Equalizer
Provided in this API equalizer supports:
fixed number of ten (10) bands;
four sample rates: 11025 Hz, 22050 Hz, 44100 Hz and 48000 Hz.
The center frequencies of bands are shown in table below.
Band Index |
0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
|---|---|---|---|---|---|---|---|---|---|---|
Frequency |
31 Hz |
62 Hz |
125 Hz |
250 Hz |
500 Hz |
1 kHz |
2 kHz |
4 kHz |
8 kHz |
16 kHz |
Default gain of each band is -13 dB. To set the gains of all bands use structure equalizer_cfg. To set the gain of individual band use function equalizer_set_gain_info().
Application Example
Implementation of this API is demonstrated in the audio_processing/pipeline_equalizer example.
API Reference
Header File
Functions
-
esp_err_t equalizer_set_info(audio_element_handle_t self, int rate, int ch)
Set the audio sample rate and the number of channels to be processed by the equalizer.
- Parameters
self – Audio element handle
rate – Audio sample rate
ch – Audio channel
- Returns
ESP_OK on success
ESP_ERR_INVALID_ARG invalid arguments
-
esp_err_t equalizer_set_gain_info(audio_element_handle_t self, int index, int value_gain, bool is_channels_gain_equal)
Set the audio gain to be processed by the equalizer.
- Parameters
self – Audio element handle
index – The position of center frequencies of equalizer. If channel is mono, the index range is [0, 9]; If channel is stereo and
is_channels_gain_equalis true, the index range is [0, 9]; If channel is stereo andis_channels_gain_equalis false, the index range is [0, 19];value_gain – The value of audio gain which in
indexis_channels_gain_equal – If audio channel is stereo, the audio gain values of two channels are equal when
is_channels_gain_equalistrue, otherwise it means unequal.
- Returns
ESP_OK on success
ESP_ERR_INVALID_ARG invalid arguments
-
audio_element_handle_t equalizer_init(equalizer_cfg_t *config)
Create an Audio Element handle that equalizes incoming data.
- Parameters
config – The configuration
- Returns
The audio element handler
Structures
-
struct equalizer_cfg
Equalizer Configuration.
+——————————————————–—+ | MONO | +——————————————————–—+ | Only Left channel/Only Right channel | +——————————————————–—+ |band0|band1|band2|band3|band4|band5|band6|band7|band8|band9| +——————————————————–—+ | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | +——————————————————–—+
+——————————————————–—+——————————————————–—+ | DUAL | +——————————————————–—+——————————————————–—+ | Left channel | Right channel | +——————————————————–—+——————————————————–—+ |band0|band1|band2|band3|band4|band5|band6|band7|band8|band9|band0|band1|band2|band3|band4|band5|band6|band7|band8|band9| +——————————————————–—+——————————————————–—+ | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | +——————————————————–—+——————————————————–—+
3) Different sample rates support different EQ frequency bands. 11025: {31, 62, 125, 250, 500, 1000, 2000, 3000, 4000, 5500} 22050: {31, 62, 125, 250, 500, 1000, 2000, 4000, 8000, 11000} 44100/48000: {31, 62, 125, 250, 500, 1000, 2000, 4000, 8000, 16000}
Note
1) This figure indicate the default eq gain of every band in current equalizer. 2) Every channel have 10 band to set.
Public Members
-
int samplerate
Audio sample rate. Supported samplerate: 11025, 22050, 44100, 48000, unit: Hz
-
int channel
Number of audio channels. Supported channel: mono, stereo
-
int *set_gain
Equalizer gain
-
int out_rb_size
Size of output ring buffer
-
int task_stack
Task stack size
-
int task_core
Task running in core…
-
int task_prio
Task priority
-
bool stack_in_ext
Try to allocate stack in external memory
-
int samplerate
Macros
-
EQUALIZER_TASK_STACK
-
EQUALIZER_TASK_CORE
-
EQUALIZER_TASK_PRIO
-
EQUALIZER_RINGBUFFER_SIZE
-
DEFAULT_EQUALIZER_CONFIG()
Type Definitions
-
typedef struct equalizer_cfg equalizer_cfg_t
Equalizer Configuration.
+——————————————————–—+ | MONO | +——————————————————–—+ | Only Left channel/Only Right channel | +——————————————————–—+ |band0|band1|band2|band3|band4|band5|band6|band7|band8|band9| +——————————————————–—+ | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | +——————————————————–—+
+——————————————————–—+——————————————————–—+ | DUAL | +——————————————————–—+——————————————————–—+ | Left channel | Right channel | +——————————————————–—+——————————————————–—+ |band0|band1|band2|band3|band4|band5|band6|band7|band8|band9|band0|band1|band2|band3|band4|band5|band6|band7|band8|band9| +——————————————————–—+——————————————————–—+ | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | +——————————————————–—+——————————————————–—+
3) Different sample rates support different EQ frequency bands. 11025: {31, 62, 125, 250, 500, 1000, 2000, 3000, 4000, 5500} 22050: {31, 62, 125, 250, 500, 1000, 2000, 4000, 8000, 11000} 44100/48000: {31, 62, 125, 250, 500, 1000, 2000, 4000, 8000, 16000}
Note
1) This figure indicate the default eq gain of every band in current equalizer. 2) Every channel have 10 band to set.