AEC Data Structure and Enum Definitions¶

enum aec_adaption_e¶

Values:

enumerator AEC_ADAPTION_AUTO¶: Compute filter adaption config every frame.

enumerator AEC_ADAPTION_FORCE_ON¶: Filter adaption always ON.

enumerator AEC_ADAPTION_FORCE_OFF¶: Filter adaption always OFF.

enum shadow_state_e¶

Values:

enumerator LOW_REF¶: Not much reference so no point in acting on AEC filter logic.

enumerator ERROR¶: something has gone wrong, zero shadow filter

enumerator ZERO¶: shadow filter has been reset multiple times, zero shadow filter

enumerator RESET¶: copy main filter to shadow filter

enumerator EQUAL¶: main filter and shadow filter are similar

enumerator SIGMA¶: shadow filter bit better than main, reset sigma_xx for faster convergence

enumerator COPY¶: shadow filter much better, copy to main

struct coherence_mu_config_params_t¶

Public Members

float_s32_t coh_alpha¶: Update rate of coh.

float_s32_t coh_slow_alpha¶: Update rate of coh_slow.

float_s32_t coh_thresh_slow¶: Adaption frozen if coh below (coh_thresh_slow*coh_slow)

float_s32_t coh_thresh_abs¶: Adaption frozen if coh below coh_thresh_abs.

float_s32_t mu_scalar¶: Scalefactor for scaling the calculated mu.

float_s32_t eps¶: Parameter to avoid divide by 0 in coh calculation.

float_s32_t thresh_minus20dB¶: -20dB threshold

float_s32_t x_energy_thresh¶: X_energy threshold used for determining if the signal has enough reference energy for sensible coherence mu calculation

unsigned mu_coh_time¶: Number of frames after low coherence, adaption frozen for.

unsigned mu_shad_time¶: Number of frames after shadow filter use, the adaption is fast for

aec_adaption_e adaption_config¶: Filter adaption mode. Auto, force ON or force OFF

int32_t force_adaption_mu_q30¶: Fixed mu value used when filter adaption is forced ON

struct shadow_filt_config_params_t¶

Public Members

float_s32_t shadow_sigma_thresh¶: threshold for resetting sigma_XX.

float_s32_t shadow_copy_thresh¶: threshold for copying shadow filter.

float_s32_t shadow_reset_thresh¶: threshold for resetting shadow filter.

float_s32_t shadow_delay_thresh¶: threshold for turning off shadow filter reset if reference delay is large

float_s32_t x_energy_thresh¶: X energy threshold used for deciding whether the system has enough reference energy for main and shadow filter comparison to make sense

float_s32_t shadow_mu¶: fixed mu value used during shadow filter adaption.

int32_t shadow_better_thresh¶: Number of times shadow filter needs to be better before it gets copied to main filter.

int32_t shadow_zero_thresh¶: Number of times shadow filter is reset by copying the main filter to it before it gets zeroed.

int32_t shadow_reset_timer¶: Number of frames between zeroing resets of shadow filter.

struct aec_core_config_params_t¶

Public Members

int bypass¶: bypass AEC flag.

int gamma_log2¶: parameter for deriving the gamma value that used in normalisation spectrum calculation. gamma is calculated as 2^gamma_log2

uint32_t sigma_xx_shift¶: parameter used for deriving the alpha value used while calculating EMA of X_energy to calculate sigma_XX.

float_s32_t delta_adaption_force_on¶: delta value used in normalisation spectrum computation when adaption is forced as always ON.

float_s32_t delta_min¶: Lower limit of delta computed using fractional regularisation.

uint32_t coeff_index¶: coefficient index used to track H_hat index when sending H_hat values over the host control interface.

fixed_s32_t ema_alpha_q30¶: alpha used while calculating y_ema_energy, x_ema_energy and error_ema_energy.

struct aec_config_params_t¶

#include <aec_state.h>

AEC control parameters.

This structure contains control parameters that the user can modify at run time.

Public Members

coherence_mu_config_params_t coh_mu_conf¶: Coherence mu related control params.

shadow_filt_config_params_t shadow_filt_conf¶: Shadow filter related control params.

aec_core_config_params_t aec_core_conf¶: All AEC control params except those for coherence mu and shadow filter.

struct coherence_mu_params_t¶

Public Members

float_s32_t coh¶: Moving average coherence.

float_s32_t coh_slow¶: Slow moving average coherence.

int32_t mu_coh_count¶: Counter for tracking number of frames coherence has been low for.

int32_t mu_shad_count¶: Counter for tracking number of frames shadow filter has been used in.

float_s32_t coh_mu[AEC_LIB_MAX_X_CHANNELS]¶: Coherence mu.

struct shadow_filter_params_t¶

Public Members

int32_t shadow_flag[AEC_LIB_MAX_Y_CHANNELS]¶: shadow_state_e enum indicating shadow filter status

int shadow_reset_count[AEC_LIB_MAX_Y_CHANNELS]¶: counter for tracking shadow filter resets

int shadow_better_count[AEC_LIB_MAX_Y_CHANNELS]¶: counter for tracking shadow filter copy to main filter

struct aec_shared_state_t¶

#include <aec_state.h>

AEC shared state structure.

Data structures holding AEC persistant state that is common between main filter and shadow filter. aec_state_t::shared_state for both main and shadow filter point to the common aec_shared_t structure. [aec_shared_state_t]

Public Members

bfp_complex_s32_t X_fifo[AEC_LIB_MAX_X_CHANNELS][AEC_LIB_MAX_PHASES]¶

BFP array pointing to the reference input spectrum phases. The term phase refers to the spectrum data for a frame. Multiple phases means multiple frames of data.

For example, 10 phases would mean the 10 most recent frames of data. Each phase spectrum, pointed to by X_fifo[i][j]->data is stored as a length AEC_FD_FRAME_LENGTH, complex 32bit array.

The phases are ordered from most recent to least recent in the X_fifo. For example, for an AEC configuration of 2 x-channels and 10 phases per x channel, 10 frames of X data spectrum is stored in the X_fifo. For a given x channel, say x channel 0, X_fifo[0][0] points to the most recent frame’s X spectrum and X_fifo[0][9] points to the last phase, i.e the least recent frame’s X spectrum.

bfp_complex_s32_t X[AEC_LIB_MAX_X_CHANNELS]¶: BFP array pointing to reference input signal spectrum. The X data values are stored as a length AEC_FD_FRAME_LENGTH complex 32bit array per x channel.

bfp_complex_s32_t Y[AEC_LIB_MAX_Y_CHANNELS]¶: BFP array pointing to mic input signal spectrum. The Y data values are stored as a length AEC_FD_FRAME_LENGTH complex 32bit array per y channel.

bfp_s32_t y[AEC_LIB_MAX_Y_CHANNELS]¶: BFP array pointing to time domain mic input processing block. The y data values are stored as length AEC_PROC_FRAME_LENGTH, 32bit integer array per y channel.

bfp_s32_t x[AEC_LIB_MAX_X_CHANNELS]¶: BFP array pointing to time domain reference input processing block. The x data values are stored as length AEC_PROC_FRAME_LENGTH, 32bit integer array per x channel.

bfp_s32_t prev_y[AEC_LIB_MAX_Y_CHANNELS]¶: BFP array pointing to time domain mic input values from the previous frame. These are put together with the new samples received in the current frame to make a AEC_PROC_FRAME_LENGTH processing block. The prev_y data values are stored as length (AEC_PROC_FRAME_LENGTH - AEC_FRAME_ADVANCE), 32bit integer array per y channel.

bfp_s32_t prev_x[AEC_LIB_MAX_X_CHANNELS]¶: BFP array pointing to time domain reference input values from the previous frame. These are put together with the new samples received in the current frame to make a AEC_PROC_FRAME_LENGTH processing block. The prev_x data values are stored as length (AEC_PROC_FRAME_LENGTH - AEC_FRAME_ADVANCE), 32bit integer array per x channel.

bfp_s32_t sigma_XX[AEC_LIB_MAX_X_CHANNELS]¶: BFP array pointing to sigma_XX values which are the weighted average of the X_energy signal. The sigma_XX data is stored as 32bit integer array of length AEC_FD_FRAME_LENGTH

float_s32_t y_ema_energy[AEC_LIB_MAX_Y_CHANNELS]¶: Exponential moving average of the time domain mic signal energy. This is calculated by calculating energy per sample and summing across all samples. Stored in a y channels array with every value stored as a 32bit integer mantissa and exponent.

float_s32_t x_ema_energy[AEC_LIB_MAX_X_CHANNELS]¶: Exponential moving average of the time domain reference signal energy. This is calculated by calculating energy per sample and summing across all samples. Stored in a x channels array with every value stored as a 32bit integer mantissa and exponent.

float_s32_t overall_Y[AEC_LIB_MAX_Y_CHANNELS]¶: Energy of the mic input spectrum. This is calculated by calculating the energy per bin and summing across all bins. Stored in a y channels array with every value stored as a 32bit integer mantissa and exponent.

float_s32_t sum_X_energy[AEC_LIB_MAX_X_CHANNELS]¶: Sum of the X_energy across all bins for a given x channel. Stored in a x channels array with every value stored as a 32bit integer mantissa and exponent.

coherence_mu_params_t coh_mu_state[AEC_LIB_MAX_Y_CHANNELS]¶: Structure containing coherence mu calculation related parameters.

shadow_filter_params_t shadow_filter_params¶: Structure containing shadow filter related parameters.

aec_config_params_t config_params¶: Structure containing AEC control parameters. These are initialised to the default values and can be changed at runtime by the user.

unsigned num_y_channels¶: Number of mic input channels that the AEC is configured for. This is the input parameter num_y_channels that aec_init() gets called with.

unsigned num_x_channels¶: Number of reference input channels that the AEC is configured for. This is the input parameter num_x_channels that aec_init() gets called with.

struct aec_state_t¶

#include <aec_state.h>

[aec_shared_state_t]

AEC state structure.

Data structures holding AEC persistant state. There are 2 instances of aec_state_t maintained within AEC; one for main filter and one for shadow filter specific state. [aec_state_t]

Public Members

bfp_complex_s32_t Y_hat[AEC_LIB_MAX_Y_CHANNELS]¶: BFP array pointing to estimated mic signal spectrum. The Y_data data values are stored as length AEC_FD_FRAME_LENGTH, complex 32bit array per y channel.

bfp_complex_s32_t Error[AEC_LIB_MAX_Y_CHANNELS]¶: BFP array pointing to adaptive filter error signal spectrum. The Error data is stored as length AEC_FD_FRAME_LENGTH, complex 32bit array per y channel.

bfp_complex_s32_t H_hat[AEC_LIB_MAX_Y_CHANNELS][AEC_LIB_MAX_PHASES]¶

BFP array pointing to the adaptive filter spectrum. The filter spectrum is stored as a num_y_channels x total_phases_across_all_x_channels array where each H_hat[i][j] entry points to the spectrum of a single phase.

Number of phases in the filter refers to its tail length. A filter with more phases would be able to model a longer echo thereby causing better echo cancellation.

For example, for a 2 y-channels, 3 x-channels, 10 phases per x channel configuration, the filter spectrum phases are stored in a 2x30 array. For a given y channel, say y channel 0, H_hat[0][0] to H_hat[0][9] points to 10 phases of H_hat_y0x0, H_hat[0][10] to H_hat[0][19] points to 10 phases of H_hat_y0x1 and H_hat[0][20] to H_hat[0][29] points to 10 phases of H_hat_y0x2.

Each filter phase data which is pointed to by H_hat[i][j].data is stored as AEC_FD_FRAME_LENGTH complex 32bit array.

bfp_complex_s32_t X_fifo_1d[AEC_LIB_MAX_PHASES]¶

BFP array pointing to all phases of reference input spectrum across all x channels. Here, the reference input spectrum is saved in a 1 dimensional array of phases, with x channel 0 phases followed by x channel 1 phases and so on. For example, for a 2 x-channels, 10 phases per x channel configuration, X_fifo_1d[0] to X_fifo_1d[9] points to the 10 phases for channel 0 and X_fifo[10] to X_fifo[19] points to the 10 phases for channel 1.

Each X data spectrum phase pointed to by X_fifo_1d[i][j].data is stored as length AEC_FD_FRAME_LENGTH complex 32bit array.

bfp_complex_s32_t T[AEC_LIB_MAX_X_CHANNELS]¶: BFP array pointing to T values which are stored as a length AEC_FD_FRAME_LENGTH, complex array per x channel.

bfp_s32_t inv_X_energy[AEC_LIB_MAX_X_CHANNELS]¶: BFP array pointing to the normalisation spectrum which are stored as a length AEC_FD_FRAME_LENGTH, 32bit integer array per x channel.

bfp_s32_t X_energy[AEC_LIB_MAX_X_CHANNELS]¶: BFP array pointing to the X_energy data which is the energy per bin of the X spectrum summed over all phases of the X data. X_energy data is stored as a length AEC_FD_FRAME_LENGTH, integer 32bit array per x channel.

bfp_s32_t overlap[AEC_LIB_MAX_Y_CHANNELS]¶: BFP array pointing to time domain overlap data values which are used in the overlap add operation done while calculating the echo canceller time domain output. Stored as a length 32, 32 bit integer array per y channel.

bfp_s32_t y_hat[AEC_LIB_MAX_Y_CHANNELS]¶: BFP array pointing to the time domain estimated mic signal. Stored as length AEC_PROC_FRAME_LENGTH, 32 bit integer array per y channel.

bfp_s32_t error[AEC_LIB_MAX_Y_CHANNELS]¶: BFP array pointing to the time domain adaptive filter error signal. Stored as length AEC_PROC_FRAME_LENGTH, 32 bit integer array per y channel.

float_s32_t mu[AEC_LIB_MAX_Y_CHANNELS][AEC_LIB_MAX_X_CHANNELS]¶: mu values for every x-y pair stored as 32 bit integer mantissa and 32 bit integer exponent

float_s32_t error_ema_energy[AEC_LIB_MAX_Y_CHANNELS]¶: Exponential moving average of the time domain adaptive filter error signal energy. Stored in an x channels array with every value stored as a 32bit integer mantissa and exponent.

float_s32_t overall_Error[AEC_LIB_MAX_Y_CHANNELS]¶: Energy of the adaptive filter error spectrum. Stored in a y channels array with every value stored as a 32bit integer mantissa and exponent.

float_s32_t max_X_energy[AEC_LIB_MAX_X_CHANNELS]¶: Maximum X energy across all values of X_energy for a given x channel. Stored in an x channels array with every value stored as a 32bit integer mantissa and exponent.

float_s32_t delta_scale¶: fractional regularisation scalefactor.

float_s32_t delta¶: delta parameter used in the normalisation spectrum calculation.

aec_shared_state_t *shared_state¶: pointer to the state data shared between main and shadow filter.

unsigned num_phases¶: Number of filter phases per x-y pair that AEC filter is configured for. This is the input argument num_main_filter_phases or num_shadow_filter_phases, depending on which filter the aec_state_t is instantiated for, passed in aec_init() call.