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Important constants for tuning kb1 echo can
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/* Convergence (aka. adaptation) speed -- higher means slower */
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#define DEFAULT_BETA1_I 2048
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/* Constants for various power computations */
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#define DEFAULT_SIGMA_LY_I 7
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#define DEFAULT_SIGMA_LU_I 7
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#define DEFAULT_ALPHA_ST_I 5 /* near-end speech detection sensitivity factor */
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#define DEFAULT_ALPHA_YT_I 5
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#define DEFAULT_CUTOFF_I 128
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/* Define the near-end speech hangover counter: if near-end speech
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* is declared, hcntr is set equal to hangt (see pg. 432)
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#define DEFAULT_HANGT 600 /* in samples, so 600 samples = 75ms */
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/* define the residual error suppression threshold */
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#define DEFAULT_SUPPR_I 16 /* 16 = -24db */
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/* This is the minimum reference signal power estimate level
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* that will result in filter adaptation.
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* If this is too low then background noise will cause the filter
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* coefficients to constantly be updated.
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#define MIN_UPDATE_THRESH_I 4096
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/* The number of samples used to update coefficients using the
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* the block update method (M). It should be related back to the
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* length of the echo can.
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* ie. it only updates coefficients when (sample number MOD default_m) = 0
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* Getting this wrong may cause an oops. Consider yourself warned!
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#define DEFAULT_M 16 /* every 16th sample */
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/* If AGGRESSIVE supression is enabled, then we start cancelling residual
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* echos again even while there is potentially the very end of a near-side
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* This defines how many samples of DEFAULT_HANGT can remain before we
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#define AGGRESSIVE_HCNTR 160 /* in samples, so 160 samples = 20ms */
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/***************************************************************/
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/* The following knobs are not implemented in the current code */
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/* we need a dynamic level of suppression varying with the ratio of the
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power of the echo to the power of the reference signal this is
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done so that we have a smoother background.
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we have a higher suppression when the power ratio is closer to
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suppr_ceil and reduces logarithmically as we approach suppr_floor.
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#define SUPPR_FLOOR -64
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#define SUPPR_CEIL -24
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/* in a second departure, we calculate the residual error suppression
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* as a percentage of the reference signal energy level. The threshold
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* is defined in terms of dB below the reference signal.
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#define RES_SUPR_FACTOR -20
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#endif /* _MEC2_CONST_H */