Echo suppression with increment/decrement, quick, and time-delay counter updating
Hands-free phones with voice activity detection using a comparison of frame power estimate with an adaptive frame noise power estimate, automatic gain control with fast adaptation and minimal speech distortion, echo cancellation updated in the frequency domain with stepsize optimization and smoothed spectral whitening, and echo suppression with adaptive talking-state transitions.
1. A process of echo suppression, comprising:
A. updating, for every received and sent frame of voice data, and in a range of zero to a maximum value:
i. a count in a first hangover counter for an Idle operating state,
ii. a count in a second hangover counter for an Double-talk operating state,
ii. a count in a third hangover counter for an Far-end talk only operating state,
iv. a count in a fourth hangover counter for an Near-end talk operating state, and
v. the updating including updating the counts in the counters at a change of operating states with one of an increment/decrement updating, a quick updating, and a time-delay updating;
B. computing each of four coefficients as the relative counts of the respective first, second, third, and fourth hangover counters;
C. computing attenuations for a receive amplifier and a send amplifier as linear combinations of the four coefficients;
D. attenuating amplification of a received frame of voice data to be applied to a speaker, and attenuating amplification of a sent frame of voice data from a microphone to suppress echoes.
2. The process of claim 1 in which the increment/decrement updating includes incrementing by one the counter corresponding to the changed operating state while decrementing by one the counters corresponding to the other three states, with saturation of the counters at both zero and a maximum.
3. The process of claim 1 in which the quick updating includes resetting all counters to zero except the counter corresponding to the changed operating state without a time delay.
4. The process of claim 1 including using only the quick updating for transitions from the Idle operating state to the Double-talk operating state, the Far-end operating state, and the Near-end operating state, and for transitions from the Far-end operating state and Near-end operating state to the Double-talk operating state.
5. The process of claim 1 in which the time-delay updating includes resetting all counters to zero, except the counter corresponding to the different operating state, with a time delay.
6. The process of claim 1 including using only the time delay updating with one time delay for transitions between the Far-end operating state and the Near-end operating state.
7. The process of claim 1 including using only the time delay updating with one time delay for transitions from the Double-talk operating state to the Far-end operating state and the Near-end operating state.
8. The process of claim 1 including using only the time delay updating with one time delay for transitions between the Far-end operating state and the Near-end operating state and with another time delay for transitions between the Far-end operating state and the Near-end operating state.