaker::Speaker, public
bool pause_state_{false};
int16_t q15_volume_factor_{INT16_MAX};
int32_t q31_volume_factor_{INT32_MAX};
audio::AudioStreamInfo current_stream_info_; // The currently loaded driver's stream info