Multi-channel echo cancellation with round robin regularization

A computer-implemented method for eliminating echoes of a plurality of playback signals in a captured signal, comprising:

• decomposing the plurality of playback signals into subbands;
• processing the subbands using a recursive least squares (RLS) adaptive filter for each of the subbands;
• selecting each of the RLS adaptive filters in round robin scheme;
• regularizing the selected RLS adaptive filter to ensure stability, regularizing the selected RLS adaptive filters further comprising:
• computing a correlation matrix of the RLS adaptive filter by inverting an inverse correlation matrix;
• regularizing a correlation matrix of the RLS adaptive filter to obtain a regularized correlation matrix;
• computing a regularized inverse correlation matrix of the RLS adaptive filter from the regularized correlation matrix;
• and
• reducing echoes in the captured signal using the outputs of the RLS adaptive filters.

A method for automatically switching between two different types of echo cancellation processes when processing one or more playback signals and a captured signal containing echo, comprising:

• detecting whether the one or more playback signals is monaural;
• processing the captured signal and the one or more playback signals using a monaural echo cancellation process if the one or more playback signals are monaural;
• processing the captured signal and the one of more playback signals using a multi-channel round robin regularization echo cancellation process if the one or more playback signals are not monaural;
• using an estimation technique to estimate a correlation matrix for the multi-channel round robin regularization echo cancellation process, using the estimation technique further comprising one of:
• (a) solving a normal equation in a statistical manner using a method of steepest descent when dynamically switching from the multi-channel round robin regularization echo cancellation process to the monaural echo cancellation process;
• (b) solving the normal equation deterministically using a least squares process when dynamically switching from the monaural echo cancellation process to the multi-channel round robin regularization echo cancellation process;
• and
• dynamically switching between the monaural echo cancellation process and the multi-channel round robin regularization echo cancellation process whenever the detection changes from one type to another.

A process for canceling echoes of a plurality of playback signals in a captured signal, the captured signal comprising lower captured subbands containing lower frequencies of the captured signal and higher captured subbands containing higher frequencies of the captured signal and the plurality of playback signals comprising lower playback subbands containing lower frequencies of the plurality of playback signals and higher playback subbands containing higher frequencies of the plurality of playback signals, the process comprising:

• using a first echo cancellation process to cancel echoes from the upper captured subbands;
• and
• using a multi-channel round robin regularization echo cancellation process to cancel the echoes in the lower captured subbands, the multi-channel round robin regularization echo cancellation process further comprising:
• applying a plurality of adaptive filters, which are recursive least square (RLS) adaptive filters and each of the plurality of adaptive filters comprising an inverse correlation matrix, to each of the lower playback subbands;
• selecting each of the plurality of adaptive filters in a round robin sequence;
• regularizing the inverse correlation matrix of each selected adaptive filter;
• computing each correlation matrix from an inverse correlation matrix.