Acoustic delay measurement using adaptive filter with programmable delay buffer

An acoustic delay measurement apparatus for measuring an audio delay introduced by an audio system, comprising:

• a programmable delay buffer operative to receive an audio stream from an audio source and output a reference signal representing the audio stream, said programmable delay buffer being operative to introduce a programmable delay into the audio stream, wherein said programmable delay is based upon a maximum delay available in an adaptive filter;
• said adaptive filter responsive to said reference signal to generate an estimate signal to match, on convergence of the adaptive filter, a delayed audio stream output by the audio system, said delayed audio stream comprising said audio stream from said audio source delayed by an amount representative of an audio delay introduced by the audio system;
• and
• a processor including a coefficient analysis block, said coefficient analysis block operative to read coefficients in the adaptive filter after convergence, compute a delay introduced by the adaptive filter into said estimate signal by incrementally examining the coefficients read from said adaptive filter and determine the first coefficient that exceeds a predetermined threshold value, wherein said adaptive filter has a particular size, and if said coefficient analysis block determines that said first coefficient corresponds to the particular size of said adaptive filter, said processor sets the programmable delay introduced by said programmable delay buffer into the received audio stream to a predetermined fraction of the maximum delay available in said adaptive filter to output a new reference signal, directs the adaptive filter to converge on the new reference signal, re-computes the delay introduced by the adaptive filter for the new reference signal, and adds the re-computed delay to the programmable delay introduced by the programmable delay buffer to provide a measurement of said audio delay, and
• wherein if said first coefficient does not correspond to the particular size of said adaptive filter, the processor is operative to add the computed delay to the programmable delay introduced by the programmable delay buffer to provide the measurement of said audio delay.

A computer-implemented method of determining audio latency in an audio system, comprising:

• applying an audio stream obtained from an audio source to the audio system possessing latency;
• applying a delayed audio stream obtained from the audio system to a first input of an adaptive filter;
• applying a reference signal to a second input of said adaptive filter to permit the adaptive filter to generate an estimate signal of the delayed audio stream upon convergence, the reference signal being obtained from the audio stream after passing through a programmable delay buffer to introduce a programmable delay into the audio stream, wherein the programmable delay is based upon a maximum delay available in said adaptive filter, and wherein convergence is deemed to have occurred when a magnitude of an error signal output by the adaptive filter is less than a predetermined fraction of said delayed audio stream;
• if the adaptive filter fails to converge, incrementing the programmable delay buffer by a predetermined amount of the maximum delay available in said adaptive filter to introduce a programmable delay into the received audio stream and to generate a new reference signal for the adaptive filter and restarting the adaptive filter;
• and
• upon convergence of the adaptive filter, computing a delay introduced by the adaptive filter into the estimate signal and adding the computed delay to the programmable delay introduced by the programmable delay buffer to provide a measurement of the audio delay.